Etude in situ et expérimentale de l'effort de reproduction chez l'huître perlière Pinctada margaritifera
|Auteur(s)||Gangnery Aline1, 2|
|Affiliation(s)||1 : Ifremer, Centre de Tahiti, Polynésie Française|
|Note||Mémoire de fin d'Etudes E.S.I.T.P.A. Stage effectué sous la Responsabilité d'Alain Bodoy|
L'objectif de ce travail est l'estimation de l'effort de reproduction de l'huître perlière Pinctada margaritifera. Pour ce faire, deux expérimentations ont été mises en oeuvre :
|Résumé en anglais||
The aim of this work is to study reproductive effort of the pearl oyster Pinctada margaritifera. In order to reach this objective, two experiences were planned. First, we decidcd to follow in situ growth and reproduction of pearl oysters of three age groups : l, 2 and 3 years old. This projcct began at the end of march 1997 and is planned for one year. The results presented in this study stopped at the end of july 1997. This experience is based on the bimonthly sampling of 120 pearl oysters (40 from every age group) from the lagoon of Takapoto (Tuamotu, French Polynesia). ln a second part, an experience was lead in laboratory, on the same animals. The objective was to trigger artificially spawns and to harvest genital products to estimate values of reproductive effort. The in situ experience has shown an important and synchronous spawn at the end of may, for pearl oysters aged of 2 and 3 years. This observation allowed to estimate a reproductive effort, on the period, for these two age groups : 310 mg for the two years old and 390 mg for the three years old. Any important spawn was observcd, on the period, in one year old, although the sexual maturity is already got because of genital products presence. More generally, the reproductive cycle of Pinctada margaritifera is characterized by many partial and asynchronous spawns, ali along the year. Regressions microscopically observed, in this study, show partial and asynchronous spawns or cellular resorptions without spawn. The laboratory experience allowed to estimate a reproductive effort of the three age groups : 29 mg for the one year old, 105 mg for the two years old and 117 mg for the three years old. The results are underestimated in relation to results obtained by the in situ experience, except for one year old. However, it showed that the one year old have a small reproductive effort in relation to the two other age groups. Moreover, two years old presente a less important reproductive effort than the three years old. Finally, this experience, which was lead about two temperatures (26 and 31 °C), showed no influence of this factor on gametogenesis of the species.