Breeding and moulting of barnacles under rearing conditions

Marine Biology 108, 83-89 (1991)

Marine Biology @ Springer-Verlag 1991

Breeding and moulting of barnacles under rearing conditions M . M . EI-Komi 1 and T. Kajihara 2

1 National Institute of Oceanography and Fisheries, Kayet-Bey, A1-Anfushy, Alexandria, Egypt 2 Environmental Biology Research Center Co. Ltd. Meguro-Ku, Tokyo 153, Japan

Date of final manuscript acceptance: September 14, 1990. Communicated by M. Anraku, Tokyo

Abstract. The reproductive parameters of three species of barnacles common in warm-water regions, Balanus amphitrite Darwin, B. eburneus Gould and B. trigonus Dar- win, cultured singly or in pairs for 2 V2 yr, were com- pared. All specimens, collected f rom Tokyo Bay and studied between 1985 and 1987, were fed on newly hatched Artemia sp. larvae ( 'Tetra ' strain) and phytoplankton culture and were maintained under constant temperature (20°C) and controlled photoperiods (10 h light : 14 h dark). The breeding frequencies of these three species were equally high, f rom 2 to 4 broods m o - a in the first year; they were relatively high between October and February, averaging 3 broods m o - ~ . B. amphitrite, B. eburneus and B. trigonus produced 24, 21 and 11 broods yr -~ , respectively. Brood size was quite variable among the three species examined, yielding 4000 embryos b r o o d - a in B. amphitrite and B. eburneus and 6000 in B. trigonus. Brood interval averaged 4 to 9 d. The moul t occurred over short intervals of 4 to 10 d m o u l t - 1. Both breeding and moulting frequencies were influenced by low temperature and starvation. Self-fertilization was observed in all species and was more frequent in B. amphitrite than in B. eburneus and B. trigonus. Nutri t ional condition and temperature seemed to be the main exter- nal factors regulating both breeding and moult ing processes in barnacles.

Introduction

Barnacles are distributed world-wide. They are found in all marine environments f rom the high intertidal zone to the depths of the oceans. Barnacles are ecologically im- portant , as they represent the most common marine foul- ing animals. Some occur in estuaries and harbours, but their life cycles do not complete in fresh water (Newman and Abbot t 1980). The diversity of barnacle species is greatest in the tropical Indo-Pacific, less in the Nor th Pacific, and least in the Nor th Atlantic (Hutchins 1952).

The pattern of reproduction in barnacles varies great- ly, f rom an annual large brood or a few broods every

year, with long life span, to numerous ones that may exceed 30 broods yr -1 , with limited life span. Several studies on reproduction and moulting in European and American species have been conducted, al though with only limited experimental periods (Crisp and Davies 1955, Crisp and Patel 1958, 1961, 1969, Patel and Crisp 1960 a, b, Hurley 1973, Hines 1978, 1979). However, little is known about the ecology of Japanese species (Iwaki 1981, Kato 1982).

The present study examined the reproduction and moult ing of the common Japanese barnacles Balanus amphitrite, B. eburneus and B. trigonus. Breeding and moulting frequencies, as well as brood-size and egg-size variations, were studied through laboratory rearing experiments with long-term cultures. Some experiments on self- fertilization were also performed, as well as experiments on breeding and moulting cycles under controlled water temperature and starvation conditions.

Materials and methods

Study was performed on barnacles collected between May 1985 and July 1986 from a natural population growing on shells of the mussel Mytilus galloprovineialis, attached to a concrete pier in Yokosuka Harbour, Tokyo Bay, at a depth of 1 to 5 m. Samples, kept in wet cloth bags, were transferred immediately to the laboratory. Adult Balanus amphitrite, B. eburneus and B. trigonus, with flat basal diameters of 9 to 15 mm, were used. They were mounted on pieces of polystyrene plate (2 x 2 cm) using cyanoacrylate (Alon Alpha) adhesive, and were isolated either individually (single culture) or in pairs (paired culture) and placed in 120-ml cylindrical glass aquaria. Laboratory experiments were performed on 7 groups of paired cultures and 4 to 6 groups of single cultures for each species, from May 1985 to July 1987.

The filtered seawater in the containers was changed three or four times weekly. The medium was inspected at intervals under a binocular microscope to determine whether a brood or moult was present. Cultured specimens were maintained under a controlled temperature (20 °C) and photoperiod (10 h light: 14 h dark). They were fed with Artemia sp. larvae ('Tetra' strain) and unicellular algal culture. Newly hatched Artemia sp. nauplii were given to the barnacles at a density of 10 to 14 larvae m1-1 d -1. Dunaliella sp. and the diatoms Phaeodactylum sp. and Skeletonema eostatum, grown in

84

enriched seawater media (see Guillard 1975), were added to the aquaria as diet at a density of 5 to 10 x 103 cells ml -~ d -~.

Expelled egg masses or any liberated nauplii were counted using a counting tray, so as to estimate all the eggs in each brood. Meas- urements of egg size were made with an ocular micrometer. Egg length (major axis) and breadth (minor axis) were measured on 3 to 6 developing embryos from each brood.

In order to determine the effect of temperature on reproductive activities and moulting, additional laboratory experiments were car- ried out in an incubator under constant temperatures of 10 ° and 20°C, as well as at room temperature (9 ° to 20 °C). The effect of starvation was studied for groups of Balanus amphitrite and B. eburneus kept at 20 °C, where only the seawater was changed 3 or 4 times wk-a.

R e s u l t s

M.M. E1-Komi and T. Kajihara: Barnacles under rearing conditions

Balanus amphitrite

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Reproductive characteristics

Breeding frequency

Groups of Balanus amphitrite, B. eburneus and B. trigonus were cultured in pairs and kept at 20 °C with a constant food supply. Fig. 1 illustrates the average num- bers of broods produced per month by the seven parallel pairs. In the case of B. amphitrite, the highest number of broods occurred in December 1985, with about 7 broods too- 1, while the lowest values appeared during June and December 1986. All paired specimens were, however, able to produce 3 to 4 broods too-1, particularly from October 1985 to April 1986, even through the non-breeding season of the natural population (E1-Komi 1988). Another small increase in breeding frequency was recorded from July to October 1986 and from February to June 1987.

Balanus eburneus displayed more or less similar variations in the number of broods produced monthly, but with lower peaks of 5 broods m o - 1 for paired specimens. The number of broods for B. trigonus, on the other hand, remained low throughout the first year; however, it increased rapidly during the autumn of 1986, reaching a peak of 5 broods m o - 1 in November. This was succeeded by a rapid drop in winter and spring 1987 (excluding a small increase in April). The breeding frequencies of B. eburneus and B. trigonus were low throughout winter and early spring, during which those in natural habitats ceased breeding.

Brood parameters

The brood size (number of embryos in a brood) and number of broods recorded for cultured specimens are listed in Table 1. Balanus amphitrite exhibited consider- able variation in brood size, between 1000 to 10 000 eggs brood-1 , with larger brood sizes (10 000 to 15 000 eggs brood-1) infrequently observed. The normal brood size in B. eburneus was 1000 to 5 000 eggs, and the largest brood size did not exceed 11 000 eggs. In B. trigonus a brood size of 1000 to 10 000 eggs was common, with few numbering less than 1000.

Balanus trigonus

ii /'\" A S O N D J FMAMJ J A S O N D J FMAMJJ 1985 1986 1987

Fig. 1. Balanus spp. Average number of broods per month for three barnacles species fed and maintained at 20 °C, from August 1985 to July 1987. Seven paired barnacles were cultured for each species

Balanus amphitrite

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B r o o d i n t e r v a [ ( d ) Fig. 2. Balanus spp. Histogram showing the frequency of brood intervals of barnacles fed and maintained at 20 °C, from May 1985 to July 1987. Seven paired barnacles were cultured for each species


Group Start date

Time Number of broods for different brood sizes Total no. (d) ( x 103) broods

<1 1~5 5~10 10~15 15N20

B. amphitrite P1 May 1,1985 821 12 61 P2 Jun 1 790 15 77 P3 Jul 13 747 28 55 P4 Aug 10 719 14 44 P5 Sep 18 680 15 76 P6 Oct 15 653 11 35 P7 Dec 21 586 8 27 Sl May 17,1985 243 1 5 S2 Jun 1 158 0 2 $3 Jun 1 265 0 3 $4 Jul 1 414 0 7 $5 Aug 10 719 0 2 $6 Sep 18 680 0 3

B. eburneus Pl May 1,1985 804 33 68 P2 Jun 17 393 21 23 P3 Jul l3 747 20 32 P4 Aug 10 328 10 35 P5 Sep 18 680 24 30 P6 Nov 21 616 28 42 P7 Jan 24,1986 552 18 44 S1 Jun 17,1985 348 3 3 $2 Jul 13 54 1 1 $3 Aug 10 566 1 1 $4 Oct 15 254 1 1 $5 Dec 4 450 1 0 $6 Dec 4 152 2 0

B. trigonus P1 May 1, 1985 804 9 56 P2 Jul 13 363 5 9 P3 Aug 10 719 1 11 P4 Oct 15 653 0 7 P5 Nov 21 616 0 12 P6 Dec 21 586 1 12 P7 Feb 21,1986 542 1 11 SI Jul 13,1985 242 0 1 $2 Aug 10 719 0 1 $3 Oct 15 653 3 2 $4 Jul 12,1986 384 0 1

21 31 14 10 15 35 21 2

4 0 98 9 0 132 1 0 98 3 0 71 1 0 107

11 0 92 5 0 61 0 0 8

3 0 0 5 3 0 0 6 2 1 0 10 1 2 1 6 7 9 4 23

11 0 0 112 1 1 0 46 1 0 0 53 8 0 0 53 1 0 0 55 3 0 0 73 4 0 0 66 1 2 0 9 0 0 0 2 0 1 0 3 0 1 0 3 2 0 0 3 0 0 0 2

33 7 0 105 2 3 0 19 4 4 0 20 7 3 3 20

13 6 1 32 10 3 2 28 11 9 0 32 0 0 0 1 5 0 0 6 3 1 0 9 3 0 0 4

85

Table 1. Balanus spp. Number of broods and brood size produced in all paired (P) and single (S) cultures of barnacles fed and maintained at 20 °C

The b rood intervals in Balanus amphitrite and B. eburneus were similar, with a mean of 7 to 9 d, while those in B. trigonus showed a m e a n of 4 to 7 d (Fig. 2). Such intervals seem to be adequate for ovary development , ferti l ization, and embryon ic deve lopment to occur. In paired cultures of B. amphitrite, the two organisms produced 38 to 60 broods y r - 1 (Table 1). This is comparab le to the 26 to 60 broods y r - 1 in B. eburneus and higher than the 10 to 48 broods y r - ~ in B. trigonus.

As shown in Fig. 3, Balanus amphitrite yielded the highest n u m b e r of eggs a m o n g the three species. The m a x i m u m n u m b e r of eggs p roduced by paired specimens of B. amphitrite occurred between N o v e m b e r 1985 and March 1986, while the m i n i m u m generally occurred in the summer. Egg p roduc t ion in B. eburneus was the least, d isplaying low values t h roughou t the year. B. trigonus showed wide m o n t h l y var ia t ions in egg p roduc t ion , with

its highest rate occurring between November 1986 and February 1987.

Egg size

Fig. 4 shows the changes in egg size for paired groups of barnacles kept at constant temperature and food supply. Variations in egg size were more or less similar in all species, a l though the degree of change throughout the year was remarkable - egg size increased rapidly from June to September 1986, remained fairly cons tant unt i l December, then dropped sharply th roughout the winter (January to March), despite a constant temperature and food supply. The annua l ranges in egg length were from 200 _+ 0.0/~m in June to 264.8 _+ 9.8/~m in December 1986 for Balanus amphitrite, from 185 _ 5.8 #m in June to 266.7 +_ 7.1/zm in

86

30 5

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Fig. 3. Balanus spp. Average number of eggs produced for barnacles fed and maintained at 20°C, from August 1985 to July 1987. Seven paired barnacles were cultured for each species


260-

220-

180-

Balanus amphitrite

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cn 220-

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t986 1987 Fig. 4. Balanus spp. Monthly variations in the size of eggs in paired cultures of barnacles fed and maintained at 20 °C

August 1986 for B. eburneus, and from 281.4 + 16.3 #m in December 1986 to 233.4_+ 11.8#m in FebrUary 1987 for B. trigonus. Similar seasonal variations were observed for egg width, although variations were more pronounced for length than for width. Egg width ranged from 120 _ 0.0 #m to 152.1 + 7.0 #m, from 115 _+ 4.1 #m to 159_+ 4.5#m, and from 102.3_+ 3.5#m to 156.9 + 9,3 #m, for B. amphitrite, B. eburneus and B. trigonus, respectively.

Self-fertilization

Breeding by single barnacles kept in isolated containers at 20°C with food generally yielded different results among parallel experiments. The average brood number produced by each individual fluctuated between one and three per month. On rare occasion the specimens produced two successive broods, the first one small, the sec- ond one large and released through the moult. Balanus amphitrite produced 24 relatively large broods through self-fertilization (5 000 to 20 000 eggs, Table 1) over the 2-yr period, whereas B. eburneus produced only 9 broods through self-fertilization in one year, and brood size was smaller. B. trigonus produced larger broods than did B. amphitrite but released only 9 broods through self-fertilization during the 2-yr period.

Moulting frequency

The number of moults released monthly in paired and single cultures of the three species is shown in Fig. 5. Kept under constant temperature and supplied with food, all specimens moulted regularly. The average number of moults varied little among parallel paired and single experiments for the same species. Among Balanus amphitrite and B. eburneus, moulting activities in both paired and individual barnacles were similar, averaging 2 to 6 moults mo - 1. B. trigonus specimens, on the other hand, exhibited greater differences in moulting frequency- paired and single cultures yielded 8 and 12 moults mo - 1, respectively. The moulting intervals fluctuated from 5 to 10 d for B. amphitrite, from 6 to 10 d for B. eburneus, and from 4 to 6 d for B. trigonus (Fig. 6). In the latter species, the moult interval decreased on rare occasion to between 1 and 2 d.

Relationship between breeding and moulting

In cultured barnacles no moulting occurred when egg masses occupied the mantle cavity. The liberation of the brood was accompanied by a moult, as previously report- ed by Patel and Crisp (1961). For the species under inves- tigation here, moulting usually occurred more regularly


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1985 1986 1987 Fig. 5. Balanus spp. Average number of moults released monthly in barnacles fed and maintained at 20°C from August 1985 to July , 1987. ( - - ) paired cultures; (---) single cultures

than did breeding (Figs. 1 and 3). The moulting activity of Balanus trigonus was higher than that of the other species, a result which may be related to its lower embryonic development rate (E1-Komi 1988).

Effect of temperature

Paired adult specimens of Balanus amphitrite with devel- oped ovaries, cultured at 10°C and fed on Artemia sp. nauplii and unicellular algae, completely ceased breeding and displayed lower moulting activity throughout the 5-mo experimental period (Fig. 7). On the other hand, specimens cultured at 20 °C revealed high breeding activity and high moulting rates, particularly after one month of culturing. Similarly, barnacles reared at room temperature showed no breeding activity during the winter, when the temperature was lower than 10°C, but com- menced breeding when the temperature rose to over 10 °C in March 1987. During May 1987, when temperatures rose to ca. 20 °C, barnacles exhibited the same breeding pattern as did those kept under constant conditions.

Effect of starvation

Breeding and moulting of Balanus amphitrite and B. eburneus nearly ceased in paired cultures kept at 20°C

87

200-

100-

0

Balanus amphitrite

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o

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2

2~ Balanus eburneus

Balanus trigonus

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M o u l t i n t e r v a l ( d )

Fig. 6. Balanus spp. Histogram showing the frequency of moult intervals in paired cultures of barnacles fed and maintained at 20 °C from May 1985 to July 1987

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O o o 6 ]~0~ d:l

. -o 20 _~

8 ~o

4 / , . . . . ' ---I -~ o

< 0 ~ - ~ _ ' : _ _ _ _ _ , ....... ,

1986 1987

Fig. 7. Balanus amphitrite. Effect of temperature on breeding and moulting activities in paired cultures. (o---o) air temperature; (w-- - ) breeding at ambient temperature; (---~,) breeding at 20 °C; ( e - - e ) breeding at 10 °C; (m---B) moulting at ambient temperature; (A---A) moulting at 20°C; (e--4) moulting at 10 °C

without feeding throughout the period from May to Au- gust •985 (Fig. 8). However, they resumed their reproductive activities and moulting within a month after be- ing supplied with a mixed culture of Artemia sp. larvae and algal culture.

88

m

O

E 2"

0 "O O O

14-

Balanus amphitrite

'2 Sta rving Feeding //" / i

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Balamus eburneus

Starving Feeding ,,*,,

t I

ila . i I

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Fig. 8. Balanus spp. Experiments on the influence of starvation and refeeding on breeding ( - - ) and moulting (---) activities in B. amphitrite and B. eburneus. Paired specimens were isolated and kept at 20°C

Discussion

The duration of embryonic development in barnacles is closely correlated with the intermoult cycle (Fyhn and Costlow 1977). In the present study the succession of broods and moults in Balanus amphitrite, B. eburneus and B. trigonus confirmed that copulation takes place during early ecdysis, stimulating the organism to oviposition.

Among barnacles kept at 20 °C and fed with Artemia sp. nauplii and algal culture, breeding and moulting con- tinued successively for 2.5 yr or throughout the life span; therefore, it is reasonable to suppose that these species are highly persistent. Boreo-arctic species usually produce a single brood per year and are characterized by a long life span, large brood size, large egg size, and pro- longed embryonic development period (Crisp and Davies 1955). This pattern of reproduction may be correlated to some biological factors, such as low rates of growth and of gametic development. However, nutritional condition and temperature seem to be the principal factors regulating both breeding and moulting processes in barnacles.

In contrast, the warm temperate species Balanus amphitrite, B. eburneus and B. trigonus exhibited high egg production and successive, rapid broods at short intervals of 5 to 8 d b rood-1 . Moulting occurred every 5 to 9 d. In addition, continuous reproduction has been re- ported in other species, such as B. paeifieus in southern


California (Hurley 1973), B. amphitrite in tropical India (Paul 1942), and Elminius modestus in Brixham Harbour , South Devon, England (Crisp and Davies 1955). All these species have a short generation time (1 to 2 mo), and the planktonic larval stage until settlement lasts ca. 1 to 2 wk. Given an abundant food supply, E. modestus is able to continue breeding for 3 yr (Crisp and Davies 1955). Such a reproduction pattern may occur in the wild, and the organism usually ceases breeding for a short period (as mentioned by Giese and Pearse 1974).

Self-fertilization was more frequent in Balanus amphitrite than in B. eburneus, and was least frequent in B. trigonus. Such reproduction may occur under certain cir- cumstances, e.g. when gametogenesis is complete and copulation does not take place (Barnes and Crisp 1956, Patel and Crisp 1961).

Field studies, in conjunction with experimental studies of breeding, are an effective method to improve under- standing of barnacle reproduction.

Acknowledgements. The authors express their deep gratitude to Pro- fessor A. A. Samaan, National Institute of Oceanography and Fish- eries, Alexandria, Egypt, for critically reviewing the manuscript and making valuable suggestions. They also gratefully acknowledge the assistance and cooperation of the staff at the Laboratory of Biology Research, Ocean Research Institute, University of Tokyo, Japan, and of Dr. N. Ito and the members of Japan Marine Science and Technology for help in collecting samples.

Literature cited

Barnes, H., Crisp, D. J. (1956). Evidence of self-fertilization in certain species of barnacles. J. mar. biol. Ass. U.K 35:631-639

Crisp, D. J., Davies, P. A. (1955). Observations in vivo on the breeding of Elminius modestus grown on glass slides. J. mar. biol. Ass. U.K. 34:357-380

Crisp, D. J., Patel, B. (1958). Relation between breeding and ecdysis in cirripedes. Nature, Lond. 181:1078-1079

Crisp, D. J., Patel, B. (1961). The interaction between breeding and growth rate in the barnacle Elminius modestus Darwin. Limnol. Oceanogr. 6:105-115

Crisp, D. J., Patel, B. (1969). Environmental control of the breeding of three boreo-arctic cirripedes. Mar. Biol. 2:283-305

E1-Komi, M.M. (1988). Studies on the reproductive biology of common barnacles. Ph.D. dissertation, University of Tokyo, Japan

Fyhn, U. E. H., Costlow, J. D. (1977). Histology and histochemistry of the ovary and oogenesis in Balanus amphitrite Darwin and B. eburneus Gould (Cirripedia, Crustacea). Biol. Bull. mar. biol. Lab., Woods Hole 152:351-359

Giese, A. C., Pearse, J. S. (1974). Reproduction of marine invertebrates, Vol. 1. Academic Press, New York

Guillard, R. R.L. (1975). Culture of phytoplankton for feeding marine invertebrates. In: Smith, W.L., Chanley, M.H. (eds.) Culture of marine invertebrate animals. Plenum Press, New York, p. 29-60

Hines, A.H. (1978). Reproduction in three species of intertidal barnacles from central California. Biol. Bull. mar. biol. Lab., Woods Hole 154:262 281

Hines, A. H. (1979). The comparative reproductive ecology of three species of intertidal barnacles. In: Stancky, S. E. (ed.) Reproduc- tive ecology of marine invertebrates. Publ. Belle W. Baruch Inst. Mar. Biol. Coast. Res., Univ. South Carolina Press, Columbia, South Carolina, p. 213-234

M.M. E1-Komi and T. Kajihara: Barnacles under rearing conditions 89

Hurley, A.C. (1973). Fecundity of the acorn barnacle Balanus pac~'cus Pitsbry: a fugitive species. Limnol. Oceanogr. 18: 386- 393

Hutchins, L. W. (1952). Geographical distribution. In: Marine foul- ing and its prevention. U.S. Naval Institute, Annapolis, Mary- land, p. 91-101

Iwaki, T. (1981). Reproductive ecology of some common species of barnacles in Japan. Mar. Foul. 3:61-69

Kato, R. (1982). Ecological and taxonomical studies on the free-liv- ing nauplii of barnacles (Crustacea, Cirripedia). Ph.D. dissertation, University of Tokyo, Japan

Newman, W. A., Abbott, D. P. (1980). Cirripedia: the barnacles. In: Morris, R. D., Abbott, D. P., Hauderlie, E. C. (eds.) Intertidal

invertebrates of California. Stanford University Press, Stanford, California, p. 504-535

Patel, B., Crisp, D. J. (1960 a). Rates of development of the embryos of several species of barnacles. Physiol. Zool. 33:104-119

Patel, B., Crisp, D. J. (1960 b). The influence of temperature on the breeding and moulting activities of operculate barnacles. J. mar. biol. Ass. U.K. 39:667-680

Patel, B., Crisp, D. J. (1961). Relation between the breeding and moulting cycles in cirripedes. Crustaceana 2:89-107

Paul, M. D. (1942). Studies on the growth and breeding of certain sedentary organisms in Madras Harbour. Proc. Indian Acad. Sci. (Sect. B) 15:1-14

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Breeding and moulting of barnacles under rearing conditions