Echinoplana celerrima Haswell, 1907

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 : 35

Echinoplana celerrima Haswell, 1907

( Fig. 12 )

Echinoplana celerrima Haswell, 1907: 475–478 , pl. 36, figs 6, 7; pl. 37, figs 1–3.

Material examined: Several specimens, one sagittally sectioned. AM W.50263 (8 slides), W.50289 (10 slides), W.51292 (3 slides); AM W.50260, W.50264, W.50269, W.50273, W.50279, W.50289, W.50290, W.50291, W.51318, W.51319, W.51320, W.51323, W.51325, W.51331, W.51332,W.51334, W.51335, W.53216 (wet material). Specimens were found under rocks at low tide, collected from Australia, New South Wales: Minnie Waters 29°46’34.8”S, 153°18’08.6”E. Coll. Jorge Rodriguez and Justin McNab, December 6 th, 2019 ; Diggers Camp 29°49’01.6”S, 153°17’34.4”E. Coll. Jorge Rodriguez and Justin McNab, December 8 th, 2019 ; Port Macquarie 31°27’27.7”S 152°56’04.4”E,. Coll. Jane Williamson and Louise Tosetto, January 8 th, 2020 ; Catherine Hill Bay, Middle Camp Beach 33° 8’45.93”S, 151°38’18.00”E. Coll. Alex Hegedus and Jorge Rodriguez, May 14 th, 2018 ; Norah Head rock platform; Toowoon Bay , rocky headland adjacent to SLSC, found under rocks, 33°21’47.01”S, 151°30’7.31”E. Coll. Jorge Rodriguez, Mandy Reid and Alison Miller, May 16th, 2018 ; Pulbah Island, Lake Macquarie 33° 5’30.19”S, 151°35’27.65”E. Coll. Jorge Rodriguez, May 18 th, 2018 ; Bottle and Glass 33°50’53.9”S, 151°16’12.3”E. Coll. Jorge Rodriguez and Justin McNab, October 25 th, 2019 & February 21 st, 2020 ; Chowder Bay, Sydney Harbour 33°50’20.1”S, 151°15’16.8”E. Coll. Jorge Rodriguez, Justin McNab, Stephanie Bagala and Audrey Watson, February 21 st, 2020 ; Boat Harbour, Gerroa 34°45’02.0”S, 150°49’56.5”E. Coll. Jorge Rodriguez, Jane Williamson, Patrick Burke, Louise Tosetto and Ryan Nevatte, July 7 th, 2018 ; Shelly Beach, Eden 37°04’22.0”S, 149°54’45.6”E. Coll. Jorge Rodriguez, Jane Williamson, Patrick Burke, Louise Tosetto and Ryan Nevatte, July 10 th, 2018 . Victoria: Cape Paterson 38°40’28.6”S, 145°37’16.5”E. Coll. Jorge Rodriguez, March 25 th, 2019 ; Cats Bay, Phillip Island 38°30’24.6”S, 145°07’33.8”E. Coll. Jorge Rodriguez, Patrick Burke and Louise Tosetto, July 12 th, 2018 .

Remarks: Echinoplana celerrima possesses an elongated body shape and is characterised by the presence of a cirrus provided with numerous spines that is externally visible as a thin and often twisted brown line positioned behind the pharynx ( Fig. 12A–F ).

Echinoplana celerrima is currently the most widespread intertidal polyclad species known in southeastern Australia. Specimens belonging to this species have been rarely found in the Mediterranean Sea, which contrast with their abundance along the southeastern Australian coast. One possible explanation for this occurrence might be that specimens of E. celerrima were transported by ships from Australia to the Mediterranean Sea where they found appropriate conditions to settle. Transportation via shipping or ballast waters could be a reasonable explanation for the seemingly cosmopolitan distribution of some polyclad species ( Merory & Newman, 2005).

Molecular remarks: Echinoplana celerrima appeared together with another specimen from Tunisia sequenced by Dittmann et al. (2019) with high support (100/1.00) and short branch lengths, providing further evidence that both Australian and Mediterranean populations belong to the same species. The Echinoplana clade is located within the Leptoplanoidea superfamily but its position within it is not fully resolved. This genus is currently placed within the Gnesiocerotidae family yet Oya & Kajihara (2020) recovered Echinoplana celerrima as more closely related to genera like Leptoplana Ehrenberg, 1831 , Notoplana Laidlaw, 1903 , and Notocomplana Faubel, 1983 than Gnesioceros Diesing, 1862 , and therefore noting that Echinoplana should not be placed within Gnesiocerotidae . In this study Echinoplana was recovered in a clade with Styloplanocera Bock, 1913 , Comoplana Faubel, 1983 , and Stylochoplana ( Schmarda, 1859) in the ML analysis with strong support (75), and also with Neostylochus ancorus sp. nov. in the Bayesian analysis with high support (1.00), while Gnesioceros Diesing, 1862 , Phaenoplana Faubel, 1983 , Parabolia gen. nov., and Ceratoplana Bock, 1925a clustered together as sister taxa (73/0.57). However, even though the Gnesiocerotidae family was still recovered as paraphyletic, Echinoplana celerrima was clearly separated from the previous genera mentioned by Oya & Kajihara (2020).

Distribution: Australia: Port Jackson, New South Wales, ( Haswell 1907, type locality); Italy (Galleni 1978); New Zealand: North Island ( Holleman 2007); Tunisia: lagoon of Tunis ( Gammoudi et al. 2009).

Figures

FIGURE 12. Echinoplana celerrima Haswell, 1907. A. Dorsal view of live specimen. B. Dorsal view of a fixed specimen, treated with a clearing agent. C. Details of the pharynx and reproductive systems. D. Arrangement of the eyes. E. Sagittal reconstruction of the reproductive system. F. Histological sections of the reproductive system.