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ITUNELLA MUELLERI (HARPACTICOIDA:CANTHOCAMPTIDAE): A MARINE SPECIES WITHPREFERENCES FOR THE UPPER PART OF THELITTORAL FRINGEAuthor(s): María B. Steinarsdóttir and Agnar IngólfssonSource: Journal of Crustacean Biology, 24(3):440-446. 2004.Published By: The Crustacean SocietyDOI: http://dx.doi.org/10.1651/C-2468URL: http://www.bioone.org/doi/full/10.1651/C-2468

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ITUNELLA MUELLERI (HARPACTICOIDA: CANTHOCAMPTIDAE):

A MARINE SPECIES WITH PREFERENCES FOR THE

UPPER PART OF THE LITTORAL FRINGE

Marıa B. Steinarsdottir and Agnar Ingolfsson

Institute of Biology, University of Iceland, Sturlugata 7, IS-101 Reykjavık, Iceland

(corresponding authors (MBS): mariab@hi.is; (AI): agnaring@hi.is)

A B S T R A C T

Few animals of marine origin are found living successfully in the high littoral fringe of tidal shores, which

thus can be regarded as an extreme environment for such animals. In Iceland, a notable exception is the

semiterrestrial Orchestia gammarellus (Pallas, 1766) (Amphipoda: Talitridae). The discovery of the

harpacticoid Itunella muelleri (Gagern, 1922) in cultures of O. gammarellus prompted us to investigate

the harpacticoid further. Qualitative samples were obtained from a number of locations around Iceland, as

well as from Norway and Scotland. The samples were collected from habitats where O. gammarellus was

present or at similar tidal levels where this species was absent. Two of the sampling sites in Iceland were

under the influence of warm freshwater springs. Itunella muelleri was generally common in the upper part

of the littoral fringe of rocky shores in Iceland and was found in similar habitats in Norway and Scotland.

To estimate the vertical distribution of I. muelleri, a transect was taken along the shore in Hvassahraun,

southwestern Iceland. On the transect, I. muelleri was restricted to the uppermost stations, being the only

identifiable harpacticoid found at the highest station, well above the level of highest predicted tides.

Animals living successfully in the high littoral fringe must be able to tolerate a degree of desiccation and

a wide range of salinities and temperatures. Laboratory experiments showed that I. muelleri thrived in

high humidity out of water and also in 8 ppt and 32 ppt seawater, at both 78 and 208C. The animals

survived for months in fresh water, but they only fed sparsely and did not reproduce. The tolerance of

I. muelleri to extreme environmental conditions could make this species useful for experimental purposes

or as food for fish larvae in aquaculture.

Few animals of marine origin are found livingsuccessfully in the high littoral fringe (sensuLewis, 1964) of tidal shores, which thus can beregarded as an extreme environment for suchanimals. Semiterrestrial talitrid amphipods areamong notable exceptions at higher latitudes(Ingolfsson, 1977; Lincoln, 1979; Tsubokura etal., 1997). Also, some harpacticoid copepodscan withstand a range of salinity and tempera-ture regimes needed to live successfully inshallow rockpools in the littoral fringe, wherethey are easily exposed to environmental factorslike rain and evaporation. A striking example isthe harpacticoid genus Tigriopus Norman, 1868(Dethier, 1980; Damgaard and Davenport,1994; Davenport et al., 1997; Johnson, 2001).

When culturing the beachflea Orchestiagammarellus (Pallas, 1766) (Amphipoda: Tali-tridae), an inhabitant of the high littoral fringe inwestern Iceland, we discovered that a harpacti-coid copepod, later identified as Itunella muelleri(Gagern, 1922) (Canthocamptidae) (Fig. 1),often became abundant in the cultures. Theharpacticoids had apparently been accidentally

introduced into the beachflea cultures. There wasno standing water in the cultures, only seaweedand tissue paper wetted with seawater. Thissurprising discovery, followed by some pre-liminary investigations, prompted us to seekanswers to the following questions:Where do wefind I. muelleri in the field? Is the localdistribution of I. muelleri similar to that of O.gammarellus? How does I. muelleri performunder the different desiccation, salinity, andtemperature regimes that it is likely to encounterin the field? We hoped that answers to thesequestion might throw some light on adaptationsto the extreme environment of the littoral fringe.Also, these answers, coupled with the obviousease of culture of the species, could give someindication of its potential use, for example inecotoxicological studies or as fish food inaquaculture.

MATERIALS AND METHODS

Qualitative samples of gravel were taken at several coastallocalities in southwestern, northwestern, and eastern Iceland,and in southern and western Norway, mostly in summer and

440

JOURNAL OF CRUSTACEAN BIOLOGY, 24(3): 440–446, 2004

fall, but also in winter in some localities (Table 1). Thesamples were taken from habitats where Orchestia gammar-ellus was present, or at a similar tidal level outside thegeographical range of that species (see Ingolfsson, 1996). InJanuary 2003, qualitative samples were also taken at severalplaces below the zone occupied by O. gammarellus at Skarðand Kaldrananes, northwestern Iceland. Sections of theshore at both localities are influenced by warm freshwatersprings, and O. gammarellus is confined to these sections.The temperature at the sampling sites at Skarð andKaldrananes was measured. In addition, David Morrittkindly provided us with specimens of Itunella muellerifound living in a culture of O. gammarellus that originatedfrom animals collected at Millport, western Scotland, inAugust 2003.

On 14 May 2003, quantitative samples were taken atHvassahraun (648019N, 228099W), southwestern Iceland,from five stations, A–E, with 1 m vertical intervals betweenstations (Table 2). During mean spring tides the tidal rangeis approximately 4 m (Anonymous, 2003). Station A waslocated about 1 m vertically above the level of mean highwater springs (well beyond the level of maximum predictedhigh tides), station B was close to that level, station C wasnear the level of mean high water neaps, station D was closeto mean sea level, and station E was slightly above the levelof mean low water neaps. The shore is fairly sheltered. Thesubstratum is mixed, mostly pebbles and cobbles withvarying degrees of coarse sand between larger boulders androcks. The eulittoral part of the shore is covered withfucoids. Stations A–C were above the fucoid zone, station Cbeing just above the upper limit of Fucus spiralis L. Theuppermost periwinkles (Littorina saxatilis (Olivi, 1792)),often used to mark the upper limit of the littoral fringe (cf.Lewis, 1964), were found just above station B (at 4.17 mabove Chart Datum). Station D was in the high Ascophyllumnodosum (L.) Le Jol. zone, and station E was in the middleof the Fucus serratus L. zone. Additional samples were alsotaken from cast-up seaweed located between stations B andC. Two samples were taken at each station, each froma circular plot of 269 cm2 (demarcated by the rim of a 2-Lbucket), to a depth of approximately 10 cm. In thelaboratory, organic particles were washed from the gravelprior to fixation and than preserved in 5% Formalin.Samples were rinsed through a 125-lm sieve. Samples ofcast-up seaweed were rinsed through a 125-lm sieve andweighed wet, and animals were preserved in 5% Formalin.Harpacticoids were counted and identified to species whennecessary, but in some cases accurate species determinationwas not attempted. The substratum was dried and sievedthrough a series of sieves with 16, 8, 4, 2, and 1 mm mesh,and each size group was weighed separately.

In the laboratory I. muelleri, from a site influenced bywarm springs at Kaldrananes, was cultivated on Petri dishes(25 mL) (light regime 12D:12L) at three different salinities,0, 8, and 32 ppt and at two different temperatures,approximately 78 and 208C. The six resulting treatmentshad three replicates each, initially containing five femalesand five males each. The different environmental parametersused in the experiments were chosen in accordance with thepossible range of salinities and temperatures the animalsmight encounter in the field during summer, and furtherdirected by our facilities. Detritus, from which I. muelleriwas sorted, was used as food. Initially the cultures wereexamined daily. The number of live animals and faecalpellets were counted, and the presence of eggs (females layeggs directly into the environment), nauplii, and copepoditeswere noted. Subsequently, the cultures were checked

Fig. 1. Line drawing of a female Itunella muelleri (Gagern,1922) from the upper littoral fringe at Hvassahraun,southwestern Iceland. Scale¼ 0.1 mm.

441STEINARSDOTTIR AND INGOLFSSON: HIGH SHORE HARPACTICOID

approximately every 5 or 10 days. Cultures were kept for115 to 144 days, or until all animals were dead.

RESULTS

Distribution

In northwestern Iceland, Itunella muelleri (Fig.1) was abundant in January high on the shore ingravel sediments at the warm springs of Skarðand Kaldrananes, where the beachflea Orchestiagammarellus was also abundant. The tempera-ture range of these habitats was from 168 to228C. Itunella muelleri was only found in one ofseveral samples taken below the Orchestia zone,and it was at this time not found high on theshore 100 m or more away from the springswhere temperatures ranged 2–48C, nor atKirkjubol at that time. In September, however,we found I. muelleri in all high shore samplesthat were taken in northwestern Iceland. Thetemperature of sampling sites close to thesprings was then 14–168C, and 11–128C awayfrom the springs. The species was found inalmost all samples collected from the highlittoral fringe in southwestern and eastern Ice-land (except Viðey and Neskaupstaður), Norway(except Fevik), as well as in O. gammarelluscultures from Millport, Scotland (Table 1).

Along the shore transect at Hvassahraun,southwestern Iceland, I. muelleri was confinedto the three uppermost stations, A–C (Table 2).The species was most abundant at station B,located near the level of mean high watersprings. Itunella muelleri was also present in

some numbers in cast-up (rotting) seaweedslightly below this level. Only two otherharpacticoid individuals (which could not beidentified) were found at station A, and onlya few additional species were at stations B andC. Schizopera meridionalis Petkovski, 1954, co-occurred with I. muelleri in relatively highabundance at station B. Station C was dominatedby Heterolaophonte cf. hamondi Hicks, 1975,while Nitokra spinipes Boeck, 1865, was thesecond most abundant species there. A fewindividuals of both species were found at stationB. A dramatic increase in species diversity ofharpacticoids occurred at stations D and E. Thesubstratum at the sampling sites at Hvassahraunconsisted of varying degrees of coarse sand,while pebbles (not passing through the 16 mmmesh sieve) constituted a large portion at moststations (Table 3).

Nitokra spinipes and S. meridionalis were notinfrequently found with I. muelleri in qualitativesamples, both from southwestern and north-western Iceland. Nitokra spinipes also occurredwith I. muelleri at Olen, Norway.

Survival and Performance in Experiments

Survival was virtually 100% at all salinities (0, 8,and 32 ppt, both at 78Cand 208C) after 4 days, andwas still high after 22 days, except in fresh waterat 208C (Table 4). In reproducing populations, itsoon became difficult to separate the original ex-perimental animals from their offspring. In freshwater, half (16) of the animals were still alive at

Table 1. Localities of qualitative substrata samples. Samples were taken on the uppermost shore where Orchestiagammarellus was present, or at a similar level outside the O. gammarellus range (Kirkjubol, Reyðarfjorður, Eskifjorður,Neskaupstaður). At Skarð and Kaldrananes, additional samples were taken below the level inhabited by O. gammarellus.Note that sampling in Scotland was unusual.þ¼ I. muelleri present.

Locality Coordinates Date I. muelleri Remarks

Skarð, NW-Iceland 658299N, 208599W 11 Jan. 2003 þ Only near warm springsSkarð, NW-Iceland 658299N, 208599W 12 Sept. 2003 þKaldrananes, NW-Iceland 658469N, 218249W 12 Jan. 2003 þ Only near warm springsKaldrananes, NW-Iceland 658469N, 218249W 12 Sept. 2003 þKirkjubol, NW-Iceland 658389N, 218349W 11 Jan. 2003Kirkjubo1, NW-Iceland 658389N, 218349W 12 Sept. 2003 þGalgahraun, SW-Iceland 648059N, 218589W 14 Jan. 2003 þSkerjafjorður, SW-Iceland 648109N, 218579W Aug. 2003 þViðey, SW-Iceland 648049N, 218519W 17 Aug. 2003Reyðarfjorður, E-Iceland 658019N, 148149W 12 Oct. 2003 þEskifjorður, E-Iceland 658049N, 148019W 12 Oct. 2003 þNeskaupstaður, E-Iceland 658099N, 138429W 12 Oct. 2003Fevik, S-Norway 588239N, 88429E 2 Oct. 2003Hellvik, S-Norway 588299N, 58519E 2 Oct. 2003 þOlen, W-Norway 598369N, 58469E 3 Oct. 2003 þMillport, W-Scotland 558459N, 48549W Aug. 2003 þ Obtained from a culture of

Orchestia gammarellus

442 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 24, NO. 3, 2004

78C after 67 days, and one animal was alive after144 days. At 208C in fresh water, however, noanimals survived beyond 67 days (these culturesbecame infested with large numbers of ciliates,with unknown consequences).The number of faecal pellets that had

accumulated in the cultures after 2 days wasmuch lower in fresh water, both at 78C and208C, than in other cultures (Table 4). Pelletproduction was similar at 8 and 32 ppt, whencorresponding temperatures were compared.The pellet production was in all cases higher

in cultures at 208C than at 78C with the samesalinities, except in fresh water.No reproduction was observed in fresh water.

Reproduction occurred in all other cultures, andcopepodites undoubtedly reached adult stages inall cultures at 8 and 32 ppt, although difficultiesin separating the original adults from theiroffspring preclude us from stating this firmlyexcept for 8 ppt at 78C and 32 ppt at 208C. Thefirst eggs appeared after 2–4 days at 208C andafter 10 days at 78C (Table 4). The time of theappearance of different copepodite stages can be

Table 2. Number of individuals of harpacticoid species (or taxa) at stations A–E, and in cast-up seaweed, at Hvassahraun,southwestern Iceland.

Station

A1 A2 B1 B2 Seaweed C1 C2 D1 D2 E1 E2

Height above Chart Datum (m) 5.00 5.00 3.99 3.99 3.74 3.00 3.00 2.02 2.02 1.06 1.06Weight of sample (g) 933 2161 1062 1401 380 1041 1135 1464 1166 1601 639

Itunella muelleri (Gagern, 1922) 7 25 35 91 13 20 — — — — —Schizopera meridionalis Petkovski, 1954 — — 46 44 — — — — — — —Heterolaophonte cf. hamondi Hicks, 1975 — — 3 11 1 3276 5064 — 8 — 2Nitokra spinipes Boeck, 1865 — — 2 — — 192 128 8 — — —Parastenhelia spinosa (Fisher, 1860) — — — 1 — — — 104 8 — —Thalestridae sp. — — — — 1 — — — — — —Tisbe Lilljeborg, 1853, spp. — — — — 1 — 8 — 4 83 54Nitokra typica Boeck, 1865 — — — — — 12 — — 28 — 1Diosacchidae sp. A — — — — — — — 80 36 — —Laophontodes expansus Sars, 1908 — — — — — — — 8 4 — —Diosacchidae sp. B — — — — — — — 32 — — —Mesochra Boeck, 1865, sp. A — — — — — — — 8 — — —Parathalestris Brady and Robertson, 1873, sp. — — — — — — — 8 — — —Laophonte cf. baltica Klie, 1929 — — — — — — — — 8 — —Ectinosomatidae spp. — — — — — — — 168 24 18 6Ameiridae spp. — — — — — — — 72 16 3 1Laophonte inopinata T. Scott, 1892 — — — — — — — 24 8 3 1Amphiascoides debilis (Giesbrecht, 1881) — — — — — — — 24 4 1 —cf. Amphiascoides debilis (Giesbrecht, 1881) — — — — — — — — 4 — —Diosacchidae sp. C — — — — — — — 8 12 6 —Paramphiascopsis giesbrechti (Sars, 1906) — — — — — — — — 8 1 1Pseudonychocamptus koreni (Boeck, 1872) — — — — — — — — — 71 15Amphiascus Sars, 1905, sp. A — — — — — — — — — 26 1Ameira longipes (Boeck, 1865) — — — — — — — — — 17 1Dactylopusia vulgaris Sars, 1905 — — — — — — — — — 6 6Amphiascus Sars, 1905, sp. B — — — — — — — — — 2 1Diarthrodes major (T. and A. Scott, 1895) — — — — — — — — — — 11Laophonte Philippi, 1840, sp. — — — — — — — — — — 4Laophontidae sp. — — — — — — — — — — 4Mesochra Boeck, 1865, sp. B — — — — — — — — — 3 —Harpacticus uniremis Kroyer, 1842 — — — — — — — — — 2 —Onychocamptus horridus (Norman, 1876) — — — — — — — — — 2 —Eurycletodes (O.) similis (T. Scott, 1895) — — — — — — — — — 1 —Tegastes Norman, 1903, sp. — — — — — — — — — 1 —Paramphiascopsis longirostris (Claus, 1863) — — — — — — — — — 1 —Harpacticus septentrionalis (Klie, 1941) — — — — — — — — — 1 —Amphiascus cf. minutus (Claus, 1863) — — — — — — — — — 1 —Unidentified copepods 1 1 — — — 12 — 11 20 16 4

Number of identified species (or taxa) 1 1 4 4 4 4 3 12 13 20 15Number of individuals 8 26 86 147 16 3512 5200 555 192 265 113

443STEINARSDOTTIR AND INGOLFSSON: HIGH SHORE HARPACTICOID

taken as a measure of developmental rate. Thecopepodites developed much faster at 208C thanat 78C, while no difference was evident between8 and 32 ppt when corresponding temperatureswere compared (Table 4). The first adults wereseen at day 95 in cultures at 8 ppt at 78C, but,already at day 29 in cultures at 32 ppt at 208C.

DISCUSSION

Our studies show that Itunella muelleri iscommon in the upper part of the littoral fringeof rocky or gravelly tidal shores in Iceland, andis found in similar habitats in Norway andScotland. At Hvassahraun its vertical distribu-tion is similar to that reported for the talitridamphipod Orchestia gammarellus at nearbyGalgahraun (Ingolfsson, 1976). However, wealso found I. muelleri 30 cm vertically higher upon the shore, at a level well above predictedextreme high water springs, as well as 40 cmlower than the lower limits of O. gammarellus.We cannot of course exclude that I. muellerimayhave reached still higher on the shore than to ourtopmost station, A. To the best of our knowledgeno other marine organism at higher latitude hasbeen reported with a similar distribution on theuppermost part of tidal rocky shores, with theexception of organisms living in rockpools.Thus, the rockpool harpacticoid Tigriopusbrevicornis (O. F. Muller, 1776) has been foundin Britain in pools, extending just beyond therange of levels encompassed by high waterneaps and high water springs (Johnson, 2001). InJapan, Tigriopus japonicusMori, 1938, has beenfound in rockpools 6.5 m above high tide mark(Ito, 1970). Itunella muelleri has a wider geo-graphical distribution in Iceland than O. gam-marellus, which is confined to the warmersouthwestern coast, except for isolated occur-rences at warm springs in the northwest

(Ingolfsson, 1996). Itunella muelleri thrives onalgal detritus, and may be found both on cast-upseaweed lying on the shores, as well as theinterstices between pebbles and cobbles in thesubstrata, as is often O. gammarellus (personalobservation). In Iceland, I. muelleri has pre-viously been recorded in small numbers froma fully saline tidal pool situated at a level slightlybelow mean low water neaps, but only in wintermonths (October–January) (Steinarsdottir et al.,2003). This possibly suggests some downwardmigration in fall, as does the absence of thespecies at high-level sites away from warmsprings at Skarð and Kaldrananes in January, aswell as from such sites at Kirkjubol at that time.Additionally, I. muelleri has been identifieda number of times from floating seaweed out atsea in all seasons (personal observation).

Worldwide, I. muelleri appears restricted tothe northern hemisphere, having been recordedfrom Ireland (Roe, 1958), Scilly Islands (Wells,1961), Scotland (present study), Norway (pres-ent study), Sweden (Noodt, 1954), Finland(Noodt, 1970), the Karelian coast of the WhiteSea (Chislenko, 1967), Germany (Gagern, 1922;Kiefer, 1960), Italy (Argano et al., 1995; Bereraet al., 2001), Greece (Berera et al., 2001) andfrom the Black Sea (Apostolov, 1969). Itsdistribution thus covers a wide latitudinal range

Table 3. Distribution of particle sizes at stations inHvassahraun, southwestern Iceland. Figures show percent-age dry weight of substrata retained by each sieve.

Sieve mesh size

Stations 16 mm 8 mm 4 mm 2 mm 1 mm ,1 mm

A 45.5 5.3 6.0 12.4 15.5 15.3B 50.5 6.6 4.0 6.0 8.5 24.4C 9.9 8.8 9.5 7.6 12.3 51.9D 37.4 15.6 12.4 15.8 11.3 7.5E 71.3 19.5 7.2 1.5 0.3 0.2

Table 4. Performance of Itunella muelleri at different salinities and temperatures. – no data.

Salinity Fresh water 8 ppt 32 ppt

Temperature 78C 208C 78C 208C 78C 208C

Individuals alive after 4 days (n ¼ 30) 30 27 30 30 30 30Individuals alive after 22 days (n ¼ 30) 26 5 24 26 28 ?Number of faecal pellets on day 2 1.7 6 1.2 1.7 6 0.6 25.7 6 14.5 108.3 6 21.0 21.7 6 9.1 93.3 6 7.8First egg on day number 10 2 10 4First nauplius on day number 22 3 10 4First copepodite 1 on day number 57 10 49 10First copepodite 2 on day number 67 10 57 10First copepodite 4 on day number 80 18 88 18First adult on day number 95 — — 29

444 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 24, NO. 3, 2004

in Europe. The information on habitat type inthese areas is scant. Habitats are described asbrackish water (Gagern, 1922; Noodt, 1970),coastal groundwater (Apostolov, 1969), rockpools (Roe, 1958), moist sand (Noodt, 1954;Wells, 1961), algae (Noodt, 1970), decomposingvegetation and detritus (Kiefer, 1960; Chislenko,1967), and salt marshes (Kunz, 1939 in Lang,1948). Previous papers on zonation of harpacti-coids on tidal shores have focussed on sedimentsbelow mean high water springs (e.g., Wells,1961; Harris, 1972; Coull et al., 1979; Moore,1979). However, Wells (1961) records a fewspecimens of I. muelleri, from the ‘‘strandline’’and ‘‘average high tide level,’’ on the Isle ofScilly. These observations agree fairly well withthose made here and also show I. muelleri to beflexible in habitat choice.The wide geographical distribution of I.

muelleri and its choice of habitats suggest a widetolerance to environmental conditions. Thespecies apparently thrives equally well at 8 pptand 32 ppt, and at 78C and 208C, although bothdevelopmental rate and feeding rate are muchhigher at the higher temperature. Noodt (1970)records the species from Tvarminne, Finland,where the salinity is approximately 6 ppt, whileother localities from which the species isrecorded are often described as brackish waters,and some are evidently fully marine. Ourexperiments suggest that the species should beable to tolerate the range in salinity it mayencounter in the field easily, and it can surviveand feed at a low rate in fresh water forprolonged periods, although it is probablyunable to reproduce. The harpacticoid Nitokraspinipes, which often co-occurs with I. muelleri,is known to tolerate a wide range of salinities(Ganning, 1971), and it can even breed at 0.5 ppt(Wulff, 1972). Tigriopus spp. can tolerate anextraordinary range of salinities, from almostfresh to supersaline (e.g., Davenport et al.,1997). While I. muelleri thrives when continu-ously submerged, it also does well whenexposed, at least if the humidity is high. Thisis in agreement with the observations of DavidMorritt who reports (personal communication)that he has frequently found his cultures of O.gammarellus swarming with harpacticoids, nowidentified as I. muelleri.The high tolerance to desiccation and varying

salinities and temperatures and its ease of culturecould potentially make I. muelleri a valuableexperimental animal, for example in ecotoxico-logical studies on a par with the harpacticoids

Tisbe spp. (Barata et al., 2002) and N. spinipes(Breitholtz and Bengtsson, 2001), or for massproduction as food for larval fish in aquaculture(Rhodes and Daniels, 2001). The generationtime observed for I. muelleri, from the appear-ance of the first egg to the appearance of the firstadult stage, took at most 25 days at 208C. Furtherexperiments on I. muelleri are needed tocompare it to species already in use, some ofwhich have generation times of 8–10 days atcertain environmental conditions (reviewed byHicks and Coull, 1983).The harpacticoids N. spinipes and Schizopera

meridionalis were encountered several times insamples along with I. muelleri, in both north-and southwestern Iceland, and N. spinipes alsoin western Norway. Itunella muelleri and S.meridionalis have previously been found to-gether in samples from ground water and dampsand on the east coast of Sweden (Noodt, 1954).Nitokra spinipes is common on the east coast ofSweden in brackish water rock pools (Ganning,1971; Wulff, 1972) and is found in many partsof the world (reviewed by Lang, 1948).Heterolaophonte cf. hamondi, which dominatedin high abundance at station C at Hvassahraun,has previously been recorded high on the shoreon the alga Pelvetia canaliculata (L.) Decne. etThur in England (Hicks, 1975).In conclusion, Itunella muelleri is a marine

animal unusually well adapted to the extremeenvironment of the upper littoral fringe of tidalshores.

ACKNOWLEDGEMENTS

We thank Olafur Patrick Olafsson and Konstantın Shcher-bak for help in collecting samples and Konstantın Shcherbakfor Russian translations. We thank David Morritt forsamples of Itunella muelleri from Scotland and for in-formation on harpacticoids in cultures of Orchestiagammarellus. Jorundur Svavarsson kindly read an earlyversion of the manuscript, and made many constructivesuggestions. We are also thankful for the helpful commentsof two anonymous reviewers.

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RECEIVED: 3 November 2003.ACCEPTED: 9 April 2004.

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