The immature part of the testis in Salamandra salamandra (L.) (Amphibia, Urodela).

The immature part of the testis in the European fire salamander, Salamandra salamandra, consists of cephalo-caudally orientated zones of primary spermatogonia, secondary spermatogonia, primary spermatocytes, secondary spermatocytes and spermatids associated with follicle cells. Germ cells and follicle cells are arranged in lobules separated from each other by a vascularized connective tissue. Primordial germ cells are dispersed throughout the testicular stroma, preferably near the efferent ductules. They possess a multilobated nucleus, irregularly arranged mitochondria, nuage material, and a few lipid droplets. Primary spermatogonia are characterized by a more spherical nucleus, a coronal distribution of cell organelles--mainly mitochondria--small amounts of smooth endoplasmic reticulum, and lipid droplets. Secondary spermatogonia exhibit an irregular distribution of cell organelles with increased amounts of vesicular profiles of smooth endoplasmic reticulum; they are highly interdigitated and connected by intercellular bridges. In this stage degenerative processes may take place. Primary spermatocytes are provided with basal bodies and peripheral microtubules. Secondary spermatocytes and spermatids will be described elsewhere. Follicle cells and their projections surround each germinal cyst. Their nucleated parts are commonly localized in the central part of the lobule. Follicle cells and lobule boundary cells are very similar to fibrocytes. Already in the primary spermatocyte zone, both cell types show ultrastructural features indicating a setting in glandular activity.