Ingestion of inorganic mercury by juvenile black tiger prawns (Penaeus monodon) alters biochemical markers.

There is a lack of information regarding the effects on biochemical markers in invertebrates diet-exposed to inorganic mercury. In the present study, juvenile black tiger prawn (Penaeus monodon) were fed with food dosed with mercuric chloride (low: 0.2 mg kg-1; medium: 0.77 mg kg-1; high: 1.41 mg kg-1; higher: 2.52 mg kg-1) and control (0.03 mg kg-1) over 12 days. At the end of exposure periods, ventral nerve cord, compound eyes and muscle were dissected for biochemical marker analyses (acetylcholinesterase - AChE; lipoperoxidation - LPO; glutathione S-transferase - GST; catalase - CAT). Prawn muscle showed an increase in total mercury concentration over time for low and high treatments, but did not show an accumulation in comparison to controls. AChE activity tended to decrease over time in all tissues. CAT activity increased over time in controls and lower dose treatments but was suppressed in the higher treatment relative to controls on day 12; indicating that inorganic mercury is impacting the normal stress response by reducing the capacity to degrade hydrogen peroxide. In contrast, no effect was observed in LPO and GST activity. A depuration treatment was performed and compared to medium treatment; only AChE and GST activities from muscle showed significant difference, with AChE activity from depuration treatment lower than medium treatment, while the opposite was observed in GST activity. Overall, the low mercury accumulation observed over 12 days of exposure may have limited the biochemical stress responses, which could also have limited the detection of differences in the depuration treatment relative to medium treatment.