Effects of heavy metal pollutants on polytene chromosomes of Chironomid larvae
Journal Title: International Journal of Experimental Research and Review - Year 2016, Vol 3, Issue 2
Abstract
The non-biting midges of genus Chironomus are well known biological indicator and widely used test organism for water quality studies. The larvae of this most abundant and widely distributed species of aquatic ecosystem are characterized by the presence of giant polytene chromosomes with very good banding pattern. The karyological characteristics of polytene chromosome have been used to show chromosomal aberration under action of heavy metal pollutants like copper, cadmium, lead, chromium, etc. Both structural and functional changes in response to heavy-metals have been shown in polytene chromosomes of chironomid larvae of different species from anthropogenically polluted water bodies and in laboratory cultures. Structural changes in response to heavy metal involve numerous inversions, deletions, duplications, deficiencies, centromeric breakages, telomere condensations/ de-condensations, amplification of some polytene areas, desynapses, alteration in puffing pattern etc. In some chironomid species it has been shown that the fourth chromosome has transformed into so called pompon due to heavy metal toxicity. Functional changes due to effect of heavy metal include higher or lower activity of puffs and Balbiani ring (BR) system and changes in activity of Nuclear Organizer Region (NOR). All these responses have shown to be species specific and dose dependent. It has been also shown that the sites of chromosomal rearrangements are associated with certain chromosomal breakpoints which are rich in repetitive DNA sequences. All these structural and functional changes of polytene chromosome system could be used as a tool for assessment of genotoxicity in aquatic ecosystems which can provide an early warning of adverse long term effects of heavy metals on aquatic organisms.
Authors and Affiliations
Chinmoy Ghosh
Keywords
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- EP ID EP702030
- DOI https://doi.org/10.52756/ijerr.2016.v03.003
- Views 77
- Downloads 0
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