Post-Zygotic Chromosomal Rearrangements in Rainbow Trout (Salmo irideus Gibbons)

Abstract

Four age groups of the rainbow trout (<i>Salmo irideus</i>) were surveyed in an extensive cytological study. While the basic diploid complement of this species was found to consist of 104 chromosome arms, some elements united and dissociated early in embryonic life; thus within each individual fish, from two to seven distinct chromosome constitutions were identified, ranging from 2n = 58 to 2n = 65. Each somatic cell type tended to have a particular diploid chromosome number. Several multivalents were found in meiotic germ cells of both sexes. The Robertsonian type of chromosomal change which played an important part in the evolution of terrestrial vertebrates is seen within single individuals of this teleost fish.