The ultrastructure of spermatogenic cells and morphological evaluation of testicular development in the silver pomfret (Pampus argenteus)

The silver pomfret (Pampus argenteus) is a widely distributed and economically important marine fish in the Indo-Pacific. In this study, we acquired the second generation of wild P. argenteus by artificial breeding and further studied the testicular development and ultrastructure of spermatogenesis. The results of gonadosomatic index (GSI) showed the spawning period of this marine fish was from April to June. Besides, through morphological analysis, we found that P. argenteus had an anastomosing tubular testis surrounded by a layer of tunica albuginea, in which spermatogenesis occurred in cysts where the synchronous germ cells were completely surrounded by the cytoplasmic projection of Sertoli cells. Meanwhile, based on submicroscopic characteristics, the germ cells are classified into nine different types. During the ontogenesis of testis, both the early stage of spermatogenesis and sperm were observed in P. argenteus. At sperm maturation stage, different types of spermatozoa and activation of sperms occurred non-synchronously in the tubules. Cytoplasmic bridges also were observed among synchronous germ cells within the cysts, suggesting an interrelated and differentiated relationship among these germ cells.