title: Ontogeny of the complex sperm in the macrostomid flatworm Macrostomum lignano (Macrostomorpha, Rhabditophora).
abstract: Spermiogenesis in Macrostomum lignano (Macrostomorpha, Rhabditophora) is described using light- and electron microscopy of the successive stages in sperm development. Ovoid spermatids develop to highly complex, elongated sperm possessing an undulating distal (anterior) process (or "feeler"), bristles, and a proximal (posterior) brush. In particular, we present a detailed account of the morphology and ontogeny of the bristles, describing for the first time the formation of a highly specialized bristle complex consisting of several parts. This complex is ultimately reduced when sperm are mature. The implications of the development of this bristle complex on both sperm maturation and the evolution and function of the bristles are discussed. The assumed homology between bristles and flagellae questioned.
authors.affiliation: Nematology Section, Department of Biology, Ghent University, B-9000 Ghent, Belgium.
authors.forename: Maxime
authors.initials: M
authors.lastname: Willems
authors.forename: Frederic
authors.initials: F
authors.lastname: Leroux
authors.forename: Myriam
authors.initials: M
authors.lastname: Claeys
authors.forename: Mieke
authors.initials: M
authors.lastname: Boone
authors.forename: Stijn
authors.initials: S
authors.lastname: Mouton
authors.forename: Tom
authors.initials: T
authors.lastname: Artois
authors.forename: Gaëtan
authors.initials: G
authors.lastname: Borgonie
mesh_terms: D000818:Animals; D008297:Male; D008853:Microscopy; D046529:Microscopy, Electron, Transmission; D010986:Platyhelminths / Q000648:ultrastructure*; D013079:Sperm Maturation / Q000502:physiology; D013091:Spermatogenesis / Q000502:physiology*; D013094:Spermatozoa / Q000648:ultrastructure*