The signal crayfish, Pacifastacus leniusculus, is currently being used as a model organism to study the effects of environmental contamination on aquatic biota. As an aquatic invertebrate and keystone species, signal crayfish are especially sensitive to changes in the chemical composition of their habitat. In this study, acetycholinesterase (AChE) activity in tail muscle of signal crayfish exposed to the organophosphate pesticide dimethoate (0.3, 0.6, 0.9 mg/kg) and the metal zinc chloride (0.6, 0.9, 1.2 mg/kg) was characterized as well as in animals collected from sites along the Boise River with varying land use practices. Elemental total mercury (Hg0) was also measured in tail muscle, in an attempt to correlate a known AChE inhibitor to AChE activity levels. As a persistent environmental pollutant, mercury can lead to a variety of negative effects on an organisms' health, and it is therefore of interest to monitor levels of this pollutant in our waterways. AChE activity was significantly inhibited in tail muscle at all concentrations of dimethoate tested relative to a saline control however AChE was not inhibited by ZnCl2. AChE activity varied in crayfish collected from sites located downstream of urban and agricultural areas. It is predicted that mercury concentrations will follow a similar pattern.

Characterization and Expression of Acetycholinesterase and Total Elemental Mercury in Signal Crayfish, Pacifasticus Lenisculus, as a model for Contaminant Exposure in the Boise River in Southwestern Idaho