Diploid-tetraploid Complexes in the Genus Cobitis
1976; Japan Academy; Volume: 52; Issue: 8 Linguagem: Inglês
10.2183/pjab1945.52.446
ISSN0021-4280
Autores Tópico(s)Chromosomal and Genetic Variations
ResumoThree species of Cobitid fishes, Cobitis biwae, C. taenia taenia and C. taenia striata, are phenotypically indistinguishable from each other at various levels.The color patterns on body side and lamina circularis of pectral fins have been employed as the major characters for classification.But, the color patterns show considerable aberrations, and the lamina circularis of pectral fins appears only in adult males.Cytogenetic pictures of fishes serve as important tools useful not only for species identification but also for the analysis of their evolutional processes.We wish to present here some karyological features of the genus Cobitis (Cobitidae, Cyprinida), with special regard to the diploid-tetraploid complex.Materials and methods.Kidney tissues were removed, minced with scissors and suspended in fish-BSS.They were treated with colchicine (0.5 Cg/ml) for 30 minutes at room temperature.Following KC1-hypotonization (0.075 M) for 15--30 minutes, and Carnoyfixation as usual, slides were air-dried and Giemsa-stained.Nomenclature of chromosomes was made according to Levan et al. (1964), i.e.: arm ratios up to 1.7 as metacentrics ; those up to 3 as submetacentrics ; those up to 7 as subtelocentrics ; and those over 7 as acrocentrics.Results.(1) Cobitis biwae.Two types of the chromosome number, 48 and 96, were obtained in this species.Specimens collected in the waters of the Kinki district and its adjacent regions, Tottori prefecture and Shimane prefecture belonging to the Chugoku district, the Echi-river, Ado-river, Nabari-river, Ibi-river, Iinashi-river, and Hino-river were characterized by 2n, 48 chromosomes.The karyotype consisted of 10 pairs of metacentrics, 11 pairs of submeta-or subtelo-centrics and 3 pairs of acrocentrics (Fig. 1).Sometimes 1 pair of submetacentrics carried a small satellite on their short arms.On the other hand, tetraploid specimens were found to inhabit in the waters of western Honshu, such as the Yodo-river, Minamiriver, Tonda-river, Yoshino-river, Takahashi-river and Ohta-river.They were characterized by 96 chromosomes which consisted of 16
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