Meiotic Chromosome Configurations of XY and “XO” Type Males from Four Species of the Genus Chymomyza (Diptera, Drosophilidae) with a Description of the Karyotype of C. rufithorax
2002 年 67 巻 4 号 p. 383-388
詳細
2002 年 67 巻 4 号 p. 383-388
The karyotype of Chymomyza rufithorax, a species belonging to the procnemis species group of the genus Cymomyza (Diptera, Drosophilidae), is the fundamental one of Cymomyza species, consisting of a pair of rods with a proximal constriction (X chromosome), 2 pairs of large metacentric chromosomes, and a pair of dots. In males of this species, the X chromosome does not have a synaptic mate, and the chromosome number is 7. Therefore the male of this species belongs to the “XO” type, which has been reported for only 3 species in the genus Chymomyza. Meiotic chromosome configurations of the “XO” type males from C. rufithorax and C. obscuroides and the XY males from C. pararufithorax and C. costata were described. XY pairing was found in the XY males, but an X chromosome univalent was observed in the “XO” type males. Meiotic pairing configurations of other autosomes in the “XO” males were found to be similar to those in XY males. These data suggest that the Y chromosome or its pairing site might have degenerated or been eliminated from the genome during the course of speciation.
