[Ultrastructural organization of the auditory nerves of Gryllus bimaculatus and G. campestris crickets]. / Ul'trastrukturnaia organizatsiia slukhovykh nervov sverchkov Gryllus bimaculatus i G. campestris.

Electron microscopic observations have been made on transverse sections of the auditory (tympanal) nerve of the crickets at various levels from the tympanal ganglion (close to the ganglion, 150, 250, 1,000, 2,000 and 3,000 mu from the latter). In the vicinity of the ganglion, axons of the auditory receptors are separated from each other by the processes of Schwann cells. Beginning from the level of 150-250 mu, the axons are subdivided and form, with the help of collaterals, a subreceptor plexus which is similar to that found in the auditory system of the locust. Collaterals of an axon pass to the adjacent axons and deeply penetrate into the latter loosing their Schwann sheath, so that axonal membranes form a direct contact. At the site of these contacts, intracellular cleft is equal to 50-80 A. No synaptic vesicles were found in the region of the plexus. At the level of 3,000 mu, the auditory axons again attain a roundlike form and become completely isolated from each other by the processes of Schwann cells. It is suggested that in the region of the subreceptor plexus, electrotonic interaction between the receptors of the crickets takes place, as it is common in the auditory sistem of insects.