108 research outputs found
Polytene chromosomes of Chironomidae (Diptera) as a bioassay of trace-metal-induced genome instability
Chironomids are a ubiquitous group of aquatic insects that are very sensitive to environmental stress. Due to the presence of polytene ('giant') salivary gland chromosomes, it is possible to define the genome response of several Chironomid species to various stress agents. The aim of this study was to assess the genotoxic changes in populations of widely distributed chironomid species from aquatic basins in Bulgaria, Italy, Russia, U.K. and Poland, which were exposed to high concentrations of trace metals. We analyzed the structural and functional alterations of polytene chromosomes of the salivary glands of larvae belonging to three different cytocomplexes of the genus Chironomus ("thummi", "lacunarius", "pseudothummi"), and genera Glyptotendipes and Kiefferulus. Somatic structural chromosome rearrangements (para- and pericentric heterozygous inversions, deletions, deficiencies and amplifications) were used to estimate a Somatic index (S) for each population. The highest S indexes were detected in Chironomus riparius populations from locations with high concentrations of trace metals in the sediment. Each species showed specific genome responses to stress agents which we discussed in the light of the specific DNA structures and cytogenetic characteristics of the species. In larvae from polluted sediments two key structures of the salivary gland chromosomes (Balbiani Rings and Nucleolar Organizer) sharply reduced their activity to levels below those observed under non-polluted conditions. It is concluded that polytene chromosomes can be used as tools for evaluating the genotoxicity of the aquatic environment. Structural and functional chromosome alterations provide cost-effective early-warning signals of genotoxic concentrations of environmental pollutants. doi: 10.5324/fn.v31i0.1355. Published online: 17 October 2012
NOR activity in Chironomus riparius Mg. (Diptera, Chironomidae) is affected by chronic exposure to trace-metal pollution
Chromosomal Breakpoints and Transposable-elemen tinsertion Sites in Salivary Gland Chromosomes of Chironomus riparius Meigen (Diptera, Chironomidae) from Trace Metal Polluted Stations
Genotoxic effects of chromium onpolytene chromosomes of Chironomus riparius Meigen 1804 (Diptera, Chironomidae)
Abstract Genotoxic effect as tested of chronic exposure to three different concentrations of Chromium (III) on polytene chromosomes of larvae of Chironomus riparius (syn. Chironomus thummi) from the embryonic stage to the IV larval instar for two successive generations. In chromosomes AB, CD, EF and G significant differences of chromosome aberrations were found between exposed and control larvae as well as changes in functional activity (induction of novel puffs not corresponding to those induced during normal larval development in arms A, B, C and E, telomeric and centromeric decondensations especially at telomeres of chromosome G and arm C.). No significant differences were found between the effects of the three treatments nor between the two generations. In chromosome G the Balbiani Ring system (where some permanently active regions are involved in transcription of salivary proteins) appeared as a model for studying the response of the genome to Cr (III) treatment. In approximately one-third of the cel..
Does the cost of a function affect its degree of plasticity? A test on plastic sex allocation in three closely related species of hermaphrodites
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