Cheliplana deverticula Ax, 2008

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 : 468

Cheliplana deverticula Ax, 2008

Fig. 6D–F

Synonyms. Cheliplana triductibus Van Steenkiste, Volonterio, Schockaert & Artois, 2008

Material examined. New material. PORTUGAL • 1 whole mount; Algarve , Olhão; 37°01’34”N, 7°50’56”W; 13 Sep. 2011; mid-eulittoral zone at low tide, fine sand and silt from an oxygen-poor sediment layer with organic detritus at about 5 cm below the surface; HU X.2.43 • 1 whole mount and 3 serial sections; Algarve, Olhão; 37°01’34”N, 7°50’56”W; 13 Sep. 2011; high eulittoral at low tide, very coarse shell gravel, mixed with coarse sand, organic detritus and silt in tidal gully; HU X.2.44–X.2.47 .

Reference material. 1 whole mount (holotype, SMNH Type 7496) and 4 serially sectioned specimens (HU IV.1.29–IV.1.32) from Uruguay .

Known distribution. Bay of Arcachon, France ( Ax 2008). Playa Ramirez, Departamento de Montevideo, Uruguay ( Van Steenkiste et al. 2008).

Remarks. The newly collected specimens from the Algarve are colourless. A single haptic girdle is present near the caudal body end. A cylindrical pharynx is situated in the anterior half of the body and connected to the mouth through a long, unarmed prepharyngeal cavity. The mouth is situated anteriorly, closely behind the proboscis. A single, unpaired testis is positioned alongside the pharynx. The proboscis is armed with a pair of smooth hooks. A pair of soft proboscis sidepieces is present, each bearing bristles. A pair of pear-shaped seminal vesicles (vs, Fig. 6E ) connects via a pair of vasa deferentia to the distal end of the copulatory bulb (cb, Fig. 6E ). The copulatory bulb contains a granular vesicle proximally (vg, Fig. 6E ) and an armed cirrus distally ( Fig. 6D ; ci, Fig. 6E ). In the Portuguese specimens, the cirrus measures 71–79 μm (n = 2). In addition to the cirrus, a small, blind-ending accessory cirrus is present at the distal end of the copulatory bulb (ac, Fig. 6D,E ). The accessory cirrus measures 21–27 μm (n = 2) and is lined with spines identical to those of the cirrus (ac, Fig. 6D ).

The female reproductive system exhibits a number of characteristic features: a large bursa lies caudally from the ovary (b, ov, Fig. 6F ). The anterior part of the bursa has three sperm-containing compartments, from each of which a slender, sclerotised spermatic duct leads to the ovary (x, Fig. 6F ). The three ducts are wound tightly around each other. The bursa is connected to a long vagina externa.

Ax (2008) described Cheliplana deverticula based on the cirrus morphology and proboscis hooks, without reference to the female system. Van Steenkiste et al. (2008) retrieved a number of morphologically similar specimens from Uruguay and provisionally described these as Cheliplana triductibus , pending additional information on the anatomy of the female system in C. deverticula . The new specimens from Portugal now allow investigation of the female genital system, which appears to be identical to that described for C. triductibus . Furthermore, the measurements of the male copulatory organs and proboscis hooks are also in the same size range as reported for both C. triductibus and C. deverticula . Considering the publication dates of Ax (2008) and Van Steenkiste et al. (2008) (February and October, respectively), C. triductibus is considered a junior synonym of C. deverticula (International Code on Zoological Nomenclature 2015). Some minor differences were observed between the Portuguese and Uruguayan populations. The degree of sclerotisation of the spermatic ducts appears more extensive in the Portuguese specimens compared to the specimens from Uruguay. Furthermore, in the Portuguese specimens, a single cell nucleus is visible in the widened proximal part of the funnel-shaped ducts. As these observations may be attributed to either quality variations of the preserved material or intraspecific variation, we deem these differences insufficient to consider C. deverticula and C. triductibus separate species.

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.