The Structure of the Male Genital System of the Port Jackson Shark, Heterodontus portujacksoni, with Particular reference to the Genital Ducts

Abstract

The testes of H. portusjacksoni are paired cylindrical organs with a germinal ridge running longitudinally along the ventral surface. The latter produces ampullae which contain Sertoli and germinal cells, and which migrate dorsally as spermatogenesis proceeds. They evacuate near the dorsal surface of the testis to release spermatozoa, large oval eosinophilic bodies (Sertoli cell bodies) and small eosinophilic particles. All of the genital ducts are lined by a ciliated epithelium. In the rete testis it is a low columnar type; the ducts consist of the conducting tubules, which convey ampullae across the testis, and the longitudinal testis canal, which runs along the dorsal surface of the testis. Six ductuli efferentes (lined by a low pseudostratified columnar epithelium) leave the testis, course dorsally through the epigonal organ and mesorchium, and enter the epididymis. Subsequently, pairs of ductuli efferentes successively join together to form a short common ductulus efferent which then continues as the ductus epididymidis. The latter has two structurally distinct regions: the initial segment is a narrow, convoluted, pigmented duct with a very tall pseudostratified epithelium; the terminal segment is wider than the initial segment, unpigmented and lined by a low pseudostratified epithelium. It is very convoluted proximally, but widens and becomes less convoluted distally; its distal 5 cm (ampulla of ductus epididymidis) is straight and contains a muscular wall. Very few Sertoli cell bodies are present in the terminal segment of the ductus epididymidis. However, except for the ampullary region the duct receives secretions (including irregularly shaped eosinophilic bodies) from Leydig's gland (a series of branched tubular glands). Secretions from these glands seem to be involved in the formation of spermatozoa into spherical bundles. The structure of the clasper and siphon are assessed in terms of their function and significance for taxonomical purposes.