Male reproductive system in the Italian newt Lissotriton italicus (Peracca 1898) (Amphibia, Urodela): ultrastructural and morphological study with description of spermiogenesis, spermatozoon and spermatophore

摘要

The first morphological and ultrastructural description of testis, Wolffian duct, spermatophore, and spermatozoon of Lissotriton italicus is provided. The male reproductive system of this species consists of a pair of monolobed testes, fat bodies, efferent ductules, paired Wolffian duct, and the cloaca. The Wolffian duct is pseud-ostratified, consisting of an epithelium composed of an alternation of ciliated cells and non-ciliated secretory cells, with scattered basal cells. Melanocytes are found inthe basal lamina of the Wolffian duct. Spermiogenesis is of the discontinuous type. In the early spermatid nuclear elongation, flagellar extrusion and development of alarge acrosomal vesicle occur. Soon the perforatorium develops and the flagellum elongates. In the late spermatid gradual chromatin condensation and nuclear elongation is noticeable. At the end of spermiogenesis the flagellum develops marginal filament and undulating membrane. The mature sperm of L. italicus consists of a distinct head (acrosome, perforatorium, nucleus and nuclear ridge, plus the apical acrosomal barb) and a tail with axoneme, undulating membrane, and axial fiber. Nuclear ridge and apical acrosomal barb are two autapomorphic characters found in the Urodela. Several apomorphic characters for Salamandroidea are also present: elongation of the connecting piece, an apically modified acrosome vesicle, trifoliate axial fiber within the principal piece, elongate annulus, elongate midpiece, and the gentle merging of the axial fiber/principal piece into the endpiece. The spermatophore of L. italicus is formed by a cap consisting of randomly distributed spermatozoa surmounting a short pedicel.A membranelike structure involving the spermatophore is absent.