Neuromusculature of the ovijector of Ascaris suum (Ascaroidea, Nematoda): An ultrastructural and immunocytochemical study

This study used electron microscopy and confocal scanning laser microscopy interfaced with cytochemistry to study neuromuscular interrelationships in the ovijector of Ascaris suum. An extensive nerve plexus with both FaRPergic and non‐FaRPergic components extends over the outer surface of the ovijector. The non‐FaRPergic component is derived from nerve branches of the ventral nerve cord, whereas the FaRPergic component emanates from two large FMRFamide‐immunoreactive neurons. In the vagina vera, most myofibrils are circular in orientation and a number of them divide and run for short distances in longitudinal and diagonal directions, their myofilaments are also orientated in a variety of directions. Parallel nerve fibres run in tracts along the length of the vagina vera with branches that penetrate the muscle layers. The vagina uteri possesses a thicker hypodermis than that of the vagina vera. It appears rich in secretory and phagocytic vesicles and the luminal side is invested with an electron‐dense substance. The musculature of the vagina uteri is less well developed than that of the vagina vera, being restricted to circular myofibrils, with an apparent diagonal arrangement of myofilaments. Also, the innervation is less extensive in the vagina uteri with many fibres returning to the vagina vera to rejoin the nerve net and others continuing into the uteri. J. Comp. Neurol. 415:518–528, 1999. © 1999 Wiley‐Liss, Inc.