External morphology of the larva and polytene chromosomes of Thalassomya paraskevae Makarchenko, Semenchenko, Palatov & Lisanovskaya, 2024 (Diptera, Chironomidae: Telmatogetoninae) from the Bulgarian Black Sea Coast

The important larval structures of the chironomid Thalassomya paraskevae Makarchenko, Semenchenko, Palatov & Lisanovskaya, 2024, are described from specimens collected from the Bulgarian Black Sea coast town of Varna. The mandible, premandible, mentum, maxilla, antenna, clypeus and frontal apotome are described in detail. A diagnosis of the larval stage of the species is presented and compared with the closely related species Thalassomya frauenfeldi Schiner. The diploid chromosome set of T. paraskevae is 2n = 6 + B, as determined from an examination of the salivary gland chromosomes. The B chromosome was found in every individual but not in every cell. The B chromosome looks like a 'heteropycnotic' body, which in some cells has a loose structure. A characterization of the polytene chromosomes is presented, and are compared with samples from an earlier study. Low chromosomal polymorphism and two heterozygous inversions were found and the reason for this is discussed.