On captive breeding, spawning, embryonic and larval development in Horse conch, Pleuroploca trapezium (Linnaeus, 1758) from Southeast coast of India

Captive breeding, spawning and larval development of endangered gastropod, horse conch, Pleuroploca trapezium (Linnaeus, 1758) was studied and reported from Thoothukudi, Southeast coast of India for the first time. Wild collected brooders of P. trapezium were spawned after 10 months of rearing under captivity as a cluster of egg cases on the wall of the tank and also above the shell of the other horse conch. Each egg case had 150 to 460 numbers of eggs. The incubation period ranged from 23 to 30 days and 91 % of hatching was recorded. Detailed observations were made on the embryonic development and larval rearing until 40 days of post hatch (dph). The day one larvae measured 750±14.15 μm and reached an average shell size of 1830±37.48 μm after 40 dph. After 30 dph, though most of the pre-juveniles settled and crawled at the bottom of the rearing tank, the presence of active velum indicated that the competency to metamorphosis for the development of juvenile was not fully attained and complete mortality occurred. Therefore, further study is warranted using different cues to promote the metamorphosis of Pleuroploca trapezium for successful life cycle closing and juvenile production.