title: A birefringence, electron microscopy, and histochemical survey of chromosomal structure in the sperm nuclei of an echinothurid sea urchin, Araeosoma owstoni.
abstract: The mature sperm head of Araeosoma owstoni, an echinothurid sea urchin, showed positive birefringence reflecting that the overall orientation of DNA molecules was semiperpendicular toward the nuclear axis of the sperm head. Transmission electron microscopical observation of sperm in this species revealed a highly electron-dense cylindrical coil with an empty central core extending along the major axis of the sperm head. This coil had seven to eight turns along its entire length of 3.5 micron. The maximum width was 0.35 micron near the distal end of the nucleus, and the minimum width was 0.17 micron near the apical end. Lamellar substructures were also present in the sperm nucleus, appearing at the periphery of the electron-dense cylinder in a radial manner. Staining with Feulgen's reaction and acid-orcein indicated that the coil was probably composed of sperm chromosomes.
authors.affiliation: Misaki Marine Biological Station, Faculty of Science, University of Tokyo, Kanagawa, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Amemiya
authors.forename: I
authors.initials: I
authors.lastname: Uemura
authors.forename: T
authors.initials: T
authors.lastname: Shinkai
authors.forename: H
authors.initials: H
authors.lastname: Sato
mesh_terms: D000818:Animals; D001718:Birefringence; D002467:Cell Nucleus / Q000648:ultrastructure; D002875:Chromosomes / Q000648:ultrastructure*; D006651:Histocytochemistry; D008297:Male; D008854:Microscopy, Electron; D012617:Sea Urchins; D013094:Spermatozoa / Q000648:ultrastructure*