| Summary: | In two separate investigations juvenile shore crabs Carcinus maenas (L.) were exposed to sublethal levels of waterborne copper. In the first, crabs were exposed to 0, 53 and 102pg Cu 1'^ for 96h. Haemolymph was assayed for haemocyanin concentration and CuZn superoxide dismutase (SOD) activity. Samples of hepatopancreas and gill tissue were homogenised and assayed for levels of lipid peroxidation (utilising the TBARS assay), SOD activity and total glutathione levels. Results of assays perfomned on both haemolymph and tissue homogenate showed no significant differences between treatments (P> 0.05). The second investigation exposed starved animals to 0 and 102pg Cu 1"^ for 96hr. Behavioural trials showed a significant effect (P< 0.05) of copper on the time taken for exposed crabs to respond to the presence of a food item compared with control animals. However, exposed crabs were more likely to win bouts with control animals over the food item. Oxidative stress levels in tissue samples were not significantly different between treatments (P> 0.05). In a third investigation, postlarval Homarus gammarus sNere exposed to 32g KgVontrol), 571 g Kg'''('Low') and 1032g Kg^High') dietary copper, via pelleted feed, for 7 weeks. Results indicated significant differences (P< 0.05) in specific growth rate and feed conversion ratio between 'Low' treatments and control and 'High' treatments. The latter were not significantly different from each other (P> 0.05). Levels of lipid peroxidation and SOD activity were significantly different (P< 0.05) in whole body homogenates of animals fed 'Low' and 'High' diets from those fed control diet. It is suggested that a threshold level of dietary copper may exist for postlarval H. gammarus. Faculty of Science
|
|---|