Chromosome-Number Variations in the Rainbow Trout (Salmo Gairdnerii Irideus (Gibbons))

The somatic chromosomes of the rainbow trout from two localities of Hokkaido are studied by the routine air-drying method. One of six specimens studied has 58 chromosomes consisting of 23 pairs of meta- and submetacentrics, one pair of subtelocentric and 5 pairs of telocentric chromosomes. The remaining five specimens show a basic number, 2n, 60. The arm number of both groups is 104, and this seems to indicate polymorphism resulted from the Robertsonian system.