Cytogenetic structure of Chironomus plumosus (L.) (Diptera, Chironomidae) population in regard to the trophic state of the Curonian Lagoon, Baltic Sea

It is shown that the cytogenetic structure of the Chironomus plumosus (L.) population in the Curonian Lagoon has not changed significantly over the last three decades. The existing cytogenetic structure supported not only population survival, but also its proliferation in new environmental conditions caused by an increase of the trophic status of the water body. The predominance of homozygotes pluB2.2 was marked in karyofund. Both the oxygen deficiency periodically occurring in the Curonian Lagoon and the fact that the population dwells at the periphery of the species areal in the Palearctic could be reasons for this phenomenon.     

Chromosomal and genomic mutations in Chironomus plumosus (L.) (Diptera, Chironomidae) from Novozybkov raion of Bryansk oblast

The data on karyopool analysis of Chironomus plumosus from Novozybkov raion of Bryansk oblast, radioactively contaminated as a result of the Chernobyl accident, are presented. In the karyopool of this population, four types of heterozygous inversions (A1.2, B1.2, C1.2, D1.2) and a structurally small rearrangement in arm D, which is thought to be also associated with inversion, were identified. For inversions A1.2, C1.2, and structurally small rearrangement in arm D the cases of somatic mosaicism were described. The mean number of inversions per individual constituted 0.78. The number of genotypic combinations was 13. In 5% of the individuals chromosome B was identified, while 15.6% were polyploid (3n). In 1.8% of triploids somatic mosaicism for the level of polytene chromosomes was observed. Most of the larvae were characterized by partial asynapsis of the homologs in different regions of chromosome III. Specific features of the Chironomus plumosus karyopool from Novozybkov are thought to be associated with the habitation of a number of generations of this population on radioactively polluted territory.     

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.     

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.     

Seasonal variability of the karyotype structure of Chironomus plumosus (Diptera, Chironomidae) from a biotope of Kaliningrad

Chironomus plumosus larvae from the polluted Shkolnoe lake, Kaliningrad, have 2n = 8 and 2n = 8 + B. In winter season we found 11 types of hetero- and homozygous inversions in A, B, C, D, E, and F arms whereas in summer season we registered 7 types of the same inversions in A, B, C, D, and E arms. All inversions with exception of the inversion in arm C correspond to Hardy-Weinberg equilibrium. The arm IVG shows homozygous increase of centromeric heterochromatin more frequently in summer than in winter (34.4% as compared with 1.8%). The arm E has asynapsis 2 times less frequently in summer than in winter (21.4% as compared with 44.6%).     

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.     

Seasonal Dynamics of a Chironomus plumosus (L.) (Diptera,Chironomidae) Population from a Fish Pond in Southern Bohemia

A population of Chironomus plumosus (L.) from a fish pond has been investigated for two years. Quantitative benthic samples and emergence traps were used to study the seasonal dynamics. Effect of some factors on the duration of development was studied in laboratory experiments. Data on larval abundance, length frequency analysis and emergence of adults suggest a bivoltine life cycle. The population of C. plumosus investigated showed a pronounced tendency to dormancy, even under long-day conditions. Factors regulating the bivoltine life cycle are discussed.     

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.     

Peculiarities of structural organization of hemoglobin of Chironomus plumosus L. (Diptera: Chironomidae)

In Ch. plumosus and Ch. riparius there were revealed various structural hemoglobin variants including monomers, dimers, trimers, tetramers, hexamers, and octamers. The multitude of the protein organization ways seems to be based on diversity of the monomers with the approximately equal molecular weight from 12 to 16 kDa in Ch. plumosus and from 11.8 to 15.2 kDa in C. riparus. In PAGE with 8 M urea, the hemoglobins were aggregated into high molecular complexes with mol. weights about 260 and 180 kDa in Ch. plumosus and about 523 and 174 kDa in C. riparus.     

Karyofund of Chironomus plumosus (Diptera, Chronomidae) in the Palearctic region

Quantitative and qualitative analyses of chromosomal polymorphism in 38 Palearctic populations of Chironomus plumosus were made. It was shown that most of the populations studied were highly polymorphic: in average 63.2 +/- 4.0% of larvae were heterozygous for inversions with 0.95 + 0.08 heterozygous inversion per larvae. Polymorphism on the size of centromeric heterochromatin and the presence of B-chromosomes were observed in many populations studied. The karyofund of Ch. plumosus in Palearctic was estimated. In total 35 banding sequences were found in Palearctic Ch. plumosus. Fifteen banding seguences have been described for the first time. On mapping the used banding sequences, we employed the conventions of Keyl (Keyl, 1962; Devai et al., 1989) and Maximova (Maximova, 1976; Shobanov, 1994a) for arms A, C, D, E and F, and the conventions of Maximova for arms B and G.     

Resistance to anoxia of Chironomus plumosus and Chironomus anthracinus (Diptera) larvae

Survival of the midge larvae Chironomus plumosus and C. anthracinus in anoxia at 4°C was investigated. C. plumosus survived about twice as long as C. anthracinus . The corresponding LT 50 values were ca 205 and 100 d. There was no statistically significant difference between the survival in anoxia and in aerated water, which indicates that the main reason for death in anoxia is not the absence of oxygen. This main reason is presumed to be starvation. The presence of undissociated H₂S in low concentrations (ca 1.2 mg 1⁻¹) did not influence the survival. In anoxia the larvae were usually motionless and did not feed but they increased in weight due to uptake of water. During 43 d C. plumosus and C. anthracinus increased ca. 10%.     

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.     

Karyofunds of Chironomus plumosus (L.) (Diptera, Chironomidae). V. terminal and interstitial populations

The study of polytene chromosomes of Chironomus plumosus from Rybinsk reservoir, its inflows and surrounding water bodies allow to mark out two type's of population. Terminal populations--presented by karyoforms with concrete limited composition of genotype combinations and zygotic arm combinations, which adapted to specific complex of the habitat factors. The immediate exchange of genes between different terminal populations is absent (even they placed in nearness) from allochronie of life cycles and impossibility of larvae-immigrants to finish ontogenesis in unfit for they habitat conditions. Interstitial populations inhabit the biotopes, where the karyoforms of two or more terminal populations can to finish ontogenesis and to reproduce. The genetic exchange between terminal population implement through interstitial populations.     

Intercontinental karyotypic differentiation of Chironomus entis Shobanov, a Holarctic member of the C. plumosus group (Diptera, Chironomidae).

Analysis of banding sequences of polytene chromosomes in Palearctic (Russian) and Nearctic (North American) Chironomus entis shows strong karyotype divergence between populations on the two continents. Four out of seven chromosomal arms in the North American C. entis karyotype are characterized by sequences found only in the Nearctic. In total, 44 banding sequences are now known for this species across the Holarctic, including 22 exclusively Palearctic, 6 Holarctic, and 16 exclusively Nearctic sequences. The degree of cytogenetic differentiation between Palearctic and Nearctic C. entis populations is an order of magnitude greater than differentiation among populations within either continent, but is only one third as great as the cytogenetic distance between the sibling species C. entis and C. plumosus. C. entis is the only sibling species of C. plumosus uncovered during cytological identification of Chironomus species from more than 50 North American lakes, indicating that the plumosus sibling-species group is much smaller in the Nearctic than in the Palearctic, where a dozen sibling species are known. Cytogenetic distance values calculated between Nearctic and Palearctic representatives of both C. entis and its sibling species C. plumosus are similar, but result from different patterns of karyotype divergence. New World C. entis is distinguished from Old World populations by the 16 uniquely Nearctic sequences, four of which occur in the homozygous state. In contrast, North American C. plumosus has fewer uniquely Nearctic sequences, and only one that occurs as a homozygote. However, four chromosomal arms in C. plumosus that are polymorphic in the Palearctic show fixation, or near fixation, of Holarctic sequences in the Nearctic C. plumosus karyotype. Thus, both the fixation of Holarctic sequences, and the occurrence or fixation of distinctly Nearctic sequences, contribute significantly to karyotype divergence. Patterns of karyotype divergence in Palearctic and Nearctic populations of different Holarctic chironomid species are discussed relative to intercontinental cytogenetic differentiation in other dipterans.     

Proportion of dead individuals in the zooplankton of the Curonian Lagoon of the Baltic Sea

Changes have been studied in space and time in the proportion of dead individuals in the zooplankton of the Curonian Lagoon. Dead individuals were found in the populations of all dominant invertebrate species. Their proportion was shown to increase during “hyperbloom” by a factor of 5 to 6. In the vegetation period without algal hyperbloom (2007), the dead individuals accounted on average for 1.9 ± 0.7% of the total abundance and 1.7 ± 0.8% of the total biomass of zooplankton; in the vegetation period with hyperbloom (2008), their proportion increased to 6.7 ± 3.0% and 5.9 ± 2.5%, respectively. Differences in sensitivity to bloom of Cianobacteria have been revealed in hydrobionts from different groups. Cladocera and nauplial Copepoda are the most sensitive groups; Cyclopoida is the least sensitive. The highest proportion of dead individuals was recorded in the most eutophicated and polluted part of the lagoon. It is suggested that parameters of zooplankton mortality be used for estimating the ecological state of the Curonian Lagoon.     

Prevalence of skin neoplastic lesions in bream (Abramis brama L.) from the Curonian Lagoon of the Baltic Sea

Skin neoplastic lesions have been studied in bream inhabiting the Curonian Lagoon of the Baltic Sea in 1999–2010. A total of 12163 fish specimens have been examined. Two types of lesions have been revealed: epidermal hyperplasia and skin papilloma, considered to be the successive stages of the epizootic cutaneous papillomatosis in fish. This disease has been registered in 18.5% of fish older than 5 years. The share of diseased specimens increases with age and reaches 62.5% in 15-year-old fish. The prevalence of lesions in males is significantly higher (12%) than in females (5.3%). The number of diseased fish in winter (30.2%) is higher than in summer (15.6%). The maximum share of fish with neoplasms has been recorded in 2006 (40%). Since 2007, there has been a trend towards a decrease in the prevalence of skin neoplastic lesions, and the average occurrence of diseased fish has reached 7.3%. The high prevalence of skin neoplasms (SNs) in bream is evidence of the unfavorable ecological situation in the Curonian Lagoon.     

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.     

Sediment development and its influence on the distribution and tube structure of Chironomus plumosus L. (Chironomidae, Diptera) in a new impoundment

Field and laboratory evidence is presented to demonstrate that colonization of a new impoundment by the early invader, Chronomus plumosus L., is strongly influenced by sediment, the depth of which affects both larval abundance and tube shape. Larvae avoid areas with little sediment, such as eroded or newly inundated shores. In laboratory experiments, larvae constructed horizontal tubes in sediments between 3 and 10 mm depth, but in deeper sediments (11–30 mm) most of the larval tubes were vertically orientated. Of these about 70% were U-shaped and the remainder J-shaped. Larval abundance was positively correlated with sediment depth in the range 0–10 mm.