[The functional morphology of polytene chromosomes in the midge Chironomus pilicornis F. from the permafrost zone reservoirs].

The karyotype and chromosomal polymorphism of Chironomus pilicornis from the reservoirs of Yakutian permafrost zone are described. In the Yakutian populations, of 10 inversion sequences 11 genotypical combinations of these were registered. The level of inversion heterozygosity is 50-70%, but in several populations it makes only 11-29%. In comparison with the Scandinavian populations, significant functional modifications of chromosomal morphology were found. They are associated with the increase in centromeric heterochromatin amount, facultative chromocentre formation, and the appearance of numerous B-chromosomes and nucleoli, including the facultative ones. A possible adaptive significance of such functional modifications conditioned by climate peculiarities is discussed.