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(T/EH013) Relating mouthpart deformities and nucleolus activity in field collected Chironomus riparius larvae. Meregalli, Giovanna1, Bettinetti, Roberta2, Pluymers, Liesbet1, Vermeulen, Angelo3, Rossaro, Bruno2, Ollevier, Frans1, 1 2 3 ABSTRACT- Chironomid mouthpart deformities and aberrations of their polytenic chromosomes are sublethal responses to toxic stress. These end-points have been used in several cases as bioindications for polluted sediments. In our study we aimed to establish whether deformities and the nucleolus activity in the polytenic chromosomes were correlated. Third instar larvae of Chironomus riparius were collected at a site downstream of a sewage plant and mostly contaminated by DDT. Larvae were then raised in the lab in aquaria containing sediment and water from the study location. During a two-week period, larvae ready to moult to the fourth instar were separated and reared individually. Within a few hours of their moult, the larvae were preserved. The percentages of deformities and of active nucleoli were assessed. The analysis showed that larvae presenting deformities in their mouthparts had a significantly higher incidence of active nucleoli in their polytenic chromosomes than normal ones. A high number of active nucleoli implies an increased rRNA synthesis. Deformed larvae therefore seem to exhibit a higher protein synthesis than normal individuals. Key words: chironomids, mouthpart deformities, polytene chromosomes, nucleolus |
