Spermatology of the genus Lepidodasys Remane, 1926 (Gastrotricha, Macrodasyida): towards a revision of the family Lepidodasyidae Remane, 1927

Abstract

 Abstract Guidi, L., Pierboni, L., Ferraguti, M., Todaro, M.A., Balsamo, M. Spermatology of the genus Lepidodasys Remane, 1926 (Gastrotricha, Macrodasyida): towards a revision of the family Lepidodasyidae Remane 1927. -Acta Zoologica (Stockholm) 85 : 211-221The spermatozoa of Lepidodasys unicarenatus and Lepidodasys sp. are filiform and composed of a cork-screw shaped acrosome, a helical nucleus surrounding a mitochondrial axis, and a 9 × 2 + 2 flagellum as in the basic structural model of the macrodasyidan sperm. The genus Lepidodasys has a debated phylogenetic position and has been linked in turn to the family Lepidodasyidae and the family Thaumastodermatidae. The sperm features of the two Lepidodasys species examined are distinct from those typical of the two families: the absence of the periaxonemal cylinder, a character shared only with Turbanellidae among Macrodasyida, could be considered as a symplesiomorphy, suggesting a basal position of the genus along the Macrodasyida clade. Moreover, a comparison of the spermatogenic process of Lepidodasys sp. with those of Acanthodasys aculeatus (Thaumastodermatidae) and Cephalodasys maximus (Lepidodasyidae) has revealed that the process of acrosome formation and nuclear morphology during spermatogenesis are peculiar in Lepidodasys sp. and differences are evident especially in the late stages of spermatogenesis. Penetrated spermatozoa were observed in the oocytes at all maturation stages in L. unicarenatus.

Ultrastructural observations on the spermatozoa of a species of Lepidodasys (Gastrotricha, Macrodasyida)

“…The Wliform cell shape of the spermatozoon, the cork-screw shaped acrosome, the helical nucleus surrounding an axial mitochondrion, and the 9 £ 2 + 2 axonemal arrangement strictly agree with the basic plan described for the sperm of the species of the order Macrodasyida (Ferraguti and Balsamo 1995;Guidi et al 2004).…”

“…The acrosome structure made of two regions, a cork-screw apical one more electron-dense than the rod-like basal one, the morphology of the nucleus-mitochondrion complex, and the absence of a periaxonemal sheath (striated cylinder) are all features shared with both species of Lepidodasys studied by Guidi et al (2004). The presence of large and irregular vesicles in the basal region of the acrosome characterizes the sperm of both the Danish species and Lepidodasys unicarenatus (Guidi et al 2004).…”

“…The absence of a striated cylinder in Lepidodasys is shared only by the family Turbanellidae and by the genus Xenodasys suggesting a basal position of these taxa (Guidi et al 2004;Marotta et al 2005).…”

“…In particular, Lepidodasys, despite it is the type genus of the family, diVers from the other genera for a number of morphological characters: the complexity of the cuticle, the presence of Y-cells containing myoWlaments, the non-striated pharyngeal myo-epithelium, the absence of circular musculature in the lateral body regions and the lack of pharyngeal pores (Rieger and Rieger 1977;Ruppert 1978). Even the ultrastructure of the mature spermatozoon diVers in showing a ribbon-like nucleus, and in lacking any accessory structure around the axoneme (Guidi et al 2004;Marotta et al 2005).…”

Unusual spermatozoa and reproductive modalities ofXenodasys eknomios(Gastrotricha: Xenodasyidae)

“…Nevertheless, it differs from the basic sperm model of the order (Ferraguti & Balsamo 1995) in showing the nucleus surrounding most of the acrosome, and a peculiar, very long connecting piece between the head and the flagellum: these two characters are probably autapomorphic. The absence of a striated cylinder and any periaxonemal accessory structure appear to be symplesiomorphies, shared only, within Macrodasyidae, with Turbanellidae and species of Lepidodasys (Guidi et al 2004). These features seem to confirm the basal position of Xenodasys within the Macrodasyida suggested by the morphological, cladistic analyses of Litvaitis (2000, 2001a).…”