S.Afr.J.ZooI.1987,22(3) 195 Observations on the reproductive cycles of eellana capensis (Gmelin, 1791) and Patella concolor Krauss, 1848 (: Prosobranchia: Patellidae)

Theresa Lasiak Department of Zoology, University of Transkei, Private Bag X1001, Umtata, Transkei.

Received 21 November 1986; accepted 6 March1987

The reproductive periodicities of the patellid Gellana capensis and Patella concolor were determined from changes in macro- and microscopic appearance of the gonads over a 14-month period. Both appear to have protracted breeding periods with several peaks in spawning activity. Problems encountered with the application of standard sampling and analytical methods to species with such cycles are discussed.

Veranderinge in makro- en mikroskopiese voorkoms van die gonades van Gellana capensis en Patella con­ color is gebruik om die reproduktiewe siklusse van hierdie diere oor 'n tydperk van 14 maande te bepaal. Beide spesies het klaarblyklik 'n vertengde broeiperiode met verskeie pieke van kuitskiet. Probleme met die toepassing van standaardmonsterneming en analitiese metodes by spesies met sulke siklusse word be­ spreek.

Most studies on the reproductive biology of intertidal (1961), under which six developmental stages are re­ molluscs which inhabit the rocky shores of southern cognized. From this, the mean developmental stage of Africa have been carried out in the cooler waters sur­ the population was estimated for each monthly sample. rounding the Cape Peninsula (Newman 1967; Branch To verify this classification scheme, each month sub­ 1974 ; Griffiths 1977 ; Joska & Branch 1983). Little is samples of gonads at different developmental stages known of the biology of subtropical east coast species. were routinely prepared for histological examination. The present study forms part of an extensive survey of The tissue was embedded in paraffin wax, sectioned at 7 the reproductive cycles of intertidal molluscs commonly ~m, stained with Delafield's haematoxylin and counter­

. found on'the Transkei coast (Lasiak 1986a, b, 1987, in stained with eosin. The sectioned material was allocated ) 0

1 press). In this paper data on the reproductive periodicity a subjective maturity index based on the differing pro­ 0

2 of two patellid limpets eellana capens;s and Patella con­ portions of various gametogenic cells present, as used for

d c%r are presented. the gastropod Turbo coronatus (Lasiak 1986a). Quan­ e t

a A brief description of the ecology of these limpets is titative analyses of some ovarian sections were made by d (

given in Branch (1975). They have similar geographical counting the numbers of pre- and post-vitellogenic r e distributions, zonation and feeding habits. Both are gen­ oocytes in 10 microscopic fields at 400x magnification. h s i eralized browsers and are found predominantly in the l b balanoid zone. C. capens;s is found from Port Alfred up Results u P into East Africa, whereas, P. conc%r occurs from Changes in the mean monthly gonad indices (G.I.) of e

h Algoa Bay up to southern Mozambique.

t male and female C. capens;s MT are shown in Figures 1a

y & b. Superimposed on these are box and whisker plots b Methods d which indicate the central tendency of the data and the e t At approximately monthly intervals, between August extreme values for each of the monthly samples. n a 1982 and September 1983, specimens of C. capens;s and Although the male gonads tended to be larger than the r g P. conc%r were collected from intertidal sandstone female gonads the patterns of development were similar. e c platforms at Hluleka, Transkei (31°49'S /29°19'E). Between September and November 1982 a sharp decline n e c Two subpopulations of C. capens;s were sampled, one in G.1. was evident, indicating that spawning had taken i l

r from the upper (HT) and the other from the mid­ place. There was no evidence of a distinct resting phase; e

d balanoid zone (MT). Spatially random collections of 20 redevelopment of the gonad appeared to take place im­ n

u to 30 of the larger individuals were made during spring mediately. Peak gonadal development was observed in

y low tide. were preserved in 10% formol­ February 1983. The subsequent gradual decline in G.1. a w seawater for a minimum period of two months to allow suggested a protracted spawning period. e t

a the gonad to harden into a compact mass. The subjective staging of histological sections showed G

The shell length of each individual was recorded prior that male C. capens;s MT maintained a higher state of t e to dissection. The gonad was exposed by cutting the foot development than females. (Figures 2a & b). Although n i

b away from the visceral mass and displacing it anteriorly. animals in breeding condition were found throughout a

S A subjective classification of gonadal development, most of the study period, ripe individuals were par­ y

b based on the size of the gonad relative to the viscer.al ticularly prevalent in August/September 1982, January/

d mass, was made for each specimen. This technique fol­ February and September 1983. Sharp drops in the pro­ e c lowed the modification of Orton, Southward & Dodd portion of mature oocytes indicate that major spawnings u d

o (1956) classification scheme proposed by Ballantine took place between September and October 1982 and r p e R 196 S.-Afr.Tydskr.Dierk.1987,22(3)

jective staging of histological sections indicated two capansis peaks in gonadal activity from August to October, and 10 TIDE (a)

Discussion

5 Several methods have been used to determine repro­ 4 ductive periodicity in limpets. Extensive use has been 3 made of subjective gradings based on the visual appear­ 2 ance of the gonad, in terms of size, shape, colour and texture (Orton et a/. 1956 ; Fritchman 1961a, b & c ; Ward 1966 ; Blackmore 1969 ; Rao 1973 ; Picken 1980 ; 5 Creese & Ballantine 1983). Widespread use of this tech­ 4 nique reflects the fact that it requires virtually no equip­ 3 ment and relatively little skill, it is also quick and easy to

. 2 apply. This technique, coupled with the estimation of ) 0

1 gonad indices has, in the past, been used to accurately 0

2 pinpoint the spawning periods of several South African

d 5 patellid limpets (Branch 1974). However, no marked dif­ e t 4 a ferences in the visual appearance of P. conc%r gonads d 3 (

were observed during the present investigation. r 2 e Although sharp drops in the G.!. value were evident in h s i C. l both· MT and HT capensis, spawning periods could b not be clearly defined solely from visual subjective grad­ u A SON 0 J F M A M J J A 5 P

ings. The combination of G.!. and histological tech­ e h TI ME (months) niques used in the present study, however, indicated that t

y both C. capensis and P. conc%r have protracted

b Figure 1 The reproductive cycles of (a) female MT Cel/ana

d capensis, (b)-male MT C. capensis, (c) female HT C. capensis, breeding periods with several peaks in spawning activity. e t The afore-mentioned studies, employing subjective

n (d) male HT C. capensis, (e) female Patella conc%r and (f) a gradings, dealt with species exhibiting well-defined re­ r male P. conc%r determined on the basis of subjective visual g productive cycles with single annual spawning periods.

e grading of gonadal development. The mean monthly gonad c However, the efficacy of this technique is clearly de­ n index (G.I.) is shown superimposed on box and whisker plots e

c pendent not only on the length of the spawning season

i which indicate central tendencies and extreme values each l but also on the degree of gametogenic synchrony within r month. e

d the population. n

u Protracted breeding seasons have been reported more

y frequently in acmaeid and fissurellid limpets' (Ward

a from February to April 1983 (Figure 3a). w Comparison of box and whisker plots (Figures la-d) 1966; Underwood 1974; Creese 1980; Bretos, Tesorieri e t

a indicated that development in C. capensis HT was less & Alvarez 1983) than in patellid limpets. The present G synchronous than that exhibited by C. capensis MT. study indicates that spawning in C. capensis MT took t e Spawning in male C. capensis HT took place between place between September and October and from n i b November and December 1982 and from January to February to April. However, spawning activity in C. a

S capensis HT was not so well defined. This difference

April 1983. Greater variability was evident in the G.I. y

b values of female C. capensis HT which suggests that may reflect poorer developmental synchrony within the

d spawning activity was poorly synchronized. Some high shore population. Slight variations in the spawning e c spawning took place between November and December, activity of subpopulations of a related C. tram­ u d

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d Fipre 1 The reproductive cycle of (a) female MT Cel/ana capensis, (b) male MT C. capensis, (c) female HT C. capensis and (d) e c male HT C. capensis based on the proportion of the monthly sample at each maturity stage (d h d , d : developing; r: ripe; sp: u 2 3 d spawned). o r p e R 198 S.-Afr .Tydskr .Dierk.1987 ,22(3)

vidual limpets. However, Branch (1974) and Creese 80 C capensis MT (1980) consider multiple spawnings to reflect the pos­ 60 12 10 sibility that a variable proportion of the population may spawn throughout the breeding period. Recent studies 40 on trochid gastropods (Garwood & Kendall 1985) have 20 indicated that complete spawning does not always take place, it may be replaced by several partial spawnings. 80 Histological studies involving the analysis of oocyte dia­ meter frequencies and counts of mature oocytes per unit (I) 4 ....QI 60 weight of gonad can fulfil this need. Precise knowledge >- 0 of spawning extent and periodicity are needed prior to 0 40 0 ,~,~:T QI the assessment of gonadal output. Previous attempts L 11 '~' ....::J 20 (Branch 1975) to assess the effects of exploitation on 0 ::E gonadal output of P. concolor must be treated with .... P concolor caution as no information was then available on the go­ 80 13 nadal cycle. 60 4/,t'M The relative expense, in terms of time, money and ef­ / 40 fort, involved in studies of invertebrate reproduction frequently necessitates compromises in either analytical 20 methods and/or sampling frequency. Careful con­ sideration needs to be given to both sampling and pro­ A SON 0 J F M A M J J A 5 cessing strategies. Methodology adequate for species with well-defined cycles involving a single spawning TI ME {months> period may not be suitable for use in species exhibiting protracted spawning. Figure 3 The reproductive cycles of (a) MT Cellana capensis, (b) HT C. capensis and (c) Patella concolor as indicated by the Acknowledgements percentage of mature oocytes observed. Vertical bar indicates the standard deviation. Numbers above the bar indicate This project was funded by the University of Transkei.

. Prof A.H. Dye is thanked for his constructive comments ) sample size. 0

1 on the first draft of this paper. 0 2

d References e Fletcher (1984). Most species of the genus Cellana ex­ t a hibit protracted breeding periods with several peaks in BALLANTINE, W.J. 1961. The population dynamics of d (

spawning activity (Rao 1973 ; Underwood 1974 ; Creese Patella vulgata and other limpets. Ph.D. thesis, Queen r e & Ballantine 1983; Fletcher 1984). Unlike the majority Mary College, University of London. h s i L. l of Patella species, which have marked annual cycles BLACKMORE, D.T. 1969. Studies of Patella vulgata 1. b (Branch 1981), protracted breeding was evident in P. Growth, reproduction and zonal distribution. 1. Exp. u P

con color with major spawnings occurring between Sep­ Mar. Bioi. Ecol. 3: 200-213. e h tember and November and from February to March. In BRANCH, G.M. 1974. Ecology of Patella Linnaeus from t

y the Western Cape, Branch (1974) noted that warm­ the Cape Peninsula, South Africa. 2. Reproductive b water patellids tended to breed in spring-summer, cycles. Trans Roy. Soc. S. Afr. 41: 111-160. d e t whereas cold-water and ubiquitous species bred in BRANCH, G.M. 1975. Notes on the ecology of Patella n a autumn-winter. He also found spawning to be more pro­ concolor and Cellana capensis and the effects of human r g tracted and less defined in populations from warmer consumption on limpet populations. 2001 Afr. 10: 75-85. e c waters. A recent study (Robson 1986) on the Natal coast BRANCH, G.M. 1981. The biology of limpets: physical n e

c has shown that P. aphanes also has a somewhat pro-· factors, energy flow, and ecological interactions. i l tracted breeding cycle involving two peaks in spawning Oceanogr. Mar. Bioi. Ann. Rev. 19: 235-380. r e

d activity between January and February and from April BRETOS, M., TESORIERI, I. & ALVAREZ, L. 1983. n

u to June. The biology of maxima Sowerby ( :

y Further work is needed to establish whether the time Archaeogastropoda) in Northern Chile. 2. Notes on its a w spans identified reflect effective or potential spawning reproduction. Bioi. Bull. 165: 559-568. e t

a periods of C. capensis and P. conco/or. Frequent sam­ CREESE, R.G. 1980. Reproductive cycles and fecundities G

pling is needed to determine not only how synchronous, of four common eastern Australian archaeogastropod t e but also how often and when exactly spawning takes limpets. Aust. 1. Mar. Freshw. Res. 31: 49-59. n i b place (Creese & Ballantine 1983). It is also important CREESE, R.G. & BALLANTINE, W.J. 1983. An a

S that the techniques used to assess sexual development be assessment of breeding in the intertidal limpet Cellana y 1. b capable of differentiating between partial and total radians (Gmelin). Exp. Mar. Bioi. Ecol. 67: 43-59.

d spawnings. Both Rao (1973) and Underwood (1974) FLETCHER, W.J. 1984. Variability in the reprodutive e c effort of the limpet, Cellana tramoserica. oecologia 61: u have suggested protracted breeding seasons in limpets to d

o be associated with piecemeal spawning activity by indi- 259-264. r p e R S.Afr.J.ZooI.1987,22(3) 199

FRITCHMAN, H.K. 1961a. A study of the reproductive supralittoral gastropod Littorina kraussi (Rosewater, cycle in the Californian Acmaeidae (Gastropoda) Part 1. 1970). S. Afr. J. Zool. 22: 170-172. Veliger 3: 57--63. LASIAK, T.A. In press. The reproductive cycles of three FRITCHMAN, H.K. 1961b. A study of the reproductive trochid gastropods from the Transkei coast, southern cycle in the Californian Acmaeidae (Gastropoda) Part 2. Africa. J. Moll. Stud. Veliger 3: 95-101. NEWMAN, G.G. 1967. Reproduction of the South African FRITCHMAN, H.K. 1961c. A study of the reproductive abalone, Haliotis midae. Investl. Rep. Div. Sea Fish. S. cycle in the Californian Acmaeidae (Gastropoda) Part 3. Afr. 64: 1-24. Veliger 4: 41-47. ORTON, J.H., SOUTHWARD, A.J. & DODD, J.M. 1956. GARWOOD, P.R. & KENDALL, M.A. 1985. The Studies on the biology of limpets. 2. The breeding of reproductive cycles of Monodonta Iineata and Gibbula Patella vulgata L. in Britain. J. Mar. BioI. Ass. U.K. 35: umbilicalis on the coast of Mid-Wales. J. Mar. BioI. Ass. 149-176. U.K. 65: 993-1008. PICKEN, G.B. 1980. The distribution, growth and GRIFFITHS, R.J. 1977. Reproductive cycles in littoral reproduction of the Antarctic limpet Nacella (Patinigera) populations of Choromytilus meridionalis (Kr.) and concinna (Strebel, 1908). J. Exp. Mar. BioI. Ecol. 42: Aulacomya ater (Molina) with a quantitative estimate of 71-86. gamete production in the former. J. Exp. Mar. BioI. RAO, M.B. 1973. Sex phenomenon and reproductive cycle Ecol. 30: 53-71. in the limpet Cellana radiata (Born)(Gastropoda : JOSKA, M.A.P. & BRANCH, G.M. 1983. The Prosobranchia). J. Exp. Mar. BioI. Ecol. 12: 263-278. reproductive cycle of the trochid gastropod Oxystele ROBSON, G. 1986. Aspects of the biology of a new species variegata (Anton, 1839). Veliger 26: 47-51. of South African Patella (Mollusca : Gastropoda : LASIAK, T.A. 1986a. The reproductive cycle of the Patellidae). M.Sc. thesis, Univ. of Natal, intertidal gastropod Turbo coronatus Gmelin 1791, on the Pietermaritzburg. Transkei coast. S. Afr. J. Zool. 21: 153-155. UNDERWOOD, A.J. 1974. The reproductive cycles and LASIAK, T.A. 1986b. The reproductive cycles of the geographical distribution of some common eastern intertidal bivalves Crassostrea cucullata (Born 1778) and Australian prosobranchs (Mollusca: Gastropoda ). Aust. Perna perna (Linnaeus 1758) from the Transkei coast, J. Mar. Freshw. Res. 25: 63-88.

southern Africa. Veliger 29: 226-230. WARD, J. 1966. The breeding cycle of the keyhole limpet, . )

0 LASIAK, T.A. 1987. The reproductive cycle of the Fissurella barbadensis. Bull. Mar. Sci. 16: 668-684. 1 0 2

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