M7 PM Metals in the Environment: Aquatic Biological Perspectives
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 327-329

(BRI-1118-265294) The toxicity of copper to the snail, Lymnaea stagnalis: a physiological explanation for its high sensitivity.

Brix, K^{1, 2}, Ebanks, S², Grosell, M², ¹ Ecotox, Key Biscayne, FL, USA² RSMAS, University of Miami, Miami, FL, USA

ABSTRACT- We have previously demonstrated the pulmonate snail, Lymnaea stagnalis, to be the most sensitive organism tested to date for Pb, with effects on growth in juvenile snails at 4 g l^-1 Pb. The explanation for this hyper-sensitivity involves the extremely high Ca²⁺ demand of this organism for shell formation and the effect of Pb on Ca²⁺ uptake. Interestingly, this snail also appears to be very sensitive to Cu, with a similar effect on growth in juvenile snails at a waterborne Cu concentration of 3 g l^-1. We are investigating the physiological mechanisms by which Cu inhibits juvenile snail growth. Despite the snail having similar sensitivity to both Cu and Pb for the same endpoint, the mechanisms of action are quite different for the two metals. The other major component of shell formation is CO₃^2-. While some CO₃^2- for shell formation appear to arise from endogenous CO2 production, it is clear that external HCO₃^- also provides part of the substrate needed for shell formation. Regardless of the source of CO₂, the enzyme carbonic anhydrase is required for CO₃^2- formation and inhibition of this enzyme by Cu is the hypothesized site of action. We also explore the applicability of existing biotic ligand models for predicting Cu toxicity to snails, given their fundamentally different physiology compared to invertebrates (daphnids) for which the biotic ligand model has been developed.

Key words: copper