Hemolymph acid-base balance of the crayfish Astacus leptodactylus as a function of the oxygenation and the acid-base balance of the ambient water.

The acid-base balance of the prebranchial hemolymph of the crayfish Astacus leptodactylus was studied at various acid-base balances and levels of oxygenation of the ambient water at 13 degrees C. The water acid-base balance was controlled automatically by a pH-CO2-stat. Into water of constant titration alkalinity, TA, this device intermittenly injects carbon dioxide to maintain the pH at a preset value. Water pH was reduced to the same value either by hypercapnia (at constant TA) or by adding HCl or H2SO4 to decrease the TA (at constant CO2 tension). Decrease of hemolymph pH and increase of hemolymph PCO2 were similar for the three acidic waters. Water oxygenation changes strongly affected hemolymph ABB. In crayfish living in hyperoxic water (PO2 congruent to 600 Torr) compared to those in hypoxic water (PO2 congruent to 40 Torr), hemolymph pH was 0.3 to 0.4 unit lower and hemolymph PCO2 several times higher, the exact values of pH and PCO2 depending on the controlled ambient acid-base balance. In any study of the hemolymph acid-base balance of the crayfish, it is an important to control ambient water's acid-base balance and oxygenation as it is to control its temperature, a conclusion which probably holds true for studies on all water breathers.