title: The length of a short sperm: Elongation and shortening during spermiogenesis in Cotesia congregata (Hymenoptera, Braconidae).
abstract: The spermatozoon of the parasitoid wasp Cotesia congregata is an extremely short gamete measuring less than 7 μm; it is as yet the shortest flagellated sperm to be identified. The mature sperm consists of an acrosome, surrounded by an extra cellular coat, a condensed nucleus, two uncoiled mitochondrial derivatives and a short axoneme. Testes of young adults contain a continuum of differentiation stages. Initially, the flagellum is approximately 5 μm long. It conserves its length in round, elongated and mature spermatids, but is reduced to less than 3 μm in mature spermatozoa. The nucleus is 2 μm in diameter when round, 10 μm long when it becomes a long boat-hull shaped filament, and then reduces to 3.6 μm. Thus, during development the gamete reaches a total length of 15 μm before finally reducing to less than half that length. Some traits of mature sperm anatomy are similar to related species of the Braconidae family, but others seem to be specific and could be due to the shortness of the cell. This uncommon elongation and subsequent shortening of such a tiny flagellated cell constitutes a model for both nucleus and cilium development.
authors.affiliation: Department of Microscopy, François Rabelais University, 10 Boulevard Tonnellé, 37032, Tours, France; Faculty of Bioengineering and Bioinformatics, Moscow State University, 119991, Moscow, Russia. Electronic address: rustem.uzbekov@univ-tours.fr.
authors.forename: Rustem
authors.initials: R
authors.lastname: Uzbekov
authors.affiliation: Department of Microscopy, François Rabelais University, 10 Boulevard Tonnellé, 37032, Tours, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Burlaud-Gaillard
authors.affiliation: Department of Microscopy, François Rabelais University, 10 Boulevard Tonnellé, 37032, Tours, France; NUST MISiS, Leninskiy Prospekt 4, Moscow, 119049, Russia.
authors.forename: Anastasiia S
authors.initials: AS
authors.lastname: Garanina
authors.affiliation: Research Institute for the Insect Biology, UMR CNRS 7261, François Rabelais University, Tours, France. Electronic address: christophe.bressac@univ-tours.fr.
authors.forename: Christophe
authors.initials: C
authors.lastname: Bressac
mesh_terms: D000818:Animals; D006927:Hymenoptera / Q000166:cytology* / Q000648:ultrastructure; D008297:Male; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D013091:Spermatogenesis; D013094:Spermatozoa / Q000166:cytology* / Q000648:ultrastructure
keywords: Flagellum elongation; Nucleus condensation; Parasitoid wasp; Spermatid; Testis