Karyologische Notizen. I.: Über generative Polyploidie bei Dermapteren

Abstract

Some spp. of Dermaptera show an aberrant no. of sex chromosomes. The males of Forficula auricularia have, besides the Y-chromosome, 1 or 2 X-chromosomes; the females have 2, 3, or 4 X-chromosomes. The males of 2 spp. of Anisolabis also have XXY, the females XXXX. The auth. suggests that Callan''s explanation of these abnormal numerical relations be replaced by the hypothesis that they are caused by polyploidy. Of the 8 spp. of Dermaptera known cytologically, 3 have a low haploid no. of chromosomes (5 or 6 autosomes + X or Y), while the other 5 spp. have a high haploid no. of chromosomes (11 autosomes + X, XX, or Y). According to the author''s hypothesis the low-no. spp. are diploid, the high-no. spp. tetraploid. Muller''s arguments against the occurrence of tetraploidy in animals explain only its rarity, but do not exclude it. The condition for the maintenance of tetraploidy is that the males form only XX and YY gametes and no XY gametes; this would occur most easily by the fusion of the 2 Y-chromosomes, which would explain the descr. phenomena. While the proof of polyploidy in spp. with low no. of chromosomes is very difficult, the auth. sees confirmation of his views in the results of studies on Apterygida albipennis and (?) Anechura bipunctata. The former has 24 or 23 chromosomes in the male, and is interpreted as tetraploid; but the latter has 38 chromosomes in the male, including 3 X-chromosomes and a single Y-chromosome, and is considered to be hexaploid.