Sensory Modalities and Receptive Fields in the Abdominal Nervous System of the Hermit Crab, Pagurus Granosimanus (Stimpson)

Abstract

1. The morphology and histology of the abdominal nervous system is briefly described. There are three ganglionic roots, as in the crayfish; the first innervates the pleopods and the ventral lateral area of the segment, the second innervates the sclerite of the next posterior segment, and a region posterior and dorsal to it. The third roots are exclusively motor as in the crayfish and have two branches, one of which runs to the superficial ventral muscles and the other to the central flexors. 2. Phasic fast-adapting mechano-receptors similar to those seen in annelids, with overlapping fields extending over much of the segment, have replaced the sensory hair population of the homologous roots in the crayfish. 3. The units on the left side of the animal are more sensitive to mechanical stimuli than those on the right side; this is due to the fact that the right side lies next to the whorl of the shell while the left side faces away from it. 4. Joint receptors are described, but no muscle receptor organs similar to those found in other decapods were observed.