Reproductive cycle of edible echinoderms from the Southwestern Indian Ocean: I. Tripneustes gratilla L. (Echinoidea, Echinodermatata)
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The reproductive cycle of the edible echinoid Tripneustes gratilla (Linneaus 1758) was investigated in a population located in the southwest coast of Madagascar (Toliara). The reproductive cycle was followed for two consecutive years (October 1999 to October 2001) and characterised by means of gonad and maturity indices. T. gratilla has an annual reproductive cycle mediated by seawater temperature, day length and feeding activity. The histology of the gonads revealed six different maturity stages grouped in three main reproductive phases: growing and maturing, spawning, and spent and recovering. Reproduction is seasonal. Growing and maturing stages occurred from late summer to early winter correlating with decreasing temperatures and day length. Spawning occurred during mid and later winter, when temperatures and day lengths were lowest. Spent and recovering urchins were observed from late summer to early winter. Besides, the reproductive cycle was also influenced by food quantity in t.....