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Use of Posthatching Yolk and External Forage to MaximizeEarly Growth in Apalone Mutica HatchlingsAuthor(s) Trixie N Lee Michael V Plummer Nathan E MillsSource Journal of Herpetology 41(3)492-500 2007Published By The Society for the Study of Amphibians and ReptilesDOI httpdxdoiorg1016700022-1511(2007)41[492UOPYAE]20CO2URL httpwwwbiooneorgdoifull1016700022-151128200729415B4923AUOPYAE5D20CO3B2

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Use of Posthatching Yolk and External Forage to Maximize EarlyGrowth in Apalone mutica Hatchlings

TRIXIE N LEE1 MICHAEL V PLUMMER2 AND NATHAN E MILLS3

Department of Biology Box 12251 Harding University Searcy Arkansas 72149 USA

ABSTRACTmdashPosthatching yolk in oviparous vertebrates is thought to supply the hatchling with energy for

a period of time after hatching in habitats that might require fasting To examine strategies of posthatching

energy use in Apalone mutica hatchlings were fed or not fed over periods of nine weeks in 2003 and six

weeks in 2004 Mass plastron length carapace width and body condition changed during the course of the

experiment all trajectories of change except carapace width in 2004 differed between fed and unfed

hatchlings Trajectories of fed hatchlings were significantly higher than unfed hatchlings Fed and unfed

hatchlings used internalized yolk at similar rates 50 of the yolk was depleted by day eight after hatching

and 90 by day 27 Metabolic rate (approximately 0236 ml CO2 h21) did not differ between fed and unfed

hatchlings Yolk reserves are insufficient to sustain hatchlings to the first overwintering season but with

access to external forage hatchlings appear to use yolk reserves to meet maintenance demands to support

maximal growth

In most vertebrate species the energy parentsprovide to their offspring can be divided intotwo components that used to make the embry-onic body before birth (parental investment inembryogenesis PIE) and that used to serve theoffspring after birth (parental investment incare PIC) (Congdon et al 1983 Congdon andGibbons 1990 Nagle et al 1998 2003) Inoviparous reptiles with no behavioral parentalcare PIC takes the form of yolk remaining withthe embryo after hatching thus continuingyolk-based nutrition past birth (postnatal le-cithotrophy Lance and Morafka 2001) Yolkreserves are thought to fuel the hatchling byproviding energy for maintenance activitygrowth and fat storage until the hatchling canattain a positive energy balance by foraging(Kraemer and Bennett 1981 Congdon andGibbons 1990 Fischer et al 1991 Nagle et al2003) These ideas are supported by studies ofexperimental yolk reduction in turtles (Yeo-mans 1999) lizards (Radder et al 2004) andbirds (Murakami et al 1992) and rates of yolkdepletion in turtles (Kraemer and Bennett 1981Tucker et al 1998) lizards (Troyer 1983)snakes (Ji et al 1997 1999 Ji and Sun 2000)and crocodilians (Whitehead 1990 Fischer etal 1991) The potential energetic contribution ofpostnatal lecithotrophy can be substantial

(Ewert 1991) For example residual yolk inthe turtle Gopherus agassizii permits hatchlingsto emerge from their nest disperse growburrow and hibernate over the first half yearof their lives without ever successfully foraging(Lance and Morafka 2001)

In the Smooth Softshell Turtle Apalone muticaonly 25 of the yolk lipids deposited in the eggby the ovary are used to form the offspringwhereas 75 remain in the body as fat bodiesand yolk reserves rendering A mutica with oneof the largest PIC values reported for turtles(Nagle et al 2003) This reserve could providean important energy source for hatchlings of Amutica a species that nests close to water(within 20 m Doody 1995) on clean opensandbars of large rivers and whose hatchlingsinhabit the relatively low-resource and unpre-dictable environment of the shallow wateraround sandbars (Plummer 1976 1977 Nagleet al 2003) Demands on stored energy in thisenvironment include digging out of the nestcavity dispersal from the nest to the watermaintenance growth and activities such asforaging and escape from predators

To examine strategies employed by hatchlingA mutica to use endogenous and exogenousenergy sources and to estimate the time thatyolk reserves are capable of meeting energeticrequirements we conducted laboratory experi-ments that address three questions (1) Do fedhatchlings deplete yolk reserves at a slower ratethan unfed hatchlings (2) Do fed hatchlingsgrow more rapidly than unfed hatchlings and(3) How long can stored yolk reserves fuelhatchlings

1 Corresponding Author Present address Universi-ty of Alaska Fairbanks Biology and Wildlife De-partment 211 Irving 1 Fairbanks Alaska 99775 USAE-mail fttnluafedu

2 E-mail plummerhardingedu3 E-mail nmillshardingedu

Journal of Herpetology Vol 41 No 3 pp 492ndash500 2007Copyright 2007 Society for the Study of Amphibians and Reptiles

MATERIALS AND METHODS

Eggs of A mutica were collected from 31 Mayto 20 June 2003 and 3 to 25 June 2004 from nestsconstructed on sandbars of the White River nearGeorgetown White County Arkansas Meanclutch size 6 SE in 2003 was 118 6 070 (range7ndash17) eggs and 144 6 076 (8ndash22) eggs in 2004Eggs were individually marked according toclutch with a felt-tipped pen packed in moistsand and transported to the laboratory wherethey were half-buried in 600 g of a 50 50vermiculitewater mixture in a covered 7 3 203 27 cm (H 3 W 3 L) plastic tray Waterpotential of the mixture was approximately2200 kPa (Plummer and Snell 1988) Eggs wereincubated at 30 6 05 C in Hovabater (GFQCorporation Savannah GA) incubators (Plum-mer et al 1994) Each incubator contained twoegg trays each of which initially contained 20eggs In contrast to the flexible-shelled eggs ofsome reptiles including many turtles the rigid-shelled eggs of Apalone spp are relativelyinsensitive to variation in substrate waterpotential (Packard et al 1979 1981 Gettingeret al 1984) Nevertheless to minimize variationin substrate water potential we periodicallyweighed each egg tray and added water to thevermiculite to replace mass loss by evaporation

When an egg pipped we placed a small wirecage over the egg to contain the hatchling foridentification Hatchlings were randomly as-signed to one of two experimental groups fedand unfed The two treatments containedapproximately equal numbers of hatchlingsfrom each of 16 (2003) or 24 (2004) clutchesand five incubators Food was withheld fromthe hatchlings in the unfed group whereashatchlings in the fed group were fed ad libitumthree times a week beginning on day eight afterhatching with a diet alternating between crick-ets and chopped minnows dusted with Repti-viteH vitamins The contents of the diet wereconsistent with the natural diet of A mutica(Plummer and Farrar 1981) Hatchlings weremaintained on a 12 12 L D photoperiod a daylength contained within the posthatching activ-ity season for A mutica in Arkansas (August toOctober) at room temperature (25uC) withoutthe opportunity to regulate body temperatureby basking Normal field body temperatures areunknown for A mutica However Apalonespinifera the sister species of A mutica (Meylan1987) is active within a broad range of bodytemperatures that average 25uC (Plummer et al2005) Hatchlings were housed in individual 53 12 3 12 cm (H 3 W 3 L) plastic containerswith 13 cm of water Water in containers waschanged three times a week on the daysfollowing feeding

We took several morphological measure-ments beginning on day seven after hatchingto allow time for flattening of the hatchlingrsquosbody from the spherical shape while in the eggand repeated approximately every two weeks(13ndash15 days 2003) or weekly (2004) thereafterWe towel-blotted the hatchlings until dry andthen weighed them We also measured theircarapace length maximum carapace width andplastron length and calculated body condition(body massplastron length) The original ex-perimental design required morphological mea-surements on each turtle over an approximate60-day period during August to October 2003This time frame was chosen because previousenergetic calculations with turtle (Trachemysscripta) and alligator (Alligator mississippiensis)hatchlings suggested that posthatching yolkreserves could sustain the hatchlings for ap-proximately 60ndash140 days (Fischer et al 1991)However a rapid decline in physical conditionof unfed turtles caused us to terminate theexperiments earlier The 2004 experiments wereconducted for approximately 40 days duringAugust and September After experiments wereterminated the 2003 hatchlings were overwin-tered in the laboratory and released near theirnest sites in the White River in early May 2004the 2004 experimental hatchlings were releasedin September 2004

Hatchlings for yolk depletion measurementswere taken from eight of the clutches collectedin 2004 three to four hatchlings selectedrandomly from each treatment group weresacrificed by freezing at 280uC every four daysbeginning at age four days over a period of44 days In addition yolks were obtained fromeight hatchlings from four clutches immediatelyafter pipping (age 0 days) Internalized yolkreserves were dissected out oven dried at 45uCfor 36 h and weighed on an analytical balanceWe measured rates of CO2 production of one-month-old hatchling A mutica randomly select-ed from each of three clutches within eachtreatment (seven fed seven unfed) at 25uC usinga Sable Systems TR-3 configured as an open-flow system (Beaupre and Zaidan 2001) Wemeasured CO2 production for each hatchlingevery 30 seconds for 75 continuous minutesduring each hour between 2100 and 0800 h thenormal inactive period for A mutica The SMRof each hatchling was calculated as the mean ofits lowest four hourly CO2 production ratemeasurements

This experiment was designed as a repeatedmeasures multivariate analysis of variance(MANOVA) experiment Data were analyzedusing the General Linear Model (GLM) state-ment in SAS (SAS Institute Inc Cary NC) Theprimary independent variable was feeding re-

USE OF YOLK RESERVES IN APALONE MUTICA 493

gime (Treat) Egg mass clutch and block(physical position of hatchling 2004 only) wereincluded to remove variability in growth datacaused by these factors and maximize ourability to detect variation resulting from ourexperimental treatments Dependent variableswere body mass plastron length carapacewidth and body condition Because carapacelength was difficult to measure as healthdeteriorated in unfed turtles it was eliminatedfrom the analyses For graphically presentingmorphological measurements over time weexpressed each mean as a percentage of itsinitial value To meet the assumption ofnormality body mass data were transformedby squaring and carapace width data weretransformed with natural logarithms in 2003Dried internalized yolk mass was regressed ondays after hatching for each treatment groupregression equations were compared by Analy-sis of Covariance (ANCOVA) Metabolic rateswere compared between treatment groups witha t-test and means were reported 6 SERegression analyses and t-tests were conductedwith SYSTAT Version 11 (SYSTAT SoftwareInc Richmond CA)

RESULTS

Clutch and egg mass were included in ourstatistical analysis to remove variability in thedata caused by genetic and maternal differ-ences Clutch accounted for significant variabil-ity in body mass body condition and plastronlength in 2003 (Table 1) Egg mass accounted fora significant amount of variability in bodycondition and carapace width in 2004 whereasblock accounted for a significant amount ofvariability in mass in 2004 (Table 1)

We predicted that fed hatchlings wouldincrease in mass whereas unfed hatchlingswould decrease in mass as they used their yolkreserves Consistent with our predictions fed

and unfed hatchling mass diverged throughtime in 2003 (P 0001 Table 1) with fedhatchlings slowly gaining mass whereas unfedhatchlings slowly lost mass (Fig 1) By weekfive and continuing through the rest of theexperiment univariate tests indicated that thefed hatchlings had greater mass than unfedhatchlings (Table 2 Fig 1) In 2004 both fedand unfed hatchlings lost mass but fed hatch-lings lost mass at a slower rate than unfedhatchlings (Fig 1) By week two and continuingthrough the rest of the experiment fed hatch-lings consistently had greater mass than unfedhatchlings (Table 2)

We predicted that turtles in both treatmentswould increase plastron length and carapacewidth until the yolk could no longer sustaingrowth at which point only the fed hatchlingswould continue to increase in size Consistentwith our prediction plastron length initiallyincreased in both feeding treatments (Fig 1)Furthermore plastron length diverged betweentreatments as the plastron length of unfedhatchlings began to decrease the plastronlength of fed hatchlings continued to increasein both years (Fig 1 2003 P 5 0010 2004 P 50022 Table 1) Plastron length was significantlygreater in fed hatchlings by week nine of 2003and beginning in week four in 2004 (Table 2)Also consistent with our prediction carapacewidth diverged between feeding treatments in2003 (P 0001 Table 1) Carapace widthincreased initially in both treatments but onlythe fed hatchlings continued to increase incarapace width after week five (Fig 1) Howev-er univariate tests indicated a significant dif-ference between the fed and unfed carapacewidths only during week three (Table 2)Although there were significant differences incarapace width between feeding treatmentsduring all weeks in 2004 (Table 2) the hatch-lings in both treatments responded similarlythrough time (P 5 0540 Table 1) thus we could

TABLE 1 Repeated-measures MANOVA to test for within subject effects on plastron length body masscarapace width and body condition

Source df Plastron length Mass Carapace width Body condition

2003 N 5 100 F P F P F P F P

Time 4 83 164 0172 070 0591 026 0903 132 0270Time3Egg mass 4 83 175 0147 111 0358 019 0944 191 01167Time3Clutch 44 344 234 0001 145 0037 119 0200 224 0001Time3Treat 4 83 357 0010 2374 0001 1032 0001 2479 0001

2004 N 5 60

Time 5 37 099 0435 202 0098 274 0033 301 0022Time3Egg mass 5 37 087 0512 167 0167 279 0031 271 0035Time3Clutch 55 205 097 0540 102 0449 115 0249 119 0197Time3Treat 5 37 301 0022 742 0001 083 0540 811 0001Time3Block 10 76 168 0102 280 0005 091 0530 169 0098

494 T N LEE ET AL

FIG 1 The relationship between percent of initial body mass plastron length carapace width and bodycondition to age in fed (closed symbols) and unfed (open symbols) Apalone mutica hatchlings in 2003 (leftcolumn) and 2004 (right column) Plotted are mean 6 SE

USE OF YOLK RESERVES IN APALONE MUTICA 495

not conclude that there was a difference incarapace width caused by the feeding treatment

Body condition diverged between feedingtreatments in both years (2003 P 00012004 P 0001 Table 1) After an initialdecrease in body condition the fed hatchlingsin 2003 increased in body condition whereasthe unfed hatchlings decreased in body condi-tion (Fig 1) Beginning in week five andcontinuing throughout the experiment fedhatchlings consistently had better body condi-tion than unfed hatchlings (Table 2 Fig 1)Body condition decreased in both feedingtreatments during 2004 but unfed hatchlingsdecreased in body condition at a faster rate thanfed hatchlings (Fig 1) Univariate tests indicat-ed that the fed hatchlings maintained a signifi-cantly better body condition beginning in weektwo and continuing throughout the rest of theexperiment (Table 2)

Hatchlings used yolk reserves at a comparablerate regardless of feeding condition A regres-sion analysis showed a significant negativerelationship between internalized yolk dry massand time after hatching in both feeding treat-ments and indicated that hatchlings used yolkreserves at a constant rate (Fig 2 fed log10 drymass 5 20557ndash0036 age N 5 42 R2 5 0785F140 5 1464 P 0001 unfed log10 dry mass 520576ndash0038 age N 5 42 R2 5 0813 F140 51734 P 0001) There was no significantdifference in rate of yolk depletion between fedand unfed hatchlings (ANCOVA F181 5 0639P 5 0426) Hatchling dry mass was notcorrelated with yolk dry mass (R2 5 0064 P5 0549 N 5 90) Because the effect of time oninternalized yolk mass did not differ between

treatments we pooled the data and calculateda common regression equation (log10 yolk drymass 5 20547ndash0038 age N 5 84 R2 5 0819 F188

5 3977 P 0001) This equation predicts that50 of the internalized yolk in a hatchling isdepleted by day eight 75 by day 16 and 90 byday 27 The standard metabolic rate of fedhatchlings (0236 6 0017 ml CO2 h21 N 5 7) didnot differ from unfed hatchlings (0235 6 0023 mlCO2 h21 N 5 7 t12 5 0035 P 5 0972) PooledSMR was 0236 6 0014 ml CO2 h21 (N 5 14)

DISCUSSION

One function of residual yolk may be toincrease hatchling fitness in unpredictable lowresource environments (Lance and Morafka2001) The productivity of lotic ecosystems thepreferred habitat of A mutica generally isconsiderably lower and more unpredictablethan the productivity of lentic systems (Whit-taker and Likens 1973) Furthermore fastingmay be induced in these microhabitats andforced further by conflicts between fitness-enhancing activities Mrosovsky and Sherry(1980) argue that the many examples of natu-rally occurring fasting that have been observedmay arise from conflicts between feeding andmore pressing activities such as thermoregula-tion incubation territory defense and predatoravoidance For A mutica hatchlings the highrisk of predation (Iverson 1991 Morafka et al2000) especially by birds (Janzen et al 2000MVP pers obs) may be a deterrent to foraging(Nagy 2000) and force the hatchling to rely onits residual yolk Reserves may also provide

TABLE 2 Analyses of variance results for effects of feeding treatment on morphological traits within eachweek All df 5 1

2003 N 5 100 Week 1 Week 3 Week 5 Week 7 Week 9 mdash

Plastron length F 016 005 120 284 505 mdashP 0692 0827 0277 0096 0027 mdash

Body mass F 327 143 1240 1906 3849 mdashP 0074 0234 0001 0001 0001 mdash

Carapace width F 253 428 117 054 021 mdashP 0116 0042 0283 0463 0649 mdash

Body condition F 384 347 1669 2659 5408 mdashP 0053 0066 0001 0001 0001 mdash

2004 N 5 60 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6

Plastron length F 036 037 153 816 646 863P 0554 0544 0223 0007 0015 0005

Body mass F 028 533 1160 1859 2313 2630P 0600 0026 0002 0001 0001 0001

Carapace width F 492 447 514 532 1238 1116P 0032 0041 0029 0026 0001 0002

Body condition F 003 681 1308 1423 2446 2746P 0863 0013 0001 0001 0001 0001

496 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

MATERIALS AND METHODS

Eggs of A mutica were collected from 31 Mayto 20 June 2003 and 3 to 25 June 2004 from nestsconstructed on sandbars of the White River nearGeorgetown White County Arkansas Meanclutch size 6 SE in 2003 was 118 6 070 (range7ndash17) eggs and 144 6 076 (8ndash22) eggs in 2004Eggs were individually marked according toclutch with a felt-tipped pen packed in moistsand and transported to the laboratory wherethey were half-buried in 600 g of a 50 50vermiculitewater mixture in a covered 7 3 203 27 cm (H 3 W 3 L) plastic tray Waterpotential of the mixture was approximately2200 kPa (Plummer and Snell 1988) Eggs wereincubated at 30 6 05 C in Hovabater (GFQCorporation Savannah GA) incubators (Plum-mer et al 1994) Each incubator contained twoegg trays each of which initially contained 20eggs In contrast to the flexible-shelled eggs ofsome reptiles including many turtles the rigid-shelled eggs of Apalone spp are relativelyinsensitive to variation in substrate waterpotential (Packard et al 1979 1981 Gettingeret al 1984) Nevertheless to minimize variationin substrate water potential we periodicallyweighed each egg tray and added water to thevermiculite to replace mass loss by evaporation

When an egg pipped we placed a small wirecage over the egg to contain the hatchling foridentification Hatchlings were randomly as-signed to one of two experimental groups fedand unfed The two treatments containedapproximately equal numbers of hatchlingsfrom each of 16 (2003) or 24 (2004) clutchesand five incubators Food was withheld fromthe hatchlings in the unfed group whereashatchlings in the fed group were fed ad libitumthree times a week beginning on day eight afterhatching with a diet alternating between crick-ets and chopped minnows dusted with Repti-viteH vitamins The contents of the diet wereconsistent with the natural diet of A mutica(Plummer and Farrar 1981) Hatchlings weremaintained on a 12 12 L D photoperiod a daylength contained within the posthatching activ-ity season for A mutica in Arkansas (August toOctober) at room temperature (25uC) withoutthe opportunity to regulate body temperatureby basking Normal field body temperatures areunknown for A mutica However Apalonespinifera the sister species of A mutica (Meylan1987) is active within a broad range of bodytemperatures that average 25uC (Plummer et al2005) Hatchlings were housed in individual 53 12 3 12 cm (H 3 W 3 L) plastic containerswith 13 cm of water Water in containers waschanged three times a week on the daysfollowing feeding

We took several morphological measure-ments beginning on day seven after hatchingto allow time for flattening of the hatchlingrsquosbody from the spherical shape while in the eggand repeated approximately every two weeks(13ndash15 days 2003) or weekly (2004) thereafterWe towel-blotted the hatchlings until dry andthen weighed them We also measured theircarapace length maximum carapace width andplastron length and calculated body condition(body massplastron length) The original ex-perimental design required morphological mea-surements on each turtle over an approximate60-day period during August to October 2003This time frame was chosen because previousenergetic calculations with turtle (Trachemysscripta) and alligator (Alligator mississippiensis)hatchlings suggested that posthatching yolkreserves could sustain the hatchlings for ap-proximately 60ndash140 days (Fischer et al 1991)However a rapid decline in physical conditionof unfed turtles caused us to terminate theexperiments earlier The 2004 experiments wereconducted for approximately 40 days duringAugust and September After experiments wereterminated the 2003 hatchlings were overwin-tered in the laboratory and released near theirnest sites in the White River in early May 2004the 2004 experimental hatchlings were releasedin September 2004

Hatchlings for yolk depletion measurementswere taken from eight of the clutches collectedin 2004 three to four hatchlings selectedrandomly from each treatment group weresacrificed by freezing at 280uC every four daysbeginning at age four days over a period of44 days In addition yolks were obtained fromeight hatchlings from four clutches immediatelyafter pipping (age 0 days) Internalized yolkreserves were dissected out oven dried at 45uCfor 36 h and weighed on an analytical balanceWe measured rates of CO2 production of one-month-old hatchling A mutica randomly select-ed from each of three clutches within eachtreatment (seven fed seven unfed) at 25uC usinga Sable Systems TR-3 configured as an open-flow system (Beaupre and Zaidan 2001) Wemeasured CO2 production for each hatchlingevery 30 seconds for 75 continuous minutesduring each hour between 2100 and 0800 h thenormal inactive period for A mutica The SMRof each hatchling was calculated as the mean ofits lowest four hourly CO2 production ratemeasurements

This experiment was designed as a repeatedmeasures multivariate analysis of variance(MANOVA) experiment Data were analyzedusing the General Linear Model (GLM) state-ment in SAS (SAS Institute Inc Cary NC) Theprimary independent variable was feeding re-

USE OF YOLK RESERVES IN APALONE MUTICA 493

gime (Treat) Egg mass clutch and block(physical position of hatchling 2004 only) wereincluded to remove variability in growth datacaused by these factors and maximize ourability to detect variation resulting from ourexperimental treatments Dependent variableswere body mass plastron length carapacewidth and body condition Because carapacelength was difficult to measure as healthdeteriorated in unfed turtles it was eliminatedfrom the analyses For graphically presentingmorphological measurements over time weexpressed each mean as a percentage of itsinitial value To meet the assumption ofnormality body mass data were transformedby squaring and carapace width data weretransformed with natural logarithms in 2003Dried internalized yolk mass was regressed ondays after hatching for each treatment groupregression equations were compared by Analy-sis of Covariance (ANCOVA) Metabolic rateswere compared between treatment groups witha t-test and means were reported 6 SERegression analyses and t-tests were conductedwith SYSTAT Version 11 (SYSTAT SoftwareInc Richmond CA)

RESULTS

Clutch and egg mass were included in ourstatistical analysis to remove variability in thedata caused by genetic and maternal differ-ences Clutch accounted for significant variabil-ity in body mass body condition and plastronlength in 2003 (Table 1) Egg mass accounted fora significant amount of variability in bodycondition and carapace width in 2004 whereasblock accounted for a significant amount ofvariability in mass in 2004 (Table 1)

We predicted that fed hatchlings wouldincrease in mass whereas unfed hatchlingswould decrease in mass as they used their yolkreserves Consistent with our predictions fed

and unfed hatchling mass diverged throughtime in 2003 (P 0001 Table 1) with fedhatchlings slowly gaining mass whereas unfedhatchlings slowly lost mass (Fig 1) By weekfive and continuing through the rest of theexperiment univariate tests indicated that thefed hatchlings had greater mass than unfedhatchlings (Table 2 Fig 1) In 2004 both fedand unfed hatchlings lost mass but fed hatch-lings lost mass at a slower rate than unfedhatchlings (Fig 1) By week two and continuingthrough the rest of the experiment fed hatch-lings consistently had greater mass than unfedhatchlings (Table 2)

We predicted that turtles in both treatmentswould increase plastron length and carapacewidth until the yolk could no longer sustaingrowth at which point only the fed hatchlingswould continue to increase in size Consistentwith our prediction plastron length initiallyincreased in both feeding treatments (Fig 1)Furthermore plastron length diverged betweentreatments as the plastron length of unfedhatchlings began to decrease the plastronlength of fed hatchlings continued to increasein both years (Fig 1 2003 P 5 0010 2004 P 50022 Table 1) Plastron length was significantlygreater in fed hatchlings by week nine of 2003and beginning in week four in 2004 (Table 2)Also consistent with our prediction carapacewidth diverged between feeding treatments in2003 (P 0001 Table 1) Carapace widthincreased initially in both treatments but onlythe fed hatchlings continued to increase incarapace width after week five (Fig 1) Howev-er univariate tests indicated a significant dif-ference between the fed and unfed carapacewidths only during week three (Table 2)Although there were significant differences incarapace width between feeding treatmentsduring all weeks in 2004 (Table 2) the hatch-lings in both treatments responded similarlythrough time (P 5 0540 Table 1) thus we could

TABLE 1 Repeated-measures MANOVA to test for within subject effects on plastron length body masscarapace width and body condition

Source df Plastron length Mass Carapace width Body condition

2003 N 5 100 F P F P F P F P

Time 4 83 164 0172 070 0591 026 0903 132 0270Time3Egg mass 4 83 175 0147 111 0358 019 0944 191 01167Time3Clutch 44 344 234 0001 145 0037 119 0200 224 0001Time3Treat 4 83 357 0010 2374 0001 1032 0001 2479 0001

2004 N 5 60

Time 5 37 099 0435 202 0098 274 0033 301 0022Time3Egg mass 5 37 087 0512 167 0167 279 0031 271 0035Time3Clutch 55 205 097 0540 102 0449 115 0249 119 0197Time3Treat 5 37 301 0022 742 0001 083 0540 811 0001Time3Block 10 76 168 0102 280 0005 091 0530 169 0098

494 T N LEE ET AL

FIG 1 The relationship between percent of initial body mass plastron length carapace width and bodycondition to age in fed (closed symbols) and unfed (open symbols) Apalone mutica hatchlings in 2003 (leftcolumn) and 2004 (right column) Plotted are mean 6 SE

USE OF YOLK RESERVES IN APALONE MUTICA 495

not conclude that there was a difference incarapace width caused by the feeding treatment

Body condition diverged between feedingtreatments in both years (2003 P 00012004 P 0001 Table 1) After an initialdecrease in body condition the fed hatchlingsin 2003 increased in body condition whereasthe unfed hatchlings decreased in body condi-tion (Fig 1) Beginning in week five andcontinuing throughout the experiment fedhatchlings consistently had better body condi-tion than unfed hatchlings (Table 2 Fig 1)Body condition decreased in both feedingtreatments during 2004 but unfed hatchlingsdecreased in body condition at a faster rate thanfed hatchlings (Fig 1) Univariate tests indicat-ed that the fed hatchlings maintained a signifi-cantly better body condition beginning in weektwo and continuing throughout the rest of theexperiment (Table 2)

Hatchlings used yolk reserves at a comparablerate regardless of feeding condition A regres-sion analysis showed a significant negativerelationship between internalized yolk dry massand time after hatching in both feeding treat-ments and indicated that hatchlings used yolkreserves at a constant rate (Fig 2 fed log10 drymass 5 20557ndash0036 age N 5 42 R2 5 0785F140 5 1464 P 0001 unfed log10 dry mass 520576ndash0038 age N 5 42 R2 5 0813 F140 51734 P 0001) There was no significantdifference in rate of yolk depletion between fedand unfed hatchlings (ANCOVA F181 5 0639P 5 0426) Hatchling dry mass was notcorrelated with yolk dry mass (R2 5 0064 P5 0549 N 5 90) Because the effect of time oninternalized yolk mass did not differ between

treatments we pooled the data and calculateda common regression equation (log10 yolk drymass 5 20547ndash0038 age N 5 84 R2 5 0819 F188

5 3977 P 0001) This equation predicts that50 of the internalized yolk in a hatchling isdepleted by day eight 75 by day 16 and 90 byday 27 The standard metabolic rate of fedhatchlings (0236 6 0017 ml CO2 h21 N 5 7) didnot differ from unfed hatchlings (0235 6 0023 mlCO2 h21 N 5 7 t12 5 0035 P 5 0972) PooledSMR was 0236 6 0014 ml CO2 h21 (N 5 14)

DISCUSSION

One function of residual yolk may be toincrease hatchling fitness in unpredictable lowresource environments (Lance and Morafka2001) The productivity of lotic ecosystems thepreferred habitat of A mutica generally isconsiderably lower and more unpredictablethan the productivity of lentic systems (Whit-taker and Likens 1973) Furthermore fastingmay be induced in these microhabitats andforced further by conflicts between fitness-enhancing activities Mrosovsky and Sherry(1980) argue that the many examples of natu-rally occurring fasting that have been observedmay arise from conflicts between feeding andmore pressing activities such as thermoregula-tion incubation territory defense and predatoravoidance For A mutica hatchlings the highrisk of predation (Iverson 1991 Morafka et al2000) especially by birds (Janzen et al 2000MVP pers obs) may be a deterrent to foraging(Nagy 2000) and force the hatchling to rely onits residual yolk Reserves may also provide

TABLE 2 Analyses of variance results for effects of feeding treatment on morphological traits within eachweek All df 5 1

2003 N 5 100 Week 1 Week 3 Week 5 Week 7 Week 9 mdash

Plastron length F 016 005 120 284 505 mdashP 0692 0827 0277 0096 0027 mdash

Body mass F 327 143 1240 1906 3849 mdashP 0074 0234 0001 0001 0001 mdash

Carapace width F 253 428 117 054 021 mdashP 0116 0042 0283 0463 0649 mdash

Body condition F 384 347 1669 2659 5408 mdashP 0053 0066 0001 0001 0001 mdash

2004 N 5 60 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6

Plastron length F 036 037 153 816 646 863P 0554 0544 0223 0007 0015 0005

Body mass F 028 533 1160 1859 2313 2630P 0600 0026 0002 0001 0001 0001

Carapace width F 492 447 514 532 1238 1116P 0032 0041 0029 0026 0001 0002

Body condition F 003 681 1308 1423 2446 2746P 0863 0013 0001 0001 0001 0001

496 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

gime (Treat) Egg mass clutch and block(physical position of hatchling 2004 only) wereincluded to remove variability in growth datacaused by these factors and maximize ourability to detect variation resulting from ourexperimental treatments Dependent variableswere body mass plastron length carapacewidth and body condition Because carapacelength was difficult to measure as healthdeteriorated in unfed turtles it was eliminatedfrom the analyses For graphically presentingmorphological measurements over time weexpressed each mean as a percentage of itsinitial value To meet the assumption ofnormality body mass data were transformedby squaring and carapace width data weretransformed with natural logarithms in 2003Dried internalized yolk mass was regressed ondays after hatching for each treatment groupregression equations were compared by Analy-sis of Covariance (ANCOVA) Metabolic rateswere compared between treatment groups witha t-test and means were reported 6 SERegression analyses and t-tests were conductedwith SYSTAT Version 11 (SYSTAT SoftwareInc Richmond CA)

RESULTS

Clutch and egg mass were included in ourstatistical analysis to remove variability in thedata caused by genetic and maternal differ-ences Clutch accounted for significant variabil-ity in body mass body condition and plastronlength in 2003 (Table 1) Egg mass accounted fora significant amount of variability in bodycondition and carapace width in 2004 whereasblock accounted for a significant amount ofvariability in mass in 2004 (Table 1)

We predicted that fed hatchlings wouldincrease in mass whereas unfed hatchlingswould decrease in mass as they used their yolkreserves Consistent with our predictions fed

and unfed hatchling mass diverged throughtime in 2003 (P 0001 Table 1) with fedhatchlings slowly gaining mass whereas unfedhatchlings slowly lost mass (Fig 1) By weekfive and continuing through the rest of theexperiment univariate tests indicated that thefed hatchlings had greater mass than unfedhatchlings (Table 2 Fig 1) In 2004 both fedand unfed hatchlings lost mass but fed hatch-lings lost mass at a slower rate than unfedhatchlings (Fig 1) By week two and continuingthrough the rest of the experiment fed hatch-lings consistently had greater mass than unfedhatchlings (Table 2)

We predicted that turtles in both treatmentswould increase plastron length and carapacewidth until the yolk could no longer sustaingrowth at which point only the fed hatchlingswould continue to increase in size Consistentwith our prediction plastron length initiallyincreased in both feeding treatments (Fig 1)Furthermore plastron length diverged betweentreatments as the plastron length of unfedhatchlings began to decrease the plastronlength of fed hatchlings continued to increasein both years (Fig 1 2003 P 5 0010 2004 P 50022 Table 1) Plastron length was significantlygreater in fed hatchlings by week nine of 2003and beginning in week four in 2004 (Table 2)Also consistent with our prediction carapacewidth diverged between feeding treatments in2003 (P 0001 Table 1) Carapace widthincreased initially in both treatments but onlythe fed hatchlings continued to increase incarapace width after week five (Fig 1) Howev-er univariate tests indicated a significant dif-ference between the fed and unfed carapacewidths only during week three (Table 2)Although there were significant differences incarapace width between feeding treatmentsduring all weeks in 2004 (Table 2) the hatch-lings in both treatments responded similarlythrough time (P 5 0540 Table 1) thus we could

TABLE 1 Repeated-measures MANOVA to test for within subject effects on plastron length body masscarapace width and body condition

Source df Plastron length Mass Carapace width Body condition

2003 N 5 100 F P F P F P F P

Time 4 83 164 0172 070 0591 026 0903 132 0270Time3Egg mass 4 83 175 0147 111 0358 019 0944 191 01167Time3Clutch 44 344 234 0001 145 0037 119 0200 224 0001Time3Treat 4 83 357 0010 2374 0001 1032 0001 2479 0001

2004 N 5 60

Time 5 37 099 0435 202 0098 274 0033 301 0022Time3Egg mass 5 37 087 0512 167 0167 279 0031 271 0035Time3Clutch 55 205 097 0540 102 0449 115 0249 119 0197Time3Treat 5 37 301 0022 742 0001 083 0540 811 0001Time3Block 10 76 168 0102 280 0005 091 0530 169 0098

494 T N LEE ET AL

FIG 1 The relationship between percent of initial body mass plastron length carapace width and bodycondition to age in fed (closed symbols) and unfed (open symbols) Apalone mutica hatchlings in 2003 (leftcolumn) and 2004 (right column) Plotted are mean 6 SE

USE OF YOLK RESERVES IN APALONE MUTICA 495

not conclude that there was a difference incarapace width caused by the feeding treatment

Body condition diverged between feedingtreatments in both years (2003 P 00012004 P 0001 Table 1) After an initialdecrease in body condition the fed hatchlingsin 2003 increased in body condition whereasthe unfed hatchlings decreased in body condi-tion (Fig 1) Beginning in week five andcontinuing throughout the experiment fedhatchlings consistently had better body condi-tion than unfed hatchlings (Table 2 Fig 1)Body condition decreased in both feedingtreatments during 2004 but unfed hatchlingsdecreased in body condition at a faster rate thanfed hatchlings (Fig 1) Univariate tests indicat-ed that the fed hatchlings maintained a signifi-cantly better body condition beginning in weektwo and continuing throughout the rest of theexperiment (Table 2)

Hatchlings used yolk reserves at a comparablerate regardless of feeding condition A regres-sion analysis showed a significant negativerelationship between internalized yolk dry massand time after hatching in both feeding treat-ments and indicated that hatchlings used yolkreserves at a constant rate (Fig 2 fed log10 drymass 5 20557ndash0036 age N 5 42 R2 5 0785F140 5 1464 P 0001 unfed log10 dry mass 520576ndash0038 age N 5 42 R2 5 0813 F140 51734 P 0001) There was no significantdifference in rate of yolk depletion between fedand unfed hatchlings (ANCOVA F181 5 0639P 5 0426) Hatchling dry mass was notcorrelated with yolk dry mass (R2 5 0064 P5 0549 N 5 90) Because the effect of time oninternalized yolk mass did not differ between

treatments we pooled the data and calculateda common regression equation (log10 yolk drymass 5 20547ndash0038 age N 5 84 R2 5 0819 F188

5 3977 P 0001) This equation predicts that50 of the internalized yolk in a hatchling isdepleted by day eight 75 by day 16 and 90 byday 27 The standard metabolic rate of fedhatchlings (0236 6 0017 ml CO2 h21 N 5 7) didnot differ from unfed hatchlings (0235 6 0023 mlCO2 h21 N 5 7 t12 5 0035 P 5 0972) PooledSMR was 0236 6 0014 ml CO2 h21 (N 5 14)

DISCUSSION

One function of residual yolk may be toincrease hatchling fitness in unpredictable lowresource environments (Lance and Morafka2001) The productivity of lotic ecosystems thepreferred habitat of A mutica generally isconsiderably lower and more unpredictablethan the productivity of lentic systems (Whit-taker and Likens 1973) Furthermore fastingmay be induced in these microhabitats andforced further by conflicts between fitness-enhancing activities Mrosovsky and Sherry(1980) argue that the many examples of natu-rally occurring fasting that have been observedmay arise from conflicts between feeding andmore pressing activities such as thermoregula-tion incubation territory defense and predatoravoidance For A mutica hatchlings the highrisk of predation (Iverson 1991 Morafka et al2000) especially by birds (Janzen et al 2000MVP pers obs) may be a deterrent to foraging(Nagy 2000) and force the hatchling to rely onits residual yolk Reserves may also provide

TABLE 2 Analyses of variance results for effects of feeding treatment on morphological traits within eachweek All df 5 1

2003 N 5 100 Week 1 Week 3 Week 5 Week 7 Week 9 mdash

Plastron length F 016 005 120 284 505 mdashP 0692 0827 0277 0096 0027 mdash

Body mass F 327 143 1240 1906 3849 mdashP 0074 0234 0001 0001 0001 mdash

Carapace width F 253 428 117 054 021 mdashP 0116 0042 0283 0463 0649 mdash

Body condition F 384 347 1669 2659 5408 mdashP 0053 0066 0001 0001 0001 mdash

2004 N 5 60 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6

Plastron length F 036 037 153 816 646 863P 0554 0544 0223 0007 0015 0005

Body mass F 028 533 1160 1859 2313 2630P 0600 0026 0002 0001 0001 0001

Carapace width F 492 447 514 532 1238 1116P 0032 0041 0029 0026 0001 0002

Body condition F 003 681 1308 1423 2446 2746P 0863 0013 0001 0001 0001 0001

496 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

FIG 1 The relationship between percent of initial body mass plastron length carapace width and bodycondition to age in fed (closed symbols) and unfed (open symbols) Apalone mutica hatchlings in 2003 (leftcolumn) and 2004 (right column) Plotted are mean 6 SE

USE OF YOLK RESERVES IN APALONE MUTICA 495

not conclude that there was a difference incarapace width caused by the feeding treatment

Body condition diverged between feedingtreatments in both years (2003 P 00012004 P 0001 Table 1) After an initialdecrease in body condition the fed hatchlingsin 2003 increased in body condition whereasthe unfed hatchlings decreased in body condi-tion (Fig 1) Beginning in week five andcontinuing throughout the experiment fedhatchlings consistently had better body condi-tion than unfed hatchlings (Table 2 Fig 1)Body condition decreased in both feedingtreatments during 2004 but unfed hatchlingsdecreased in body condition at a faster rate thanfed hatchlings (Fig 1) Univariate tests indicat-ed that the fed hatchlings maintained a signifi-cantly better body condition beginning in weektwo and continuing throughout the rest of theexperiment (Table 2)

Hatchlings used yolk reserves at a comparablerate regardless of feeding condition A regres-sion analysis showed a significant negativerelationship between internalized yolk dry massand time after hatching in both feeding treat-ments and indicated that hatchlings used yolkreserves at a constant rate (Fig 2 fed log10 drymass 5 20557ndash0036 age N 5 42 R2 5 0785F140 5 1464 P 0001 unfed log10 dry mass 520576ndash0038 age N 5 42 R2 5 0813 F140 51734 P 0001) There was no significantdifference in rate of yolk depletion between fedand unfed hatchlings (ANCOVA F181 5 0639P 5 0426) Hatchling dry mass was notcorrelated with yolk dry mass (R2 5 0064 P5 0549 N 5 90) Because the effect of time oninternalized yolk mass did not differ between

treatments we pooled the data and calculateda common regression equation (log10 yolk drymass 5 20547ndash0038 age N 5 84 R2 5 0819 F188

5 3977 P 0001) This equation predicts that50 of the internalized yolk in a hatchling isdepleted by day eight 75 by day 16 and 90 byday 27 The standard metabolic rate of fedhatchlings (0236 6 0017 ml CO2 h21 N 5 7) didnot differ from unfed hatchlings (0235 6 0023 mlCO2 h21 N 5 7 t12 5 0035 P 5 0972) PooledSMR was 0236 6 0014 ml CO2 h21 (N 5 14)

DISCUSSION

One function of residual yolk may be toincrease hatchling fitness in unpredictable lowresource environments (Lance and Morafka2001) The productivity of lotic ecosystems thepreferred habitat of A mutica generally isconsiderably lower and more unpredictablethan the productivity of lentic systems (Whit-taker and Likens 1973) Furthermore fastingmay be induced in these microhabitats andforced further by conflicts between fitness-enhancing activities Mrosovsky and Sherry(1980) argue that the many examples of natu-rally occurring fasting that have been observedmay arise from conflicts between feeding andmore pressing activities such as thermoregula-tion incubation territory defense and predatoravoidance For A mutica hatchlings the highrisk of predation (Iverson 1991 Morafka et al2000) especially by birds (Janzen et al 2000MVP pers obs) may be a deterrent to foraging(Nagy 2000) and force the hatchling to rely onits residual yolk Reserves may also provide

TABLE 2 Analyses of variance results for effects of feeding treatment on morphological traits within eachweek All df 5 1

2003 N 5 100 Week 1 Week 3 Week 5 Week 7 Week 9 mdash

Plastron length F 016 005 120 284 505 mdashP 0692 0827 0277 0096 0027 mdash

Body mass F 327 143 1240 1906 3849 mdashP 0074 0234 0001 0001 0001 mdash

Carapace width F 253 428 117 054 021 mdashP 0116 0042 0283 0463 0649 mdash

Body condition F 384 347 1669 2659 5408 mdashP 0053 0066 0001 0001 0001 mdash

2004 N 5 60 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6

Plastron length F 036 037 153 816 646 863P 0554 0544 0223 0007 0015 0005

Body mass F 028 533 1160 1859 2313 2630P 0600 0026 0002 0001 0001 0001

Carapace width F 492 447 514 532 1238 1116P 0032 0041 0029 0026 0001 0002

Body condition F 003 681 1308 1423 2446 2746P 0863 0013 0001 0001 0001 0001

496 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

not conclude that there was a difference incarapace width caused by the feeding treatment

Body condition diverged between feedingtreatments in both years (2003 P 00012004 P 0001 Table 1) After an initialdecrease in body condition the fed hatchlingsin 2003 increased in body condition whereasthe unfed hatchlings decreased in body condi-tion (Fig 1) Beginning in week five andcontinuing throughout the experiment fedhatchlings consistently had better body condi-tion than unfed hatchlings (Table 2 Fig 1)Body condition decreased in both feedingtreatments during 2004 but unfed hatchlingsdecreased in body condition at a faster rate thanfed hatchlings (Fig 1) Univariate tests indicat-ed that the fed hatchlings maintained a signifi-cantly better body condition beginning in weektwo and continuing throughout the rest of theexperiment (Table 2)

Hatchlings used yolk reserves at a comparablerate regardless of feeding condition A regres-sion analysis showed a significant negativerelationship between internalized yolk dry massand time after hatching in both feeding treat-ments and indicated that hatchlings used yolkreserves at a constant rate (Fig 2 fed log10 drymass 5 20557ndash0036 age N 5 42 R2 5 0785F140 5 1464 P 0001 unfed log10 dry mass 520576ndash0038 age N 5 42 R2 5 0813 F140 51734 P 0001) There was no significantdifference in rate of yolk depletion between fedand unfed hatchlings (ANCOVA F181 5 0639P 5 0426) Hatchling dry mass was notcorrelated with yolk dry mass (R2 5 0064 P5 0549 N 5 90) Because the effect of time oninternalized yolk mass did not differ between

treatments we pooled the data and calculateda common regression equation (log10 yolk drymass 5 20547ndash0038 age N 5 84 R2 5 0819 F188

5 3977 P 0001) This equation predicts that50 of the internalized yolk in a hatchling isdepleted by day eight 75 by day 16 and 90 byday 27 The standard metabolic rate of fedhatchlings (0236 6 0017 ml CO2 h21 N 5 7) didnot differ from unfed hatchlings (0235 6 0023 mlCO2 h21 N 5 7 t12 5 0035 P 5 0972) PooledSMR was 0236 6 0014 ml CO2 h21 (N 5 14)

DISCUSSION

One function of residual yolk may be toincrease hatchling fitness in unpredictable lowresource environments (Lance and Morafka2001) The productivity of lotic ecosystems thepreferred habitat of A mutica generally isconsiderably lower and more unpredictablethan the productivity of lentic systems (Whit-taker and Likens 1973) Furthermore fastingmay be induced in these microhabitats andforced further by conflicts between fitness-enhancing activities Mrosovsky and Sherry(1980) argue that the many examples of natu-rally occurring fasting that have been observedmay arise from conflicts between feeding andmore pressing activities such as thermoregula-tion incubation territory defense and predatoravoidance For A mutica hatchlings the highrisk of predation (Iverson 1991 Morafka et al2000) especially by birds (Janzen et al 2000MVP pers obs) may be a deterrent to foraging(Nagy 2000) and force the hatchling to rely onits residual yolk Reserves may also provide

TABLE 2 Analyses of variance results for effects of feeding treatment on morphological traits within eachweek All df 5 1

2003 N 5 100 Week 1 Week 3 Week 5 Week 7 Week 9 mdash

Plastron length F 016 005 120 284 505 mdashP 0692 0827 0277 0096 0027 mdash

Body mass F 327 143 1240 1906 3849 mdashP 0074 0234 0001 0001 0001 mdash

Carapace width F 253 428 117 054 021 mdashP 0116 0042 0283 0463 0649 mdash

Body condition F 384 347 1669 2659 5408 mdashP 0053 0066 0001 0001 0001 mdash

2004 N 5 60 Week 1 Week 2 Week 3 Week 4 Week 5 Week 6

Plastron length F 036 037 153 816 646 863P 0554 0544 0223 0007 0015 0005

Body mass F 028 533 1160 1859 2313 2630P 0600 0026 0002 0001 0001 0001

Carapace width F 492 447 514 532 1238 1116P 0032 0041 0029 0026 0001 0002

Body condition F 003 681 1308 1423 2446 2746P 0863 0013 0001 0001 0001 0001

496 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

a sufficient supply of energy to allow thehatchlings to learn to maximize foraging atminimal cost For example many young ani-mals reduce activity when at risk of predation(Skelly 1992 Killen and Brown 2006) and thereserves of hatchling A mutica could provide anenergy buffer to allow reduced foraging underpredation pressure

The primary energy budget components ofhatchlings are maintenance growth associatedcosts of growth and activity (Wieser 1994)During times when fasting is not necessitatedjuvenile animals with energy reserves couldadopt different energy use strategies Forexample hatchlings with posthatching yolkreserves and access to external energy resourcescould conserve yolk reserves for later use(Radder et al 2004) grow more quickly toescape size-limited predation (Troyer 1983Iverson 1991 Janzen et al 2000 Morafka etal 2000) and increase adult body size andcorresponding clutch size (Congdon and vanLoben Sels 1993 van Buskirk and Crowder1994) or increase activities such as foraging(Peach and Thomas 1986 Vidal et al 2002)

Yolk conservation does not appear to bea strategy of A mutica hatchlings becausehatchlings in both feeding treatments depletedyolk at the same rate In chicks posthatchingyolk is depleted as it enters circulation as lipidand is assumed to be used for energy (Noy andSklan 2001) Thus depletion may translatedirectly into use in A mutica as well Yolkreserves of newly hatched A mutica containapproximately 175 kcal (M V Plummer S JBeaupre T N Lee and N E Mills unpubldata) sufficient to sustain a hatchling at

standard metabolic rate (SMR) for approximate-ly 54 days at 25uC (using our pooled SMRestimate and assuming constant yolk composi-tion) Because the metabolic rate of an activehatchling would likely be 2ndash33 SMR andbecause triacylglycerol the primary storagelipid in A mutica yolk (Nagle et al 2003) maybe preferentially used in development (Nagle etal 1998) a more accurate estimate of sustain-ability would be about 40 days This estimatemay still be too liberal because the bodycondition of our unfed hatchlings significantlydiverged from fed hatchlings as early as 14ndash35 days after hatching This divergence suggeststhat it may be necessary for hatchlings to foragesuccessfully before hibernation to obtain certainnon-caloric nutrients not available in the reserveyolk At the Georgetown locality on the WhiteRiver A mutica hatchlings emerge from nestsfrom late July to mid-August and begin hiber-nation in mid-October (MVP pers obs) a peri-od of approximately 60ndash80 days According toour estimates of sustainability and yolk de-pletion results the yolk reserve of an A muticahatchling is insufficient to sustain the hatchlinguntil its first hibernation

Hatchlings in the fed treatment had greatermasses and body sizes with the exception ofcarapace width in 2004 than unfed hatchlingsTrachemys scripta hatchlings with experimental-ly reduced reserves also grew more slowly thanhatchlings with full reserves but did not feeddifferently (Yeomans 1999) These results sug-gest that these species of turtles may useposthatching yolk for maintenance and anyenergy intake above maintenance requirementsto maximize growth However although themasses and body sizes of fed A mutica hatch-lings were greater they were not always in-creasing Mass can only increase in animalsobtaining external forage but access to externalresources does not guarantee an increase inmass During both years but more notably in2004 some hatchlings in the fed treatment neverfed and some fed only occasionally The in-clusion of these individuals in the analysislowered the means of the fed treatment in allmorphological measurements Also the initialincreases of body size may not have indicatedearly growth but changes in body shapeAccurate linear body measurements on newlyhatched softshells are difficult to obtain until thetransformation from a spherical shape in theegg to the final flattened body shape iscompleted We waited one week after hatchingbefore taking initial body measurements how-ever the sharp increases in plastron length andcarapace width in week three of 2003 and weektwo of 2004 (Fig 1) suggests the flatteningprocess continued past one week The initial

FIG 2 The relationship between log dry mass ofinternalized yolk and age in fed and unfed Apalonemutica hatchlings Upper regression line 5 fed (N 542) lower regression line 5 unfed (N 5 42) Thecommon regression equation for pooled data is log10

dry yolk mass (g) 5 20547ndash0038 age (days)

USE OF YOLK RESERVES IN APALONE MUTICA 497

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

decrease in body condition in both years waslikely in part caused by the continued increasein plastron length resulting from flatteningdisproportional to the change in mass

Feeding condition may differentially affect therate of yolk depletion in various taxonomicgroups For example fed hatchlings of A muticaused yolk at the same rate as unfed hatchlings butgrew faster indicating a strategy to meet main-tenance demands with yolk and fuel growth costswith external forage In contrast depletion ofreserve yolk is faster in fed fish (Mani-Ponset etal 1996) chicks (Noy and Sklan 1999) anda lizard (Pandav et al 2006) Noy and Sklan(1999) suggest that the chickrsquos strategy is to usethe yolk to support preferential growth and finalmaturation of the small intestine and Pandav etal (2006) propose that the lizard may use the yolkto meet increased metabolic demands fromspecific dynamic action Vidal et al (2002) arguedthat reserve yolk was depleted more rapidly inunfed than fed newly hatched squid because theunfed squid must increase activity to learn toforage to avoid starvation

The faster growth in fed A mutica hatchlingstheoretically should have been accompanied bya metabolic increase above SMR (cost of growthWieser 1994 Nagy 2000) however we wereunable to detect differences in metabolic ratesbetween fed and unfed hatchlings The similaritymay be a result of the procedures used duringSMR measurement or it may have resulted froma behavioral or physiological compensation inthe neonatersquos energy budget (Nagy 2000) In-deed the expected cost of rapid neonate growthhas not been confirmed in most reptile speciesthat have been studied (Nagy 2000 Brown et al2005 but see Beaupre and Zaidan 2001)Metabolic rates decreased and remained lowfor at least 60 days after hatching in Chrysemyspicta (Peterson and Kruegl 2005) and lowerstandard metabolic rates resulted in highergrowth rates in hatchling Chelydra serpentina(Steyermark 2002) In their exposed habitat Amutica hatchlings may also minimize energyexpenditure by reducing metabolic rate throughcryptic inactivity in response to predation risk(Janzen et al 2000) and possibly through sub-optimal body temperatures attained by relaxedbasking However the limited amount of storedenergy in reserve yolk necessitates successfulforaging to avoid starvation before the firstoverwintering and the effectiveness and timingof hatchling foraging are unknown

In summary when external forage is avail-able and conflicts between feeding and otheractivities do not induce fasting residual yolk ofhatchling A mutica indirectly supports growthby meeting maintenance costs to allow exoge-nous energy use for maximal growth However

yolk reserves of A mutica can sustain a hatchlingin absence of external forage for approximately40 days and cannot sustain the hatchling untilthe first overwintering Future investigation isneeded to elucidate the apparent paradox of fedhatchlingsrsquo increased growth rate at a metaboliccost similar to unfed hatchlings

AcknowledgmentsmdashTurtle eggs were collectedunder Scientific Collecting Permit 675 issued bythe Arkansas Game and Fish Commission Thisresearch was approved by the Harding Univer-sity Animal Care Committee and is in accordancewith the booklet lsquolsquoGuidelines for Use of LiveAmphibians and Reptiles in Field Researchrsquorsquo(1987 American Society of Ichthyologists andHerpetologists The Herpetologistsrsquo League andthe Society for the Study of Amphibians andReptiles) A Faculty Development Grant anda grant from the Margaret M Plummer MemorialResearch Fund at Harding University fundedportions of this research We thank S Beaupre foruse of his metabolic lab and J Van Dyke forinsightful comments on the manuscript

LITERATURE CITED

BEAUPRE S J AND F ZAIDAN III 2001 Scaling of CO2

production in the Timber Rattlesnake (Crotalushorridus) with comments on cost of growth inneonates and comparative patterns Physiologicaland Biochemical Zoology 74757ndash768

BROWN T K K A NAGY AND D J MORAFKA 2005Costs of growth in tortoises Journal of Herpetol-ogy 3919ndash23

CONGDON J D AND J W GIBBONS 1990 Turtle eggstheir ecology and evolution In J W Gibbons (ed)Life History and Ecology of the Slider Turtlepp 109ndash123 Smithsonian Institution Press Wash-ington DC

CONGDON J D AND R C VAN LOBEN SELS 1993Relationships of reproductive traits and body sizewith attainment of sexual maturity and age inBlandingrsquos Turtles (Emydoidea blandingi) Journal ofEvolutionary Biology 6547ndash557

CONGDON J D J W GIBBONS AND J L GREENE 1983Parental investment in the Chicken Turtle (Dier-ochelys reticularia) Ecology 64419ndash425

DOODY J S 1995 A Comparative Nesting Study ofTwo Syntopic Species of Softshell Turtles (Apalonemutica and Apalone spinifera) in SouthcentralLouisiana Unpubl masterrsquos thesis SoutheasternLousiana University Hammond

EWERT M A 1991 Cold torpor diapause delayedhatching and aestivation in reptiles and birds In DC Deeming and M W J Ferguson (eds) EggIncubation Its Effects on Embryonic Developmentin Birds and Reptiles pp 173ndash191 CambridgeUniversity Press New York

FISCHER R U F J MAZZOTTI J D CONGDON AND R EGATTEN JR 1991 Post-hatching yolk reservesparental investment in American Alligators fromLouisiana Journal of Herpetology 25254ndash256

498 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

GETTINGER R D G L PAUKSTIS AND W H N GUTZKE1984 Influence of hydric environments on oxygenconsumption by embryonic turtles Chelydra serpen-tina and Trionyx spiniferus Physiological Zoology57468ndash473

IVERSON J B 1991 Patterns of survivorship in turtlesCanadian Journal of Zoology 69385ndash391

JANZEN F J J K TUCKER AND G L PAUKSTIS 2000Experimental analysis of an early life-history stageavian predation selects for larger body size ofhatchling turtles Journal of Evolutionary Biology13947ndash954

JI X AND P Y SUN 2000 Embryonic use and post-hatching yolk in the Gray Rat Snake Pytas korros(Colubridae) Herpetological Journal 1013ndash17

JI X P Y SUN S Y FU AND H S ZHANG 1997Utilization of energy and nutrients in incubatingeggs and post-hatching yolk in a colubrid snakeElaphe carinata Herpetological Journal 77ndash12

JI X X F XU AND Z H LIN 1999 Influence ofincubation temperature on characteristics of Dino-don rufozonatum (Reptilia Colubridae) hatchlingswith comments on the function of residual yolkZoological Research 20342ndash346

KILLEN S S AND J A BROWN 2006 Energetic cost ofreduced foraging under predation threat in newlyhatched ocean pout Marine Ecology ProgressSeries 321255ndash266

KRAEMER J E AND S H BENNETT 1981 Utilization ofposthatching yolk in Loggerhead Sea TurtlesCaretta caretta Copeia 1981406ndash411

LANCE V A AND D J MORAFKA 2001 Post natallecithotroph a new age class in the ontogeny ofreptiles Herpetological Monographs 15124ndash134

MANI-PONSET L E GUYOT J P DIAZ AND R CONNES1996 Utilization of yolk reserves during post-embryonic development in three teleostean spe-cies the Sea Bream Sparus aurata the Sea BassDicentrarchus labrax and the Pike-Perch Stizostedionlucioperca Marine Biology 126539ndash547

MEYLAN P A 1987 The phylogenetic relationships ofsoft-shelled turtles (family Trionychidae) Bulletinof the American Museum of Natural History1861ndash101

MORAFKA D J E K SPANGENBERG AND V A LANCE2000 Neonatology of reptiles HerpetologicalMonographs 14353ndash370

MROSOVSKY N AND D F SHERRY 1980 Animalanorexias Science 207837ndash842

MURAKAMI H Y AKIBA AND M HOIGUCHI 1992Growth and utilization of nutrients in newlyhatched chick with or without removal of residualyolk Growth Development and Aging 5675ndash84

NAGLE R D V J BURKE AND J D CONGDON 1998 Eggcomponents and hatchling lipid reserves parentalinvestment in kinosternid turtles from the south-eastern United States Comparative Biochemistryand Physiology 120B145ndash152

NAGLE R D M V PLUMMER J D CONGDON AND R UFISCHER 2003 Parental investment embryo growthand hatchling lipid reserves in softshell turtles(Apalone mutica) from Arkansas Herpetologica59145ndash154

NAGY K 2000 Energy costs of growth in neonatereptiles Herpetological Monographs 14378ndash387

NOY Y AND D SKLAN 1999 Energy utilization innewly hatched chicks Poultry Science 781750ndash1756

mdashmdashmdash 2001 Yolk and exogenous feed utilization inthe posthatch chick Poultry Science 801490ndash1495

PACKARD G C T L TAIGEN T J BOARDMAN M JPACKARD AND C R TRACY 1979 Changes in massof softshell turtle (Trionyx spiniferus) eggs incubat-ed on substrates differing in water potentialHerpetologica 3578ndash86

PACKARD G C T L TAIGEN M J PACKARD AND T JBOARDMAN 1981 Changes in mass of eggs ofsoftshell turtles (Trionyx spiniferus) incubated un-der hydric conditions simulating those of naturalnests Journal of Zoology 193A81ndash90

PANDAV B N B A SHANBHAG AND S K SAIDAPUR2006 Functional significance of posthatching re-sidual yolk in the lizard Calotes versicolor Journalof Herpetology 40385ndash387

PEACH H C AND V G THOMAS 1986 Nutrientcomposition of yolk in relation to early growth ofCanada geese Physiological Zoology 59344ndash356

PETERSON C C AND A KRUEGL 2005 Peaked temporalpattern of embryonic metabolism in an emydidturtle (Chrysemys picta picta) Journal of Herpetol-ogy 39678ndash681

PLUMMER M V 1976 Some aspects of nesting successin the turtle Trionyx muticus Herpetologica 32353ndash359

mdashmdashmdash 1977 Activity habitat and population struc-ture of the turtle Trionyx muticus Copeia1977431ndash440

PLUMMER M V AND D B FARRAR 1981 Sexual dietarydifferences in a population of Trionyx muticusJournal of Herpetology 15175ndash179

PLUMMER M V AND H L SNELL 1988 Nest siteselection and water relations of eggs in the snakeOpheodrys aestivus Copeia 198858ndash64

PLUMMER M V C E SHADRIX AND R C COX 1994Thermal limits of incubation in embryos ofsoftshell turtles (Apalone mutica) Chelonian Con-servation and Biology 1141ndash144

PLUMMER M V T L CRABILL N E MILLS AND S LALLEN 2005 Body temperatures of free-rangingsoftshell turtles (Apalone spinifera) in a smallstream Herpetological Review 36371ndash375

RADDER R S B A SHANBHAG AND S K SAIDAPUR 2004Yolk partitioning in embryos of the lizard Calotesversicolor maximize body size or save energy forlater use Journal of Experimental Zoology301A783ndash785

SKELLY D 1992 Field evidence for a cost of behavioralantipredator response in a larval amphibianEcology 73704ndash708

STEYERMARK A C 2002 A high standard metabolicrate constrains juvenile growth Zoology 105147ndash151

TROYER K 1983 Posthatching yolk energy in a lizardutilization pattern and interclutch variation Oeco-logia 58340ndash344

TUCKER J K N I FILORAMO G L PAUKSTIS AND F JJANZEN 1998 Residual yolk in captive and wild-caught hatchlings of the Red-Eared Slider Turtle(Trachemys scripta elegans) Copeia 1998488ndash492

VAN BUSKIRK J AND L B CROWDER 1994 Life-historyvariation in marine turtles Copeia 199466ndash81

USE OF YOLK RESERVES IN APALONE MUTICA 499

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL

VIDAL E A G F P DIMARCO J H WORMUTH AND PG LEE 2002 Influence of temperature and foodavailability on survival growth and yolk utiliza-tion in hatchling squid Bulletin of Marine Science71915ndash931

WHITEHEAD P J 1990 Yolk depletion and metabolicrate of hatchling Crocodylus johnstoni Copeia1990871ndash875

WHITTAKER R H AND G E LIKENS 1973 In G MWoodwell and E V Pecan (eds) Carbon in theBiota pp 281ndash300 United States National Techni-cal Information Service Springfield VA

WIESER W 1994 Cost of growth in cells and organ-isms general rules and comparative aspectsBiological Reviews 681ndash33

YEOMANS S R 1999 Parental Investment in Care inTurtles Unpubl PhD diss University of GeorgiaAthens

Accepted 19 April 2007

500 T N LEE ET AL