Ultrastructure of the copulatory stylet and accessory spines in Haplopharynx quadristimulus (Turbellaria)

Abstract

The copulatory organ of Haplopharynx quadristimulus Ax, 1971 (Carolina form, Rieger, 1977 consists of a proximal prostatic vesicle and a distal stylet apparatus comprising a central tubular stylet and four to five peripheral accessory spines . By electron microscopy it could be seen that the stylet and spines were intracellular specializations . The copulatory organ can be interpreted as a specialization of an epithelial canal extending from the testes to the body wall . In the complex stylet apparatus, the epithelium was differentiated into six cell types. The stylet, which was formed in a matrix syncytium next to the prostatic vesicle, extended into the lumen of the stylet canal . The interior of the stylet apparatus contained one group of cells that had thick ciliary rootlets and another that had rootlet-like ribbons .The cells that contain the rootlets enveloped bundles of longitudinally arranged muscles. The accessory spines were formed in cells which lay peripheral to the muscle bundles . The spines, stylet, rootlet-like ribbons, and rootlets had similar patterns of periodic cross striations . The similarity in striation patterns suggests that the accessory spines and stylet are composed of modified ciliary rootlets. Hydrobiologia 132, 157-163 (1986).

The first multi-gene phylogeny of the Macrostomorpha sheds light on the evolution of sexual and asexual reproduction in basal Platyhelminthes

“…11), all of which are characterized by having paired seminal vesicles, a central funnel-shaped stylet (i.e. consisting of a conical mouth and a narrow nearly parallel stem) and four (or sometimes five, see Doe, 1986b) accessory spines: (i) Haplopharynx quadristimulus Ax 1971 (Fig. 11A) (body 4-5 mm, stylet 80-82 lm and with a wide mouth and a 50 lm stem, accessory spines 65-67 lm with proximal ends strongly spatulate); (ii)…”

Structure of the male copulatory apparatus in Prognathorhynchus busheki (Platyhelminthes, Kalyptorhynchia)

“…Stylet. The intracellular (or intrasyncytial) formation of the stylet in P. busheki is like that of copulatory hard structures in most flatworms studied by TEM to date, including the stylets and accessory spines in Macrostomorpha (Doe , ,b; Brüggemann , ), stylets in Proseriata (Lanfranchi ; Ehlers & Ehlers ; Brüggemann ), cirri in Proseriata (Martens & Schockaert ; Martens ; Jouk et al. ; see also below), stylets in Kalyptorhynchia (Brüggemann ), and stylets in Dalytyphloplanoida (Brüggemann , , , ).…”

Ultrastructural investigations on the differentiation of genital hard structures in free-living platyhelminths and their phylogenetic significance

“…The structure and formation mode of the stylet as it must have existed in the Rhabditophora stem species can be found again, presumably with little change, as a plesiomorphy in the macrostomid Haplopharynx sp . (see Doe, 1985), the proseriate Carenscoilia bidentata (see Ehlers & Ehlers, 1980), and probably in most stylet-or needle-bearing proseriates . On the other hand, the microtubular framework instead of microfibrils in the hard structures of the macrostomid genera Macrostomum (see Doe, 1982) and Paromalostomum represents an apomorphy within the Macrostomida .…”