The karyotypic characteristics and chromosome polymorphism of three species of blood-feeding flies (Simuliidae, Diptera) inhabiting the Kola Peninsula and the Baikal Region

Karyotypes of three species of black flies inhabiting the Kola Peninsula and the Baikal Region--Schoenbaueria pusilla, Gnus rostratum and G. decimatum--have been first described. The diploid number of these species is 2n = 6. The main identification signs of all chromosomes of the set were revealed and a high level of polymorphism in heterozygote inversions was found out. The detected heterozygote inversions are irregulary located in chromosomes, which is interpreted as an effective mechanism of populations highly adapted to different ecological conditions.     

Triploidy in populations of three species of black flies of the genus Prosimulium roubaud (Diptera, Simuliidae)]

Karyotypes of 94 larvae belonging to species of black flies of the genus Prosimulium Rouband were studied on aceto-orcein stained squashes of 94 larvae belonging to three species of Prosimulium: P. isos Rubzov, P. pecticrassum Rubzov, and P. pamiricum Chubareva et Petrova. All the larvae appeared to be triploid parthenogenetic females, with no males being found. The structural peculiarities of these polytene chromosomes suggest a heterozygous nature of the examined larvae.     

Photographic map of the polytene chromosomes of Cochliomyia hominivorax

Abstract.  Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) is one of the most important myiasis-causing flies and is responsible for severe economic losses to the livestock industry throughout the Neotropical region. A polytene chromosome map is an invaluable tool for the genetic analysis and manipulation of any species because it allows the integration of physical and genetic maps. Cochliomyia hominivorax has a diploid number of 12 chromosomes (2 n  = 12): five pairs of autosomes and one pair of sex chromosomes (XX/XY), which do not polytenize. We created a new photomap of the polytene chromosomes of C. hominivorax describing its five autosomes (chromosomes 2–6). Pupal trichogen cells, which have chromosomes with a high degree of polytenization, were used to elaborate this map. The photomap was made by comparing 20 different nuclei and choosing, for each chromosome segment, the region with the highest resolution. Thus, we present a new photomap of the five autosomes of this species, with a total resolution of 1450 bands.     

Karyotype structure in species of Propsilocerus genus (Diptera, Chironomidae)

Karyotype structure and polytene chromosome banding patterns were studied in two Orthocladiinae siblings--Propsilocerus akamusi (China) and Propsilocerus jacuticus (Russia). Both species have haploid number of chromosome typical for Orthocladiinae (n = 3). An unusual structure of centromeric regions was observed in all three chromosomes of karyotypes in both species. Photomaps of polytene chromosomes are presented. A comparison of karyotypes of P. akamusi and Propsilocerus jacuticus revealed a high level of homology in their banding sequences, however, the presence of fixed paracentric inversions in chromosomal arms IR, IIR, IIIR of Propsilocerus jacuticus has shown a clear-cut phylogenetic divergence. No chromosomal polymorphism was found in both species.     

Cytotaxonomic characteristics of the genus Glyptotendipes Kieffer (Chironomidae, Diptera) from fish and retention ponds (Silesia, southern Poland)

The cytotaxonomic characteristics of species of the genus Glyptotendipes (Chironomidae): G. glaucus Meigen, G. paripes Edwards, and G. barbipes (Staeger) are described. The studied material was collected from a fish pond at Go?ysz and a sewage retention pond at Chybie in Silesia. All the studied species have the chromosome set 2n = 8, but with many specific structural and functional changes. The cytogenetic data of G. glaucus showed that the studied specimens of this species have been produced by the introgressive hybridization of two sibling species: G. glaucus x G. pallens, and subsequent crossing-over in the hybrid chromosome CD. Owing to this process, the band pattern of chromosome arm D coincided with those of G. pallens. New aberrations (homo- and heterozygous deletions in arm G as well as heterozygous inversions in chromosome arm B) were detected in G. glaucus. Specific band sequences were discovered in chromosomes of G. paripes. The band patterns established in chromosomes AB and G of this species were identical with those of Siberian populations. The banding patterns of the polytene chromosomes of G. barbipes do not differ from the standard. However, high frequency of pericentric inversion of chromosome AB was established. Many new puffs were found in the polytene chromosomes of all the studied species. Their nucleolar organizer was very sensitive to environmental changes. In G. glaucus it appeared in three different states: very active, slightly active, and heterozygous state. The organic pollution existing in the sewage retention pond may contribute to possible mutations and chromosomal damage in Glypotendipes species. Structural and functional rearrangements of the polytene chromosomes of these species mobilized their genomes and provide for survival under polluted conditions.     

Global diversity of black flies (Diptera: Simuliidae) in freshwater

Black flies are a worldwide family of nematocerous Diptera whose immature stages are confined to running waters. They are key organisms in both aquatic and terrestrial ecosystems, but are perhaps best known for the bloodsucking habits of adult females. Attacks by black flies are responsible for reduced tourism, deaths in wild and domestic birds and mammals, and transmission of parasitic diseases to hosts, including humans. About 2,000 nominal species are currently recognized; however, certain geographical regions remain inadequately surveyed. Furthermore, studies of the giant polytene chromosomes of larvae reveal that many morphologically recognized species actually consist of two or more structurally indistinguishable (yet reproductively isolated) sibling species. Calculations derived from the best-known regional fauna—the Nearctic Region—reveal that the actual number of World black fly species exceeds 3,000. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Banding Pattern of Polytene Chromosomes as a Representation of Universal Principles of Chromatin Organization into Topological Domains

Drosophila polytene chromosomes are widely used as a model of eukaryotic interphase chromosomes. The most noticeable feature of polytene chromosome is transverse banding associated with alternation of dense stripes (dark or black bands) and light diffuse areas that encompass alternating less compact gray bands and interbands visible with an electron microscope. In recent years, several approaches have been developed to predict location of morphological structures of polytene chromosomes based on the distribution of proteins on the molecular map of Drosophila genome. Comparison of these structures with the results of analysis of the three-dimensional chromatin organization by the Hi-C method indicates that the morphology of polytene chromosomes represents direct visualization of the interphase nucleus spatial organization into topological domains. Compact black bands correspond to the extended topological domains of inactive chromatin, while interbands are the barriers between the adjacent domains. Here, we discuss the prospects of using polytene chromosomes to study mechanisms of spatial organization of interphase chromosomes, as well as their dynamics and evolution.     

兴义维蚋多线染色体研究（英文）

首次在国内对兴义维蚋Simulium (Wilhelmia) xingyiense的多线染色体进行研究, 并提供其多线染色体标准图。选取兴义维蚋的成熟幼虫, 用改良苯酚品红染色法进行唾腺多线染色体制备, 并进行测量、 描述及分析。结果表明： 兴义维蚋多线染色体数目为3对（2n=6）。Ⅰ号染色体具中央着丝粒, Ⅱ和Ⅲ号染色体均为亚中央着丝粒染色体。核仁组织者区位于Ⅰ号染色体短臂近着丝粒端。巴尔比尼氏环和双泡位于Ⅱ号染色体短臂近中央位置。3对染色体的着丝粒区可形成明显的染色中心。兴义维蚋多线染色体具有多态性的倒位, 倒位频率为0.64。兴义维蚋多线染色体的着丝粒、 核仁组织区、 巴氏环、 双泡等主要特征性结构的位置及形态恒定一致,可作为该种的重要鉴别特征。其多态性的倒位可为该蚋种在细胞水平上进行蚋类分类鉴别和系统发育等研究提供基础资料。     

Homology of Balbiani Ring DNA in two closely related Chironomus species

Cytogenetic analysis indicates that Balbiani Ring 2 (BR 2) in the two sibling species Chironomus tentans and Chironomus pallidivittatus arises from identifically banded segments in the salivary gland polytene chromosomes, although chromosomal rearrangements have occurred. In situ hybridization of BR 2 RNA to the polytene chromosomes of each individual species, as well as their F1 hybrids, reveals that the repetitious BR 2 DNA in the two species has, within the limits of the technique, retained identity of nucleotide sequences and degree of repetition. The DNA of the naturally expressed BR 1 and BR 3 in both species and that ot the galactose induced BR 6 in C. pallidivittatus did not hybridize with BR 2 RNA, indicating that these BR's are different from BR 2 with regard to sequence content.     

Karyotype and morphology of Chironomus anthracinus Zett. (Diptera, Chironomidae) from eastern Kazakhstan

Larval morphology and polytene chromosomes of Chironomus anthracinus from eastern Kazakhstan have been described. Larvae have no lateral tubules on VII abdominal segment, but have paired ventral tubules on VIII abdominal segment. 2 n = 8 (A1.1 B1.1 C2.2 D1.1 E1.1 F1.1 G1.1). Two nucleoli are present in arms IVG and IIIF. Mapping of chromosomes, apart from antC2 arm, was performed after Shobanov (1996). B-chromosomes have been discovered in this species for the first time (in 19.4% individuals). Heterozygous inversions occurred in arms LA and IIIE in 46% of individuals. Compared to C. anthracinus from Yaroslavl Region, differences in morphology and karyology observed in this species from eastern Kazakhstan are related to habitation of the population examined in the deep-water Lake Markakol on the boundary of the area range.     

Morphological diversity of centromere regions in polytene chromosomes of blackflies (Diptera, Simulidae)

Karyotypes of more than 120 species of 33 genera of the Palearctic blackflies (Simuliidae) were studied on squashed acetoorcein stained preparations of salivary gland polytene chromosomes in larvae. In the course of evolution of the family, a significant complication was noticed in the morphology of centromere regions of polytene chromosomes. In plesiomorphic species, centromeres are not pronounced morphologically and the general picture does not differ from that of other bands and interbands of the polytene chromosome. In species with apomorphic characters, a distinct precentromeric heterochromatin appears, whose manifestation is responsible for morphological diversity of centromere zones in polytene chromosomes. They are represented either by conspicuous slightly thickened heterochromatic bands or by large amplified blocks of heterochromatin or puff-like structure, being considerably extended as a result of despiralization of precentromeric heterochromatin. There are species, which more commonly lack chromocentre and their chromosomes are separated. Some other species have ectopic contacts between pricentromeric heterochromatin. In some species, this heterochromatin is organized as a compact chromocentre. This has been found only in representatives of southern latitudes, most frequently in evolutionarily young species with narrow specialization.     

Chromosomal evolution of the Hawaiian Telmatogeton (Chironomidae,Diptera)

It is only in the Hawaiian Islands that species of the otherwise marine genus Telmatogeton have evolved into freshwater. An analysis of polytene chromosomes and karyotypes of two marine species and five freshwater species revealed that paracentric inversions and centric fusions were important in chromosomal evolution. The sequence of polytene chromosome bands common to most species, established as the Telmatogeton standard sequence, is found in a population of T. torrenticola from West Maui. Most species and other populations of T. torrenticola may be derived from the standard sequence by paracentric inversions. Similarities with the standard band sequence places T. japonicus (n=7) rather than T. pacificus (n=4) in the proposed phylogeny as the species closest to the marine ancestor of the freshwater species. One of three species (T. fluviatilis from Oahu, T. torrenticola from West Maui, or an undescribed species from East Maui), each with seven pairs of chromosomes is considered to be closest to the original freshwater species. T. torrenticola is a complex species in which there is an accumulation of fixed inversions and centric fusions in stepwise fashion in populations from west to east (West Maui n=7; East Maui n=6; Kohala Mountains n=5 and Mauna Kea n=4 both from the island of Hawaii). The population of T. torrenticola from Molokai has a reduced chromosome number (n=4) and fixed inversions. T. abnormis and T. hirtus, the only species which exhibit differentiated sex chromosomes, may be derived from the standard sequency by paracentric inversions. T. abnormis (n=4) has a simple XY system and T. hirtus (n=3/4) has a complex XY₁Y₂ system. Unique sequences of bands, differences in staining intensity of puffs and bands, and an inversion form the basis for the differentiation of the various Y-chromosomes in these species.     

Behavior of polytene chromosomes of rhynchosciara angelae at different stages of larval development

Summary Polytene chromosomes in cells of salivary gland, Malpighian tubules and intestine of Rhynchosciara angelae are very favorable for study. The polytene chromosomes of the salivary gland are among the largest available for cytogenetics work. The ones in Malpighian tubules and in some parts of the intestine are as large and as favorable for cytological studies as the salivary chromosomes of many species of Drosophila.Two additional characteristics of Rhynchosciara make these flies excellent material for studies on the development of polytene chromosomes. 1.It is possible to observe the banding pattern of the polytene chromosomes at many stages of the larval life for at least 30 days before pupation, and 2. since the gregarious larvae develop simultaneously, one can sample the group at any stage desired. Sampling the group every day, it is possible to follow the development of the chromosomes as though one studied a single individual by observing it every day.We have followed in detail the behavior of the bands in two sections of chromosome B and in one section of chromosome C, at different stages of larval development. Some regions of the chromosomes which are represented by typical euchromatic bands at one stage of the larval development may develop in enormous bulbs, and later on may return to the banded stage again.The formation of the bulbs is not uniform in different sections of the same or of different chromosomes. In section 2 of chromosome B a certain locus swells enormously and then develops an enormous bulb, and later returns to the banded stage. At the point where the bulb was formed there is an accumulation of DNA, in amounts probably several times greater than before the bulb formation. In section 3 of chromosome B and section 3 of chromosome C the extra accumulation of DNA preceeds the formation of the bulb and is maintained during and after it. In the bulb formed in section 3 of chromosome C a single band seems to be responsible for the process.As shown by several authors, experimental evidence suggests that a gene is located within a band. The bulb formation in polytene chromosomes may then be morphological evidence of gene activities. This type of bulb formations and of return to the banded stage is a property of many chromosomes bands, during larval development. This type of behavior of many bands in polytene chromosomes is related to the process of nucleolus formation. However, this behavior may be found in almost all (if not in all) bands of the polytene chromosomes. If so, the behavior of the nucleolus organizer region is only a special case of this general process.The accumulation of DNA in different parts of the chromosome in cells of the same or of different tissues may be an argument against the theory of the constancy of the amount of DNA in all cells of a species. The bulb formations is not peculiar to R. angelae but occurs in several other Diptera.     

Amplification of subtelomeric sequences in "long" telomers of Drosophila melanogaster polytene chromosomes

Drosophila melanogaster heat-resistant stock T32 is characterized by additional chromatin in the telomeres of the X and 2L chromosomes. Moreover, elevated (32 degrees C) temperature provokes high instability in the telomere morphology, so that sublines can be obtained which have additional chromatin in different chromosomes. Morphological patterns of telomeres in each subline are stable, if flies are kept at 23 degrees C. It was demonstrated using this model that additional chromatin in the "long" telomeres hybridizes actively with 3H-labelled telomere-associated Dm665 probe. The "short" telomeres show far weaker hybridization, if any, with Dm665. This means that morphological changes in the telomeres of polytene chromosomes result from different degree amplification of the telomere-associated sequences.     

Isolation of a genomic clone for Drosophila sn-glycerol-3-phosphate dehydrogenase using synthetic oligonucleotides

A genomic clone containing Drosophila sn-glycerol-3-phosphate dehydrogenase sequences has been isolated using a mixture of synthetic tridecanucleotides as a hybridization probe. The clone as well as the synthetic probe mixture was found to hybridize to an abundant poly(A)+ RNA of 1700 bases. A partial DNA sequence obtained for a 40-amino acid region containing the oligonucleotide hybridization site was found to agree with the known Drosophila protein sequence data for this region of the protein. In situ hybridization of this clone to the polytene chromosomes of wild type flies and flies bearing chromosomal aberrations that delimit the Gpdh+ locus have allowed us to decisively place the gene in the distal region of 26A on the left arm of the second chromosome.     

柑桔始叶螨与柑桔全爪螨染色体制备方法与核型探讨

采用一种新的染色体制备方法,成功地制备和观察了柑桔始叶螨和柑桔全爪螨的中期染色体。柑桔始叶螨的核型n=4、2n=8,柑桔全爪螨的核型n=3、2n=6或n=4、2n=8。C显带与扫描电镜结果显示,柑桔始叶螨与柑桔全爪螨为全着丝粒染色体,并存在混倍性现象。     

B chromosome polymorphism of blackflies (Diptera, Simuliidae) from the north-western region of Russia

We have studied karyofonds of natural populations and B-chromosome morphology of 8 species of blackflies from the North-Western region of Russia: Odagmia ornata Mg., Hellichiella crassa Rubz., Simulium morsitans Edw., Simulium argyreatum Mg., Shoenbaueria pusilla Fries., Cnetha fontinalis Radzv., Stegopterna duo-decimata Rubz., and Archesimulium tuberosum Lundstr. For this purpose we made slides of squashed blackflies larvae with salivary gland polytene chromosomes stained by aceto-orcein, in addition to similarly stained slides with mitotic chromosomes from gonads and ganglia. Morphology of polytene B-chromosomes of Shoenbaueria pusilla Fries., Cnetha fontinalis Radzv., Stegopterna duodecimata Rubz., and Archesimulium tuberosum Lundstr. has been first described. B-chromosome polymorphism was found in all species, but the number of B chromosomes was conserved within each differences in polytene individual. Stable and distinct interspecific differences in the morphology of polytene B-chromosomes were demonstrated, and these characters are advisable to use to distinguish the species. We have investigated for the first time karyofonds of Od. ornata populations from Arkhangelsk Region (Solovetskie Islands) and Leningrad Region (railway station Sablino), and those of S. argyreatum populations from Murmansk Region (Kandalaksha environs) and Karelia (railway station Chupa). A long term study of Od. ornata and S. argyrestum population from North-Western Russia revealed interspecific and interpopulation dynamics of the occurrence of specimens with B-chromosomes. Some populations showed an increased percentage of individuals with B-chromosomes. It is suggested that B-chromosomes may play a role in adaptation of polulations to severe environmental conditions.