||Boudry Pierre, Leitao Alexandra, McCombie Helen, Thiriot-Quievreux Catherine
||Genetics in Aquaculture VII
||Growth, Genetic, Aneuploidy, Crassostrea gigas, Pacific oysters
||Cytogenetic abnormalities arising both in mitosis and meiosis are known to be common in bivalves. Here we review result obtained from the observations of somatic aneuploidy in different populations of the commercially important Pacific oyster, Crassostrea gigas. The oysters studied were either (1) produced in IFREMER hatcheries between 1986 and 1999, (some of these were part of the EU funded programme GENEPHYS); or (2) collected from wild populations along the French Atlantic coast. Chromosome numbers were scored from 30 mitotic metaphases in gill tissue per individual studied. Aneuploid cells (2n - X) were observed in all the 13 populations studied. A highly significant negative correlation was observed between the level of aneuploidy and growth, i.e. fast growing animals in each population showed less aneuploidy than slow growing animals. In one of these populations, this negative correlation was established at the individual level by comparison of individual growth performances recorded under common controlled conditions. The transmission of aneuploidy, from parents to their progenies, was investigated; but the inheritance of this phenomenon could not be demonstrated. However, a genetic basis, associated with the geographic origin of the parents, was suggested. The study of the aneuploidy level in six full-sib families, showing contrasting growth performances under common controlled conditions, implied a genetic base for the control of aneuploidy and the aneuploidy-growth relationship.