Abstract
The ultrastructure of mature spermatozoan was examined by TEM and SEM for 11 species of Gasterosteoidei: Hypoptychidae (Hypoptychus dybowski), Aulorhynchidae (Aulichthys japonicus, Aulorhynchus flavidus), and Gasterosteidae (Gasterosteus aculeatus, G. wheatlandi, Pungitius pungitius, P. tymensis, P. sinensis, P. kaibarae ssp., Culaea inconstans, and Spinachia spinachia). All spermatozoa were characteristic of a uniflagellate anachrosomal aquasperm type, but with significant variations. Nuclei, characterized in all species by a very shallow nuclear fossa, were grouped into four morphological types, ranging from an elongate temple bell shape to fully spherical. Coaxial arrangements of the proximal and distal centriole were confirmed in most species. A centriolar plug and accessory appendage were observed in some gasterosteid species, and a centriolar adjunct shared by Aulorhynchus flavidus and the gasterosteids. Mitochondria were divided into ring and tube-shaped types, separable at the generic level. Sperm morphology indicated paraphyly of Aulorhynchidae as presently recognized. Similarly, sperm structure did not support our molecular phylogeny placing Gasterosteus as the sister taxon of other gasterosteid genera.
