title: Variation in the egg cell forming region of Gyrodactylus kobayashii Hukuda, 1940 (Monogenea:Gyrodactylidae).
abstract: The egg cell forming region of Gyrodactylus kobayashii from goldfish (Carassius auratus) is a thin nucleated cytoplasmic layer surrounding the developing egg cell (= oocyte). The cytoplasm contains numerous elougate membranes. As parasites age, the egg cell forming region becomes electron lucent. The apical membrane of the egg cell forming region becomes disrupted in places. A basal matrix is indistinct in new-born and young worms, becoming more evident as worms grow older. Numerous pits (= basal pits) are found along the basal plasma membrane of worms with a mature male system. These pits appear to be stable components of the membrane and resemble hemidesmosomes. Basal pits were co-incident with sperm in the egg cell forming region in 3 of 5 worms examined. The function of the basal pits of G. kobayashii could not be determined. It is postulated, however, that they either assist sperm to traverse the egg cell forming region to fertilize the egg cell or stabilize the egg cell forming region against damage by sperm traversing this layer. The egg cell forming region encloses a large egg cell and 1 or more smaller differentiating egg cells. The ripening egg cell has a large nucleus and extensive cytoplasm. The cell has a thickened membrane. Large vacuoles and invaginations at the periphery of the egg cell appear to engulf cytoplasm of the egg cell forming region.
authors.affiliation: Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Australia. m.jones@mailbox.uq.oz.au
authors.forename: M K
authors.initials: MK
authors.lastname: Jones
authors.forename: I
authors.initials: I
authors.lastname: Ernst
authors.forename: I D
authors.initials: ID
authors.lastname: Whittington
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D002589:Cestoda / Q000648:ultrastructure*; D003593:Cytoplasm / Q000648:ultrastructure*; D005260:Female; D006054:Goldfish / Q000469:parasitology; D008297:Male; D008854:Microscopy, Electron; D009865:Oocytes / Q000648:ultrastructure*; D010053:Ovary / Q000648:ultrastructure; D012098:Reproduction; D013737:Testis / Q000648:ultrastructure