Intraindividual chromosomal polymorphism in green sunfish (Lepomis cyanellus) as evidence of somatic segregation

Cyprininae phylogeny revealed independent origins of the Tibetan Plateau endemic polyploid cyprinids and their diversifications related to the Neogene uplift of the plateau

Origin and diversification of the Tibetan polyploid cyprinids (schizothoracins) may help us to explore relationships between diversification of the cyprinids and the Tibetan Plateau uplift. Cyprininae phylogeny was analyzed using mitochondrial and nuclear DNA sequences to trace origins of polyploidy and diversifications of schizothoracins. Ancestral states reconstruction for ploidy levels indicated that the Cyprininae was diploid origin and the schizothoracin clades tetraploid origins. There were two diversification rate shifts along with diversification of the cyprinine fishes in response to the Tibetan uplift. The unusual diversification shifts were located to branches subtending the clades of Tibetan polyploid cyprinids. Our analyses suggested that (i) phylogeny of Cyprininae recovered two independent origins of the Tibetan polyploidy schizothoracins; (ii) diversifications of the schizothoracins were closely related to the Neogene uplift of the Tibetan plateau in the following ways: the relatively ancient Late Oligocene-Middle Miocene adaptive radiation may be associated with the uplift of the southern Tibet and Himalaya; the Middle Miocene-Early Pleistocene lineage-specific diversification broadly coincident with major phase of the Neogene Tibetan uplift; and the most recent Pleistocene diversification shift in Schizothorax closely coincident with the successive Kunlun-Huanghe and Gonghe movements of the Tibetan uplift and the glaciation-induced climate oscillations on the plateau.

Chromosome polymorphism in the rainbow trout (Salmo gairdneri Richardson)

Chromosome preparations from lymphocyte cultures of 50 rainbow trout were studied. Diploid chromosome numbers of 59, 60, 61, 62 and 63 were found in different individuals in which the arm number (NF) was 104. Intraindividual polymorphism was found at a low level in 25 of the fish. The results suggest that numerous chromosome polymorphisms exist in rainbow trout.

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.