Studies on the ultrastructure of spermiogenesis and spermatozoon of tongue fish,Cynoglossus semilaevis günther

Ultrastructures of spermiogenesis and spermatozoon of commercially valuable tongue fish Cynoglossus semilaevis Günther were investigated by means of transmission electron microscopy. The study shows that the spermiogenesis of C. semilaevis can be divided into four stages, and the course of spermatid differentiation included flagellum development, chromatin compaction, nuclear fossa formation, migration of diplosome and mitochondria with structural change and disappearance of residual cytoplasm. No acrosome was observed in spermatozoon of C. semilaevis. The nucleus of sperm was U‐shaped; the nuclear fossa was deep with a centriolar complex at the bottom composed by proximal centriole and basal body. Five to six mitochondria were located behind the nucleus in a circle, forming the midpiece of sperm. The sperm tail, 43±2.4 μm (n=5) long, had lateral fins and sacciform tissues in some parts of the tail, with axoneme shown of a typical ‘9+2’ pattern. The ultrastructural observation revealed that the sperm of C. semilaevis is of a primitive type among teleostean fish species.