Otobothrium cysticum (Mayer, 1842) Dollfus, 1942

Beveridge, Ian & Justine, Jean-Lou, 2007, Redescriptions of four species of Otobothrium Linton, 1890 (Cestoda: Trypanorhyncha), including new records from Australia, New Caledonia and Malaysia, with the description of O. parvum n. sp., Zootaxa 1587, pp. 1-25 : 22-23

Otobothrium cysticum (Mayer, 1842) Dollfus, 1942

Syn. Tetrarhynchus cysticus Mayer, 1842

Types: none indicated in original description.

Type host: Chelonia mydas (Linnaeus, 1758) .

Type locality: not stated.

Site in host: peritoneum.

Material examined: from Chelonia mydas : 2 specimens, Port-Étienne (now Nouadhibou), Mauritania ( MNHN BD 28-32,33); 1 specimen, Heron Island, Qld, Australia (QM G 206393).

Remarks. Otobothrium cysticum was described by Mayer (1842) based on plerocerci from the body cavity (peritoneum) of a green turtle, Chelonia mydas Linnaeus, 1758 . As no tentacles were everted, the description was extremely limited. Dollfus (1942) redescribed the species based on additional specimens from C. mydas from Mauritania, but none of the tentacles were everted in his material. This was confirmed by examination of all of the relevant material in MNHN as well as specimens from the same host species in Australia in which, once again, the tentacles were not everted. Dollfus (1942) also attributed to this species plerocerci from the stomach wall of the crocodilian Osteolaemus tetraspis (Cope, 1861) from the Congo, the teleost Dentex macrophthalmus (Bloch, 1791) from Castiglione (now Bou Ismaïl) (MNHN BD 28-35), Algeria, and from the stomach wall of the elasmobranch Carcharhinus melanopterus (Quoy & Gaimard, 1824) from Egypt (MNHN BD 28-30, 31, 42), in each of which the tentacles were partly everted. These specimens in MNHN were re-examined but were not from the type host and therefore their conspecificity is contestable. In these specimens, tentacles were partially everted and limited observations on the tentacular armature were made ( Dollfus 1942, figs. 153–156). However, the description of the tentacular armature is limited and does not allow unequivocal identification. Palm (1995) proposed that O. cysticum was a synonym of O. crenacolle and corroborated this conclusion based upon an examination of all available specimens ( Palm & Overstreet 2000). The latter examination included examination of material from Sphyrna zygaena (USNPC 7695) which is here considered to contain two distinct species, one being designated as a neotype for O. crenacolle . Based on these observations, Palm’s identifications of “ O. cysticum ” are potentially a composite of at least two species and are not now readily attributable to either or any of the various species considered to be O. cysticum by Palm (1995).

Here, O. cysticum is considered to be a species inquirenda since neither the tentacular armature nor the mature segments are known. Any attributions to this species must therefore be considered highly dubious. Even if it were possible to obtain specimens from turtles with everted tentacles, the current study suggests that features of the mature segment are critical in the identification of species and therefore, without adults, this taxon will not be identifiable in the future. The numerous plerocerci reported in the literature as O. cysticum have not been examined as it is appears that adults are required to identify species within this group.