ACETYLCHOLINESTERASE INHIBITION AND ALTERED LOCOMOTOR BEHAVIOR IN THECARABID BEETLE PTEROSTICHUS-CUPREUS - A LINKAGE BETWEEN BIOMARKERS AT2 LEVELS OF BIOLOGICAL COMPLEXITY

The establishment of cause-effect relationships is fundamental for the interpretation and the predictive value of biomarker responses measur ed at all levels of biological complexity. In the present study, the b iochemical exposure biomarker acetylcholinesterase (AChE) inhibition w as related to locomotor behavior, representing a general effect biomar ker at the organismal level. Both sexes of the carabid beetle Pterosti chus cupreus were intoxicated with three doses of the organophosphorou s insecticide dimethoate. Five elements of their locomotor behavior we re measured for 4 h employing computer-aided video tracking, whereupon the whole body AChE activity was measured in the individual beetle. A ChE inhibition was strongly correlated with dimethoate dose in both se xes. Alterations in the locomotor behavior were directly correlated wi th AChE inhibition in male beetles, which responded by reducing the ti me in locomotion, average velocity, and path length and by increasing the turning rate and frequency of stops. Females responded similarly a t the two highest doses, whereas their locomotor behavior was not sign ificantly different from the control group at the lowest dimethoate do se, suggesting a sex-dependent difference in behavioral sensitivity to minor AChE depressions. The results demonstrate that automated measur ements of locomotor behavior is at least as sensitive an endpoint to o rganophosphate poisoning as the AChE assay. Further, the correlation b etween the molecular and behavioral responses in individual beetles in dicates a mechanistic relationship between the two biomarkers.