Chironomus bernensis Klȍtzli

Michailova, Paraskeva, 2024, Markers in the polytene chromosomes of freshwater Chironomus Meigen (Diptera, Chironomidae) species, Zootaxa 5453 (4), pp. 511-537 : 533

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 .

Figures

FIGURE 21. Polytene chromosomes of Chironomus bernensis. The numbers on the chromosome arms indicate the “basic”sequences.The large arrows show the localization of the centromere region. The small arrow on chromosome G indicates the marker sequences required for species identification. BR—Balbiani Ring, NOR—Nuclear Organizer Region. A, B, C, D, E, F, G—arms of the chromosomes. Scale bar, 10µm.