Discocelis tigrina ( Blanchard, 1847 ) Lang, 1884

Pérez-García, Patricia, Gouveia, Filipa, Calado, Gonçalo, Noreña, Carolina & Cervera, Juan Lucas, 2024, Acotylea (Platyhelminthes, Polycladida) from the southern and western Iberian Peninsula, with the description of five new species, Zoosystematics and Evolution 100 (4), pp. 1487-1513 : 1487-1513

Discocelis tigrina ( Blanchard, 1847) Lang, 1884

Fig. 16

Polycelis tigrina Blanchard, 1847 .

Leptoplana tigrina ( Blanchard, 1847) Diesing, 1850 .

Elasmodes tigrinus ( Blanchard, 1847) Stimpson, 1857 .

Material examined.

• MNHNC MB 16-000128 , Station 4 , 28 October 2018, 30 mm long ; • MNHNC MB 16-000129 , Station 5 , 22 April 2019, 39 mm long ; • MNHNC MB 16-000130 , Station 6 , 5 May 2019, 34 mm long ; • MNHNC MB 16-000131 , Station 8 , 16 May 2018, 25 mm long ; • MNHNC MB 16-000132 , Station 9 , 15 May 2018, 12 mm long ; • MNCN 4.01/4088 , Station 10 , 21 February 2019, 18 mm long ; • MNCN 4.01/4089 , Station 10 , 21 February 2019, 20 mm long ; • MNCN 4.01/4090 , Station 11 , 29 April 2014, 20 mm long ; • MNCN 4.01/4091 , Station 11 , 9 October 2014, 16 mm long ; • MNCN 4.01/4092 , Station 11 , 19 February 2015, 11 mm long .

Description.

Living specimens between 11 mm and 39 mm in length (21.45 ± 9.51). Body shape oval, with rounded anterior and posterior ends. Dorsal surface smooth, light brown with many dark brown spots throughout the body, more concentrated in the main axis (Fig. 16 A ). Ventral face pale brown without spots (Fig. 16 B ). Without tentacles. Marginal, tentacular, and cerebral eyes present (Fig. 16 C ). Tentacular clusters with approximately 21 eyes each, and cerebral clusters with 32 eyes each. Pharynx ruffled, centrally positioned, and with deep pharyngeal folds. Oral pore opens at the end of the first third of the pharynx. Male and female systems open into a common genital atrium between the second and the last third of the body.

Remarks.

The genus Discocelis comprises seven accepted species and is considered the genus with the largest number of species within the Discocelidae family. Three of these species exhibit a spotted dorsal pattern: D. japonica Yeri & Kabiraki, 1918 , D. pusilla Kato, 1938 , and D. parvimaculata Beveridge, 2000 . These species are distributed on the Pacific coasts, whereas D. tigrina is considered an endemic species of the Mediterranean ( Patzner et al. 2005).

Biology.

Under stones, living on the rocky shore (Fig. 16 D ). Sometimes observed among brown algae, Dictyota dichotoma (Ochriphyta) , and close to meadows of Caulerpa prolifera (Chlorophyta) (only in the Ria Formosa environment). It is known that this species frequently appears in association with bivalves ( Gammoudi et al. 2017). Indeed, some of the specimens in our study were also found inside the empty shells of mussels. This finding is common within acotylean worms, as they are predators of a wide variety of molluscs ( Galleni et al. 1980, Bahia 2016, Gutiérrez et al. 2023); hence, we could assume that this species feeds on them.

Distribution.

This species has a wide distribution within the Mediterranean Sea and the Atlantic. The localities where Discocelis tigrina was reported are Sicily ( Blanchard 1847); the Gulf of Naples ( Lang 1884); the Peninsula de Rio de Oro, Western Sahara, and Port-Étienne; Mauritania ( Palombi 1939); the coast of Catalonia ( Novell 2001 Gammoudi and Tekaya 2012); the Canary Islands ( De Vera et al. 2009; Cuadrado et al. 2017); Asturias ( Marquina et al. 2014 b); Galicia ( Noreña et al. 2015); and Tunisia ( Gammoudi and Tekaya 2012; Gammoudi et al. 2012; Gammoudi et al. 2017). This is the first record of this species in Portugal (Avencas, Arrabida, Troia, Lagos, and Faro) and Andalusia.

Figures

Figure 16. Discocelis tigrina (MNHNC MB 16-000128): A. Dorsal view of the living specimen; B. Ventral view; C. Detail of the eyes (MNCN 4.01 / 4089); D. Example of the habitat where the specimens were found.