Response of Chironomus striatapennis Larvae Exposed to Three Heavy Metals

Abstract

In this experiment, estimation of LC50 of Lead (Pb), Cadmium (Cd) and Mercury (Hg) was carried out when Chironomus striatapennis was exposed to different treatment doses. Chi square was used to test for heterogeneity and the result was found to be significant (p<0.05) in all three metals. Fourth instar larvae were collected from breeding aquarium under laboratory conditions and exposed for 96 hours to different doses of Pb, Cd and Hg for static bioassay to measure the LC50. Ten fourth instar larvae were placed in 100 ml beaker with 50 ml of each test solution. Larvae were exposed to six different concentrations, consisting of five trials. A control was also maintained wherein organisms were exposed to distilled water. Larvae were not fed during the toxicity tests. All beakers were free from tube forming materials. Data of mortality were subjected to probit analysis. Results showed that sensitivity of larvae to metals was Hg> Cd >Pb. C. striatapennis showed noticeable response in LC50 study and was sensitive to low doses of heavy metals. Several secondary consumers have preferred this larva as their food. So unplanned industrialization may increase the level of heavy metals in the aquatic ecosystem which will accumulate slowly but definitely in different trophic level and at the same time unusual death of these larvae may indirectly change the equilibrium of the aquatic ecosystem.