Biodiversity of Family Chironomidae (Diptera) in Srebarna Lake (North-East Bulgaria) and Genome Instability of Some Species from Genus Chironomus Meigen, 1803

The biodiversity of the family Chironomidae, Diptera in Lake Srebarna - a lake of natural origin, a Biosphere Reserve and a Ramsar Site of International Importance was studied. The conducted study revealed high concentrations of phosphates and some heavy metals (Cu, Pb, Zn, Mn, Fe) in the water. High concentrations of heavy metals (Cd, Cu, Pb, Mn) in the sediment were also found. Through the detailed analysis of the external morphology of the larvae and the species- specific cytogenetic markers of the polytene chromosomes of the larvae, we established a total of 16 genera and 11 species. Ten genera and eight species were new to the fauna of the lake. For the first time, we reported malformations in the larvae of some genera Endochironomus, Chironomus and Glyptotendipes (0.84÷2.04%) and species (Endochironomus tendens - 0. 29%). Genomic instability realized through somatic structural chromosomal aberrations in the polytene chromosomes of the four species of the genus Chironomus was found. Based on these aberrations, the Somatic index (S) was calculated (C. nuditasis, S-3.25; C. annularius, S-5.75; C. balatonicus, S-7.5 C. pallidivittatus, S-4.50). In addition, inherited chromosome aberrations have been observed, which were important for the adaptation of species to specific living conditions. The reasons of genomic instability and the importance of Chironomus species for determining the degree of pollution of aquatic ecosystems were discussed.