title: Ultrastructural study of spermiogenesis and the spermatozoon of Crepidostomum metoecus (Digenea: Allocreadiidae), a parasite of Salmo trutta (Pisces: Teleostei).
abstract: Spermiogenesis and the spermatozoon of Crepidostomum metoecus, an intestinal parasite of brown trout Salmo trutta, were studied by transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone in front of 2 centrioles associated by an intercentriolar body. Each centriole is linked to a striated rootlet, and gives rise to a flagellum. The rotation of flagella is greater than 90 degrees; their fusion with the median cytoplasmic extension is proximodistal and asynchronous. The spermatozoon is formed after constriction of arched membranes. The spermatozoon possesses 2 axonemes of the 9 + "1" pattern, a nucleus, mitochondria, and glycogen. A major feature is the presence, in the anterior part, of external ornamentation and a lateral expansion associated with spinelike bodies. Another attribute is the presence of 2 mitochondria rather than just 1, as in most of the digenean spermatozoa. To our knowledge, this study is the first undertaken with a species of the Allocreadiidae.
authors.affiliation: Parasites and Mediterranean Ecosystems Laboratory, Faculty of Sciences and Technology, University of Corsica, F-20250 Corte, Corsica, 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*; 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*