Effects of the organophosphorous pesticide, dimethoate, on cardiac and acetylcholinesterase (AChE) activity in the shore crab Carcinus maenas

The potential use of biochemical and physiological responses as biomarkers of organophosphate exposure and/or effect were assessed in the shore crab ( Carcinus maenas). Male crabs were assigned to one of four dimethoate treatments (0, 0.5, 1.0 or 2.0 mg l −1). Cardiac activity was measured non-invasively before and during dimethoate exposure using automated interpulse duration assessment. Heart rates decreased significantly in a concentration-dependent manner ( p < 0.05). Serial measurements of acetylcholinesterase activity in haemolymph samples taken from crabs before and after exposure indicated that 2 mg l −1 dimethoate also significantly reduced acetylcholinesterase activity ( p < 0.05). The percentage inhibition in acetylcholinesterase activity was correlated with the percentage reduction in heart rate following dimethoate exposure ( r = 0.55, p < 0.01). This suggests that organophosphates may directly effect neuronal control of the heart. The experiments indicate that non-destructive, serial measurements of cardiac activity and acetylcholinesterase activity are valuable biomarkers of organophosphate exposure and adverse effects.