Threshold concentrations of cations in environmentally determining the distribution borders of river crayfish (Astacus astacus L.) in fresh reservoirs

摘要

The content of sodium, potassium, calcium, and magnesium in the hemolymph of river crayfish caught in nature is maintained at levels of 178.0 +/- 2.5, 7.1 +/- 0.5, 17.3 +/- 0.7, and 3.0 +/- 0.1 mmol/L, accordingly. It is shown that the threshold concentrations of sodium, potassium, calcium, and magnesium in water determining the distribution borders of river crayfish in fresh reservoirs is 0.0087-0.0174, 0.0046-0.0087, 0.0105-0.0222, and 0.0012-0.0033 mmol/L, accordingly. The reduction of water mineralization is accompanied by a significant increase in the gradients of the cation concentration between the organism and the environment, which is accompanied with a higher load on the maintenance of the water-salt exchange. A comparative analysis of the threshold concentrations of the above mentioned elements for river crayfish, roach, perch, goldfish, crucian, two species of two-folding mollusks, and Spirogyra filamentous alga is performed.