Fine structural observations on the process of spermiation in the holocephalan fish Hydrolagus colliei.

The process of spermiation in the ratfish Hydrolagus colliei is described and compared with that in mammals and amphibians. Spermiation in this species involves prior fluid space expansion both within the apical parts of the Sertoli cytoplasm and in the spaces between Sertoli cells and spermatids. The apical ends of Sertoli cells fragment, including the parts immediately around the spermatid acrosomes. Intercellular material between the spermatid tips and the Sertoli cells dissolves. Concurrently an opening from the seminiferous follicle into the efferent ductule is made by means of changes in cell shape and separation of Sertoli cells and efferent ductule cells that adhere to each other up to the time of sperm release.