Chironomus sp. J – an elusive species from the Chironomusplumosus (Linnaeus, 1758) sibling-species group (Diptera, Chironomidae)

The karyotypes of six African Chironomus species (Chironomus alluaudi Kieffer, 1913, Chironomus transvaalensis Kieffer, 1923, Chironomus sp. Nakuru, Chironomus formosipennis Kieffer, 1908, Chironomus prope pulcher Wiedemann, 1830, Chironomus sp. Kisumu) were investigated; four of these karyotypes were described for the first time (Chironomus sp. Nakuru, Chironomus formosipennis, Chironomus prope pulcher, Chironomus sp. Kisumu). Of the six Chironomus karyotypes, three had “pseudothummi” cytocomplex chromosome arms combinations AE CD BF G (Chironomus alluaudi, Chironomus transvaalensis, Chironomus sp. Nakuru), two had “thummi”cytocomplex arms combinations AB CD EF G (Chironomus formosipennis, Chironomus prope pulcher), and one had “parathummi”armcombinations AC BF DE G (Chironomus sp. Kisumu). Thus, three of the ten main cytocomplexes known were detected in Africa. Detailed photomaps of all chromosome arms, with the exception of arms B and G, were prepared for the karyotypes of Chironomus alluaudi, Chironomus transvaalensis, Chironomus sp. Nakuru, Chironomus prope pulcher; the karyotypes of Chironomus formosipennis, Chironomus sp. Kisumucould only be fragmentarily mapped.Endemic African banding sequences were characteristic for most of the chromosomal arms in all species studied. However, basic sequences, which can be present in different Chironomus species on different continents (Wülker, 1980; Kiknadze et al. 2008), were also detected also in several African species (Chironomus alluaudi, Chironomus sp. Nakuru, and Chironomus formosipennis). The banding sequences of African species studied allow discussion of the derivation of modern banding patterns from hypothetical species, living before separation of cytocomplexes and continents.

Species Chironomussp.propeagilis Kiknadze, Siirin, Filippova et al., 1991 belongs to the Ch.plumosus group of sibling species. It was described on the basis of its karyotype and analysis of isozymes from one population in the Urals but since then no quantitative data on chromosomal polymorphism of this species have been published. The goal of this study is to broaden our knowledge of the chromosomal polymorphism and distribution of the Chironomussp.propeagilis, which, along with the data on chromosomal polymorphism of other species from the Ch.plumosus group, can give us a better understanding of the connection between chromosomal polymorphism and ecological conditions of habitats. The specimens of Chironomussp.propeagilis were found only in 8 natural populations from the Urals, Western Siberia and Kazakhstan, which allows us to conclude that the species range of Chironomussp.propeagilis is not as wide as for most other species from Ch.plumosus group. An analysis of chromosomal polymorphism in these 8 natural populations of Chironomussp.propeagilis has been performed. All of the studied populations were either monomorphic or showed very low level of chromosomal polymorphism, with 4.4-8.7% of heterozygous specimens per population and 0.04-0.08 heterozygotic inversion per larvae. The total number of banding sequences found in the banding sequence pool of Chironomussp.propeagilis is 10. The mapping of banding sequence p'ag2B3 is presented for the first time. Besides inversions, one reciprocal translocation was found in a population from Kazakhstan, B-chromosome was found in one population from the Urals region of Russia, and heterozygosity of the level of expression of Balbiany rings in arm G was observed in several studied populations.

Chromosomal polymorphism has been investigated in 7 natural populations from West Europe, West Siberia and Sakha Republic (Yakutia). The pool of polytene chromosome banding sequences of this species includes 15 banding sequences. The chromosomal polymorphism has been revealed in 5 of chromosomal arms. The most polymorphic is the arm B, there are 4 banding sequences in it. There are 3 banding sequences in the arm A. The arms D, E and G have 2 banding sequences. No chromosome rearrangements have been found in the arms C and F. The populations of Chironomus cingulatus differ clearly in the number and frequencies of banding sequences. This is evidence of that different gene sequences are adaptive in different populations.

Chromosomal polymorphism has been studied in 31 natural populations of Ch.borokensis. For 11 out of 31 populations quantitative analysis of chromosomal polymorphism has been performed. Data from previous publications (10 populations) have also been used to perform an overview of the chromosomal polymorphism of Ch.borokensis and to establish the species range. Most studied populations show a high level of chromosomal polymorphism: on average 66.1 ± 2.6% of specimens were heterozygotes with 1.1 ± 0.6 heterozygotic inversions per larvae. The number of banding sequences found in populations varied from 7 to 18 per population with an average of 12 ± 3. Inversions were found in all chromosomal arms. Besides inversions, B-chromosome was present in 13 populations, and 5 translocations were found. The total number of banding sequences found in banding sequence pool of Ch.borokensis is 40. Twenty six banding sequences are described for the first time for the species.

The karyotype structure and chromosomal polymorphism were studied in several European (European part of Russia and the Netherlands) and Asian (Siberia and Kazakhstan) populations of Chironomus luridus Strenzke, 1959. Inversion poly- morphism was detected in six of the seven chromosome arms: three banding sequences detected in arm A, six sequences in arm B, two sequences in arm C, three sequences in arm E, fi ve sequences in arm F, and two sequences in arm G. Only arm D was mono- morphic in all studied populations. In total, 22 banding sequences were recorded in Ch. luridus; they form the banding sequence pool of this species. Thus, Ch. luridus can be regarded as a very polymorphic species. However, the European and Asian populations differed considerably in the levels of polymorphism: the Asian populations were less polymorphic, containing only 8 to 10 sequences, whereas the European populations had 11 to 16 sequences. The new banding sequences lurA3, lurB5, lurE3 were found in Asian populations, whereas the sequences lurB2, lurB3, lurB4, lurB6, lurE2, lurF1, lurF2a, lurF3, lurF4, and lurG2 аre lacked. The total level of inversion heterozygosity in the Asian populations was 12-25% versus 78-80% in the European populations.

Chromosomal polymorphism in natural populations of Drosophila willistoni from Uruguay and southern Brazil was investigated in order to understand the genetic characteristics and evolutionary potential of these almost geographically marginal populations. The level of chromosomal polymorphism in samples from Uruguay was higher than in those from the southernmost Brazilian state of Rio Grande do Sul. The increase in the polymorphism of these populations, in which the species almost reaches its southern limit, contradicts the low level of paracentric inversion polymorphism expected under the central-marginal chromosomal polymorphism cline previously reported. The high frequency of some inversions and the presence of unique inversions in samples from Uruguay indicate the uniqueness of these populations.

Banding sequences of five chromosomal arms (A, C, D, E, and F), accounting for about 70% of the total genome size in 63 Chironomus species, were used as phylogenetic markers to analyze divergence patterns of the linear genome structure during the evolution. The number of chromosomal breakpoints between the pairs of banding sequences compared served as a measure of divergence. It was demonstrated that the greater the divergence between the species compared, the higher the number of chromosomal breakpoints and the smaller the size of the conserved chromosomal regions. A banding sequences comparison in sibling species demonstrated a lower number of chromosomal breakpoints; the breakpoint number was maximum in a comparison of the banding sequences in the subgenera Chironomus and Camptochironomus. The use of the number of chromosomal breakpoints as a divergence measure provided establishment of phylogenetic relationships between 63 Chironomus species and discrimination of sibling species groups and cytocomplexes on a phylogenetic tree.

The present study, which is one of the longest temporal (two decades) and largest spatial (different parts of India covered) investigations on inversion polymorphism in natural populations of D. ananassae, was undertaken to understand the dynamics of inversion polymorphism in a broad and comprehensive manner. Forty-five natural populations from different ecogeographic regions of the country (covering the regions from Kashmir to Kanniyakumari and Gujarat to Nagaland) were analysed for chromosomal inversions. All the populations show the presence of the three cosmopolitan inversions, frequencies of which vary among the populations analysed. Simple correlations between frequencies of different inversions and regression analysis of inversion frequencies with latitude, longitude and altitude were insignificant. This reinforces the concept of rigid polymorphism in D. ananassae. Genetic divergence (spatial and temporal) at the level of chromosomal polymorphism among natural populations was calculated. Results show spatial divergence but no temporal divergence. Rigid polymorphic systems of D. ananassae did not show long-term directional trends. On the basis of the present study, and after including comparisons with the studies conducted more than two decades ago, the most important conclusion to be drawn is that the three cosmopolitan inversions in D. ananassae segregate within populations at fairly similar frequencies, and the general geographic pattern has remained constant.

Chromosomal polymorphism is described for natural populations of Chironomus pallidivittatus in both the Palearctic and Nearctic regions. The Palearctic populations studied exhibit 24 banding sequences, whereas 10 banding sequences have been recorded from Nearctic C. pallidivittatus. In total, 29 sequences and 37 genotypic combinations have been found. Of the 29 sequences known, only 5 are Holarctic (common to both the Nearctic and Palearctic), 19 are exclusively Palearctic, and 5 are Nearctic. The karyotype of Nearctic C. pallidivittatus is characterized by specific, homozygous Nearctic sequences in arms B and G and fixed Holarctic inversion sequences in the other arms. Only two chromosome arms in C. pallidivittatus, but all seven arms in the sibling species Chironomus tentans, differ between Palearctic and Nearctic forms by the presence of unique, homozygous sequences in the Nearctic karyotype. This indicates a great difference in the cytogenetic histories of these closely related species; much less karyotypic divergence between continents has occurred in C. pallidivittatus than in C. tentans. The cytogenetic distance between Palearctic and Nearctic populations of C. tentans is higher (DN = 1.62) than in C. pallidivittatus (DN = 0.27). Thus, Palearctic and Nearctic C. tentans should be regarded as sibling species, but Palearctic and NearcticC. pallidivittatus are best viewed as strongly divergent races of the same species. A photomap of polytene chromosomes of C. pallidivittatus is presented in which banding sequences are mapped by using C. tentans as a standard.

Twelve natural populations of Drosophila ananassae from India were analysed for chromosome inversions. The chromosomal analysis revealed the presence of all three previously described cosmopolitan inversions in the populations studied. The frequency of inversions and the level of inversion heterozygosity vary significantly among populations. The x2 values calculated to measure the difference in karyotype frequencies between populations demonstrate highly significant variation in most of the cases. To quantify the amount of genetic differentiation at the level of chromosomal polymorphism in these populations, the average genetic identity (I) has been calculated on the basis of frequencies of different gene sequences. The values of I suggest that Indian populations of D. ananassae have undergone considerable amount of genetic divergence at the level of chromosomal polymorphism.

Comparison of polytene chromosome banding sequences and estimation of the degree of chromosomal divergence according to the number of intrachromosomal breakpoints were applied to reconstruct the chromosomal phylogeny in the genus Chironomus. A measure for detecting differences in the banding sequences based on the concept of complexity decomposition (Gusev et al., 2001) was developed. For the first time, a phylogenetic tree based on analysis of the banding sequences in five chromosome arms (A, C, D, E, and F), comprising about 70% bands of the genome, was constructed. The ArmsACDEF tree displayed distinct clusters of banding sequences complying with the species taxonomy (affiliation with groups of sibling species and individual cytocomplexes). These clusters comprised 79% of the sequences studied; the rest 21% appeared unclustered and belonged to the species outside any sibling group. Comparison of the phylogenetic trees for banding sequences based on different set of arms demonstrated a relative independence of banding sequence evolution in individual arms. Distinctness and stability of clusters in the phylogenetic tree increased with the number of arms involved in the analysis. The data obtained demonstrate an essential influence of changes in gene arrangement on species divergence.

Occurrence and clinical manifestations of tick-borne rickettsioses in Western Siberia: First Russian cases of Rickettsia aeschlimannii and Rickettsia slovaca infections

During long time a great interest was revealed to the Romanov breed by many sheep farmers of the world. To preserve and develop the breed, it is necessary to use modern approaches to assess its inbred breed diversity. One of most perspective for population-genetic researches is cytogenetic that allows to investigate the integrity of the chromosomal set and prevent the spread of unwanted genetic abnormalities in the population. The spontaneous chromosomal to aberration have a selective value in a breed formative process, that are fixed in generations. A level of chromosomal polymorphism is additional description of tribal value of animals, that can be taken into account at the selection of animals of wanted type. An analysis of chromosomal polymorphism of sheep is basis for forming of new knowledge about the dynamics of genetic structure in the populations of animals. The cytogenetics of animals collected considerable knowledge about influence of karyotype on the processes of individual development. With the help of cytogenetic studies, changes in chromosomes that are transmitted to offspring, and correspondingly affect the signs of an animal's organism, are detected. The object of the study was the number of sheep of the Romanov breed (n = 10), which are breeding in the breeding farm "Bach and family" (Kyiv region). The material for chromosomal preparations was the blood of sheep aged 1 to 3 years old that was taken from the jugular vein. The cytogenetic study was carried out at the Genetics Laboratory of the Institute of Animal Breeding and Genetics named after M.V.Zubeta (Chubinskoye village) using special techniques and related equipment. To obtain the preparations of chromosomes, samples of the culture of leukocytes of peripheral blood of animals were used. For analysis and photographing, those metaphase plates were selected, in which the chromosomes were separate from each other. On one drug (glass), from one to ten metaphase plates were examined, and to analyze the karyotype, 50 and more metaphase plates were analyzed. Obtained experimental data was processed by the method of variation statistics using the computer programs EXCEL. The results of the cytogenetic analysis of the sheep of the Romanov breed showed that they all have a chromosomal set typical of the domestic breed of sheep. The chromosomal set of investigated sheep is represented by 54 chromosomes, of which 26 pairs of autosomes and one pair of sex chromosomes (XX or XY). The results of the metaphysical analysis allowed to fix a certain part of stable aberrations. Among 457 metaphase plates 81 aberrant cells (17.7%) were identified, of which aneuploid cells – 6.25%, polyploidy – 0.75%, cells with chromosomal ruptures – 0.25%, chromosomal pair fragments frequency – 0.37%, and the frequency of cells with asynchronous divergence of the centromeric regions of the chromosomes (ARTSRH) was 2.5%. Since the frequency of aberrant cells (n = 240) in a small population is 17.7%, this indicates that the detected violations in the chromosomal set of sheep are not accidental in nature and have an heritable basis. Thus, the results of the cytogenetic study of the sheep of the Romanov breed obtained from us show that their karyotypes have a characteristic chromosome set and structure for this species of animals. At the same time, in the studied animals, there is an individual chromosomal variability, which in turn may be associated with their productive or reproductive qualities. This argument is the basis for continuing our research on the chromosomal polymorphism of sheep of Romanov and other breeds.

Structural chromosome changes are widely described in different vertebrate groups and generate genetic, phenotypic and behavioral diversity. During the evolution of loricariids, several rearrangements (fissions, fusions, inversions) seem to have occurred. Hypancistrus, tribe Ancistrini, are highly demanded for fishkeeping around the world. In this tribe, the diploid chromosome number 2n = 52 is considered a synapomorphy, and paracentric-type inversions appear to be involved in the chromosomal evolution of the tribe. The present study investigated the karyotypes of H. zebra and H. cf. debilittera using cytogenetic, classical and molecular tools, as well as DNA barcoding. Data reveal that, although diploid number in both species corroborates the proposed synapomorphy for the tribe, there is a complex karyotype dynamics, reflected in the intense chromosomal polymorphism, resulting from rearrangements involving ribosomal regions (5S and 18S rDNA), which are suggested to be paracentric inversions. Besides, DNA barcode confirms reciprocal monophyletism between the species, validating the existence of two species, only. This scenario, coupled with genomic instability caused by exogenous sequences such as Rex-3 retrotransposons and the species' sedentary lifestyle, which helps the fast polymorphism fixation, may reflect different phenotypic color patterns in natural populations, as observed in H. cf. debilittera.

Elymus diae is an octoploid (2n = 56) littoral species that grows in small isolated populations on the Aegean islands. A striking chromosomal polymorphism was found in twenty plants raised from seeds collected from four natural populations. All four populations had unique satellite and marker chromosome constitutions. Further chromosomal polymorphism was observed among plants originating from one of these populations. There were similarities in the appearance of the satellite chromosomes in E. diae, E. rechingeri and E. striatulus which denotes a close relationship between the three species. This is ascertained by a karyotype analysis of a polyhaploid individual of E. diae. The genome formula J4J4J(4)J(4)J5J5J6J66 or J4J4J(4)J(4)J(1)J(1)J6J66 was suggested for the species. Analysis of the satellite and marker chromosomes in 33 plants raised from seeds obtained in the greenhouse, following open pollination, inferred a predominance of self-fertilization or intrapopulation crosses. Aneuploids were found among plants raised from seeds collected in nature or obtained in the greenhouse. During meiosis, paired chromosomes usually appeared as bivalents and rarely as multivalents. Univalents occurred frequently which might be related to the prevailing chromosomal polymorphism. In the polyhaploid, most of the pollen mother cells had 4–7 bivalents which evidenced the presence of two closely related genomes. During the first pollen mitosis, chromosome numbers of 28 and 27 were observed in octoploid plants, whereas in the polyhaploid there were variable chromosome numbers.