Change in intracellular concentration of free amino acids as a factor of euryhalinity in the crayfish Astacus astacus

Abstract

1. 1. Astacus astacus survives in twice-diluted seawater in spite of the fact that the osmoregulatory mechanism which is active in freshwater maintains the concentration of the blood at an even higher level than that of the diluted seawater. 2. 2. In these conditions, the degree of hydration and the potassium content of the abdominal muscle show only a very slight modification. 3. 3. The adaptation results from an increase of intracellular concentration which is partly due to an increase of free amino acids. 4. 4. While the increase of blood concentration, in a crayfish transferred from fresh water to twice-diluted seawater, amounts to a change in Δ of 0·24°C, the increase in concentration of intracellular amino acids corresponds to 0·15°C, which shows that the free amino acids play an important role in the mechanism of adjustment.