Markers in the polytene chromosomes of freshwater Chironomus Meigen (Diptera, Chironomidae) species Author Michailova, Paraskeva text Zootaxa 2024 2024-05-22 5453 4 511 537 http://dx.doi.org/10.11646/zootaxa.5360.3.8 journal article 10.11646/zootaxa.5453.4.3 1175-5326 11239735 B535A3FF-151C-4070-9BE7-2FE6E3238847 Chironomus bernensis Klȍtzli Chromosome set is 2n = 8. Chromosomes AD, BC are metacentric, chromosome EF—submetacentric, chromosome G—telocentric ( Fig. 21 ). The centromere regions of the chromosomes are the dark thin bands. Chromosome arms A and E have NORs—a marker of the species. There is slightly expressed BR in chromosome arm B. Another marker of the species is the ectopic pairing between different chromosome arms. The chromosome arm F with inverted sequences (F2.2). No NOR in chromosome G, and only one BR. The homologues of chromosome G are pared except for a small section near to the centromeric region. A marker of the species is the narrowing in the middle of chromosome G, on both sides of which there are two dark bands, between which several lighter and dark ones ( Fig. 21 ). The polytene chromosomes of C. bernensis are very sensitive to pollutants and numerous somatic chromosome alterations were identified ( Michailova et al . 2016 ). These authors found for first time an additional B chromosome in a species from a polluted region. Kiknadze et al (2016) reported for different heterozygous inversions in all chromosome arms. Seventy-three larvae were analyzed. Collection sites : Plovdiv : Mariza River , Chaj River , Dimitrovgrad: Banskra River .