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 plumosus (Linnaeus) The chromosome set is 2n = 8. Two chromosomes AB and CD are metacentric, EF—submetacentric and G chromosome is telocentric. The centromere regions of all chromosomes are distinct ( Fig. 11 ). The arm A is with inverted sequences (A2.2). The species has four BRs—three in chromosome G and one in chromosome arm B. The homologues of chromosome G are unpaired. The NOR of chromosome G is near to the centromere region. Between the BR , located near to the NOR and the other BR there is a narrowing of the chromosome and many dark and light bands ( Fig. 11 )—markers of the species. The species is highly polymorphous, characterized by the presence of a polymorphous system of inversions which involved the transition of a standard homozygous type of the karyotype through heterozygotization into another homozygous type ( Michailova 2014 ). This author reported for an additional B chromosome in Bulgarian populations ( Fig. 11 ). Four hundred and two individuals were studied . Collection sites : Sofia : Pancharevo Lake , Russe —fish pool Mechka, Burgas — Atanasovsko Lake , Durankulak Lake , Balchik—temporary water basin .