Ultrastructure of late spermatids and spermatozoa during spermiogenesis in longtooth grouper Epinephelus bruneus from Jeju, Korea.

Ultrastructural characteristics of late spermatids and spermatozoa during spermiogenesis in longtooth grouper Epinephelus bruneus from Jeju, Korea were investigated using transmission and scanning electron microscopy. The spermiogenesis type of E. bruneus belongs to type I because of nuclear rotation occurrence. The spherical head of late spermatids and spermatozoa ultrastructurally consist of apple-shaped nucleus, nuclear notch (Y or branch-shaped) and nuclear fossa. The midpiece contains the proximal centriole (9+0 microtubule structure), two centrioles connection structure (three osmophilic filaments), the distal centriole (9+0 microtubule structure), an osmophilic basal foot, two necklaces (six or seven osmophilic particles) and osmophilic alar sheets. It contains six to nine spherical mitochondria showing two rows arrangement type. Also a flagellum (9+2 microtubule structure) presents six swelling shaped segments type lateral fins with regular interval. Consequently, ultrastructural features of E. bruneus spermatids and spermatozoa contribute to provide useful systematic characters for taxonomic purpose. It may contribute to study that whether ultrastructural features of cellular organelles (cytoplasmic canal, necklace and lateral fins) correlate to physiological function or not on the duration of motility and survival in fish spermatozoa.