Revision of the banding sequence pool and new data on chromosomal polymorphism in natural populations of Chironomus agilis Shobanov et Djomin, 1988 (Diptera, Chironomidae)

Quantitative and qualitative analysis of chromosomal polymorphism in 19 natural populations of Ch. agilis had been performed. Most studied populations showed a medium level of chromosomal polymorphism: on average 45±3.0% of specimens are heterozygotes with 0.52±0.01 heterozygotic inversion per larvae. Besides inversions, B-chromosomes were found in two populations. The total number of banding sequences found in banding sequence pool of Ch. agilis is 16. Three banding sequences – p’agiB3, p’agiD3, p’agiF3 – are described for the first time.

Karyotype and COI gene sequence of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the Gydan Peninsula, Russia

The karyotype features and gene COI sequence of Chironomus heteropilicornis Wülker, 1996 from the Gydan Peninsula are presented for the first time. Nine banding sequences were determined, eight of them hpiA2, hpiB1, hpiC1, hpiC2, hpiD1, hpiE1, hpiF3 and hpiG1 were previously known from European, Georgian (South Caucasus) and Siberian populations. One new banding sequence for Ch. heteropilicornis, hpiB2, was found. The hpiA2 banding sequence was found in all individuals, and this is its second finding after the Georgian population (Karmokov 2019). The hpiF3 banding sequence was found only in the homozygous state. Additional B-chromosomes are absent. The genetic distances (K2P) between Ch. heteropilicornis COI gene sequence from Gydan Peninsula and Norway are 1.1­–1.3%, and Georgia – 1.8%, much lower than the commonly accepted threshold of 3% for species of genus Chironomus Meigen, 1803. The phylogenetic tree for COI gene sequences estimated by Bayesian inference showed geographically determined clusters of Norway and Gydan and a separate lineage of the Georgian population of Ch. heteropilicornis. The analysis of karyotype and COI gene sequences shows that the population of Ch. heteropilicornis from the Gydan Peninsula has an intermediate position within the Ch. pilicornis group between Georgian, Yakutian and Norwegian populations. The position of Ch. pilicornis Fabricius, 1787 from Canada and Greenland on the phylogenetic tree is discussed.

Karyotype characteristics, chromosomal polymorphism and gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus

The study presents data on the karyotype characteristics, features of chromosomal polymorphism and the gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus. We found 8 banding sequences in the Caucasian population. Overall, The Caucasian population of the species can be characterized as having a low level of polymorphism. We found one new banding sequence hpiA2 in the banding sequence pool of Ch. heteropilicornis. We observed inversion polymorphism only in the arm F. The dendrogram of genetic distances by Nei criteria (1972) shows a clear separation of the Caucasian population from populations of Siberia. At the same time, the distance between populations of Siberia and the population of South Caucasus (0.379–0.445) almost reach the mean distance (0.474 ± 0.314) between subspecies (Gunderina 2001). Due to this, we can assume that the population of South Caucasus separated from Siberian populations at the level of subspecies. Constructed on data for COI gene sequences the phylogenetic tree estimated by the Bayesian inference shows that the sequences of Ch. heteropilicornis from the South Caucasus form a separate line in the general branch of Ch. heteropilicornis sequences. At the same time, calculated K2P genetic distances between Ch. heteropilicornis sequences from Norway and Caucasus (2.0–2.2%) do not exceed the 3% threshold for the genus Chironomus.

Integrated systematics of the Simuliidae (Diptera): evolutionary relationships of the little-known Palearctic black fly Simulium acrotrichum

Simulium (Simulium) acrotrichum Rubtsov, a black fly from Central Asia, provides a platform for examining the evolutionary relationships of selected species groups in the subgenus Simulium Latreille. The female, male, pupa, and larva of S. acrotrichum are properly associated and morphologically redescribed and illustrated. The banding sequence of the larval polytene chromosomes is compared with that of the Simulium subgeneric standard, from which it differs by nearly 30 fixed rearrangements. Structural and chromosomal features indicate that S. acrotrichum is the sister species of S. flavidum Rubtsov. Simulium acrotrichum can be placed confidently in a group consisting of the S. malyschevi Dorogostaisky, Rubtsov, and Vlasenko and S. reptans (L.) groups, which are part of a larger clade that also includes the S. jenningsi Malloch group. This more inclusive clade is defined chromosomally by a minimum of four fixed inversions, compared with the standard map for the subgenus Simulium. All four inversions are uniquely derived relative to the two selected outgroups, Simulium (Psilozia) vittatum Zetterstedt and Simulium (Boophthora) erythrocephalum (De Geer). The independent monophyly of the S. malyschevi and S. reptans groups, however, cannot be tested without study of additional group members. The problems illustrated by the taxonomic identity and phylogenetic placement of S. acrotrichum argue for an integrated approach to simuliid systematics, drawing from the character stores of morphology, cytology, and molecular biology.

Taxonomy and biology of Simulium clarkei Stone & Snoddy(Diptera: Simuliidae), a poorly known black fly of the southeastern United States

Simulium clarkei Stone & Snoddy was the least known species of black fly in the eastern United States prior to our recent collections from southern Virginia (type locality) to southern Georgia, which yielded good series of all life stages after the egg. On the basis of these collections, we describe the female and the banding patterns of the polytene chromosomes, redescribe the larva, pupa, and male, and provide biological and distributional information. Simulium clarkei most closely resembles S. emarginatum Davies, Peterson, & Wood, but can be distinguished by the banding sequence of its larval polytene chromosomes and the shape of the male ventral plate.

Nanometre scale textures in agate and Beltane opal

We have carried out TEM observations of agates of geode origin and Beltane opals. Optically observable individual fibres in agates are composed of many fine fibres which consist of quartz crystallites of 8 to 100 nm in length stacked together parallel to <110> or <100> with c-axes perpendicular to the fibre elongation. The optically observable systematic striations in agate are found to consist of cyclic alternation of layers due to variation in grain size and porosity. Large quartz crystals, protruding into the spaces of geodes, represent the last stage of formation of these bands, and are merely a continuation of the banding sequence. Nanometre scale textures of cristobalite fibres were revealed in Beltane opals. The cristobalite crystallites have the size of 3 to 20 nm in length and are also stacked together. Our TEM results suggest that embryonic particles were formed in their corresponding growth environments and agglutinated to form fibres.

The polytene chromosomes of Simulium (Ectemnaspis) ignescens Roubaud and the related species Simulium "C," both from Colombia

The paper describes the polytene chromosomes of Simulium (Ectemnaspis) ignescens from Colombia and compares them with those of a sympatric undescribed species designated Simulium "C." The two species share the entire banding sequence of chromosome arms IS, IL, and IIIS. Their IIIL arms differ by a single fixed inversion, but their second chromosomes exhibit multistep arrangement differences that were not completely resolved. The nucleolar organizer of S. ignescens is in the base of IIIS, that of Simulium "C" in the base of IS. Polymorphisms in IIS of S. ignescens exhibit partial sex linkage; no sex differential segments were demonstrated in Simulium "C." Common autosomal polymorphisms of both species involve preferentially chromosome III. Preliminary studies indicate that the chromosome maps of S. ignescens can serve as standards for other neotropical Simulium Latreille species including the important vectors of Onchocerca volvulus and Mansonella ozzardi.

RELATIONSHIPS OF THE POLYTENE CHROMOSOMES OF DROSOPHILA MEDIOSTRIATA AND D. GRISEOLINEATA

Comparisons of the polytene chromosomes of late third instar larvae of Drosophila mediostriata (tripunctata group) and D. griseolineata (guaramunu group) revealed that distinct banding and puffing similarities exist between the species. The most impressive similarities were found to exist between the 3rd mediostriata and the 2nd griseolineata chromosomes; almost the entire length of this element of the former species could be homologized with that of the latter. Two simple inversions could account for the differences in banding sequence for this element if one were to disregard the fact that the griseolineata 2nd chromosome was considerably longer than the mediostriata 3rd.The amount of similarity found between the chromosomes of the species considered here is greater by far than that which can be found when mediostriata is compared to other species of the tripunctata group. It is concluded that the grouping of the species of this section of the phylogenetic tree of Drosophila must be reviewed and possibly revised.