Proprioception from Nonspiking Sensory Cells in a Swimming Behavior of the Sand Crab, Emerita analoga

Abstract

Crabs of the genus Emerita swim by beating the uropods (the most posterior pair of segmental appendages). Two patterns of motor coordination of the uropod beat correlate with two kinds of behavior: “true” swimming and treading water. The essential difference between the two motor patterns is the timing of the power stroke in the interval between the beginning of successive return strokes (cycle). During swimming the latency of the power stroke is correlated positively with cycle duration (80–400 msec), so that the power-stroke phase is fairly constant at 0.5–0.6, whereas during treading water the latency is short (40–60 msec) and increases only slightly over a six fold increase in cycle duration (100–700 msec), (Paul, 1971a, and this study).