| Popis: |
Various pollutants are being introduced into aquatic ecosystems both directly or indirectly as a result of industrialisation and urbanisation. Heavy metal contamination in freshwater bodies is of great concern owing to their toxicity, persistence and bioaccumulation. In toxicology, behavioural bioassays are used as a tool to assess heavy metal toxicity. Even at very low doses, chemicals can cause organisms to exhibit rapid behavioural responses. The current study deals with the acute toxicity of cadmium, zinc and their mixture to freshwater fish, Labeo rohita. Static bioassay tests were carried out to evaluate LC50 value of Cadmium (Cd), Zinc (Zn) and a mixture of both metals (Cd+Zn) for freshwater fish, L. rohita as well as the behavioural responses were also observed. Fishes were treated with various concentrations of metals for different exposure periods and per cent mortality was recorded. The objective of this study was to grasp the link between mortality and abnormal behavioural alterations of L. rohita exposed to CdCl2, ZnCl2 and a mixture of both metals (CdCl2+ ZnCl2). The major behavioural responses observed during the experiment were restlessness, jumping, erratic swimming, gulping of air at the surface, loss of equilibrium, sluggishness, opercular movements and fishes lying on the water surface before death etc. were observed in exposed fishes. The observed data showed that L. rohita can be used as a good bio-indicator for heavy metal contamination in freshwater bodies. Thus, a behavioural bioassay is more promising than lethality evaluating bioassays, which are currently employed for toxicant risk evaluation |
