etude de l’induction de ponte et de fecondation chez certains bivalves comestibles du sud de madagascar : Cas des Crassostrea gigas, Crassostrea cucullata, Anadara ehrenbergi, Modiolus auriculatus et Ruditapes philippinarum

Abstract

A study was carried out on the induction of spawning and fertilization in some edible
bivalves in southern Madagascar from January 2016 to July 2018. Five species of bivalves
were studied including Crassostrea gigas, collected in Taolagnaro, Crassostrea cucullata
harvested from Sarodrano and Ambatomilo, Ruditapes philippinarum harvested from the
coast of Toliara, Anadara ehrenbergi and Modiolus auriculatus harvested from the seagrass
beds of the Toliara Great Reef. Spawning induced by a single thermal shock and spawning
induced by a combination of thermal shock and physiological shock yielded positive results
with a success rate of 4.76% and 25% in trials, and with approximately 7,208,000 oocytes
produced by combining a heat shock and a chemical shock in Anadara ehrenbergi. Other
spawning induction techniques were not effective. Three techniques were tested for the
realization of fertilization: at room temperature, with oocyte maturation by incubation and
maturation of gametes using serotonin. The first and second methods were beneficial only in
Crassostrea. The third method was beneficial for all species. Gamete maturation was induced
with serotonin before fertilization. Cross fertilization was performed between control gametes
(not treated with serotonin) and / or gametes tested with serotonin, positive results were
obtained with an average fertilization rate of 10.23%.