Journal of the Marine Biological Association of India

Volume 39 Issue 1&2

Maturity, spawning and larval development in an intertidal snail, Cerithidea cingulata (Gmelin) (Mesogastropoda : Potamididae)

P.V. Sreenivasan

Reproductive organs in the intertidal snail, Cerithidea cingulata (Gmelin) are simple and comprise of gonad, gonoducts and open pallirl duct No sexual dimorphism is discernible externally. The male is without any copulatory organ, but wastage of sperms is avoided by formation of a spermatophore which encloses both eupyrene and apyrene sperms. Transfer of spermatophore by the male into the inhalant stream of the female during mating ensures the safe disposition of sperms into the female.

The female gonoduct is elaborate to receive, retain and release the sperm for fertilization. There is a sperm collecting gutter which receives the spermatophore and transports eupyrene sperms through the sperm collecting pouch to seminal receptacle. From there, during spawning, the sperms pass on to the site of fertilisation. The fertilised ova first pass through the albumen gland where albumen is secreted around zygote and from there through the capsular gland, where the jelly-like capsule is formed around the egg. 'Ihe e m are laid in the form of mucus string as long coils. Maximum fecundity of 17,456 e m were recorded in a single eggrtring of 232 mm long, laid by a snail of 22.5 mm in shell length. Spawning season was prolonged from January to September in the Vellar Estuary. Both male and female attained maturity at the shell length of 16 mm. Condition Index (Kn) was always high indicating prolonged spawning in this snail. Sex was evenly distributed in the population in different months and in different size groups. 

Cleavage commences within 30 minutes after the egg is laid. Cleavage is spiral and unequal. Trochophore is suppressed. A veliger is formed in 36 hr after spawning, but hatching takes place only after 48 hr. Planktotrophic veliger swims actively, feeds on the microalgal diet provided, searches suitable substratum and settles as spat. The newly settled spat is 8 days old and measures 300 p. The spat grows actively and attains a size of about 2 mm within 30 days.



Date : 30-12-1997