Ultrastructure of spermiogenesis and the spermatozoon in Castrada cristatispina Papi, 1951 (Platyhelminthes, Rhabdocoela, Typhloplanida)

Abstract

 AbstractCulioli, J.-L., Foata, J., Mori, C., Orsini, A. and Marchand, B. 2004. Ultrastructure of spermiogenesis and the spermatozoon in Castrada cristatispina Papi, 1951 (Platyhelminthes, Rhabdocoela, Typhloplanida). -Acta Zoologica (Stockholm) 85 : 245-256 Spermiogenesis in Castrada cristatispina begins with the formation of a zone of differentiation containing two centrioles with associated striated rootlets and an intercentriolar body between them. The centrioles give rise to two parallel, free flagella of the Trepaxonemata 9 + '1' pattern, growing out in opposite directions. Spermatids undergo a latero-ventral rotation of the flagella and a subsequent disto-proximal rotation of centrioles, and a distal cytoplasmic projection appears. The former rotation involves the compression of a row of microtubules and allows the recognition of a ventral side and a dorsal side. At the end of the differentiation, the centrioles and cortical microtubules lie parallel to the sperm axis. The modifications of the intercentriolar body and the migration of the nucleus and the centrioles toward the distal projection are described. The mature spermatozoon of C. cristatispina is filiform, tapered at both ends and shares several features with the other Rhabdocoela gametes. Nevertheless, the posterior extremity is capped by an electron-dense material. A gradient between mitochondria and dense bodies exists along the sperm axis. This study has enable us a phylogenetic approach of the Rhabdocoela through a comparison of the ultrastructural features of C. cristatispina with the other Rhabdocoela taxa. We propose the disto-proximal rotation of centrioles as a synapomorphy of the Rhabdocoela.

Ultrastructural description of the spermatogenesis and spermatozoa in Phaenocora unipunctata (Platyhelminthes, Neotyphloplanida)

“…Both species have a constant number of microtubules, but it is lower in P. unipunctata (32–33) than in P. anomalocoela (57–58 based on the figures in Watson & Rohde, ). Among the Typhloplanidae, a constant number of microtubules has been only mentioned for a Rhynchostominae, Castrada cristatispina (Culioli et al, ). Conversely, in many investigations the number of microtubules in the different regions of the sperm cell was variable.…”

“…Many characters have been used as to hypothesize their phylogeny, but the taxonomy within this group is still uncertain (Watson & Rohde, ). Differences in sperm morphology and spermiogenesis have been found at high taxonomic levels within this taxon (Watson & Rohde, ; Watson, ; Culioli et al, ; Culioli, Foata, Mori, & Marchand, ,b), but the variation at lower taxonomic levels is still not clear.…”

“…Ultrastructural studies of spermiogenesis and sperm morphology have provided many characters used as apomorphies and morphological evidence to set up the phylogeny of the Platyhelminthes (Hendelberg, ; Ehlers, ; Justine, ; Watson, ; Zamparo, Brooks, Hoberg, & McLennan, ; Ndiaye, Bakhoum, Sène, Diagne, & Miquel, ; Bakhoum et al, ; Littlewood, Bray, & Waeschenbach, ; Bakhoum et al, ). However, lack of investigations on many free‐living groups has been a limiting factor (Sopott‐Ehlers, ; Watson & Jondelius, ; Culioli, Foata, Mori, Orsini, & Marchand, ; Gammoudi, Salvenmoser, Harrath, Tekaya, & Egger, ).…”

“…The Rhabdocoela Neotyphloplanida comprises two taxa, Limnotyphloplanida and Thalassotyphloplanida (Willems et al, ; Van Steenkiste et al, ). Among the Limnotyphloplanida, details of sperm ultrastructure have been published for nine Typhloplanidae ( Bothromesostoma personatum , Castrada cristatispina , Castrada natans , Mesocastrada fuhrmanni , Mesostoma georgianum , Mesostoma lingua , Mesostoma viaregginum , Strongylostoma radiatum and Phaenocora anomalocoela ) (Henley, Costello, Thomas, & Newton, ; Watson, and references therein; Culioli et al, ; Culioli et al, ), three Dalyelliidae ( Gieysztoria sp., Halammovortex nigrifrons and Jensenia angulata ) (Watson, and references therein), and 11 Temnocephalida ( Actinodactylella blanchardi , Didymorchis sp., Troglocaridicola sp., Craspedella sp., Decadidymus gulosus , Temnocephala axenos , Temnocephala iheringi , Temnosewellia dendyi , Temnosewellia geonoma , Temnosewellia minor and Diceratocephala boschmai ) (Watson, and references therein). Among the Thalassotyphloplanida, there are studies of only nine species belonging to three families: Byrsophlebidae ( Maehrenthalia sp.…”

“…In contrast, studies on intrageneric variation of the ultrastructure of sperm and spermatogenesis are scarce among free‐living Platyhelminthes. In Neotyphloplanida, they have only been undertaken for the genera Castrada , Mesostoma , Maehrenthalia , Temnocephala and Temosewellia (Watson, and references therein; Culioli et al, ). However, such studies are relevant to ascertain which characters are significant to support phylogenetic hypothesis on different taxonomic levels.…”