Stylochoplana clara Kato, 1937

Rodríguez, Jorge, Hutchings, Pat A. & Williamson, Jane E., 2021, Biodiversity of intertidal marine flatworms (Polycladida, Platyhelminthes) in southeastern Australia, Zootaxa 5024 (1), pp. 1-63 : 37

Stylochoplana clara Kato, 1937

( Fig. 13 )

Stylochoplana clara Kato, 1937: 357–359 , fig. 5, text figs 15, 16.

Material examined: One specimens sagittally sectioned. NMV F248134.1 – F248134.3 (3 slides). Specimen collected from Australia, Victoria, Cape Paterson, Boat Ramp area , found intertidally on the blades of the seagrass Amphibolis antarctica , 38°40’28.6”S, 145°37’16.5”E. Coll. Audrey Falconer and Jorge Rodriguez, March 25 th, 2019 .

Remarks: The studied specimen agreed with the original description from Kato (1937a). Externally, the specimens are of similar small size (5 mm long), with a broad and rounded anterior part of the body, nuchal tentacles with few (2–3) tentacular eyes and a light green colouration with visible intestinal and reproductive systems ( Fig. 13A–C ). The studied specimens also present small circular spots of white pigment evenly distributed around the anterior margin that are not mentioned in the original description. The pharynx is located in the middle of the body and appears poorly plicated, with the mouth opening in the hind end ( Fig. 13B ). The male apparatus is provided with an oval-shaped seminal vesicle with a thick muscular layer, an elongated and greatly enlarged prostatic vesicle lined with tall smooth glandular epithelium, and a long and muscular unarmed penis papilla. The female system presents a thickened vagina externa provided with a small protrusion that Kato (1937a) describes as a bursa copulatrix. The vagina interna loops dorsally over the male copulatory system before receiving the oviducts and is provided with an oval Lang’s vesicle ( Fig. 13B, D, E ).

Kato (1937a) notes that this species was commonly found living on the seagrass Zostera and Phyllospadix , while the specimens from this study were found on a similar wide-leafed seagrass, Amphibolis antarctica .

Molecular remarks: Stylochoplana clara appeared nested within the Leptoplanoidea superfamily with strong support (95/0.96) and as part of a common clade with Styloplanocera fasciata ( Schmarda, 1859) , Comoplana agilis ( Lang, 1884) and Echinoplana celerrima Haswell, 1907 with strong BS support (73) in the ML analysis while the Bayesian analysis had lower support (0.57) and included Neostylochus ancorus sp. nov. This clade appeared as most closely related to another clade formed by Parabolia megae gen. et sp. nov., Gnesioceros sargassicola (Mertens, 1833) , and Phaenoplana kopepe Oya & Kajihara, 2019 with high support (90/1.00).

Distribution: Japan: Misaki (Kato 1937), Susaki near Simoda ( Kato 1944).

New record: Australia, Victoria, Cape Paterson.

Genus Ceratoplana Bock, 1925a

Ceratoplana Bock, 1925a: 4–30 , pl. I, fig. 1, text figs 1–7.

Diagnosis (after Faubel 1983): Stylochoplanidae with well-developed oblong tentacles. Mouth arranged far behind the centre of the very long pharyngeal cavity. Seminal vesicle immediately behind the pharynx. Lining epithelium of the prostatic vesicle provided with cilia. Penis long, narrow and unarmed. Gonopores separated. Female apparatus with ductus vaginalis. Vagina interna and ductus vaginalis open into a common female atrium. Lang’s vesicle lacking.

Type species: Ceratoplana colobocentroti Bock, 1925a .

Figures

FIGURE 13. Stylochoplana clara Kato, 1937. A. Dorsal view of live specimen. B. Details of the pharynx and reproductive systems. C. Arrangement of the eyes. D. Sagittal reconstruction of the reproductive system. E. Histological sections of the reproductive system.