Physiological responses to acute silver exposure in the freshwater crayfish (cambarus diogenes diogenes)— a model invertebrate?

Abstract

Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 6 0.17 mg silver/L (19.4% as Ag1) in moderately hard freshwater under flow-through conditions for 96 h exhibited ionoregulatory disturbance, elevated metabolic ammonia (Tamm) production and substantial silver accumulation in the gills, hemolymph, and hepatopancreas. The ionoregulatory disturbance included both a generally reduced unidirectional Na1 influx and an increased unidirectional Na1 efflux, leading to a substantial net loss of Na1 from the silver-exposed crayfish. The Na1 uptake in silver-exposed crayfish differed overall from controls, while the increased Na1 efflux recovered to control values 48 h into the 96 h of exposure. The general inhibition of Na1 uptake could be explained by a reduced sodium/potassium-adenosine triphosphatase (Na/K-ATPase) activity in terminally obtained gill samples from the silverexposed crayfish. The silver-induced effect on Na1 uptake and loss translated to reduced hemolymph Na1 concentrations but not significantly reduced hemolymph Cl2 concentrations. Hemolymph Tamm and Tamm efflux both increased in silver-exposed crayfish, indicating an increased metabolic Tamm production. The present study demonstrates that the toxic mechanism of waterborne silver exposure in freshwater crayfish resembles that of freshwater teleost fish. The crayfish might therefore be a useful model system for extending current environmental regulatory strategies, currently based on teleost fish, to invertebrates.