Idioplana australiensis Woodworth, 1898

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 : 27

Idioplana australiensis Woodworth, 1898

( Fig. 8 )

Idioplana australiensis Woodworth, 1898: 63–64 , figs 2–5.

Material examined: One specimen sagittally sectioned. AM W.50276 (6 slides). A specimen was collected from Australia, New South Wales, Toowoon Bay , rocky headland adjacent to SLSC, found under rocks at low tide, 33°21’47.01”S, 151°30’7.31”E. Coll. Jorge Rodriguez, Mandy Reid and Alison Miller, May 16 th, 2018 .

Remarks: The studied specimen agreed with the original species description in 1898 from Hope Islands (Great Barrier Reef, Australia). Externally, Idioplana australiensis is characterised by possessing a circular body shape, a pair of nuchal tentacles, marginal eyes in a band along the anterior body margin and a brownish orange colouration ( Fig. 8A, B ). Internally, I. australiensis presents a free prostatic vesicle with ridged glandular epithelium, an ovalshaped seminal vesicle, a very short penis papilla, and a female system that extends dorsally over the male copulatory system provided with an anchor-shaped Lang’s vesicle ( Fig. 8C, D ). Woodworth describes the general colour as bluish to yellowish or reddish, where the former can be attributed to the colouration of the intestine when seen through the dermis and the latter being the pigmentation of the dorsal surface ( Fig. 8A ). Some small differences with the original specimen are the body form, described as slug-like while the present specimen had a more rounded shape, and the distance between the gonopores, originally described as more closely together than in the currently studied specimen which can be attributed to the preservation process.

Molecular remarks: Idioplana australiensis appeared in a common clade with Idioplana atlantica Bock, 1913 and another specimen of I. australiensis from Phillip Island (Victoria, Australia), both sequenced by Litvaitis et al. (2019), with high support (100/1.00). The specimen described in this study, however, appeared more closely related to I. atlantica from Bocas del Toro ( Panama) than the other specimen of I. australiensis , also with high support (97/0.91). This difference is most likely due to a mislabelling of the name of the sequences, where the sequence of I. atlantica would be that of I. australiensis and vice versa. Since no morphological data was provided for these species, another possibility for this difference could be the absence of additional molecular data, as only 28S sequences are available on the GenBank database for these species.

Distribution: Australia, Great Barrier Reef, Hope Islands ( Woodworth 1898, type locality).

New record: Australia, New South Wales, Toowoon Bay. This record represents a major range extension of this species distribution.

Figures

FIGURE 8. Idioplana australiensis Woodworth 1898. A. Dorsal view of live specimen (left), detail of the pharynx (centre) and arrangement of the eyes (right). B. Detail of marginal eyes (left and right) and a tentacle with tentacular eyes (centre). C. Sagittal reconstruction of the reproductive system. D. Histological sections of the reproductive system.