Thysanozoon brocchii ( Risso, 1818 )

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 : 50-51

Thysanozoon brocchii ( Risso, 1818)

( Fig. 21 )

Tergipes brocchii Risso, 1818: 313 .

Planaria brocchii Risso, 1826: 264 .

Thysanozoon brocchii Grube, 1840: 55 ; Grube, 1855: 140–144, pI. 6, figs 4, 5.

Eolidioceros brocchii Quatrefages, 1845: 140–142 , pl. 3, figs 15, 16; pl. 5, fig. 1.

Thysanozoon brocchii Lang, 1884: 525–535 , pl. 6, figs 3, 4; Stummer-Traunfels, 1895: 113; Yeri & Kaburaki, 1918: 34–35, pl. 1, fig. 11; Plehn, 1899: 448–449; Kato, 1934: 133; Pearse, 1938: 85; Palombi, 1939: 135; Hyman, 1940: 485.

Planaria tuberculata Delle Chiaje, 1829 , Vol. 3: 119–120, pI. 35, figs 29–31; Delle Chiaje, 1841, Vol. 3: 132; Vol. 5, p. 112, pl. 112, figs 29–31.

Thysanozoon tuberculatum Grube, 1840: 55 .

Planaria verrucosa Delle Chiaje, 1829 , Vol. 4: 191, pl. 108, figs 1, 4, 5.

Thysanozoon diesingii Grube, 1840: 54–56 , fig. 9; Schmarda, 1859, p. 29; Stummer-Traunfels, 1895: 700, 723.

Planaria dicquemaris Delle Chiaje, 1841 , Vol. 3: 132; Vol. 5, p. 112; pl. 36,

figs 1, 4, 5; pl. 109, fig. 20.

Thysanozoon dicquemaris Oersted, 1844: 41 .

Stylochus papillosus Diesing, 1836: 316 .

Thysanozoon papillosum Grube, 1840: 56 .

Eolidiceros panormus Quatrefages, 1845: 142–143 , pl. 3, figs 2–4, 17; pl. 6, figs. 6, 13.

Thysanozoon panormus Diesing, 1850: 213 , 214.

Planeolis panormus Stimpson, 1857: 2 ; Diesing, 1862: 554, 555.

Thysanozoon fockei Diesing, 1850: 213 ; Diesing, 1862: 556.

Material examined: Two specimens, one sagittally sectioned. NMV F248136.1 – F248136.6 (6 slides); AM W. W. 53221 (wet material). Specimens were collected from Australia, Victoria, Coal Point, Harmer’s Haven 38°39’18.8”S, 145°33’57.1”E. Coll. Jorge Rodriguez, March 27 th, 2019 .

Remarks: Thysanozoon brocchii can be easily distinguished from the other intertidal marine flatworms by the presence of numerous papillae on the dorsal surface and a pair of squared pseudotentacles on the anterior body margin ( Fig. 21A–C ). Furthermore, Thysanozoon is also characterised by the presence of a duplicated male copulatory organ, consisting of a pair of penis papillae armed with a stylet ( Fig. 21D–F ). The studied specimens presented different shades of brown background colouration with transparent margins interrupted by white spots. The dorsal papillae appeared pointed or more rounded depending on the specimen and presented the same white spots of pigmentation present along the body margin. One of the specimens also presented a white median line along the dorsal surface and on the pseudotentacles ( Fig. 21A ).

Thysanozoon brocchii has been described as a cosmopolitan species by Bahia et al. (2015) and Pitale & Apte (2017). Bahia states that specimens from Brazil can have slender papillae and black to greyish colouration, while the European ones present a red marginal band. Pitale & Apte (2017), after comparative examinations of different T. brocchii specimens from around the world, reached the conclusion that there exist variable colour morphs of this species, and established a series of possible colour combinations. The studied Australian specimens fit within the following categories: dorsal ground colour: brown and light brown; ground colour pattern: brown pigments, brown papillae; papillae colour pattern: white dots, margin colour transparent; margin colour pattern: white spots.

Molecular remarks: The two sequenced specimens from Australia appeared together with three other specimens of Thysanozoon brocchii from Brazil ( Bahia et al. 2017), Azores ( Cuadrado et al. 2021) and Florida ( USA) ( Litvaitis et al. 2019) with high support (100/1.00) and short branch lengths.

Distribution: Naples, Italy ( Risso 1818, type locality) and other parts of the Mediterranean Sea, United Kingdom, Algeria, Suez Canal ( Palombi 1928), South and West Africa, Florida, Brazil ( Bahia et al. 2012; 2014; 2015), Argentina, Borneo, Vietnam, Japan and New Zealand ( Prudhoe 1985; Quiroga et al. 2004), India ( Pitale & Apte 2017), Florida, Colombian Caribbean, Canary Islands ( Vera et al. 2008).

New record: Australia, Victoria, Coal Point, Harmer’s Haven.

Figures

FIGURE 21. Thysanozoon brocchii (Risso, 1818). A. Dorsal view of live specimens. B. Detail of the pseudotentacles. C. Details of the male reproductive systems. D. Detail of the dorsal papillae in a fixed specimen. E. Sagittal reconstruction of the reproductive system. F Histological sections of the reproductive system.