Possibilities of the sexual selection at the young stage of the Salmonid fishes - I. Sex chromosomes in the kokanee salmon Oncorhynchus nerka.

Abstract

The precise constitution of chromosomes from the young kokanee salmon Oncorhynchus nerka was stably obtained by means of the short-term (for 4-7 days) fin cultures. All ten females have 58 diploid chromosomes set consisting of 46 meta- (M) and submetacentrics (SM), and 12 acrocentrics (A), while all ten males have 57 chromosomes (2n) consisting of 47M and SM, and 10 A. The male always has one less chromosome than the female but both sexes have the same NF (nombre fondamental), 104. These results strongly indicate that the male has the X1X2-Y, while the female has the X1X1-X2X2 in sex chromosome complexes. This fact would make it possible to select males and females at the young stage of the kokanee salmon without sacrifice of the materials.