Behavioural and biochemical alterations in Penaeus monodon post-larvae diet-exposed to inorganic mercury.

Mercury is a metal naturally present in the environment with concentrations in aquatic systems increasing annually due to human activities. This represents a great concern mainly due to its high toxicity to organisms and consequences for human health. Most studies regarding the toxic effect of mercury have focussed on freshwater species using water as the exposure and uptake pathway. In contrast, the present study investigated the effects of dietary exposure of mercury to the marine crustacean Penaeus monodon post-larvae during 96 h to evaluate changes in behaviour (swimming activity and risk taken) and in biochemical biomarkers [acetylcholinesterase (AChE) and glutathione S-transferase (GST)]. Results showed a decrease in swimming activity with an increase in mercury exposure, but no changes were observed regarding the behavioural response 'risk taken'. Prawns from medium (0.56 μg g-1) and high (1.18 μg g-1) treatments had their GST activity reduced in relation to the beginning of experiment (time 0), while AChE activity was increased in the low (0.15 μg g-1) treatment in relation to time 0. In the present study, behaviour analysis were clearer than biochemical biomarkers and results might indicate P. monodon populations from a mercury contaminated environment might be at risk, since the behavioural alterations observed increases the risk of predation.