Embryonic development of the central projection of auditory afferents (Schistocerca gregaria, Orthoptera, Insecta).
The auditory system of Schistocerca gregaria is a well investigated sensory network in the adult grasshopper. Here we present a first study on the embryonic development of this neuronal network. Focussing on the auditory receptor cells we show that they differentiate axonal processes at around 45% of embryonic development. These axons fasciculate with the intersegmental nerve and enter the central nervous system by 45-50% of development. First collaterals sprout into the major arborization area, the frontal auditory projection area of the metathoracic ganglion by 60%. This projection increases in density until an adult-like morphology is established by 90% of development. Furthermore, by the end of embryogenesis all three types of receptor fiber projections can be distinguished. This development is independent of a hearing ability, which develops much later during postembryonic life. The auditory projection co-develops with the fusion of neuromeres to the metathoracic ganglion, the formation of the target neuropile areas and the expression of the synapse associated molecule synapsin. Fasciclin I and Lachesin, both potential axon-guidance molecules, are expressed strongly on both, peripheral and central auditory pathways and, although much weaker, within the synaptic target area.
Schäffer
S
S
Georg-August-Universität Göttingen, Abt. Neurobiologie, Institut für Zoologie und Anthropologie, Berliner Str. 28, 37073 Göttingen, Germany.
Lakes-Harlan
R
R
D000818:Animals; D001306:Auditory Pathways / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D002232:Carbocyanines; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002490:Central Nervous System / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D004625:Embryo, Nonmammalian / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D005456:Fluorescent Dyes; D017952:Ganglia, Invertebrate / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D006110:Grasshoppers / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D009415:Nerve Net / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D009475:Neurons, Afferent / Q000378:metabolism / Q000648:ultrastructure*
C035005:3,3'-dihexadecylindocarbocyanine; D002232:Carbocyanines; D015816:Cell Adhesion Molecules, Neuronal; D005456:Fluorescent Dyes; C051641:fasciclin I