Innervation of testes in the tilapia Oreochromis niloticus

Abstract

The innervation of the testes of Oreochromis niloticus was examined immunohistochemically and ultrastructurally. Many thick nerve bundles, which penetrate the testes via the mesorchium, are distributed in the wall surrounding the efferent duct. The neurons appear to terminate at the surface of smooth muscle cells in the efferent duct wall. Thin nerve bundles penetrate the interstices among lobules containing cysts of spermatogenic germ cells. Terminal ends of these nerve fibres also make contact with smooth muscle cells enclosing lobules and with the surface of steroid-producing Leydig cells (SPC). These observations suggest that innervation of the testis may not only control the contracting and relaxing of smooth muscle cells but also control steroid secretion. Some fibres containing many electron-dense granules were observed in the interstices near the cluster of SPC. Such granules suggest that these fibres may be peptidergic.