Pelopscreadium, Dronen, Norman O., Blend, Charles K., Khalifa, Refaat M. A., Mohamadain, Hoda S. & Karar, Yasser F. M., 2016

Dronen, Norman O., Blend, Charles K., Khalifa, Refaat M. A., Mohamadain, Hoda S. & Karar, Yasser F. M., 2016, Pelopscreadium aegyptense n. gen., n. sp. and Pelopscreadium spongiosum (Bray & Cribb, 1998) n. comb., (Digenea: Lepocreadiidae), each from disjunct populations of the Yellow boxfish, Ostracion cubicus Linnaeus (Ostraciidae), Zootaxa 4127 (3), pp. 567-578 : 569

Genus Pelopscreadium n. gen.

Type-species: Pelopscreadium spongiosum ( Bray & Cribb, 1998) n. comb. Syn. Bianium spongiosum Bray & Cribb, 1998

Etymology. The generic designation is derived from the name of the Greek god, Pelops, the grand-son of Zeus, who had his shoulder eaten accidentally by Demetrius; thus, “Pelops” refers to the empty (= eaten) vacuolated cells composing the sponge-like lateral patches/pads located laterally in the forebody (i.e. at the “shoulders”) of members of the new genus and the suffix “creadium” broadly refers to the affinities of the new genus to other members of the Lepocreadiinae.

Diagnosis. Body spinose, elongate-oval; maximum breadth at or posterior to level of ventral sucker. Forebody about a third of body length. No scoop present, but large internal patches of vacuolated cells form sponge-like patches (i.e. “shoulder pads”) termed “pelops” (“pelop” sing.) laterally in forebody from anterior extremity to about 1/3 body length. Pre-oral lobe present, often inconspicuous. Oral sucker spherical to transversely elongateoval, subterminal. Ventral sucker spherical, pre-equatorial, smaller than oral sucker. Prepharynx short. Pharynx transversely oval, well developed, papillate around anterior opening. Esophagus short. Intestinal bifurcation in posterior part of forebody. Ceca two, long, terminating short of posterior extremity near body wall; no ani present. Testes two, smooth to lobed, tandem, contiguous or nearly so, post-ovarian, in posterior third of body. Posttesticular region short. External seminal vesicle tubular or sac-like. Cirrus-sac large, claviform, extends some distance into hindbody. Internal seminal vesicle oval, in posterior region of cirrus-sac. Pars prostatica elongate oval to oblong, distinct, lined with anuclear blebs (distal extremities of prostatic cells). Ejaculatory duct short to long, well developed, usually folded to some extent. Genital atrium distinct. Genital pore ventro-submedian in forebody. Ovary immediately pre-testicular, sometimes contiguous with anterior testis, dextral to almost medial, composed of multi-lobed acini. Seminal receptacle oval to elongate-oval, sinistral to ovary. Laurer’s canal opens on dorsal surface about level of anterior end of seminal receptacle. Uterus pre-testicular, intercecal. Metraterm distinct, with somewhat thickened wall coated on outside with cells containing large nuclei. Vitellarium follicular; fields extend from level of intestinal bifurcation to posterior extremity, confluent in forebody and in post-testicular region; follicles present laterally but not dorsal to ceca. Eggs relatively numerous, operculate, oval. Excretory vesicle Ishaped, wide, extends almost to level of intestinal bifurcation. Excretory pore terminal to slightly subterminal and dorsal. In intestine of marine teleosts (mainly Tetraodontiformes ) in tropical to subtropical waters.

Remarks. As many as 26 marine species have been assigned at one time or another to Bianium as defined by Stunkard (1931), Yamaguti (1971), Bray et al. (1996) and Bray (2005). The most recent taxonomic structuring of Bianium is that of Gibson (2015), who lists nine species in the genus. One of the species acknowledged by Gibson (2015), B. spongiosum , does not conform to Bianium and does not key out to any known species in the genus (see Bray et al. 1996). As Bray & Cribb (1998, p. 143, 145) noted in their discussion on B. spongiosum , “It is far from certain into which genus this species is best placed. The nature of the termination of the ceca, the follicular ovary, the papillate pharynx and the host all point to the fact that this form is close to the diploproctodaeine genera Bianium , Diploproctodaeum and Diploproctodaeoides . It differs from these; however, in lacking any evidence of an anterior ‘scoop’ or lateral flaps … In B. spongiosum no evidence for a scoop is seen, but laterally in the forebody there are distinct sponge-like lateral patches, which appear to be made up of large vacuolated cells. B. spongiosum does not key readily to a known diploproctodaeine genus in Bray et al. (1996), but it clearly does not have a complete scoop, so we have considered Bianium to be the best current repository”. In addition, Bray & Cribb (1998) pointed out that B. spongiosum could be distinguished from other species of Bianium in the key of Sey (1995, p. 19) due to the presence of its sponge-like shoulder pads. We are only aware of B. spongiosum and the new species described herein possessing these unique spongiform pelops, in the anterolateral forebody. Bianium spongiosum is herein assigned to Pelopscreadium n. gen. as the type-species, Pelopscreadium spongiosum ( Bray & Cribb, 1998) n. comb. One member of Lobatocreadium Madhavi, 1972 , Lobatocreadium ryukyuense Machida & Kuramochi, 1999 , has a somewhat similar general morphology (body shape, disposition of testes in the hindbody, acinous ovary, anterior wave-like projections on the pharynx or papillate projections, lack of ani, and a similar placement of the genital pore) to P. spongiosum and the new species described herein; however, like the other members of Lobatocreadium , it lacks the large internal patches of vacuolated cells that form the “sponge-like pads” laterally in the forebody.