Ontogeny of the complex sperm in the macrostomid flatworm Macrostomum lignano (Macrostomorpha, Rhabditophora).
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.
Willems
Maxime
M
Nematology Section, Department of Biology, Ghent University, B-9000 Ghent, Belgium.
Leroux
Frederic
F
Claeys
Myriam
M
Boone
Mieke
M
Mouton
Stijn
S
Artois
Tom
T
Borgonie
Gaëtan
G
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*