Evidence of differential chromosome loss in aneuploid karyotypes of the Pacific oyster, Crassostrea gigas

The G-banding technique was performed on aneuploid karyotypes from gill tis sue of the Pacific oyster, Crassostrea gigas, to assess whether chromosome losses could be explained by differential chromosomal susceptibility and to clarify the negative correlation between aneuploidy and growth rate previo usly reported in different populations of this oyster. The study of 95 G-ba nded aneuploid karyotypes showed that only 4 of the 10 chromosome pairs (vi z. 1, 5, 9, and 10) of C. gigas were affected by the loss of one homologous chromosome. Pairs 1, 9, and 10, which were lost in 56, 33, and 44% of case s, respectively, may be considered to be differentially affected. Hypothese s on this differential chromosomal susceptibility are discussed.