||Le Moullac Gilles, Hui Belinda, Vonau Vincent, Levy Peva, Cochard Jean-Claude
||Ifremer - Département d’Aquaculture en Polynésie Centre du Pacifique, BP 7004, 98719 Taravao, French Polynesia
||11th Pacific Science Inter-Congress, 02-06 March 2009, Tahiti, French Polynesia
||Pearl oyster, reproduction, gametogenesis, broodstock
||Preliminary experiments allowed defining basic requirements of Pinctada margaritifera for somatic and gonadic growth in controlled conditions. This study was continued by observation of the gametogenesis at a cellular level. In April/May 2008, 125 oysters were conditioned for 30 days in 25 tubular tanks (30 L). Water was renewed 4 times/hour. A mixed (v:v) diet of Isochrysis galbana (T-Iso) and Chaetoceros gracilis was supplied continuously. A control batch of 125 oysters was maintained in trays in the lagoon. An initial sample of 30 individuals was made. Gonadic changes were first characterized using a gonadal development index (GDI) based on the ratio of the gonad area to the total visceral mass area on a sagittal section of the body. Histological sections were made to analyse gametogenesis cellular lines. Initial and final GDI distribution of control oysters did not vary and followed the normal law. In conditioned oysters GDI distribution appeared flattened. Analysis of GDI data showed that reproductive effort was significantly lower (P<5%) in conditioned oysters. Histological analysis of female gonad revealed that oocyte size increased significantly in conditioned females but not in controls. Male cell lines observation showed that only spermatozoa remained in conditioned oyster. Gametogenesis process appears then to have been stopped or slowed down in conditioned animals. This experiment showed that the techniques allowed to finish the development of already present germinal cells but seemed to put an end to gametogenesis. Further studies will focus on the capacity of P. margaritifera to maintain its gonad activity in captivity.