Histological and histochemical observations on the testis of Gobius paganellus

Summary Histological and histochemical observations on the testis of Gobius paganellus during all seasons of the year are described. In the yearly reproductive cycle, spawning in the Gulf of Naples occured from June through August, testicular recovery and relative inactivity from September through December, and active spermatogenesis from January to May.Germ cells develop as clones from single primary spermatogonia, each clone in a follicle enveloped by cells which are interpreted as Sertoli cell homologues.Glandular tissue is present in large amounts both in the form of interstitial islets and as a large mass along the length of the mesorchium. Cholesterolpositive lipids and ⁵-3-hydroxysteroid dehydrogenase, presumptive evidence for steroid production, are present exclusively in this tissue.Lipids are present in the glandular cells in acidic and neutral forms. The acid fats are the more abundant, but neutral lipids increase in amount in the period April-June. There is, furthermore, a cyclic variation in lipid droplet size, small droplets being present in the spring (during active spermatogenesis) and fewer, larger droplets during the fall (post-spawning period). Phospholipids are lacking.Lactic dehydrogenase activity was weak in the relatively inactive postspawning period, but was much more intense during active spermatogenesis.The glandular tissue in the testis of Gobius is interpreted as homologous with the interstitial (Leydig) tissue found in the testes of higher vertebrates.This investigation was supported by research grant RG-6455 from the Division of General Medical Sciences, U.S. Public Health Service.Postdoctoral Fellow from the Division of General Medical Sciences, U.S. Public Health Service. Supported in part by U.S. Public Health Service Training Grant 5 Tl GM-136, Department of Biological Structure, University of Washington, School of Medicine, Seattle, Washington, U.S.A.