Spermatological characteristics of the Trypanorhyncha inferred from new ultrastructural data on species of Tentaculariidae,Eutetrarhynchidae, and Progrillotiidae

The present study focuses on the ultrastructural characteristics of both spermiogenesis and the spermatozoon in the order Trypanorhyncha. New ultrastructural data are presented for two species of the unexplored superfamily Tentacularioidea, Nybelinia queenslandensis, and Kotorella pronosoma. The present study also provides supplementary data on the superfamily Eutetrarhynchoidea, with the analysis of spermiogenesis and spermatozoon of two progrillotiids, Progrillotia dasyatidis and Pro. pastinacae, and new ultrastructural data concerning spermiogenesis in the eutetrarhynchids Dollfusiella spinulifera and Parachristianella trygonis. Spermiogenesis in trypanorhynchs follows the Bâ and Marchand's type I and the ultrastructural organisation of the mature spermatozoon corresponds to the Levron et al.’s type I. The most remarkable characters concerns the number of electron-dense plates constituting the intercentriolar body during spermiogenesis and in the variability of the arc-like row of thick cortical microtubules present in the anterior areas of the spermatozoon because of its variability according to the species.