Extracellular and intracellular ionic changes in crayfish Astacus astacus exposed to nitrite at two acclimation temperatures

Abstract

Freshwater crayfish, Astacus astacus, were exposed to two concentrations of ambient nitrite (0.5 and 1.0 mM) at two acclimation temperatures (6°C and 16°C) for 1 week. The concentration of nitrite in the haemolymph increased with increasing temperature and ambient level of nitrite. The haemolymph/water concentration ratio was the same at the two ambient nitrite concentrations but increased with temperature. Haemolymph nitrite reached concentrations that were 12 and 16 times higher than the water values at 6°C and 16°C, respectively. Nitrite accumulation induced a decrease in the haemolymph chloride concentration that far exceeded the rise in haemolymph [NO 2]. Haemolymph sodium concentration decreased significantly but less than haemolymph chloride. A large decrease in muscle tissue potassium concentration was seen in nitrite-exposed animals at both temperatures. In midgut gland tissue, the potassium concentration tended to increase, suggesting that the K + efflux mechanism that was stimulated in muscle tissue was absent (or less affected) in midgut gland tissue, and that part of the potassium lost from muscle may have been taken up by the midgut gland.