The Response of Genome of the Chironomidae (Diptera) to Heavy Metal Pollution in Two Rivers of Southern Poland

The effects of heavy metals pollution in two Polish rivers on the genome of phylogenetically distant species of the family Chironomidae were studied. The concentrations of Pb, Zn and Cd in the channel sediments of Chechło and Biała Przemsza Rivers were many times higher than reference data, as a result of over 50 years of the lead and zinc ores extraction. In the studied species Prodiamesa olivacea Meigen, P. bureschi Michailova, Chironomus riparius Meigen and C. annularius Meigen, genome instability was evaluated by somatic and inherited chromosome aberrations. On the basis of somatic alterations, the somatic index (S) has been calculated and demonstrated highest value in the genus Chironomus (S = 2 in C. annularius). This index is a good biomarker for assessing the genotoxic effect of contaminants in the sediments. Cells with aberrations in P. olivacea were significantly higher than those in P. bureschi (G=7.381, P<0.01). Different types of ectopic conjugations between chromosome arms appeared with very high frequency in P. bureschi (61.15%) and P. olivacea (81.95%) but in Chironomus spp. occurred in single cells only (about 3%). The mouthpart deformities were detected with highest frequency in P. olivacea (26.9%). The results showed that the species of different genera have a species-specific genome reaction to stress agents in the environment. The data obtained support the idea that these species can be useful in biomonitoring studies in aquatic ecosystems.