THE EFFECT OF TRANSFER AND LABORATORY ACCLIMATION ON THE ACID-BASE AND ELECTROLYTE STATUS OF THE FRESHWATER UNIONID MUSSEL ANODONTA ANATINA (L.)

The effect of different conditions of transfer (+;1 °C withwater, +20 °C with and without water) from the natural habitatand laboratory acclimation procedure (with and without bottomsediment) on the acid-base and electrolyte status of the freshwateruniomd mussel Anodonta anatina (L.) was studied. The shift inthe acid-base status of A. anatina during the transfer was smallerat 1°C than at 20°C. The pO₂ content of the haemolymphdeclined significantly under all three transfer conditions.Neither the transfer nor the laboratory acclimation affectedhaemolymph Na⁺]. However, during transfer at 1°C the haemolyraphCa²⁺] did not change, whereas K⁺] increased up to three fold.Haemolymph Ca²⁺] increased when mussels were transferred at20°C After a 17-day aquarium acclimation, the pO₂ of all the musselskept in the sediment had returned to the field level and thetransfer seemed to have had no effect on the pCH of the haemolymph.Conversely, in the groups kept without sediment, the pO₂ continuouslyremained above the field level. Whereas the K⁺] of all themussels declined to the field level, the haemolymph Ca²⁺] remainedelevated throughout the entire acclimation period of 17 days. (Received 22 May 1995; accepted 20 October 1995)