Accumulation of lead and its effects on Na balance in the freshwater crayfishCherax destructor

Abstract

The accumulation of lead in tissues of the freshwater Australian crayfish Cherax destructor and its effect on ion and osmoregulation were investigated. Crayfish were exposed to two different lead concentrations for up to 21 days, either 100 mg · 1–1 or a sublethal concentration of 0.5 mg · 1–1, to determine the distribution of lead in exposed crayfish. The gills were the primary site of lead accumulation at both concentrations, with crayfish exposed to 100 mg · 1–1 accumulating 46.4 mg Pb2+ · g–1 wet weight. However, there was a marked difference in the distribution of lead at the two concentrations. C. destructor exposed to sublethal lead levels maintained osmotic pressure and the haemolymph ion concentrations of Na, K, Mg, and Cl. However, there was a 37% decrease in haemolymph Ca concentration in Pb-exposed crayfish after 21 days. While Na homeostasis was maintained, there was a 50% decrease in unidirectional sodium influx in long-term-exposed crayfish, which correlated with a 40% inhibition of Na+/K+-ATPase activity in gill homogenates from long-term-exposed C. destructor. The ability of Pb-exposed crayfish to activate Na transport was also reduced by 70% as determined from the maximum rate of net Na uptake. Thus the accumulation of large lead burdens in the gills and the reductions in Na flux rates will effectively restrict the distribution of C. destructor into soft water bodies. The ability of C. destructor to rapidly accumulate and tolerate the effects of lead indicate that this species is a suitable candidate as a bioindicator of freshwater lead contamination. J. Exp. Zool. 281:270–279, 1998. © 1998 Wiley-Liss, Inc.