Studies on the activation of crustaceans mechanoreceptors. The movement receptors of the crab Pachygrapsus crassipes Randall and the movement and stretch receptors of the crayfish Procambrus Clarkii (Girard)

Abstract

The activation of crab movement receptors and of crayfish movement and stretch receptors was studied. It was found that the adequate stimulus to movement receptors is a change of the length of the elastic strand into which they send their distal processes. One group of movement receptors responds to shortening of the strand; and another group to its lengthening. A hypothesis is presented that accounts for the differential sensitivity of these two groups of cells, and the difference between movement and position receptors in the same sense organ. It was found that the movement receptors may be activated by nicotine as well as by mechanical means; and that nicotine activation differs in a significant manner from mechanical activation. The unusual spiking pattern of movement receptors was examined using intracellular and extracellular recording. The mode of activation by nicotine and the intracellular recording data are combined to form a partial explanation of the movement receptors’ discharge pattern. Caffeine was found to block the mechanical activation of movement receptors and it is concluded that this is due to a direct effect on the mechanotransducer membrane. Several drugs which affect the crayfish stretch receptor were found to have no effect on movement receptors and conversely nicotine and caffeine were found to have no effect on stretch receptors. Stretch receptors were subjected to the same mechanical stimuli used on the movement receptors and the responses of the two types of end organs compared. The similarities and differences of movement and stretch receptors are discussed.