Muscle receptor organs of the crayfish,Cherax destructor: Organisation of central projections of stretch receptor neurons

Abstract

The stretch receptor neurons of the abdominal muscle receptor organs of crayfish enter the ventral nerve cord and branch to send axons to the brain and to the last abdominal ganglion. They mediate local reflexes in the ganglion of entry and adjacent ganglia but evidence from previous cobalt filling and histology suggested that local branching is limited and variable and does not accord closely with physiological evidence. We examined the fine structure of the branching in a large number of preparations from large animals of the crayfish Cherax destructor,which is also a large species, to determine whether the increased resolution afford by size would permit us to detect previously undetected patterns. We found some predictable features in the pattern of fine branching in the ganglion of entry and adjacent ganglia that could explain some of the apparent anomalies. We also examined the relative positions of the hook-shaped projections from different segments where they terminate in the last abdominal ganglion by differentially staining the stretch receptors with Co++ and Ni++. We found evidence for somatotopic organisation in the longitudinal position of the endings. J. Exp. Zool. 279:243–253, 1997. © 1997 Wiley-Liss, Inc.