Pseudobiceros stellae Newman & Cannon, 1994

(Fig. 6)

Material examined and locality: One mature specimen (27x 13 mm, live, ZMTAU-VR 25179; GenBank ID: MH047293) preserved in ethanol 70%, collected at Mikhmoret, Israeli eastern Mediterranean Sea (32° 24' N, 34° 52’ E) on 22 May 2016.

Habitat: Specimen found on the rocky shore, under rocks during low tide (1 m depth).

Distribution: Heron Island (Type locality), Tree Island, Great Barrier Reef, Australia and Madang Island, Papua New Guinea (Newman & Cannon 1994). Lizard Island and Coral Bay, Australia (Newman & Cannon 1997); Hawaii, Galapagos Island, Indonesia, Marshall Island, and possibly the Red Sea (Poulter 1987; Newman & Cannon 2005); Kavaratti Island (Apte & Pitale 2011) and Nancowry Island, India (Sreeraj & Raghunathan 2015); Singapore (Ong et al. 2015). In this study, the specimen was found at Mikhmoret, Eastern Mediterranean Sea, Israel.

External anatomy. Oval and elongated body with ruffled margin (Fig. 6A, B). Dorsal surface black with numerous white dots distributed over the entire body. Some dots are small and are more evenly distributed than the larger ones that aggregate and form large white clusters. Raised dorsal midline with larger patches of white close to each other, forming a wide irregular band posteriorly. A fine line of white microdots at the anterior end (Fig. 6A). Ventral side black, translucent towards the margin (Fig. 6B). Square, lateral ruffled pseudotentacles, black in coloration with white tips (Figs. 6C). Indistinguishable pseudotentacular eyes due to the dark pigment. Cerebral eyespot located in a clear oval area (Fig. 6C). Short and ruffled pharynx with simple folds located anteriorly (Fig. 6B). Two conspicuous male gonopores located posterior to the pharynx. Female gonopore located in the midline close to the male gonopores. Presence of a large sucker behind the female gonopore (Fig. 6B).

Taxonomic remarks. Pseudobiceros stellae, Pseudobiceros bajae, and Pseudobiceros caribbensis BOLAÑOS, QUIROGA & LITVAITIS, 2007 comprised a group of species with dark background and white spots over the dorsal surface. However, P. stellae has a “flower-like” organization of the white dots not seen in any of the other two species. Although our specimen displays such particular arrangement, the clusters are not regularly distributed as mentioned in the original description. In addition, our animal exhibits large white blotches along the midline that have not been observed in previous reports (Poulter 1987; Newman & Cannon 1994; Apte & Pitale 2011; Sreeraj & Raghunathan 2015; Ong et al. 2015). Therefore, we considered that this feature could be related to the specific condition of the collected specimen (excessive clustering of dots or depigmentation) rather than a case of color variation.

Two other species with similar color pattern are Pseudoceros josei NEWMAN & CANNON, 1998 and the morphotype of Pseudoceros maximus LANG, 1884 reported for Tunisia (Gammoudi & Tekaya 2012; Gammoudi et al. 2011, 2017). However, these are characterized by a single male gonopore instead of two as seen in P. stellae. Because researchers frequently fail to present detailed observations of the ventral side of the animal, polyclad taxonomy is replete with misidentifications, synonyms, and erroneous geographic distribution records. For instance, Newman & Cannon (2005) indicated that P. stellae has been reported in the Red Sea. However, no specific location, photographic record or additional information was provided. Hence, at this point it is not possible to confirm that P. stellae is distributed in both the Mediterranean and the Red Sea, potentially representing another Lessepsian species. This highlights the importance of a thorough examination of actual specimens and the avoidance of describing polyclad species based only on photographic records.