TWO POPULATIONS CHROMOSOME POLYMORPHISM OF RAINBOW TROUT, ONCORHYNCHUS MYKISS (WALBAUM) FROM CENTRAL CHILE

Abstract

There are diffcrences in the chromosome polymorphism found in two populations of fish farm and introduced Oncorhynchus mykiss. Diploid numbers corrcspond to 2n - 58 to 2n = 61 and 2n = 60 to 2n = 63 rcspcctivcly. Arm number (NF1 in all individuáis was 104. It was possible to identificó chromosomes by chromosome measurcments. C and AgAsNOR banding. There are correspondences between chromosomic and somatic sex (XX/XY systeml. The distributional pattern of constitutive heterochromatin makes easy to recognize certain homologs. Active DNAr cistrons are located in a small metacentric pair. in correspondence with a secondary constriction. Intraindividual polymorphism was found in 15% of the sampled individuáis.The results suggest that the polymorphism is determined by robertsonian rearrangements berween larger metacentric and telocentric chromosomes. The polymorphism range in the introduced raimbow trout suggest its European origin.