Ultrastructural Examination of Spermiogenesis and SpermatozoonUltrastructure in Congo tetra Phenacogrammus interruptus Boulenger,1899 (Ostariophysi: Characiformes: Alestidae)

摘要

Ultrastructural studies of spermiogenesis in Phenacogrammus interruptus usingtransmission electron microscopy revealed that the process is characterized by flagellumdevelopment, formation of a cytoplasmic canal, nuclear rotation, and nuclear fossaformation. Chromatin compaction proceeds during spermatid transformation within thespermatocysts as well as after spermiation within the lumen of the efferent ducts. Thespermatozoon is of primitive type and exhibits characters typical for Type I aquasperm. Thehead consists of a spherical nucleus with highly condensed chromatin and a centrally locatedelectron lucent area connected to a moderate-sized nuclear fossa. The nuclear fossa containcentrioles in perpendicular rrangement, surrounded by osmiophilic fibrous material. In theshort midpiece, several mitochondria and vesicles are unevenly distributed in the cytoplasmforming the cytoplasmic collar at the base of the nucleus. The cytoplasmic collar surroundsthe initial part of the flagellum, running in the cytoplasmic canal. The flagellar axoneme has atypical pattern (9×2+2) and the flagellum contains membranous compartments in the portionimmediately posterior to the termination of the cytoplasmic canal.