Cholinesterase activity as potential biomarker in two bivalves

In this study, the pH, temperature and substrate specificity for cholinesterases (ChE) assay in two bivalves was optimized: the Spanish mussel Mytilus galloprovincialis and the Asiatic clam Corbicula fluminea. The optimal values found are pH 7, 25°C, 2 mM of acetylthiocholine (ASCh) as substrate for M. galloprovincialis and pH 8, 25°C, 5 mM propionylthiocholine (PrSCh) for C. fluminea. The apparent K(m) are 30 and 70 μM for the two bivalves, respectively. In comparison with some other crustaceans and fishes, the levels of ChE activity were found to be low. The in vitro and in vivo sensitivities of the ChEs activity toward two well known pesticides: carbaryl and methylparathion (or its oxon derived form) are comparable to that observed in fishes but less than that found in crustaceans. Although further studies should be done, and other contaminants tested, the studied bivalves can be considered as interesting 'sentinel' species in the monitoring of the acute water contamination by pesticides.