Pericelis byerleyana ( Collingwood, 1876 )

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 : 250-252

Pericelis byerleyana ( Collingwood, 1876)

( Figs. 8 )

Synonyms: Typhlolepta byerleyana Collingwood, 1876 ; Pericelis cf. hymanae Newman & Cannon, 2003; Pericelis sp. 3 Newman & Cannon, 2003.

Material examined and locality: Two mature specimens 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) . a) One specimen (29x 14 mm, ZMTAU-VR25162), preserved in ethanol 70%. Collecting date on 21 March 2013. b) One specimen (26x 13 mm, ZMTAU-VR25163, (GenBank ID: MH047291 ), preserved in ethanol 70%. Collecting date on 29 May 2015.

Habitat: Specimens found in reef habitats (12–15 m depth).

Distribution: Pulo Barundum, Borneo, Pacific Ocean (Type locality) ( Collingwood, 1876). Maldives, Laccadive Islands & Mauritius Island, Indian Ocean ( Laidlaw 1902; Palombi 1938); Gulf of Tadjoura, Djibouti, Gulf of Aden, Somalia ( Meixner 1907); Rotuma Island, Fiji ( Laidlaw 1903); Micronesia ( Kato 1943; Newman et al. 2003); Japan ( Kato 1944); Australia and Indonesia ( Kato 1944; Prudhoe 1989); Eilat, northern Gulf of Aqaba, Red Sea ( Prudhoe 1989). In this study, specimens were found in Eilat in accordance to the locality given by Prudhoe (1989).

External anatomy. Large, oval, and elongated body with ruffled margins. Dorsal surface light brown with well-defined roundish cream circles of different sizes forming a reticulate pattern. Presence of smaller circles between the interstices of the larger. Midline with a darker brown coloration and larger and more spaced rings becoming smaller and more numerous toward the margin ( Fig. 8A ). Light brown ventral surface lacking the reticulate pattern ( Fig. 8B ). Indistinct, small pseudotentacles formed by simple folds of the anterior margin and with numerous pseudotentacular eyes at the tip ( Fig. 8C ). Cerebral eyes arranged in two elongated and separated clusters located in a clear area. More numerous eyes posteriorly extending to thin lines of less and more scattered eyes anteriorly ( Figs. 8C ). Marginal eyes surrounding the entire body. In the anterior area, few pre-cerebral eyes are also present ( Fig. 8C ). A large ruffled pharynx, highly branched located centrally ( Fig. 8B ). Separate male and female gonopores. The male gonopore is located immediately after the pharynx and the female pore close to male gonopore. Small sucker located posteriorly and close to the female gonopore ( Fig. 8B ).

Taxonomic remarks. Currently, the genus Pericelis contains four valid species ( Faubel 1984; Tyler et al. 2006–2018), mainly distinguished by the color and pattern. Of these, P. byerleyana , P. cata , and P. orbicularis , share a similar reticulated brown pattern. However, P. cata differs from P. byerleyana by the conspicuous pseudotentacles with black tips, patchy background with irregular-shaped white circles, and a few black spots scattered over the dorsal surface. On the other hand, P. orbicularis has a dark brown pigment forming a loose network pattern instead of well-defined white rings as seen in P. byerleyana . Moreover, P. orbicularis has a more developed sucker. Despite their morphological similarity, a comparison based on available molecular data for P. cata ( EU679114 ), P. orbicularis ( EU679116 ), and P. byerleyana ( MH047291 ), using about 950 base pairs of the 28S rDNA gene, revealed species-specific changes allowing us to clearly distinguish three different species ( Table 3).

In addition, P. byerleyana has been frequently found in the Indian Ocean and the Indo-Pacific region whereas P. cata and P. orbicularis have been found in the Atlantic Ocean including the Caribbean and the Gulf of Mexico ( Schmmarda 1859; Hyman 1955b; Marcus & Marcus 1968; Quiroga et al. 2004). A previous record of P. byerleyana was poorly presented by Prudhoe (1989) for Israel. Thus, we present a detailed description of the species based on the external morphology, high quality photographs, and molecular sequence data ( MH047291 ) for future comparisons with other pericelid species.

Figures

FIGURE 8. Pericelis byerleyana. (A) Dorsal view, in vivo. (B) Ventral view of the live specimen showing the pharynx, uteri, and sucker. (C) Close-up of the anterior region showing the pseudoentacles and the cerebral, pre-cerebral, and marginal eyes; ce: cerebral eyes; me: marginal eyes; mt: marginal tentacles; pe: pre-cerebral eyes; ph: pharynx; su: sucker; u: uteri.