PARENT SESSION
19 - Pesticide Ecotoxicology
8:00 AM to 6:30 PM, Monday, 13 May 2002
Exhibition Area

(19-08) Asessment of tributyltin and triphenyltin toxicity using esterase enzyme activities in the isopod Asellus aquaticus.

O'Neill, Anne^*,1, Galloway, Tamara¹, Depledge, Michael¹, ¹ Plymouth Environmental Research Centre, Plymouth, Devon UK

ABSTRACT- The freshwater isopod Asellus aquaticus is prevalent throughout the Northern hemisphere and is known to inhabit organically polluted waters. Isopods are integral components in regulating and maintaining food chains and consequently are an ideal test species for assessing the sub-lethal effects of contaminant exposure in field and laboratory experiments. Previous field experiments in the Mersey catchment have shown statistically significant differences in esterase activities between sites contaminated by complex mixtures of xenobiotics including tributyltin (TBT) and triphenyltin (TPT). The aim of this investigation was to determine the effects of TBT and TPT on esterase activities in A. aquaticus in controlled laboratory exposures. Environmentally realistic concentrations of TBT and TPT exposure were selected. For a period of 5 days, individuals were exposed via water (g l^-1) or diet (g kg^-1)to TBT/TPT over a range of concentrations (0.01, 0.05, 0.1, 0.5 and 1.0). Enzyme activities were determined in whole body homogenates using an optimised microtitre plate method. The substrates acetylthiocholine, propionyl thiocholine and s-phenyl thioacetate were used to characterise esterases present within the organism. The ecological relevance of the results is discussed in relation to the physiology and survival of the organism.

Key words: Biomarker, Cholinesterase, Isopoda, Pesticides