オンブバッタ集団における常染色体の過剰部分による多型

概要

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Chromosomal variation was examined in a population of Atractomorpha bedeli (2n ♀ = 20 = 18+ XX, 2n♂ = 19 = 18+ X). Sample males and females were collected at Tabira-chyo, Kitamatsuura-gun, Nagasaki Prefecture. The bivalents of the 9th chromosome (the smallest among the complement) showed a block of heterochromatin (proximal segment) and small amount of euchromatin (distal segment) at diplotene of primary spermatocytes. Two types of 9th chromosome were distinguishable, S (segmented) with a supernumerary segent and N (non-segmented) without it. The supernumerary segment was euchromatic. Difference between the two types were the same as that found in a population in Korea (Kayano et al. 1993). The 9th bivalents of heterozygous males (S/N) were distinguishable from homozygous males (N/N) at diplotene and first metaphase (MI) of primary spermatocytes. Of 30 males of the Tabira population 14 were homozygotes (N/N) and 16 were heterozygotes (S/N). A homozygote for the segmented chromosome (S/S) was not found. As far as five follicles were examined for each male, no male was found to have a B chromosome.