Ultrastructure features of spermiogenesis and spermatozoa of sparid fish Rhabdosargus sarba (Forsskål, 1775) from Red SEA, Jeddah coast

Abstract

Transmission and scanning electron microscopy were used to investigate the ultrastructure of spermatogenesis of the Sparid fish Rhabdosargus sarba. The testis is lobular in shape and spermatogensis is of unrestricted type. Spermatogonia occur isolated or in clusters within the seminiferous lobules. The germ cells are found in cysts formed by sertoli cell processes. Cells within cysts are found in the same developmental stage. Spermiogenesis is characterized by chromatin condensation, movement of the centrioles, flagellum development, nuclear rotation, nuclear indentation and nuclear fossa formation, reduction of the cytoplasm and differentiation of the flagellar complex. Ultrastructurally the spermatozoa of R. sarb belonges, like that of other sparid fish, to the teleosean type 1 spermatozoan with the flagellum axis perpendicular to the nuclear fossa. It has an ovoidal head, a short, cylindrically shaped midpiece and a long tail region. The nucleus reveals a deep invagination (nuclear fossa) in which the centrriolar complex is located, and a satellite nuclear noch shaped like a bell. The centriolar complex lies inside the nuclear fossa and is composed of a proximal and a distal centriole. The two centerioles are perpendicular to each other. The distal centriole is traversed by a conspicuous basal plate in its base. At the neck of the flagellum the necklace is observed. A nuclear noch is located above the proximal centeriol. The short midpiece houses two spherical mitochondria. The flagellum is inserted medio-laterally into the head, contains the conventional 9+2 axoneme.