Long-term retainment of some chromosomal inversions in a local population of Belgica antarctica Jacobs (Diptera, Chironomidae)

Abstract

Genome of antarctic endemic Belgica antarctica Jacobs has been sequenced. However, no set of inversion diagnostic markers has ever been assigned for the species. Using the classical method of polytene chromosome squash preparation, we found three heterozygous inversions located on the second (two heterozygous inversions) and third chromosomes (one heterozygous inversion) in the Belgica antarctica population of a cape of Wiencke Island, 500 m to SW from Port Lockroy. The chromosome set and chromosome variability did not differ from those described in the literature (Atchley and Davis 1979). Every salivary gland chromosome had its own markers by which it can be determined. However, we did not find a sex-linked inversion on chromosome III and heterozygous inversion on chromosome I, reported in earlier studies. For the first time, we observed a strong heterochromatin band in chromosome III at the telomere of one arm. Our data show not only the stability of the described inversions in the population but also the usefulness of the squash preparation technique in the studies of genetic variability of Belgica antarctica in present time.

External Morphology of Larvae of Belgica antarctica Jacobs, 1900 (Diptera, Chironomidae) Obtained from Two Locations in Maritime Antarctica

“…Larvae were collected in February 2020 during the 25th Ukrainian Antarctic expedition. All specimens were preserved in 3:1 ethanol-acetic acid fixative for cytogenetic analysis [18]. The samples were held at −20 • C and transported to Ukraine.…”

A chromosome map of Belgica antarctica Jacobs (Diptera: Chironomidae) from Antarctica, including chromosome variability

“…However, the inversion reported in chromosome I and the sex-linked inversion in chromosome III were not detected. Michailova et al (2021) also first noted the presence of a dark band in chromosomes in a few cells. However, they only examined а small sample of B. antarctica individuals from a single location.…”

“…In such cases, cytological studies of polytene chromosomes provide a useful tool. Although the B. antarctica genome has been sequenced (Kelley et al 2014), a set of diagnostic indel markers has yet to be determined (Michailova et al 2021). Martin (1962) described the presence of inversions in two of the three chromosomes of B. antarctica: an inversion in chromosome III and a large inversion in chromosome I.…”

“…In addition, we analysed chromosomal variability in sample material collected from two separate locations on Galindez Island (Argentine Islands, western coast of the Antarctic Peninsula). We also performed a comparative chromosomal analysis of material obtained from these two locations and, using statistical analyses, identified differences in the occurrence of common chromosomal abnormalities of the populations present at these sampling locations and others reported by Martin (1962), Atchley & Davis (1979) and Michailova et al (2021).…”

Unsupervised learning for detection of possible sexual dimorphism in larvae of Belgica antarctica Jacobs (Diptera, Chironomidae)

“…Belgica antarctica Jacobs (Diptera: Chironomidae) is a wingless insect with complete metamorphosis from the Orthocladiinae subfamily endemic to the western shore of the Antarctic Peninsula (Usher and Edwards 1984, Convey and Block 1996, Kovalenko et al 2021, Kozeretska et al 2022. In recent years, this midge has been studied actively in numerous research on its genomic, phylogenetic, physiological, biochemical, ecological, and life cycle features (e.g., Benoit et al 2009, Allegrucci et al 2012, Harada et al 2014, Kelley et al 2014, Kawarasaki et al 2019, Finch et al 2020, Potts et al 2020, Ajayi et al 2021, Michailova et al 2021a, Spacht et al 2021, Yoshida et al 2021). In addition, recently, Michailova et al (2021b) described the external morphology of the 4 th instar larvae of this species.…”