Coordination of locomotor activity of mollusc Lymnaea stagnalis at nutrition: Role of the internal medium acid-base balance (pH)

The correlation was studied between the hemolymph pH value and the locomotion rate in the mollusc Lymnaea stagnalis at different degree of activation of the food-procuring behavior. It is established that the hemolymph pH value remains unchanged in the satiated (hungry), freely moving Lymnaea individuals, and, hence, it does not determine the locomotor activity of molluscs in these functional states. In the course of food consumption, locomotion decreases significantly, which is due to an observed decrease of the hemolymph pH. This effect is realized through the corresponding changes of electrical activity of motoneurons of the locomotor network of the Lymnaea nervous system (PeA-cluster). It is suggested that the pH value plays the modulating role in coordination of activities of the nervous centers of the mollusc nutrition and locomotion.