Cheliplana curacaoensis, Gobert & Diez & Monnens & Reygel & Van Steenkiste & Leander & Artois, 2021

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 : 463-464

Cheliplana curacaoensis n. sp. Van Steenkiste & Leander

Fig. 5

Etymology. The species epithet refers to the island of Curaçao, where the species was found.

Material examined. Holotype. CURAÇAO • 1 whole mount; Boka Samí , Sint Michielsbaai; 12°08’52”N, 68°59’56”W; 21 Apr. 2018; coarse sand with some organic material in permanent, shallow pool; MI4182.

Other material. CURAÇAO • 1 whole mount; The Water Factory ; 12°06’39”N, 68°57’29”W; 19 Apr. 2016; coral sand between coral at about 7 m deep; MI4183 .

Description. Live specimens are very large, up to 2 mm long and pink to orange in colour ( Fig. 5A ). No haptic girdle was observed. The proboscis (p, Fig. 5A ) is armed with a pair of smooth, 28-μm-long, curved hooks and 15- μm-long hook supports. Sidepieces were not observed. The mouth opening is positioned shortly behind the proboscis and connected to the barrel-shaped pharynx (ph, Fig. 5A ) through a long, seemingly unarmed, prepharyngeal tube. Intestine very dark and occupying the third quarter of the body (int, Fig. 5A ).

A large, single testis is positioned adjacent to and partly behind the pharynx (t, Fig. 5A ). The male copulatory organ lies directly posterior to the intestine. Paired seminal vesicles enter the copulatory bulb proximally (vs, Fig. 5A,B ). The 360-μm-long, elongate copulatory bulb has a sinusoidal shape and is surrounded by strong longitudinal and very weak circular muscles. It contains a proximal internal seminal vesicle provided with longitudinal muscles (ivs, Fig. 5B,D ), a long ejaculatory duct (de, Fig. 5B,D ) and a 265-µm-long, sinusoidal cirrus (ci, Fig. 5A–D ). The ejaculatory duct is folded in live specimens and stretches out when the cirrus is everted. The cirrus is armed with spines that become increasingly longer and thinner, from about 5 μm in the proximal part to 10 μm in the distal part (ci, Fig. 5A–D ). The distal wall of the cirrus and copulatory bulb is sclerotised and folds over to form a 40–50-µmlong, urn-shaped cap or papilla around the distal part of the cirrus (pp, Fig. 5B–D ). The cirrus and ejaculatory duct can be everted through this sclerotised cap (as in Fig. 5C–D ).

The bursa (b, Fig. 5A–B ) and ovary lie adjacent to the copulatory organ. The bursa contains sperm in its anterior part and stretches out posteriorly as a vacuolated tissue (b, Fig. 5A–B ). It connects to a vagina externa, the opening of which is located subterminally. Glands indicate the position of the common genital opening in the posterior 1/5 of the body.

Figures

FIGURE 5. Cheliplana curacaoensis n. sp. A. Live specimen. B. Detail of the atrial organs in a live specimen. C. Detail of the penis papilla and everted cirrus in a whole-mounted specimen. D. Detail of the male copulatory bulb, penis papilla and everted cirrus in a whole-mounted specimen (background edges automatically generated using the Content-Aware Fill tool in Adobe Photoshop). Scale bars: A = 100 μm; B = 50 μm; C–D = 20 μm.