Proprioceptors with central cell bodies in insects

Abstract

A common feature of invertebrate sense organs is that the cell bodies of the sensory neurones are located in the periphery, close to the site of stimulus reception. For some phyla of invertebrates examples are known where sensory cells have their somata inside the central nervous system (CNS), but none are yet known for the insects. In this report we describe a proprioceptive organ in the locust thorax that consists of an elastic strand that is supplied with terminal branches of a small group of sensory neurones. The somata of these neurones are not located in the periphery, but inside the third thoracic ganglion. Our findings indicate that at least a small number of cell bodies in insect ganglia may belong to sensory neurones, rather than to motoneurones, interneurones or neurosecretory cells.