MORPHOLOGICAL DIVERSITY OF CENTROMERE REGIONS IN POLYTENE CHROMOSOMES OF BLACKFLIES
(DIPTERA, SIMULIIDAE)
L. A. Chubareva,1 N. A. Petrova,1 E. A. Kachvoryan 2
1 Zoological Institute RAS, St. Petersburg, Russia 199034, and 2 Molecular Biology Institute, National Academy of Sciences,
Yerevan, Armenia 375014
Karyotypes of more than 120 species of 33 genera of the Palearctic blackflies (Simuliidae) were studied on squashed acetoorcein stained preparations
of salivary gland polytene chromosomes in larvae. In the course of evolution of the family, a significant complication was noticed in the morphology of centromere
regions of polytene chromosomes. In plesiomorphic species, centromeres are not pronounced morphologically and the general picture does not differ from that of
other bands and interbands of the polytene chromosome. In species with apomorphic characters, a distinct precentromeric heterochromatin appears, whose
manifestation is responsible for morphological diversity of centromere zones in polytene chromosomes. They are represented either by conspicuous slightly
thickened heterochromatic bands or by large amplified blocks of heterochromatin or puff-like structure, being considerably extended as a result of despiralization
of precentromeric heterochromatin. There are species, which more commonly lack chromocentre and their chromosomes are separated. Some other species have
ectopic contacts between pricentromeric heterochromatin. In some species, this heterochromatin is organized as a compact chromocentre. This has been found
only in representatives of southern latitudes, most frequently in evolutionarily young species with narrow specialization.
Key words: Palearctic blackflies, polytene chromosomes, centromere zones
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