Studies on the extra- and intracellular acid-base status and its role on metabolic depression in the land snail Helix lucorum (L.) during estivation

Abstract.

The aim of the present study was to examine the acid-base status of extra- and intracellular fluids and its possible role on the regulation of the metabolic rate of Helix lucorum during prolonged estivation. For this purpose, the rate of oxygen consumption for active and estivating snails was determined. The acid-base status was also examined in the hemolymph and tissues from active and estivating snails acclimated at 25 °C. In addition, the buffer values of hemolymph and tissues were determined in order to examine whether there is a change in the snails during estivation. The rate of oxygen consumption decreased significantly within the 1st 10 days of estivation from 122.51±10 µl.g^–1.h^–1 to 25.86±5.2 µl.g^–1.h^–1, indicating a marked decrease in metabolic rate. P _CO2 increased within the 1st 20 days of estivation from 13.52±0.68 mmHg to 25.09±2.05 mmHg, while the pH of hemolymph (pH_e) decreased from 7.72±0.04 to 7.44±0.06. The level of bicarbonates decreased in the hemolymph of estivating snails, indicating a metabolic acidosis, which was moderate in extracellular fluids. In contrast to pH_e, the intracellular pH (pH_i) was maintained in the tissues of estivating H. lucorum, indicating a regulation of pH_i despite the developed hypercapnia. According to the results presented here, it seems that the timing of pH_e changes does not correlate with the timing of metabolic rate reduction in estivating H. lucorum.