Chromosome cytology and polymorphism in the California High Sierra golden trout (Salmo aguabonita).

The population variability in chromosome karyotype was examined in six samples of California High Sierra golden trout, Salmo aguabonita. From the analysis of 1,318 cells from anterior kidney tissue of 92 specimens, the modal diploid chromosome number was 2n equals 58 with 104 chromosome arms. Of cells with 2n equals 58 chromosomes, the typical karyotype was one containing 44 chromosomes with median centromeres, 2 chromosomes with submedian centromeres, 2 with subterminal centromeres and 10 with terminal centromeres. In addition, many cells contained a chromosome with a prominent satellite. Variability in chromosome number within the six populations followed a Robertsonian pattern and permitted the identification of two distinct population distributions. One population, made up of two samples, was more variable than the other and supported the hypothesis that this population was of golden trout times rainbow trout hybrid origin. Texamination of metaphase 1 cells from testes showed numerous ring and rod multivalents consistent with the random nature of Robertsonian variability.