Indian J. Fish., 45(3) : 301-305, Jul.-Sep., 1998

Reproductive cycle in an ellobiid nucleus A. SHANMUGAM Centre of Advanced Study in Marine Biology, Parangipettai - 608 502, India

ABSTRACT

The histology of the ovotestis and the reproductive cycle of Cassidula nucleus which shows protandry were studied. This ellobiid snail attains the first sexual maturity at a size of 16.0 mm (shell length). Since it is a protandric hermaphrodite the male and female genital ducts are fully developed alternatively. The male phase starts in September (premonsoon) when the male reproductive system is fully developed. The female reproductive ducts start developing in November (monsoon). Upto the end of January (postmonsoon) the bursa copulatrix is filled with mucous only. The penis and the anterior part of the vas deferens are distinct during the male phase only. From February onwards copulation takes place, mostly during night. Following this, the egg-laying starts from middle of April (first part of summer season) and extends for another month. In the beginning of July the enter into the spent stage and remain upto August during which time no sex cells are present in the ovotestis. The cycle is repeated for the subsequent year.

Introduction collected from Pichavaram mangroves (Lat. 11° 29'N; Long. 79° 49'E) (Fig. 1) Though many studies are available for one year. Five hundred snails were on the reproductive cycle of the pul- dissected to study the ovotestis, in fresh monate snails in other waters, Morton, condition, for the sex and maturity 1954, 1955a, 1955b; Duncan, 1959, stages. The ovotestis of part of the snails Richards, 1962; Apley, 1970; Wu, 1972; were fixed in Zenker's fixative, dehy­ Rudolph 1980, no work is available in drated, embedded in celloidin paraffin, the Indian waters except that of according to Peterfi's method and sec­ Shanmugam (1987) on Pythia plicata, tioned (6/i). The sections were stained in antother ellobiid snail from Pichavaram Weigert's haematoxylin with Biebrich mangroves. Hence an attempt has been scarlet as counterstain. made to study the reproductive cycle of Cassidula nucleus from Pinchavaram To demonstrate the seasons prevail­ mangroves of the Vellar estuary. ing in the present study area, the calender year was divided into four Material and methods seasons viz., January to March (post of 7.5 to 35.8 mm were monsoon), April to June (summer), July

A. Shanmugam 304

The penis and the anterior part of maturity in Gyraulus (Richards, 1962); the vas deferens are very distinct likewise the male genital tract of the during the male phase, but they are not aphalic individuals oiBulinus truncatus so during the female phase and thus also does not mature (de Larambergue, throughout the year. 1939; Wu, 1972). From February onwards the copula­ In having a short male phase fol­ tion takes place mostly during night. In lowed by a longer female phase, C. each pair, one snail acts as a male and nucleus agrees very well with P. plicata the other as female. The female repro­ (Shanmugam, 1987) and C. tridentatum ductive ducts are at their maximum (Morton, 1954). In C. nucleus the male development while the male reproduc­ phase starts in September and contin­ tive ducts (prostate and other ducts) are ues till November when the ovotestis is reduced in size and appear as thin tubes fully filled with oocytes; while in C. running adjacent to the anterior mu­ tridentatum the male phase begins in cous gland. late June and continues until the end of August by which time the ovotestis is Egg-laying starts form the middle of fully occupied by the oocytes (Morton, April and extends upto the end of May 1954) and in P. plicata the male phase after which the ovotestis is completely starts in november and continues till empty and devoid of any sperms or the female phase starts in January oocytes till August. The cycle is re­ followed by a longer female phase peated during the subsequent year also. (Shanmugam, 1987). But Morton (1955 Discussion a) reported that in the marine ellobiid snail Leucophytia, there is a male phase Protandry is a general phenomenon in autumn and winter and preceeding observed in pulmonates. As in C. nu­ female phase in spring and summer cleus, the protandry has also been with cessation of breeding activity in reported in Limnaea luteola (Seshaiya, July. Further Morton (1954) correlated 1927, Carychium tridentatum (Morton, the growth of Carychium in snails 1954), Leucophytia (Morton, 1955 a), hatched in June and undertaken their Otina otis (Morton, 1955 b), Physa sperm production in July of the follow­ fontinalis (Duncan, 1959), Stagnicola ing year. elodes (Rudolph, 1980) and P. plicata (Shanmugam, 1987). In C. nucleus the penis and the anterior vas deferens are indistinct Histologically, in P. fontinalis the during the female phase as observed in male reproductive system developed C. tridentatum (Morton, 1954). How­ fully before the development of the ever, this is in contrast with P. plicata female reproductive system (Duncan, (Shanmugam, 1987) and Leucophytia 1959). But in Melampus bidentatus the (Morton, 1955 a) in which there is no male and female genital system are disappearance of penis or vas deferens simultaneously matured and developed during the female phase. which is in contrast to the reported protandry throughout the family Ello- The egg-laying starts from the mid­ biidae (Apley, 1970). The male genital dle of April and extends for another system is retarded at the first sexual month in C. nucleus whereas P. plicata Reproductive cycle in an ellobiid snail 305 starts egg-laying from the end of (Isidora) contrrtus Michand. Bull. June and intensifies during July Biol. Fr. Belg., 73 : 19-321. (Shanmugam, 1987). The former attains Morton, J. E. 1954. Notes on the ecology and its first sexual maturity at a shell annual cycle of Carychium triden- length of 16.0 mm whereas the latter tatum at Box Hill. Proceedings Mala- attains at a shell length of 10.0 mm. cological Society London, 31 : 30-45. C. nucleus spawns once in a year as Morton, J. E. 1955 a. The functional mor­ reported for P. plicata (Shanmugam, phology of the British Ellobidae (Gas­ 1987). The former starts spawning in tropoda : ) with special the middle of April while the latter from reference to their digestive and repro­ ductive systems. Trans. Royal Phil. the end of June. Duncan (1959) reported Soc. London (B), 239 : 89-160. that in P. fontinalis, a Mediterranean species collected from Traparnaud dur­ Morton, J. E. 1955 b. The functional mor­ ing 1954, there were two breeding phology of Otina otis, a primitive seasons in a year. The second being marine pulmonate. J. mar. biol. Ass. U. K, 34. much shorter, occurring in September and October. Richards, C. S. 1962. Retarded development of the male reproductive system in a Acknowledgments Florida Gyraulus. Trans. Am. Microsco. Soc., 81 : 347-351. The author is thankful to the Direc­ tor, CAS in Marine Biology for provid­ Rudolph, P. H. 1980. Sequence of secretory ing all facilities. Thanks are also due to product formation in maturing repro­ the Department of Environment and ductive systems of the freshwater University Grants Commission for the lymnaeid snail Stagnicola elodes (Say). Trans. Am. Microsco. Soc, 99(2) : financial assistance. 193-200. References Seshaiya, R. V. 1927. On the breeding habit Apley, M.L. 1970. Field studies of life and fecundity of the snail Limnaea history, gonadial cycle and reproduc­ luteola Lamarck (Formatypica). J. tive periodicity in Melampus Bombay Nat. Hist. Soc, 32 : 154-162. bidentatus (Pulmonata : ). Shanmugam, A. 1987. Studies on Pythia Malacologia, 10(2) : 381-397. plicata (Gray) ( : Pulmo­ Duncan, C.J. 1959. The life cycle and ecology nata : Ellobiidae) from Pitchavaram of the freshwater snail Physa mangroves, Ph.D. Thesis, Annamalai fontinalis (L). J. Anim. Ecol. , 28 : University. 97-117. Wu, S. K. 1972. Comparative studies on a Larambergue, M. De. 1939. Etude de 1' polyploid series of the African snail autofecondation chez les gastropdes genus Bulinus (Bassommatophora : pulmones. Recherches sur 1' aphallie Planorbidae). Malacol. Rev., 5 : 95- et la fecondation chez Bullinus 164.