A phasic-tonic proprioceptor in the telson of the crayfish Procambarus clarki (Girard)

Summary A proprioceptor in the telson of the crayfish Procambarus clarki was found, which is made up of about five units. These show range fractionation, i.e. different threshold distributions and their response to bending of the telson has a transient and a stationary component. The peak frequencies reached during the period of the transient component were shown to increase with increasing bending velocity and had — with the exception of one case — the highest values when extension (contrary to flexion) was imposed. The position characteristic discharge frequencies of the stationary component and their variation with different telson positions were considerably smaller. The receptor signals movement and position to the central nervous system and is therefore called a phasictonic one.I am grateful to Prof. Dr. T. H. Bullock for his hospitality and interest in this work and also want to thank Mr. John W. Thorson for many constructive discussions. This work was aided by grants from the U.S. Public Health Service, National Science Foundation and Office of Naval Research to Prof. Dr. T. H. Bullock.