title: Spermiogenesis and spermatozoon ultrastructure of Nicolla wisniewskii (Digenea: Opecoelidae), an intestinal parasite of brown trout Salmo trutta (Pisces: Teleostei).
abstract: Spermiogenesis and ultrastructure of spermatozoon of Nicolla wisniewskii (Digenea, Opecoelidae), an intestinal parasite of Salmo trutta, were studied by electron microscopy. Spermiogenesis follows the general pattern found in the Digenea. It begins with the formation of a differentiation zone, including striated rootlets associated with 2 centrioles and an intercentriolar body. The flagella undergo a rotation of greater than 90 degrees. Then, their fusion with the median cytoplasmic process is proximodistal and asynchronous. A peculiarity was observed before the fusion of flagella, i.e., the attachment zones joined as 2 pairs by an electron-dense bridge. The mature spermatozoon is characterized by 2 axonemes, cortical microtubules, a nucleus, 2 mitochondria, external ornamentation, and spinelike bodies. At the posterior end of flagella, the spermatozoon is also characterized by the presence of a central element of the axoneme and without the 9 microtubule doublets. These results were compared with those of the other digeneans and, in particular, with other species of Opecoelidae. It appears that the number of cortical microtubules and their localization in the spermatozoon may be an interesting feature of their phylogeny.
authors.affiliation: Laboratory Parasites & Mediterranean Ecosystems, Faculty of Sciences and Technics, University of Corsica, F-20250 Corte, Corse, France. quilichini@univ-corse.fr
authors.forename: Yann
authors.initials: Y
authors.lastname: Quilichini
authors.forename: Joséphine
authors.initials: J
authors.lastname: Foata
authors.forename: Antoine
authors.initials: A
authors.lastname: Orsini
authors.forename: Bernard
authors.initials: B
authors.lastname: Marchand
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000469:parasitology*; D007411:Intestinal Diseases, Parasitic / Q000469:parasitology / Q000662:veterinary; D007422:Intestines / Q000469:parasitology; D008297:Male; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D013091:Spermatogenesis; D013094:Spermatozoa / Q000648:ultrastructure*; D014200:Trematoda / Q000502:physiology* / Q000648:ultrastructure; D014201:Trematode Infections / Q000469:parasitology / Q000662:veterinary*; D014337:Trout / Q000469:parasitology*