Effects of temperature and feeding regimes on gametogenesis and larval production in the oyster Crassostrea gigas

J. Chávez-Villalba, J.-C. Cochard, M. Le Pennec, J. Barret, M. Enríquez-Díaz, C. Cáceres-Martínez-2003

Journal of Shellfish Research, 22(3): 721-731

Abstract:

The effect of feeding regimes and temperature on the beginning of gametogenesis in the Pacific oyster Crassostrea gigas (Thunberg) was examined under laboratory conditions. Oysters from two different culture sites in France, Baie des Veys (Department Manche) and La Tremblade (Department Charente-Maritime), were collected in January 2000 and exposed to four treatments, involving a period of maintenance at 10°C with or without feeding followed by a conditioning period at 19°C with or with feeding. Routine conditioning procedures at 19°C (direct conditioning), with or without food, were performed at the same time and were used as controls. Oocyte size was used to describe the evolution of gametogenesis in all treatments. Contrasting responses were noticed between samples from Baie des Veys (BV-oysters) and La Tremblade (LT-oysters). BV-oysters containing more tissue reserves than specimens from the other location used carbohydrates to support gametogenesis, while LT-oysters used proteins to fuel oocyte development. During the initial period at 10°C, fed BV-oysters began gametogenesis and produced mature oocytes, while unfed BV-oysters began gametogenesis, but at a slower rate. Fed LT-oysters began gametogenesis at 10°C, whereas unfed LT-oysters remained unchanged (early gametogenesis stage) during the cold phase and only initiated gametogenesis when the temperature was increased. Oysters conditioned without food produced significantly less oocytes than specimens conditioned with food, but no differences in larval yield (D-larvae) were detected amongst the different conditions and sampling locations. Only LT-oysters kept without food throughout the experiment did not produce oocytes at the end of the conditioning period. These experiments demonstrate that oocyte production in C. gigas is dependent upon food supply and temperature, but that oocyte quality under controlled conditions appears to be related to stored reserves in natural settings.

(Unité Mixte de Recherche (U.M.R.) ventre National de Recherche Scientifique (C.N.R.S.) 6539, Institut Universitaire Européen de la Mer, 29280, Plouzané, France, e-mail: jechavez@cibnor.mx)

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