Comparative Analysis of the Karyotypes and Karyopools of Midges Chironomus nuditarsis and Ch. curabilis (Chironomidae, Diptera)

摘要

Karyoforms formerly revealed for Chironomus nuditarsis were found to belong to different species: karyoform I, to Ch. nuditarsis and karyoform II, to Ch. curabilis. A comparative analysis of these two species is presented. Both of them have 2n = 8, thummi cytocomplex. These two species differ clearly in the amount of the near-centromeric heterochromatin (which is much greater in Ch. curabilis), type of centromere (n-type in Ch. curabilis and s-type in Ch. nuditarsis), localization of the interstitialheterochromatin, and phenotypic pattern of bands in polytene chromosomes (caused by a certain compactness of bands in Ch. curabilis). The total number of chromosomal band sequences (CBS) is 13 in Ch. nuditarsis and 14 in Ch. curabilis, the number of species-specific CBS is 4 and 7, and that of genotypic combinations 17 and 8, respectively. In various parts of Ch. nuditarsis distribution range, certain combinations of fixed CBS were revealed in arms A, B, and G of polythene chromosomes: in Central Europe, ndt Al.l, Bl.l, Gl.l; in eastern Europe, ndt A3.3, Bl.l, G2.2; in southwestern Siberia, ndt A3.3, B2.2, G2.2. In Ch. curabilis, certain combinations of fixed CBS were revealed in arms A and B: in Central European populations, cur A2.2, D2.2 and in eastern European ones, cur Al.l, Bl.l. In the overlapping areas of distribution ranges of these species, fixed CBS in arms A and B were always identical in both species. In Ch. nuditarsis, the chromosome polymorphism by heterozygous paracentric inversions was found in arms A, B, C, and G; in Ch. curabilis, in A, B, D, and F. The number of inversions per individual is up to 0.93 in Ch. nuditarsis and up to 0.63, in Ch. curabilis. Mapping of already known CBS is refined: that of Ch. nuditarsis ndt (AB)l.l, ndt Bl, ndt Cl, ndt El, and ndt Fl and that of Ch. curabilis, cur Al, cur (AB)l.l, curBl, curB2, curEl.