Ultrastructural Study of Spermiogenesis and Mature Spermatozoa of Ranatra unicolor with Special Reference to Centriole Adjunct (Heteroptera, Nepidae)

Spermiogenesis and spermatozoa of Ranatra unicolor (Nepidae, Heteroptera) were examined ultrastructurally. Two characters previously reported to be typical for hemipteran spermatozoa were present. In other respects the sperm ultrastructure differed : the centriole adjunct was well developed and characterized by an unusual disposition and size in mature spermatozoon. The mature nucleus still contained uncondensed chromatin lamellae and the basal half of the acrosome was displaced to a lateral position of the nucleus. Modified microtubules in Ranatra are probably formed during the disappearance of microtubules.