本邦産イタチ属食肉類2種 (ニホンイイズナ及びホンドオコジョ) の比較核型分析

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タイトル別名
  • Comparative Analysis of Karyotypes in the Japanese Mustelids, <I>Mustela nivalis namiyei</I> and <I>M. erminea nippon</I>
  • ホンポウサン イタチゾク ショクニクルイ 2シュ ニホンイイズナ オヨビ ホン

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Chromosomes of two closely related species of mustelids, Mustela nivalis namiyeiandM. erminea nippon, have been studied in detail by means of G-and C-banding techniques. Remarkable dissimilarities in the chromosome constitution as well as in the chromosome numbers were found; the former, the Japanese least weasel, has 38 chromosomes containing six pairs of large metacentrics, and the latter, the Japanese ermine, has 44 chromosomes, lacking such large metacentrics. Of these large metacentrics, five pairs carry large blocks of C-heterochromatin on their short arms. In both species, a conspicuous secondary constriction was detected on the juxtacentromeric region of one of the small acrocentrics; from the AgI-staining this was regarded as a nucleolus organizer region.<BR>On the basis of the chromosome size and arm ratio, all of the ermine's chromosomes could be paired correspondingly with the least weasel's chromosomes, exclusive of the large C-heterochromatin blocks. The total chromosome length (TCL) of the least weasel is estimated to be about 22.4% longer than that of the ermine; nevertheless, the former has fewer chromosomes than the latter by six chromosomes. The discrepancy in the TCL corresponded to the total length of the large C-band blocks (i.e., homogeneously faintly stained G-negative regions) of the least weasel. Based on the statistical analysis on the ratio of the length of the X-chromosome to TCL, the karyological rela-tionship between the two mustelid species studied could be explained by the duplicating growth of C-heterochromatin, translocation and Robertsonian fusion. Probable mecha-nisms of karyotype evolution in the Japanese mustelids are briefly discussed.

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