Sublethal physiological changes in freshwater crayfish, Astacus astacus, exposed to nitrite: haemolymph and muscle tissue electrolyte status, and haemolymph acid-base balance and gas transport

Abstract

Crayfish, Astacus astacus, were exposed to 0.8 mM environmental nitrite for up to seven days to investigate nitrite-induced perturbations of crustacean homeostasis. Nitrite accumulated in the haemolymph to 8–10 mM within two days, whereafter the extracellular concentration remained constant. This was associated with a substantial decrease in haemolymph chloride and a smaller decrease in sodium, whereas other haemolymph ions (potassium, calcium, magnesium, bicarbonate and lactate) were unchanged. In muscle a pronounced decrease in potassium concentration occurred, whereas sodium, calcium and magnesium concentrations were unaffected. It is proposed that K + efflux from intracellular compartments constitute a general response to nitrite. The extracellular acid-base status changed towards a respiratory alkalosis. Haemolymph P O 2 increased and the haemocyanin concentration decreased. The respiratory pigment itself, however, appeared only marginally affected by nitrite. Oxygen transport accordingly was not severely perturbed, and lactate levels remained low. The mechanisms underlying the responses to nitrite are discussed, and physiological changes in crayfish are compared with corresponding nitrite-induced effects in teleost fishes.