PARENT SESSION

(07-03) Physiology of Silver Toxicity to Freshwater and Marine Crustaceans.

Hogstrand, Christer^*,1,2, Bury, Nicolas¹, Walker, Paul¹, Bianchini, Adalto³, Walsh, Patrick², ¹ King's College London, London, UK² University of Miami, RSMAS/MBF, Miami, FL³ Departimento de Ciencias Fisiologicas, Fundacao Universidade Federal do Rio Grande, Rio Grande do Sul, Brazil

ABSTRACT- Research on freshwater fish has shown that acute toxicity to silver is primarily caused by inhibition of Na+ and sometimes Cl- uptake across the gills. The critical mechanism appears to be inhibition of the Na/K-ATPase that drives sodium and chloride transport. Similarly, osmoregulatory disturbances seem to be responsible for acute toxicity to silver in marine fish, but here the intestine is an additional target. Toxic effects of silver to freshwater crustaceans resemble, but are not identical to those in freshwater fish. Exposure of Gammarus pulex resulted in reduction of the whole body sodium concentration, an effect that could be reversed by increasing the sodium concentration of the water. Silver also caused a decrease in whole body calcium concentration. This effect does not occur in fish. The situation in marine invertebrates is very different, because many of them do not regulate sodium and chloride when in seawater. Thus, to most marine invertebrates inhibition of Na/K-ATPase at the body surface would be unlikely to have the vast systemic effects that are observed in silver exposed freshwater organisms. Indeed, haemolymph sodium and chloride concentrations in silver exposed marine shore crab, Carcinus maenas, were not consistently affected by silver exposure. Instead, silver caused a dose-dependent increase in haemolymph magnesium concentration. While most marine crustaceans have a body fluid composition that is similar to that of saltwater, all of them exclude Mg2+ from the haemolymph. Thus, present data suggests that inhibition of Mg2+ efflux is a target for silver in marine crustaceans. Ongoing research on other invertebrate species should provide more in-depth mechanistic information on silver toxicity to marine animals.

Key words: silver, physiology, mechanisms, invertebrates