A review of the genus Chironomus (Diptera,Chironomidae)

Analysis of the banding pattern of the salivary gland chromosomes of Chironomus tepperi indicates that, despite a somewhat modified male hypopygium, the relationships of this species are close to the other Australian species of the genus, particularly to Ch. oppositus. No inversion polymorphism has been found in Ch. tepperi and this, together with the relatively high chiasma frequency as measured at metaphase I, would appear to be an adaptation to provide genetic variability necessary for its colonizing ability.     

Chromosomal variability in natural populations of Chironomus cingulatus meigen (Diptera, Chironomidae)

Chromosomal polymorphism has been studied in seven natural populations of Chironomus cingulatus from Western Europe, Western Siberia, and the Republic of Sakha (Yakutia). The banding sequences pool of the species includes 15 banding sequences. Chromosomal polymorphism was revealed in five out of seven chromosomal arms. Arm B is the most polymorphic with four banding sequences. There are three banding sequences in arm A. Arms D, E, and G have two banding sequences. None of the chromosome rearrangements were revealed in arms C and F. The populations of C. cingulatus differ clearly in their number and frequency of banding sequences, which indicates that different gene sequences are adaptive in different populations.     

Succession of Chironomus Meigen Species (Diptera,Chironomidae) in Newly Filled Ponds

The colonization by Chironomus spp. of two ponds filled after a dry period was investigated. Field data were collected by means of quantitative benthic samples and emergence traps. C. melanescens. C. annularius, C. riparius, C. piger, C. luridus, C. obtusidens, C. plumosus, C. dorsalis and Camptochironomus tentans were determined cytotaxonomically in ponds investigated. C. melanescens and C. annularius appear to be the most characteristic species colonizing in high numbers in newly filled ponds. Larvae of C. annularius grew more slowly in ponds compared with the former one which resulted in a characteristic succession of both larval types. Most species mentioned disappeared completely from the ponds investigated after the metamorphosis of a single cohort. They were replaced by C. plumosus which was often attended by C. annularius in smaller ponds.     

Locomotory modes in the larva and pupa of Chironomus plumosus (Diptera, Chironomidae)

The locomotory kinematics of Chironomus plumosus larvae and pupae were investigated in order to determine how different locomotory techniques may be related to (a) possible underlying patterns of muscle activation and (b) the particular lifestyles and behaviours of these juvenile stages. Larvae display three independent modes of motile activity: swimming, crawling and whole-body respiratory undulation. Swimming and respiratory undulation involve the use of metachronal waves of body bending which travel in a head-to-tail direction. Whereas swimming is produced by side-to-side flexures of the whole body, respiratory undulation employs a sinusoidal wave. Crawling appears to result from an independent programme of muscle activation. Instead of a longitudinally transmitting metachronal wave of body flexure, a simultaneous arching of the body, combined with the alternating use of the abdominal and prothoracic pseudopods as anchorage points, produces a form of locomotion analogous to caterpillar-looping. Larval swimming has a set speed and rhythm and is an 'all-or-nothing' locomotory manoeuvre, but the neural programme controlling larval crawling is adaptable; switching from a less to a more slippery substrate resulted in a shorter, faster stepping pattern. The pupa displays two swimming modes, somersaulting and eel-like whole-body undulation, the former being principally a brief, escape manoeuvre, the latter being a faster form of locomotion employed to deliver the pupa to the surface prior to adult emergence. Comparison with the pupa of the culicid Culex pipiens shows that this insect also uses the somersault mechanism but at a higher cycle frequency which produces a faster swimming speed. This appears to be related to differences in lifestyle; the surface-living culicid pupa is exposed to greater predator threat than the bottom-dwelling chironomid pupa, and consequently needs a faster escape.     

Karyotypic features of Chironomus entis and Chironomus borokensis (Diptera, Chironomidae) from Lake Kotokel (Lake Baikal Basin)

Karyotypes and chromosomal polymorphism of sympatric sibling species Chironomus entis and Chironomus borokensis from Lake Kotokel were studied. Five inversion banding sequences were found in C. entis, including p’entA16, p’entB9, and p’entF6 that are new for the species; in C. borokensis, four inversion banding sequences were revealed, borA4 being new for the species. The level of chromosome polymorphism in C. entis and C. borokensis can be considered similar: 54.2 and 53.8% heterozygosity, 0.67 and 0.73 inversions per individual, respectively. The new data are compared with those on C. entis population from Lake Kotokel obtained in 1981 and those of C. borokensis from Lake Dukhovoe (Lake Baikal basin) obtained in 1983.     

Subsidies for production of Chironomus calligraphus larvae (Chironomidae,Diptera) in the laboratory

The objective of this study was to evaluate the effect of temperature, type of mineral substrate, and type and amount of feed on the growth of Chironomus calligraphus as a subsidy for the production of Chironomus larvae to feed the fish. Egg production was evaluated at 22, 25, and 28?°C on fine (0.074–0.210?mm), or silty sand (0.002–0.250?mm), and no mineral substrate as control. For larval production, 0.10, 0.20, and 0.30?mg/larvae of fish feed, poultry feed, or turkey manure were used as food. The highest number of egg masses was produced when mineral substrates and 25?°C were used, but the higher number of eggs/mass was registered in the control. Therefore, the total number of eggs and hatched larvae produced was the same in the presence or in the absence of mineral substrates (p?>?0.05). The best results for survival and growth were recorded for larvae reared with fish or poultry food. The increase in the amount of feed was correlated with weight gain only for larvae fed with poultry feed, with no reduction in survival.     

Cytogenetic studies of Chironomus circumdatus from India (Diptera: Chironomidae)

Chironomus circumdatus is one of the most common and wide-spread species in India. Cytogenetic studies pertaining to the mitotic and polytene chromosomes, nucleolar organizer regions, C-banding and naturally occurring chromosomal polymorphism have been carried out for the first time in this Indian species. Altogether seven inversions comprising six paracentric and one pericentric are detected in the Indian populations. The distribution of inversions in relation to different environmental conditions is discussed.     

Karyotype and morphology of Chironomus wulkeri (Diptera, Chironomidae) from Lake Baikal region

The karyotype and morphology of the Palaearctic chironomid, Chironomus wulkeri Filinkova et Belyanina 1993, inhabiting the Baikal coast were studied. The banding patterns of chromosomal arms B, C, and D are presented for the first time. The karyotype and chromosome polymorphism of Ch. wulkeri from the Baikal population have no significant difference from those in northern Sweden and the Polar Ural populations. One heterozygous inversion in arm A was found in 38% of larvae. A comparative morphological analysis of 46 quantitative characters of larvae from Baikal region and the Polar Urals showed that they did not differ from each other. However, there are some differences in the width of the ventromental plates and height of the mentum.     

Some carotenoids in Chironomus annularius Meig. larvae (Diptera : Chironomidae)

Summary The author investigated the presence of various carotenoids in the body of the larvae of the Chironomus annularius MEIG. moquito (Diptera: Chironomidae) by means of columnar and thin-layer chromatography.The investigations revealed the presence of the following carotenoids in the larvae: -carotene, -carotene, canthaxanthin, cryptoxanthin, lutein, astacene and a kind of xanthophyl which was not possible to identify more closely.     

The role of glycogen during the ontogenesis of Chironomus anthracinus (Chironomidae, Diptera)

Large fluctuations in glycogen content were found in larvae, pupae and adults of Chironomus anthracinus (Zetterstedt) from the profundal zone of Lake Esrom, Denmark. In 2nd, 3rd and 4th instar larvae the glycogen concentration (expressed as percentage of dry weight) increased during periods of aerobic conditions to a maximum of 25%, but decreased in periods of hypoxia longer than two months to 10–12% in young larvae. A further decrease to about 5% took place, when moulting from 2nd to 3rd or from 3rd to 4th instar occurred after overturn. Prior to pupation the glycogen concentration was restored to 26–28%. The glycogen concentration approximated 22% in young pupae, but decreased during the pupal stage and newly hatched adults contained 12–15%. Finally, the glycogen store of both males and females was further reduced during the swarming period. Thus, glycogen seems to be an important energy source (1) during periods with hypoxic conditions, (2) during periods with high internal energy requirement such as ecdyses and metamorphosis, and (3) during the non-feeding adult life stage.     

Cytogenetic characteristics of species of the Chironomus plumosus group (Chironomidae, Diptera) in Finland

The cytogenetic characteristics of species of the Chironomus plumosus group in Finland were examined. The species included C. balatonicus Devai, Wülker, Scholl, C. entis Shobanov, C. plumosus L., C. muratensis Ryser, Scholl, Wülker, and two karyotypes of unknown species. All belonged to the thummi complex having 2n = 8 chromosomes, with arm combinations of AB, CD, EF, G. In C. balatonicus arms A to G the band sequences corresponded with those of other populations. A new band sequence was found in arm B. In C. entis an arm A had a band sequence similar to those in C. agilis. A large pericentric inversion was observed in chromosome AB. The arms B to G had band sequences typical for C. entis. The chromosome arms A and B in C. plumosus from Lake Marsjon had band sequences corresponding to those of C. agilis and C. entis, respectively. C. plumosus from Helsinki may be a more divergent population with a large amount of centromere heterochromatin. C. muratensis was not distinguishable by band sequences from those of other Palaearctic populations. Two new karyotypes similar to those of species of the plumosus group have been described.     

Karyotype and morphology of larvae of Chironomus (Chironomidae, Diptera) from the Caspian Sea

Karyotype and morphology of Chironomus sp. larvae from the Caspian Sea have been described. 2n = 8. Chromosomal arm combination is AB, CD, EF, G (cytocomplex thummi). All chromosomes display conjugation of homologues. Centromere areas are of s-type. The nucleolar organizer and two Balbiani rings are disposed in arm C, and another Balbiani ring is in arm B. Half larvae have heterozygotic paracentric inversions in arm D. The larva belongs to salinarius form. One scleritis is colorless, an occipital scleritis is light and irregularly colored. Premandible has 4-5 cogs. Epipharingeal ridge has 18-23 dens. This new species is close to salinarius group, especially to Ch. albidus Konst., but differs from it at the larva stage in the structure of non-massive basal antenna segment, in the presence of large quantity of premandible denses, in light color of occipital scleritis, and in a series of morphometric rates. A similarity berween Ch. paraalbidus and Ch. albidus, on the one hand, and Boeotendipes, on the other one, has been found out.     

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.     

Site specific differentiation in metal tolerance in the midge Chironomus riparius (Diptera,Chironomidae)

Metal tolerance in Chironomus riparius (Diptera) populations from contaminated streams was studied by comparing the effects of cadmium, zinc and iron on first generation laboratory reared midges. First instar larvae were exposed for four days, after which surviving larvae were counted and their length measured. Larvae from two highly polluted sites, kept under control conditions, grew substantially slower than those from other populations. All populations showed the same growth responses to increased zinc concentrations, but differences were found in the responses to both cadmium and iron. Since population differentiation was demonstrated in first generation laboratory animals, it is suggested that the differences between populations of C. riparius have a genetic basis.     

The chromosomal polymorphism and divergence of populations in Chironomus nuditarsis Str. (Diptera, Chironomidae)

The karyotype structure and chromosomal polymorphisms were investigated in 6 natural and 2 laboratory populations of Chironomus nuditarsis from Europe and Asia. The pool of rearranged polytene chromosome banding sequences of this species was determined that includes 16 inversion banding sequences and sequences with giant DNA-knobs (ndtG1k, ndtG2k). Obvious differences were demonstrated in the level of chromosomal polymorphism between European and Asian (Siberian) populations: the former were highly polymorphic, while the latter were practically monomorphic. It was suggested to consider the Siberian populations as marginal one. Cytogenetic distances between populations of C. nuditarsis as well between C. nuditarsis and the related species C. plumosus were estimated. The data obtained show that chromosomal rearrangements play a very important role in cytogenetic divergence of populations.