Pseudoceros duplicinctus Prudhoe, 1989

Velasquez, Ximena, Bolaños, D. Marcela & Benayahu, Yehuda, 2018, New records of cotylean flatworms (Platyhelminthes: Polycladida: Rhabditophora) from coastal habitats of Israel, Zootaxa 4438 (2), pp. 237-260 : 240-242

Pseudoceros duplicinctus Prudhoe, 1989

( Fig. 2 )

Synonyms: Pseudoceros prudhoei ( Newman & Cannon 1994, 1998, 2003, 2005; Gosliner et al. 1996; Apte & Pitale 2011, Dixit & Raghunathan 2013; Marquina et al. 2015); Pseudoceros cf. prudhoei ( Maghsoudlou & Rahimian 2014) .

Material examined and locality: a) One mature specimen (30x 10 mm live, ZMTAU-VR 25166) preserved in ethanol 70%. Collected at Mikhmoret, Israeli eastern Mediterranean Sea (32° 24' N, 34° 52’ E) on 1 June 2015.

b) One mature specimen (28x 10 mm, fixed, ZMTAU-VR 25167; GenBank ID: MH047292 ) preserved in ethanol 70%. Collected at Achziv, Israeli eastern Mediterranean Sea (33° 2' N, 35° 6’ E) on 8 December 2015.

Habitat: Specimens found in the rocky shore, intertidally under rocks (1–2 m depth), and in subtidal rocky reef habitats (5 m depth).

Distribution: Inhaca Island, Mozambique (Type locality) ( Prudhoe 1989); Heron Island, Great Barrier Reef, Australia and Madang, Papua New Guinea ( Newman & Cannon 1994); Lizard Island, Australia ( Newman & Cannon 1998, Marquina et al. 2015); Maldives, Micronesia, Philippines, Marshal Island, Japan, Hawaii, and Kenia ( Gosliner et al. 1996; Newman et al. 2003; Newman & Cannon 2005); Kavaratti Island, Andaman and Nicobar Islands, India ( Apte & Pitale 2011; Dixit & Raghunathan 2013); and Qeshm Island, Iran Maghsoudlou & Rahimian (2014). In this study specimens were found along the Israeli Mediterranean coast.

External morphology. Oval and elongated body with a slightly folded margin ( Fig. 2A ). Dorsal background velvety black with two distinct marginal bands surrounding the entire body. The inner band is wide and white followed by a narrow yellow margin ( Fig. 2A ). The ventral side has the same pattern ( Fig. 2B ). Simple black pseudotentacles with yellow tips but without the extension of the inner white band ( Fig. 2A ). Dorsal pseudotentacular eyes arranged in two scattered lines between the pseudotentacles. Small cluster of cerebral eyes located in a clear area with an inverted heart shape ( Fig. 2C ). Ruffled pharynx with complex folds located anteriorly. Separate gonopores. Single male gonopore located posterior to the pharynx followed by a close female gonopore. Small sucker posterior to the female gonopore ( Fig. 2B ).

Taxonomic remarks. Pseudoceros duplicinctus is one of the many early polyclad records that has remained ignored in the literature. As a result, the new species Pseudoceros prudhoei was created by Newman & Cannon (1994) without considering the resemblance in color and pattern between both species. Since then, different putative morphotypes of P. prudhoei have been recorded ( Newman & Cannon 2005; Apte & Pitale 2011; Dixit & Raghunathan 2013; Maghsoudlou & Rahimian 2014; Marquina et al. 2015), but neither completely matches the original diagnosis ( Table 2) nor refers to the similarity with P. duplicinctus . P. prudhoei only differs from P. duplicinctus by the yellow outer marginal band instead of orange. Because Prudhoe (1989) based his description on a single preserved specimen and a water-color painting of the specimen when alive, we consider this difference inappropriate to treat P. duplicinctus and P. prudhoei as two separate species.

The specimens found in Israel vary from the original description of P. duplicinctus by the presence of a velvety black dorsal surface and a white inner marginal band instead of a dark brown background and a pale blue margin. This is not surprising since it is widely known that color is greatly affected by the content of the intestinal branches, geographic location, habitat, and overall animal health ( Newman & Cannon 1994; 2003; 2005; Bahia et al. 2014; Bolaños et al. 2016). In fact, Marquina et al. (2015) noticed that the inner band of a presumed morphotype of P. prudhoei can fade from bluish grey to whitish and the dorsal background varies from dark to light brown. This variation was also observed in another specimen from India ( Apte & Pitale 2011) and even in pictures associated with the original description of P. prudhoei ( Newman & Cannon 1994; 2003). Additional records identified as Pseudoceros cf. prudhoei from Iran, also showed the velvety black and white inner margin as seen in our specimens as well as another record from India ( Newman & Cannon 2005; Dixit & Raghunathan 2013; Maghsoudlou & Rahimian 2014). Interestingly, a common feature of all the above-mentioned reports, including the specimens in this study, is the lack of numerous dark brown microdots over the whole dorsal surface described by Newman & Cannon (1994) as a distinctive character for P. prudhoei ( Table 2). Based on these observations, it is likely that P. duplicinctus represents another pseudocerotid conflicting species with a high level of color variation and therefore, we consider that all the morphotypes previously described as P. prudhoei are junior synonyms of P. duplicinctus . Our statement is supported by a molecular analysis of our specimen and two other morphotypes from Australia using nucleotide sequences of the D1-D2 expansion segment of the 28S rDNA gene which revealed very little differences among individuals (M. Litvaitis, pers.comm).

Pseudoceros depiliktabub NEWMAN & CANNON, 1994 is another species that closely resembles P. duplicinctus . However, P. depiliktabub is considered to have three marginal bands: an inner dark green a middle yellow-cream, and an outer orange rim. Despite being described with an orange margin as P. duplicinctus , additional photographic records show that P. depiliktabub can also display a yellow rim with white dots scattered over the dorsal surface ( Newman & Cannon 2003; 2005). Despite their close similarity in color and pattern, at this point it is not possible to make final conclusions about the synonymy of these two species due to the lack of molecular data and additional reports of P. depiliktabub . Molecular studies are needed to validate and confirm species identities. However, we are contributing with our sequence for P. duplicinctus ( MH047292 ), as a reference for future comparisons that help in resolving this issue.

Finally, P. duplicinctus is known from the Indian and the Indo-Pacific Oceans and to date, there are no records for other regions. Therefore, P. duplicinctus represents the first record for the Mediterranean Sea, adding to the list of non-indigenous platyhelminthes for the area together with Boninia neotethydis CURINI- GALLETI & CAMPUS, 2007 and Maritigrella fuscopunctata NEWMAN & CANNON, 2000 (Curini-Galletti & Campus 2007; Crocetta et al. 2015). This species has also been sighted in different locations on the Tel Aviv coast, indicating that P. duplicinctus might be established on the Israeli Mediterranean coast.

Figures

FIGURE 2. Pseudoceros duplicinctus. (A) Dorsal view, in vivo. (B) Ventral view of the live specimen showing the reproductive structures and sucker. (C) Close-up of the anterior region showing the pseudotentacles, pseudotentacular eyes and cerebral eyes. ce: cerebral eyes; fg: female gonopore; mg: male gonopore; pe: pseudotentacular eyes; pt: pseudotentacles; su: sucker.