title: Spermiogenesis and sperm ultrastructure of Machilontus sp (Insecta: Archaeognatha) with phylogenetic consideration.
abstract: The sperm structure of the jumping bristletail Machilontus sp has been described. The species shares several sperm characteristics with other genera of the same order Archaeognatha. During late spermiogenesis the spermatid bends at half of its length with the two limbs closely apposed within the same plasma membrane. The sperm has a helicoidal bi-layered acrosome with a filamentous perforatorium and a long nucleus. The elongated flagellum consists of an axoneme with 9 accessory microtubules external to the 9+2, two rows of conventional mitochondria and two accessory bodies. The accessory bodies are located lateral to the axoneme and are probably responsible for the shifting of the accessory tubules in two opposite groups of 5 and 4 tubules, respectively. These sperm characteristics represent common traits of all Archaeognatha.
authors.affiliation: Department of Life Sciences, University of Siena, Via A. Moro 2, I-53100 Siena, Italy.
authors.forename: Pietro Paolo
authors.initials: PP
authors.lastname: Fanciulli
authors.affiliation: Department of Life Sciences, University of Siena, Via A. Moro 2, I-53100 Siena, Italy.
authors.forename: David
authors.initials: D
authors.lastname: Mercati
authors.affiliation: Sugadaira Montane Research Center, University of Tsukuba, Nagano 386-2204, Japan.
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Machida
authors.affiliation: Department of Life Sciences, University of Siena, Via A. Moro 2, I-53100 Siena, Italy. Electronic address: romano.dallai@unisi.it.
authors.forename: Romano
authors.initials: R
authors.lastname: Dallai
mesh_terms: D000177:Acrosome / Q000648:ultrastructure; D000818:Animals; D054468:Axoneme; D002467:Cell Nucleus / Q000648:ultrastructure; D007313:Insecta / Q000502:physiology* / Q000648:ultrastructure*; D008297:Male; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008870:Microtubules / Q000648:ultrastructure; D010802:Phylogeny; D013045:Species Specificity; D013082:Sperm Tail / Q000648:ultrastructure; D013087:Spermatids / Q000648:ultrastructure; D013091:Spermatogenesis; D013094:Spermatozoa / Q000648:ultrastructure*
keywords: Electron microscopy; Insect phylogeny; Insect spermiogenesis; Insect ultrastructure