Larval development and seed production in the 'whelk' Babylonia spirata

Abstract

The larval development of the whelk, Babylonia spirata (Linnaeus, 1758) (Neogastropoda: Buccinidae) which forms a major component of the bycatches of shrimp trawlers of south- west coast of India was studied and its seed production techniques were developed. The broodstock, which were conditioned at low temperature of 26 - 28OC, spawned intermittently between January to April, and again during September to December, 2002. Each spawner laid an average 35 transparent egg capsules, which were firmly attached to the substratum by a slender stalk. Fertilized eggs of 260 to 280pm diameter started their development within the transparent egg capsule itself by spiral cleavage and progressively developed into morula, blastula, trochophore and veliger stages. The larvae hatched out as veliger between the 7th and 8th day after spawning and these were reared in the hatchery. Percentage of survival, feeding rate and settling percentage of the larvae were studied in detail. Optimum stocking density of the larvae was found to be 150/1 which resulted in 65% settlement of the larvae. Chaetoceros calcitrans was given as feed till settling stage and after that the juveniles were fed with shrimp meat. Details of the spawning, morphology of capsule and growth of the larvae are presented in the paper.