Spermatozoal ultrastructure and the main biological characteristics of Paracanthobrama guichenoti

Ultrastructure of spermatozoon was observed by transmission and scanning electron microscope in Paracanthobrama guichenoti. The results showed that the sperm of Paracanthobrama guichenoti consisted of a head, a midpiece and a tail. The head was ovoid in shape, of which the main structure was nucleus. It had no acrosome and at its caudal end the nucleus had an implantation fossa within 1/2 depth of the chromatin. The nucleus consisted of electron dense chromatin materials and contained irregularly netlike gap. The midpiece consisted of the centriolar complex and the sleeve. The sieve, which contained a high number of mitochondria and vesicles, was connected to the posterior end of the nucleus. The main structure of the tail was axoneme, which was slim and long. The structure of the tail was of the typical "9+2" model. At the proximal end of the tail there were many vesicles outside the axoneme. The distal end of the tail, however, did not contain any vesicles.