Pseudobiceros apricus Newman & Cannon, 1994

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 : 243-244

Pseudobiceros apricus Newman & Cannon, 1994

( Fig. 3 )

Material examined and locality: One mature specimen (17x 10 mm, live, ZMTAU-VR 25165) preserved in ethanol 70%. Collected at the Inter University Institute for Marine Sciences ( IUI), Eilat, Israel, northern Gulf of Aqaba, Red Sea (29° 30.211’ N, 34° 55.068’ E) on 10 December 2013.

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

Distribution: Heron Island, Great Barrier Reef, Australia (Type locality) ( Newman & Cannon 1994). In this study, the specimen was found in Eilat, northern Gulf of Aqaba, Red Sea.

External morphology. Oval and elongated body, slightly tapered posteriorly ( Fig. 3A ). Translucent dorsal surface with blackish-dark brown coloration. Numerous small white dots scattered over the entire dorsal surface with bigger white dots forming irregular and spaced clusters. Raised dorsal midline, darker in coloration. White dots of different size around the margin ( Fig. 3A ). Pseudotentacles square-like, slightly ruffled, dark black with white tips and small white dots in between ( Fig. 3A, B ). Unrecognizable pseudotentacular eyes due to the black pigment. Small cerebral eyespot located in a clear area ( Fig. 3B ). Ruffled pharynx with simple folds located anteriorly ( Fig. 3C ). Two separate male gonopores located posterior and on each side of the pharynx. Female gonopore located in the midline, posterior to the male gonopores. Presence of a conspicuous sucker behind the female gonopore ( Fig. 3C ).

Taxonomic remarks. Pseudobiceros apricus was originally described by Newman & Cannon (1994) as having a transparent orange background with white microdots and a black marginal band with white dots. The specimen found in Israel differs from the original description by having a brownish-black dorsal surface and the absence of a black marginal band. Color and pattern variations for P. apricus were later revealed by the same authors, presenting photographic records of translucent dark brown to black background animals without the black marginal band ( Newman & Cannon 2003, p.81; 2005). This second morphotype resembles our specimen. Again, we inferred that the variation in the dorsal coloration is due to differences in habitat and intestinal content. In addition, it is possible that the dark overall pigment of the body makes the black margin indistinguishable in some cases.

P. apricus is included within the color pattern group 3 characterized by spots and dots ( Newman & Cannon 1994, 1997). In this group, only Pseudobiceros bajae ( HYMAN, 1953) and Pseudobiceros stellae NEWMAN & CANNON, 1994 also exhibit translucent dark background with small scattered white dots. Although P. bajae has similar square, ruffled pseudotentacles, it does not have white pseudotentacular tips. Also, it differs from P. apricus by the absence of white dots bordering the margin and the individual, evenly spaced small dots do not form clusters. On the other hand, P. stellae has a similar configuration of dots and clusters as P. apricus but unlike this species, clusters in P. stellae are arranged in a flower-like pattern, the marginal band is not clear, and the pseudotentacles are highly developed. P. apricus is a rare species, infrequently sighted and has been only recorded in Australia. P. apricus is recorded for the first time in the Red Sea and Israel.

Figures

FIGURE 3. Pseudobiceros apricus. (A) Dorsal view, in vivo. (B) Close-up of the anterior region in a preserved animal showing the pseudotentacles and cerebral eyes. (C) Ventral view of the preserved specimen showing the pharynx, reproductive structures, and sucker. ce: cerebral eyes; fg: female gonopore; m: mouth; mg: male gonopore; ph: pharynx; pt: pseudotentacles; su: sucker.