Organization of rhythmic buccal motor output of Lymnaea stagnalis in the absence of food.

The pond snail Lymnaea stagnalis exhibits spontaneous rasping movements in the absence of food which are thought to be involved in food searching activity. Rasping activity is patterned into bouts, separated by periods of quiescence. Recordings from buccal feeding motoneurons in the isolated CNS reveal similar bouts of rhythmic motor output, though the modal cycle period is significantly longer than that shown by intact snails. Log survivorship curves of interval data from both intact animals and isolated CNS indicate that the pattern of motor output is controlled by at least two processes, one generating intervals between rasps within a bout, and the other generating intervals between bouts of rasping. When compared to well-fed individuals, 2-day-starved snails show significant enhancement of the probability function for generation of intervals between rasps within a bout; the function underlying between-bout intervals is not significantly affected.