Behavioural effects of mercury on grass shrimp

Subacute exposure (0.05 ppm) to mercuric chloride significantly impairs the conditioned avoidance responses of grass shrimp Palaemonetes pugio Holthuis, when tested in an aquatic avoidance apparatus. Control animals learn to avoid a shock after the onset of a light which followed a period of dark-adaptation. A third group of shrimp, which establish an avoidance curve similar to the controls, quickly lose its ability to avoid being shocked when exposed to mercury in the final days of the experiment. These experiments demonstrate the value of a simple behavioural index for establishing subacute toxicity standards for organisms in aquatic ecocystems.