Negative correlation between aneuploidy and growth in the Pacific oyster, Crassostrea gigas: ten years of evidence

This study unites previous and new observations that chromosome loss in som atic cells of juveniles of the Pacific oyster Crassostrea gigas is associat ed with reduced growth rate. New data were obtained from four hatchery-prod uced progenies. Within each progeny, oysters of identical age were sampled and classified as fast-growing or slow-growing according to their shell len gth, or live weight. Chromosome numbers were individually scored from 30 ra ndomly chosen metaphases from gill tissue. Although the diploid chromosome number in C. gigas is 2N = 20, hypodiploid cells of 2N = 19, 18 or 17 were observed in all progenies. The difference in percentage of aneuploidy betwe en fast- and slow-growing oysters ranged from 5% to 22% and was highly sign ificant. In one progeny, a highly significant negative correlation (R-2 = 0 .58) was observed between individual level of aneuploidy and growth perform ances individually recorded under common controlled conditions. The consist ency of the negative relationship between growth rate and aneuploidy was ob vious in all populations studied between 1988 and 1999. However, when compa ring aneuploidy between fast- and slow-growing oysters, two different group s of populations can be clearly distinguished. The question remains to dete rmine the cause of these differences. (C) 2001 Elsevier Science B.V. All ri ghts reserved.