title: Ultrastructure of sperm cells in the female gonoduct of Xiphinema.
abstract: The ultrastructure of the sperm cells in the female gonoduct of the nematodes Xiphinema theresiae and X. pinoides is described. The nucleus of the sperm cells is composed of several electron-dense clumps of chromatin that is not surrounded by a nuclear envelope. A layer of mitochondria, in which the mitochondrial cristae are only rarely visible, lies around the nuclear material. In the surrounding cytoplasm packets of electron-dense fibres are abundant. The sperm in the uterus have the following surface differentiations: highly intertwined protrusions between adjacent sperm cells, protrusions coinciding with the plication of the inner uterine wall and a slightly undulated surface towards the uterine lumen. It is argued that in the uterus, the sperm cells actively move in proximal direction by a mechanism resembling pseudopodial movement, in which the packets of fibres are involved. In the oviduct, the sperm cells loose their surface protrusions and the packets of fibres gradually become less abundant. Since the oviduct has no pre-formed lumen, the sperm cells appear to wedge their way along by forcing oviduct cells apart.
authors.affiliation: Rijksuniversiteit Gent, Instituut voor Dierkunde, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.
authors.forename: M C
authors.initials: MC
authors.lastname: Van De Velde
authors.forename: A
authors.initials: A
authors.lastname: Coomans
authors.forename: L
authors.initials: L
authors.lastname: Van Ranst
authors.forename: J C
authors.initials: JC
authors.lastname: De W Kruger
authors.forename: M
authors.initials: M
authors.lastname: Claeys