The ultrastructure of the cuticle of the nematode Syphacia obvelata (Rudolphi, 1802). III. Cuticle associated with the male reproductive structures

Abstract

Mamelons of male Syphacia obvelata are ventrally situated copulatory structures bounded by cuticle, and internally composed of muscles. Extracuticular spines are found at the apex of each annulus making up the mamelon. The cloaca is formed by an invagination of body wall cuticle, as is the spicule sheath (a portion of the cloacal wall surrounding the free end of the spicule). The spicule, accessory piece, and papillae are innervated and probably function as mechanoreceptors facilitating the positioning of the cloacal region over the vulva during copulation. Dense material forming the gubernaculum, spicule, and accessory piece is distinct from the body wall cuticle. The cortex and basal zones are apposed around the cloacal opening and probably strengthen this area. On the other hand, cuticle lining the cloaca is composed of cortex and an expanded inner zone of matrix material. This matrix material would allow considerable modification in the shape of the cloacal wall during copulation. The apposition of cortex and basal zones over the tip of anal papillae would ensure effective transmission of pressures to the nerve process.