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.