Cheliplana boadeni Schilke, 1970

Gobert, Stefan, Diez, Yander L., Monnens, Marlies, Reygel, Patrick, Van Steenkiste, Niels W. L., Leander, Brian S. & Artois, Tom, 2021, A revision of the genus Cheliplana de Beauchamp, 1927 (Rhabdocoela: Schizorhynchia), with the description of six new species, Zootaxa 4970 (3), pp. 453-494 : 465-466

Cheliplana boadeni Schilke, 1970

Fig. 6A–C

Material examined. New material. GERMANY • 1 whole mount; Sylt , List; 55°00’56”N, 8°26’12”E; 19 Aug. 2015; coarse sediment in the upper eulittoral zone, sediment taken by digging down to the water table at low tide; HU X.3.19 • 1 whole mount; Sylt, List; 55°00’56”N, 8°26’12”E; 19 Aug. 2015; spot with algae at breakwater, with somewhat coarser sediment than the surrounding mud; HU X.3.20 .

Note. No reference material was available to us at the time of this study.

Known distribution. Sylt, Germany ( Schilke 1970; Hoxhold 1974; Scherer 1985; Noldt 1989). Traeth Bychan, Wales, United Kingdom ( Boaden 1963).

Remarks. Boaden (1963) collected a specimen in Wales ( United Kingdom), to which he referred as Rhinepera sp. It has an unpaired ovary and testis and resembles C. remanei except for the presence of a striated, plate-like stylet instead of a cirrus. Schilke (1970) noted that this was likely a specimen of C. boadeni . Based on Boaden’s drawings and description, we are inclined to agree with Schilke’s assessment.

Boaden (1963) and Schilke (1970) report a total body length of ~ 1.5 mm. The new specimens are slightly smaller, measuring 0.7 and 1.2 mm. The single caudal haptic girdle is ochre coloured and sharply delineated. The proboscis of specimens collected by Schilke (1970) are characterised by 18–21-µm-long hooks, 23-µm-long hook supports and 24-µm-long sidepieces (sp, Fig. 6C ). Newly collected specimens from Sylt bear hooks of 20–27 μm long (h, Fig. 6C ). The oral cavity is armed with 5 rows of spines. The paired testes are positioned in front of and alongside the pharynx. Anterior to the pharynx, a connection between the testes is present. The male copulatory apparatus measures 80–130 μm and is situated in the posterior body third. The copulatory bulb consists of a globular proximal region, which contains a globular prostatic vesicle, and a more narrow, cylindrical distal part, in which the sclerotised copulatory structures are situated ( Fig. 6A–B ). The prostatic vesicle measures 62 μm by 44 μm. The sclerotised parts are described as a complex, double-walled stylet by Schilke (1970), whereas Hoxhold (1989) describes them as consisting of a 45–50-µm-long stylet with a spirally folded proximal part, surrounded by a sheathlike, ridged, 56–63-µm-long cirrus. The latter is diagonally striated in its proximal part and longitudinally striated in its distal one. Following Hoxhold’s terminology, as we did in our Fig. 6A , and in the identification key (see further), the inner part is the stylet proper, more or less hourglass shaped in the new specimen, while the outer striated part is the cirrus (ci, st, Fig. 6A ). The entire sclerotised system of the new specimens measures ~54 μm, which is well within the size range reported by Schilke (1970) (50–60 μm). It has a basal width of ~20 μm. The diagonal striation of the cirrus mentioned by Hoxhold (1989) was not observed in the new specimen.

The single ovary is in direct contact with the vitellarium. A vagina externa is present and opens into a large, undivided bursa.

Figures

FIGURE 6. A–C. Cheliplana boadeni Schilke, 1970. A. Camera lucida drawing of the cirrus and stylet. B. Photograph of the copulatory hard structures. C. Photograph of the proboscis. D–F. Cheliplana deverticula Ax, 2008. D. Camera lucida drawing of the cirrus. E. Drawing of the copulatory bulb with cirrus and seminal vesicles. F. Reconstruction of the proximal bursa end and the ovary. Only two of the three seminal ducts are shown. G–H. Cheliplana gemmifera Noldt, 1989 G. Camera lucida drawing of the cirrus. H. Photograph of the copulatory bulb in a live specimen. Scale bars: A–B, D = 50 μm; C, G = 20 μm; E = 100 μm.