Cheliplana marcusi ( Karling, 1956 ) Karling, 1983

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 : 474-475

Cheliplana marcusi ( Karling, 1956) Karling, 1983

Synonyms

Rhinepera marcusi Karling, 1956

Rhinepera divisa Schilke, 1970

Material examined. None.

Known distribution. Amrum, Germany ( Schilke 1970). Tylösand, Kattegat, Sweden ( Karling 1983). Sylt, Germany ( Noldt 1989).

Remarks (summarised from literature). The species was adequately described by Karling (1956). Live specimens are slightly reddish in colour and are 0.7 mm long. The proboscis has an overall length of 31 μm and is armed with 17–19-µm-long spines ( Schilke 1970; Karling 1983). Karling (1961, 1983) describes a pair of denticles on the proboscis hooks. While Schilke (1970) mentions a great degree of similarity in the basal part of the proboscis hooks between his specimens and the specimens described by Karling (1961), no denticles are reported for the specimens from Amrum Island.

An oral tube without spines connects the mouth, located directly behind the proboscis, to the pharynx. The common genital opening is situated near the caudal body end. A single testis is situated posterior to the pharynx.

The male copulatory apparatus is positioned at 75%. A single seminal vesicle enters the copulatory bulb proximally. The copulatory bulb contains a proximal, bulbous prostatic vesicle, which connects to an armed cirrus distally. There is a relatively large size difference between the cirrus lengths reported by Schilke (1970) (27–29 μm) and Karling (1983) (80 μm). The cirrus consists of several parts, differentiated by the organisation and shape of the spines. Proximally, the cirrus is tubular and lined with very fine spines or sclerotised warts ( Schilke 1970). This part is followed distally by a ring of somewhat larger spines, described by Karling (1983) as ‘small teeth on 3.3 μm broad plates’. More distally, the cirrus is tubular and somewhat widened compared to the proximal part, but armed with similarly fine spines. The distal sclerotised rim folds over to form a penis papilla, projecting into the male atrium.

A single ovary is situated alongside the male copulatory apparatus. A vitellarium extends between the ovary and testis.

Based on the construction of the copulatory apparatus, Karling (1983) considered R. divisa and C. marcusi to be synonymous. However, there are some interesting differences in the descriptions of these species, most notably the size difference of the cirrus and the presence of denticles on the proboscis hooks of C. marcusi . Karling (1983) dismisses these differences as being either the result of the specimens’ state of contraction or features not observed by Schilke (1970). Re-examination of Schilke’s type material, which we were unable to obtain at this time, or newly collected material from the type localities, is imperative to ascertain whether these specimens indeed belong to the same species.