Abstract


Relatively little is still known about the function, types and location of paraproctal sensory systems. This system detects and encodes four different sensory modalities: wind, touch, gustatory and olfactory. The left and right paraproct of the female locusts are located between the dorsal ovipositor, the epiproct and the ninth abdominal sclerite. They are positioned as the most posterior abdominal segments. In the present study, the distribution and the peripheral innervation of the sensory organs on the paraproct has been studied in wholemount
preparations by using the cobalt backfill techniques. The paraproct of the female locust bears hair sensilla of three basic types: a) Mechanosensory hairs (bristle or trichoid) each supplied with one sensory cell, b) Dual innervated mechanosensory hairs with a fine cuticular shaft which are restricted to the region near the posterior edges of the outer faces, c) Basiconic hairs which are multimodal receptors which encode both mechanical and chemical contact cues. The morphology and organization of the central projections of chemoreceptors and mechanoreceptors afferent from the paraproct were examined by neurobiocytin staining individual hair afferents. All afferent fibres project in the tenth neuromere of the terminal
abdominal ganglion. Projections from single multiply innervated hair sensilla do not segregate with the exception of one afferent of contact chemosensory hairs which terminate only in its segmental neuromere, as was shown for other contact chemoreceptors of the abdomen. It is
concluded that these sensilla at the very tip of the abdomen play a major role for mating, for the selection of oviposition sites and during the different oviposition subroutines.

Keywords: Neurobiology; Sensory neuron; Innervation;
Immunocytochemistry; Electrophysiological recording.