Cytogenetic variability in species of genus Chironomus (Diptera, Chironomidae) from Poland

Chromosome variability was analyzed in three Chironomus species: Chironomus plumosus L., Chironomus muratensis RYSER, SCHOLL & WULKER, and Chironomus annularius MMGEN, from the natural populations in Poland. A comparative analysis of band sequences,with other Palearctic populations was done. Chromosome band sequences of C. plumosus and C. muratensis did not differ from other Palearctic populations. A new homozygous band sequence was discovered in C. annularius. The ten sequences observed in the Polish populations of C. plumosus were represented in all cytogenetically studied European populations of this species. However, these sequences showed substantial interpopulational variation and they didn't demonstrate any geographical gradient. Some of the inversions in C. plumosus and C. annularius were also involved in the function of the so-called polymorphic system. The sensitivity of important chromosome structures (BRs and NOR) in the polytene chromosomes of C. annularius to organic contaminants in the studied area was presented. The morphology of the additional "B" chromosome found in C. plumosus can vary in different salivary gland cells. The existence of the "B" chromosome in the C. plumosus genome was considered in the light of its selective value in the studied area.