Callioplana marginata Stimpson, 1857

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 : 18-20

Callioplana marginata Stimpson, 1857

( Fig. 4 )

Callioplana marginata Stimpson, 1857: 4 , 11; Yeri & Kaburaki, 1918: 32–34, pl. 1, fig. 1; Stummer–Traunfels, 1933: 3558– 3561, figs 129–132; Kato, 1944: 52, 53, text fig. 33.

Stylochus marginatus Diesing, 1862: 569 .

Planocera marginata Lang, 1884: 445 .

Stylochus oxyceraeus Schmarda, 1859: 35 , pl. VIII, fig. 80.

Planocera oxyceraea Lang, 1884: 445 .

Diplosolenia Johnstoni Haswell, 1907: 469–471 , pl. 36, figs 1, 2.

Material examined: Five specimens, one sagittally sectioned. AM W.50270 (12 slides); AM W.50271, W.50272, W.50274, W.50275 (wet material). Specimens were collected intertidally at low tide from the following sites in Australia, New South Wales: Norah Head rock platform, 33°16’43.14”S, 151°34’12.85”E and Toowoon Bay , 33°21’47.01”S, 151°30’7.31”E. Coll. Jorge Rodriguez, Mandy Reid and Alison Miller, May 15 th & 16 th, 2018. Additional material from Australia, New South Wales, Long Reef from the collections of the Australian Museum : AM W.3695, W.3696.

Remarks: The studied specimens agree with the previous descriptions and anatomical reconstructions of C. marginata from Japan by Yeri & Kaburaki (1918) and Kato (1944). Externally, the specimens present orangecoloured conical nuchal tentacles that are colourless at the base, and a mouth situated in the centre of the body ( Fig. 4A ). The male copulatory system presents a non-muscular seminal vesicle and an oval-shaped prostatic vesicle, as well as separated ejaculatory and prostatic ducts that run parallel to each other along the elongated penis papilla. The long female system is positioned dorsal to the male copulatory system and is provided with a paired Lang’s vesicle consisting of elongated saccular bodies ( Figs 4B, C ).

Hyman (1959) notes that the description of the colouration of C. marginata varies in the following configurations: almost black with a red margin ( Schmarda, 1859); almost black with a narrow light margin ( Haswell 1907); velvety black with a tawny brown band and colourless margin ( Kato 1944); and sepia brown with a deeper brown on the inner side and a white margin subtended by an orange brown band ( Hyman 1959, based on the description provided by Elizabeth Pope). Hyman also remarks that the general pattern is a dark dorsal surface with a contrasting tawny brown to orange margin that is bordered thinly by white. In the specimens found in this study, the colouration of the dorsal surface presented a slight variation among different individuals ( Fig. 4A , bottom row). Although the background colour was black, in some specimens the area between the pharynx and the body margin appeared less pigmented, with a cloud of very small black dots. In specimens where the pigmentation appeared completely black, this paler section could also be noticed under different lighting (higher contrast/light intensity) ( Fig. 4A , top row). Furthermore, the dorsal surface could appear as brownish sepia, and the marginal band as orange, yellowish or tawny brown, depending on contrast and lighting. Body margin may also appear ruffled depending on the size of the animal ( Fig. 4A , top row).

Molecular remarks: The sequenced specimen of Callioplana marginata appeared in a common clade with the specimen from Australia sequenced by Litvaitis et al. (2019) and from Japan by Oya & Kajihara (2020) with high support (100/1.00) and short branch lengths.

Distribution: Japan: Ousima ( Stimpson 1857, type locality), Kanayama, Seto in Shirahama-cho ( Kato 1938), Amami Islands, Misaki, Sunosaki, Susaki near Simoda ( Kato 1944); Sri Lanka: Trincomalee ( Kato 1944); Australia: NSW, Port Jackson ( Haswell 1907), Long Reef near Collaroy ( Hyman 1959).

Even though this species presents a wide geographical distribution, both morphological and molecular results indicated that individuals reported from Japan and Australia are the same species. Stummer-Traunfels (1933), after reinvestigating the material of Schmarda (1859), synonymised Stylochus oxyceraeus from Trincomalee ( Sri Lanka) and Diplosolenia Johnstoni ( Australia) to C. marginata . Considering that accounts of the sexual anatomy were given for all of these specimens, which belong to the same species, the presence of C. marginata in Sri Lanka should be valid as well.

Genus Neostylochus Yeri & Kaburaki, 1920

Figures

FIGURE 4. Callioplana marginata Stimpson, 1857. A. Changes in dorsal colouration pattern with different lighting (top row); dorsal view of live specimens with differences in colouration pattern (bottom row). B. Sagittal reconstruction of the reproductive system. C. Histological sections of the reproductive system.