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Enenterum kyphosi Yamaguti, 1970 (Figs. 2, 3) Type host and locality: Kyphosus cinerascens (Forsskål), blue sea chub (Centrarchiformes: Kyphosidae), Hawaii. Other records: From Kyphosus vaigiensis (Quoy & Gaimard), brassy chub (Centrarchiformes: Kyphosidae), collected in Sodwana Bay, KwaZulu-Natal, South Africa (Bray 1986); from K. vaigiensis, collected from the Ogasawara Islands, Japan (Machida 1993); from Kyphosus sp. collected from Palau (Machida 1993). New localities: Off Amity Point, North Stradbroke Island, Moreton Bay, Queensland, Australia (27°23'53''S, 153°26'15''E); off Lizard Island, Great Barrier Reef, Queensland, Australia (14°41'10''S, 145°28'15''E). Material studied: 10 whole-mount specimens and two hologenophores (QM G240075–G240086), from Kyphosus cinerascens collected off Amity Point; five whole mount specimens and three hologenophores (QM G240087–G240094), from Kyphosus cinerascens collected off Lizard Island. Representative DNA sequences: ITS2 rDNA, ex K. cinerascens from Amity Point, three identical replicates (two from hologenophores, one from a whole worm), one replicate submitted to GenBank (ON228451); ex K. cinerascens from Lizard Island, three identical replicates (all from hologenophores), one submitted to GenBank (ON228452). 28S rDNA, ex K. cinerascens from Amity Point, three identical replicates (two from hologenophores, one from a whole worm), one submitted to GenBank (ON228454); ex K. cinerascens from Lizard Island, one replicate (from a hologenophore) submitted to GenBank (ON228455). COI mtDNA, ex K. cinerascens from Amity Point, three identical replicates (two from hologenophores, one from a whole worm), one submitted to GenBank (ON228462); ex K. cinerascens from Lizard Island, two replicates (both from hologenophores) submitted to GenBank (ON228460 – ON228461). Description: [Measurements in Table 2. Description based on vouchers and SEM images of three adult specimens]. Body robust, elongate, fusiform, slightly dorsoventrally flattened; bright yellow to orange in life with colour fading after preservation in ethanol. Tegument armed with irregular fields of minute, cylindrical spines. Oral sucker terminal, infundibuliform, partially retractable, elaborate, divided into four sections: ventral section comprised of two truncate lobes separated by distinct central cleft and longitudinal crease; lateral sections one either side, each comprised of two oblong lobes separated by distinct notch, with rear, more dorsal, lobe elongate and front, more ventral, lobe shorter and arising from ventrolateral region of rear lobe; dorsal section of oral sucker a single, large lobe with distinct, central, sagittal cleft dividing lobe into two parts, each part with small, central notch. Single row of papillae apparent on outer anterior margin of oral sucker lobes. Ventral sucker robust, round, in anterior third of body, aperture rhomboid. Prepharynx distinct, broad. Pharynx well-developed, ellipsoidal, in mid-forebody. Oesophagus short, narrow. Intestine robust, with well-developed gastrodermis, bifurcates in mid to posterior forebody; caeca reunite in anterior half of post-testicular region to form distinct common stem, attenuates posteriorly, opens at large, dorsally subterminal anus. .....Continued on the next page TABLE 2 (Continued) .....Continued on the next page TABLE 2 (Continued) Testes two, tandem, separated, ellipsoidal, approximately equal in size, with margins entire to moderately lobed, in posterior half of hindbody, medial, intercaecal. Vasa deferentia separate, narrow, pass more or less parallel along longitudinal median of body anteriorly, enter posterior end of cirrus-sac. Cirrus-sac ellipsoidal, capsule-like, with distinctly thick, muscular walls, intercaecal, extends from just posterior to caecal bifurcation to about midway behind ventral sucker. Internal seminal vesicle tubular, tightly coiled. Pars prostatica indistinct, ellipsoidal, lined with cell-like bodies. Ejaculatory duct muscular, long. Genital atrium narrow. Genital pore opens on single, small, distinct papilla midway between pharynx and anterior margin of ventral sucker. Ovary subglobular, pre-testicular, intercaecal, medial. Seminal receptacle subglobular, smaller than and postero-dorsal to ovary. Laurer’s canal not observed. Mehlis’ gland profuse, antero-dorsal to ovary. Uterus pre-ovarian, convoluted, intercaecal, passes along ventral margin of cirrus-sac to genital atrium. Eggs numerous, elongate, operculate. Vitellarium follicular; follicles profuse, distributed in dorsal, lateral, and ventral regions of body, extend from posterior margin of ventral sucker to near posterior extremity, wrap around body from dorsal midline to ventrosinistral and ventrodextral regions anterior to testes, wrap around entire body posterior to testes, sparse in testicular region. Vitelline reservoir dorsal to ovary, ellipsoidal to pyriform; collecting ducts indistinct. Excretory pore dorsally subterminal, posterior to anus. Excretory vesicle tubular, undulates anteriorly along longitudinal midline, passes dorsally to testes, bifurcates in region of ovary; collecting ducts reach as far as oral sucker. Remarks: Species delineation in the genus Enenterum has relied largely on differences in the number of oral sucker lobes visible by light microscopy of slide-mounted specimens, with counts of two, six, seven, eight, and ten being reported (Bray & Cribb 2001). However, such counts are likely to miss more subtle structural detail and be heavily influenced by the particular specimen and its method of preservation and preparation. For our specimens of E. kyphosi, the number of oral sucker lobes might be considered as eight or ten, depending upon the specimen and on the interpretation of the smaller notches in the dorsal portion of the oral sucker. These notches are not visible under light microscopy for all specimens. Thus, a count of ten lobes is possible for some specimens but not convincing for others. All other descriptions of E. kyphosi report a count of ten oral sucker lobes (Yamaguti 1970; Bray 1986; Machida 1993), however, we think there is a strong case to consider our specimens as this species. Yamaguti (1970) described E. kyphosi based on material from K. cinerascens collected from Hawaii. In addition to being collected from the same host species, our specimens agree well with the original description and have seemingly overlapping morphometrics, although the illustration of E. kyphosi provided by Yamaguti (1970, Fig. 119a) indicate that the holotype was flattened, which impairs morphometric comparison (see Huston et al. 2019a). Flattening may also provide some explanation for the differences in oral sucker lobes, as pressure during fixation may have accentuated the notches in the oral sucker in these specimens. An important feature of E. kyphosi that requires clarification is the accessory structure associated with the genital pore. In our specimens the genital pore opens through a distinct papilla, which we do not consider a true sucker (i.e., a specialised, muscular attachment organ; cf. illustration of the genital sucker of E. petrae n. sp. below). Yamaguti (1970, p. 85) described this in E. kyphosi as a “rudimentary accessory sucker in form of a muscular eversible papillae”. This contrasts with the description of Enenterum elongatum Yamaguti, 1970, described in the same publication alongside E. kyphosi and from the same host and locality, where the structure was characterised simply as a “rudimentary accessory sucker”. The illustration of the accessory sucker in E. elongatum shares the longitudinal striations typically present in Yamaguti’s illustrations of digenean suckers, but the illustration of the accessory sucker of E. kyphosi does not. Although Yamaguti (1970) may have considered papillae and accessory suckers as homologous structures, we infer that the discrepancy is more likely a result of loose language. Indeed, this appears to be the opinion reached by Bray (1986) in his report of E. kyphosi from South Africa, where he noted the only difference between his specimens and those of Yamaguti (1970) was the “so called accessory sucker, which in these specimens appears to be a genital papilla through which both male and female ducts pass”. Machida (1993) reported E. elongatum and E. kyphosi from Japan and Palau, but unfortunately did not mention accessory suckers or papillae associated with the genital pore in the description of either species or provide illustrations. Machida (1993) also noted difficulties in differentiating these two species and concluded that they may be conspecific, leaving the specific identity of his specimens somewhat ambiguous. The overall morphological evidence does not seem sufficient to consider our specimens as different from the concept of E. kyphosi and, despite the wide geographic spread of reports of this species, we think there is precedent (see Huston et al. 2021b) to consider all reports of E. kyphosi as this species, rather than a complex of morphologically similar species. Hawaii is a distinct component of the Eastern Indo-Pacific ecoregion (Spalding et al. 2007) and, because of the exceptional contribution of Yamaguti (1970), has one of the best studied digenean faunas in the IWP (Cribb et al. 2016). Although several digenean species have been reported from both Hawaii and elsewhere, there is not yet any molecular data confirming conspecificity of Hawaiian forms with those from other ecoregions. However, there is growing genetic evidence that some digenean species which occur in French Polynesia, another component of the Eastern Indo-Pacific, also occur in Australia (e.g., Lo et al. 2001; McNamara et al. 2014; Martin et al. 2018; Huston et al. 2021b; Bray et al. 2022). Furthermore, in a study of the Gorgocephalidae Manter, 1966, a digenean lineage also restricted to kyphosid fishes, Huston et al. (2021b) provided both morphological and molecular evidence that the range of Gorgocephalus yaaji Bray & Cribb, 2005, spans the breadth of the IWP, from French Polynesia to South Africa. This species was found to use multiple kyphosids across its range, including K. cinerascens in French Polynesia and K. vaigiensis in South Africa (Huston et al. 2021b). This distribution provides a precedent for the expectation that the digenean fauna of kyphosids may be widespread and strongly suggests our specimens are conspecific with those reported from Hawaii and South Africa. Molecular data from Hawaii may show that the forms from elsewhere, including our new material, are actually distinct, but until such data become available, we think considering our specimens as E. kyphosi is the most satisfactory hypothesis., Published as part of Huston, Daniel C., Cutmore, Scott C. & Cribb, Thomas H., 2022, Enenterum kyphosi Yamaguti, 1970 and Enenterum petrae n. sp. (Digenea Enenteridae) from kyphosid fishes (Centrarchiformes: Kyphosidae) collected in marine waters off eastern Australia, pp. 271-288 in Zootaxa 5154 (3) on pages 275-281, DOI: 10.11646/zootaxa.5154.3.2, http://zenodo.org/record/6644688, {"references":["Yamaguti, S. (1970) Digenetic Trematodes of Hawaiian fishes. Keigaku Publishing Co., Tokyo, 436 pp.","Bray, R. A. (1986) Some helminth parasites of marine fishes of South Africa: families Enenteridae, Opistholebetidae and Pleorchiidae (Digenea). Journal of Natural History, 20, 471 - 488. https: // doi. org / 10.1080 / 00222938600770371","Machida, M. (1993) Trematodes from kyphosid fishes in Japanese and adjacent waters. Bulletin of the National Science Museum, Tokyo Series A Zoology, 19, 27 - 36.","Linton, E. (1910) Helminth fauna of the Dry Tortugas. II. Trematodes. Papers from the Tortugas Laboratory of the Carnegie Institute of Washington, 4, 11 - 98.","Bray, R. A. & Cribb, T. H. (2001) A review of the family Enenteridae Yamaguti, 1958 (Digenea), with descriptions of species from Australian waters, including Koseiria huxleyi n. sp. Systematic Parasitology, 48, 1 - 29. https: // doi. org / 10.1023 / A: 1026533510387","Huston, D. C., Cutmore, S. C. & Cribb, T. H. (2019 a) An identity crisis in the Indo-Pacific: molecular exploration of the genus Koseiria (Digenea: Enenteridae). International Journal for Parasitology, 49, 945 - 961. https: // doi. org / 10.1016 / j. ijpara. 2019.07.001","Huston, D. C., Cutmore, S. C., Miller, T. L., Sasal, P., Smit, N. J. & Cribb, T. H. (2021 b) Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range. Zoological Journal of the Linnean Society, 193, 1416 - 1455. https: // doi. org / 10.1093 / zoolinnean / zlab 002","Spalding, M. D., Fox, H. E., Allen, G. R., Davidson, N., Ferdana, Z. A., Finlayson, M. A. X., Halpern, B. S., Jorge, M. A., Lombana, A. L. & Lourie, S. A. (2007) Marine ecoregions of the world: a bioregionalization of coastal and shelf areas. BioScience, 57, 573 - 583. https: // doi. org / 10.1641 / B 570707","Cribb, T. H., Bray, R. A., Diaz, P. E., Huston, D. C., Kudlai, O., Martin, S. B., Yong, R. Q. - Y. & Cutmore, S. C. (2016) Trematodes of fishes of the Indo-west Pacific: told and untold richness. Systematic Parasitology, 93, 237 - 247. https: // doi. org / 10.1007 / s 11230 - 016 - 9625 - 0","Lo, C. M., Morgan, J. A. T., Galzin, R. & Cribb, T. H. (2001) Identical digeneans in coral reef fishes from French Polynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules. International Journal for Parasitology, 31, 1573 - 1578. https: // doi. org / 10.1016 / S 0020 - 7519 (01) 00306 - X","McNamara, M. K. A., Miller, T. L. & Cribb, T. H. (2014) Evidence for extensive cryptic speciation in trematodes of butterflyfishes (Chaetodontidae) of the tropical Indo-West Pacific. International Journal for Parasitology, 44, 37 - 48. https: // doi. org / 10.1016 / j. ijpara. 2013.09.005","Martin, S. B., Sasal, P., Cutmore, S. C., Ward, S., Aeby, G. S. & Cribb, T. H. (2018) Intermediate host switches drive diversification among the largest trematode family: evidence from the Polypipapiliotrematinae n. subf. (Opecoelidae), parasites transmitted to butterflyfishes via predation of coral polyps. International Journal for Parasitology, 48, 1107 - 1126. https: // doi. org / 10.1016 / j. ijpara. 2018.09.003","Bray, R. A., Cutmore, S. C. & Cribb, T. H. (2022) A paradigm for the recognition of cryptic trematode species in tropical Indowest Pacific fishes: the problematic genus Preptetos (Trematoda: Lepocreadiidae). International Journal for Parasitology, 52, 169 - 203. https: // doi. org / 10.1016 / j. ijpara. 2021.08.004"]}

Enenterum petrae n. sp. (Figs. 4, 5) ZooBank LSID: http://zoobank.org/ urn:lsid:zoobank.org:act: A3CA58E4-F473-4D39-B30A-1B74794FC0FE Type host: Kyphosus vaigiensis (Quoy & Gaimard), brassy chub (Centrarchiformes: Kyphosidae). Site in host: Intestine. Type locality: Off Lizard Island, Great Barrier Reef, Queensland, Australia (14°41'10''S, 145°28'15''E). Type material: Holotype (QM G240095) and 19 paratypes, including three hologenophores (QM G240096 – G240114). Representative DNA sequences: ITS2 rDNA, four identical replicates (two from type-series hologenophores, two from whole worms), one submitted to GenBank (ON228453). 28S rDNA, two identical replicates (one from a type-series hologenophore, one from a whole worm), one submitted to GenBank (ON228456). COI mtDNA, two replicates (one from type-series hologenophore, one from a whole worm) submitted to GenBank (ON228463 – ON228464). Etymology: This species name serves as an eternal record of a mother and father’s joy and celebrates the birth of the first author’s daughter. May she live always, for in the taxonomic record there is promise of immortality in that even names relegated to synonymy are never fully forgotten. Description: [Measurements in Table 2. Description based on type-series and SEM images of four adult specimens]. Body elongate, cylindrical, broadest immediately anterior to ventral sucker, attenuates slightly towards posterior end; bright yellow to orange in life with colour fading after preservation in ethanol. Tegument armed with concentric rows of minute, palmate spines. Oral sucker terminal, infundibuliform, retractable, elaborate, divided into two sections; ventral section a single, posteriorly concave, truncate lobe; dorsal section comprised of two lateral, reniform lobes separated by distinct, sagittal cleft; when retracted, sucker folds along lines at points of connection between ventral and dorsal lobes and midway along each reniform lobe. Oral sucker appears three-lobed when protracted and six-lobed when retracted. Single line of papillae apparent along anterior margin of oral sucker lobes. Ventral sucker robust, round, in anterior quarter of body, with aperture rhomboid. Pre-pharynx distinct, muscular. Pharynx minute, ellipsoidal, in mid-forebody, contiguous with caecal bifurcation. Oesophagus essentially absent, with intestine appearing to open directly from pharynx. Intestine robust, domed in region of bifurcation, with gastrodermis well-developed, bifurcates in mid-forebody anterior to cirrus-sac; caeca reunite in posterior half of posttesticular region to form distinct common stem, attenuates posteriorly to small duct and opens at slightly dorsally subterminal anus. Testes two, tandem, ellipsoidal, separated, in mid-hindbody, approximately equal in size, medial, ventral to caeca. Post-testicular region long. Vasa deferentia separate, swollen, convoluted in anterior hindbody, enter posterior end of cirrus-sac. Cirrus-sac thick-walled, heavily invested with darkly stained gland-cells, intercaecal, ellipsoidal and reniform in dorsoventral and lateral view, respectively; posterior half dorsal to ventral sucker, anterior portion posterior to caecal bifurcation. Internal seminal vesicle tubular, convoluted. Pars prostatica elongate, vesicular, lined with clear, cell-like bodies. Ejaculatory duct long, canalicular, muscular. Genital atrium small, distinct. Genital pore closed via muscular ‘cap’ arising from tegument. Small, subglobular genital sucker situated just posterior to genital pore. Ovary subglobular, pre-testicular, ventral to caeca. Seminal receptacle adjacent to ovary, subglobular to pyriform. Mehlis’ gland anterior-dorsal to ovary, profuse. Laurer’s canal not observed. Uterus highly convoluted, preovarian, ventral to and between caeca, broadens significantly in region just posterior to ventral sucker, passes along ventral margin of cirrus-sac to genital atrium. Eggs numerous, elongate, operculate. Vitellarium follicular, restricted to hindbody; follicles profuse, distributed in dorsal, lateral, and ventral regions of body, extend from just posterior to ventral sucker to near posterior extremity, wrap around body from dorsal midline to ventrosinistral and ventrodextral regions anterior to testes, wrap around entire body posterior to testes; ventral gap in testicular region common. Vitelline reservoir contiguous with anterior margin of ovary, subglobular; collecting ducts indistinct. Excretory pore terminal; excretory vesicle originates as small duct, enlarging to form relatively straight tube, but path obscured by vitellarium; collecting ducts extend as far as oral sucker. Remarks: The structure of the oral sucker of E. petrae is unique among the known species of Enenterum, as is the relatively minute pharynx and the combination of a genital cap and accessory sucker. Together these unique features readily distinguish E. petrae from all congeners. Based on individual specimen and interpretation, the oral sucker of E. petrae might be considered to have three, five, or six lobes, highlighting potential issues of using lobe count as a means of species delineation in Enenterum. Regardless, counts of three and five lobes are not yet reported for any member of the genus and only E. mannarense possesses six lobes. The oral sucker lobes of E. mannarense are pointed, however, quite unlike the rounded lobes present in the oral sucker of E. petrae, and the orientation is different. Enenterum petrae has some superficial similarities to E. elongatum, which has been reported from Heron Island, on the Great Barrier Reef (Bray & Cribb 2002). However, while E. elongatum has a genital sucker, it has never been described with a genital cap and has always been reported as having ten distinct oral sucker lobes and a robust pharynx., Published as part of Huston, Daniel C., Cutmore, Scott C. & Cribb, Thomas H., 2022, Enenterum kyphosi Yamaguti, 1970 and Enenterum petrae n. sp. (Digenea Enenteridae) from kyphosid fishes (Centrarchiformes: Kyphosidae) collected in marine waters off eastern Australia, pp. 271-288 in Zootaxa 5154 (3) on pages 281-282, DOI: 10.11646/zootaxa.5154.3.2, http://zenodo.org/record/6644688, {"references":["Bray, R. A. & Cribb, T. H. (2002) Further observations on the Enenteridae Yamaguti, 1958 (Digenea, Lepocreadioidea) of the Indo-West Pacific region, including a new species from Western Australia. Acta Parasitologica, 47, 208 - 223."]}

Huston, Daniel C., Cutmore, Scott C., Miller, Terrence L., Sasal, Pierre, Smit, Nico J., Cribb, Thomas H. (2021): Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range. Zoological Journal of the Linnean Society 193 (4): 1416-1455, DOI: 10.1093/zoolinnean/zlab002, URL: https://doi.org/10.1093/zoolinnean/zlab002

GORGOCEPHALUS EURYALEAE SP. NOV. (FIGS 11, 12A–C; TABLES 4, 6) Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 7C5053D1-DE14-400E-A8FC-36F6E1A305B6. Type host and locality: Kyphosus gladius Knudsen & Clements (Perciformes: Kyphosidae), gladius sea chub, from off Point Peron, Rockingham, Western Australia (32°15’59’’S, 115°41’03’’E) (PP). Other hosts (definitive): Kyphosus sydneyanus (Günther, 1886) (Perciformes: Kyphosidae), silver drummer; Kyphosus cinerascens (Forsskål, 1775), highfin chub (Perciformes: Kyphosidae). Other localities: Off Rottnest Island, Western Australia (32°59’04’’S, 115°31’06’’E) (RI); Sodwana Bay, KwaZulu-Natal, South Africa (27°32’24’’S, 32°40’41’’E). Type material: Holotype (WAM V9670) ex K. gladius from off PP. Paratypes: eight whole-mount specimens and two hologenophores ex K. gladius from PP (WAM V9671– 9680); one whole-mount and three hologenophores ex K. sydneyanus from RI (WAM V9681–9684). Additional voucher material (adult): Eight wholemount and two hologenophore specimens, ex K. cinerascens from SB (NMB 732).

GORGOCEPHALUS GRABOIDES SP. NOV. (FIGS 12D–F, 13; TABLES 4, 6) Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: D684AF8B-5CF6-40A0-91AD-7B26A304D47B. Type host and locality: Kyphosus cinerascens (Forsskål, 1775), highfin chub (Perciformes: Kyphosidae) from off Lizard Island, Great Barrier Reef, Queensland, Australia (14°41’10’’S, 145°28’15’’E). Other hosts (intermediate): Echinolittorina vidua (G o u l d, 1 8 5 9) (G a s t r o p o d a: L i t t o r i n i m o r p h a: Littorinidae). Type material: Holotype (QM G238605) ex K. cinerascens from off LI. Paratypes: 14 whole mount and three hologenophore specimens ex K. cinerascens from LI (QM G238606 – G238622). Additional voucher material (intramolluscan): Five slides of cercariae and rediae ex E. vidua from LI (QM G238623–G238627). Site in host: Pyloric caeca (definitive); gonad/digestive gland (intermediate). Representative DNA sequences: Six sequences deposited for COI mtDNA (MW353677 – MW353682); six sequences deposited for 5.8S-ITS2-partial 28S rDNA (MW353959 – MW353964); four sequences deposited for partial 28S rDNA (MW353905 – MW353908); see Supporting Information, Table S2. Etymology: This species is named for its resemblance to the monsters from the Tremors films, ‘graboids’. Graboids are blind, subterranean, worm-like predators with grasping tentacles that emerge from their beaklike maws. Graboids even have complex life-cycles, transitioning through several radically different phenotypes. The name is formed by combination of ‘graboid’ and a Latinized Greek suffix indicating a resemblance or likeness, ‘oides’. Description of adult (Figs 12D–F, 13A, B, E): Measurements in Table 4. Description based on type material and SEM images of three adult specimens. Body elongate, cylindrical, broadest in region of ventral sucker, tapering slightly posteriorly. Tegument armed with alternating rows of partially overlapping comblike scales; distal portion of scales forming up to 15 distinct tendrils. Eyespot pigment sparsely scattered in forebody and anterior third of hindbody. Oral sucker terminal, partially retractable, infundibuliform, broadest in anterior region with distinct reduction in diameter about mid-length continuing through to posterior margin; margin of anterior portion bearing crown of 14 bifid tentacles; outer branch of tentacles broad, conoid; inner branch of tentacles longer than outer, tendril-like, tapering distally. Ventral sucker in anterior third of body, round, smaller than oral sucker. Prepharynx short, distinct, sigmoid or looped. Pharynx ellipsoidal to dolioform, in line with oral sucker or rotated up to 90°. Oesophagus short, bifurcates just posterior to pharynx with proximal section reaching to ventral surface and opening as ‘ventral anus’, and distal portion expanding to form caecum. Caecum single, broadest in anterior region, passes from midforebody to close to posterior extremity, terminates blindly; gastrodermis well developed. Testes two, ellipsoidal, tandem, contiguous or separated, in mid hindbody. Vasa deferentia narrow, passing relatively direct from testes to cirrus-sac. Cirrus-sac elongate, cylindrical, gently winding, reaching from just anterior to ovary to posterior margin of ventral sucker. Internal seminal vesicle tubular, loops once about mid-length, occupies less than half length of cirrus-sac. Pars prostatica distinct, vesicular, less than half length of internal seminal vesicle, lined with anuclear cell-like bodies. Ejaculatory duct distinct, approximately equal in length to, or longer than, pars prostatica; opens into genital atrium. Genital atrium narrow, posterior-dorsal and subequal to ventral sucker. Genital pore small, round to irregular, opening dorsally at level of ventral sucker. Ovary pre-testicular, pyriform, narrowing posteriorly toward union with oötype. Mehlis’ gland indistinct. Laurer’s canal opens dorsally at level of ovary. Canalicular seminal vesicle saccular, contiguous with and dorsal to ovary. Uterus narrow, passes posteriorly from oötype to anterior testis, loops back, gently winding anteriorly, forming muscular metraterm about mid-level of pars prostatica, opening into genital atrium adjacent to ejaculatory duct. Eggs few, oval, operculate, large; length often exceeding that of ovary. Vitellarium follicular, restricted to hindbody; fields reaching from about mid-cirrus-sac to near posterior extremity; dorsal, lateral and ventral fields confluent, wrap around body from dorsal midline to ventrosinistral and ventrodextral regions anterior to testes, wrap entire body posterior to testes. Vitelline reservoir between ovary and anterior testis; collecting ducts indistinct. Excretory pore terminal; excretory vesicle Y-shaped, passes anteriorly, bifurcating in testicular region, ducts passing anteriorly sinistrally and dextrally, terminating as enlarged pyriform sacs on either side of cirrus-sac. Description of redia (Fig 13C): Measurements in Table 6. Description based on voucher material. Body elongate, broadest anteriorly, tapering posteriorly. Cercarial embryos numerous, poorly developed. Mouth terminal. Pharynx dolioform. Intestine short, globular, immediately posterior and subequal in size to pharynx. Description of cercaria (Fig 13E): Measurements in Table 6. Description based on voucher material. Oculate gymnocephalous cercariae. Body elongate, fusiform. Eyespots two, in anterior forebody; additional pigment conspicuous, dispersed in forebody. Oral sucker terminal, infundibuliform. Ventral sucker post-equatorial, round. Prepharynx short, passes between eyespots. Pharynx ellipsoidal. Caecum single, terminating in region dorsal to ventral sucker. Tail longer than body, bipartite; proximal portion bearing series of lateral projections; distal portion scaled, lacking lateral projections. Excretory vesicle Y-shaped, arms extending to ventral sucker, stem extending to near posterior extremity; posterior collecting duct visible to first few scales of distal potion of tail; anterior collecting ducts not visible beyond ventral sucker. Genital primordia darkly stained, dorsal to ventral sucker. Remarks: There are no clear morphometric features that differentiate this species from Gorgocephalus kyphosi, and these two species have overlapping host ranges at both the definitive and intermediate host level. However, the cirrus-sac can again be used for differentiation. In G. kyphosi, the ejaculatory duct is short and the internal seminal vesicle and pars prostatica each occupy about half of the cirrus-sac, whereas in G. graboides the internal seminal vesicle occupies less than half of the cirrus-sac and the pars prostatica is less than half the length of the internal seminal vesicle; the remaining space is occupied by a long, distinct ejaculatory duct, which is about as long as, or longer than, the pars prostatica. Furthermore, the genital atrium is larger than the ventral sucker in specimens of G. kyphosi, whereas in G. graboides the two features are similar in size. From Gorgocephalus euryaleae, G. graboides differs in having a shorter pars prostatica (occupying less than half, rather than more than half, of the cirrus-sac) and in having a longer ejaculatory duct (equal or greater in length than the pars prostatica vs. shorter than the pars prostatica). Although both species share K. cinerascens as a host, they appear to be geographically isolated from one another. From Gorgocephalus manteri, G. graboides differs primarily in having a larger body and in having vitelline follicles restricted to the hindbody, rather than having them extend into the forebody. The cirrus-sac of G. graboides also lacks the strong sigmoidal shape of that of G. manteri and based on the calculations of Bray & Cribb (2005), G. manteri has, as a percentage of body length, a much greater body width (28–34% vs. 8–11%), lesser ovary to ventral sucker distance (~5% vs. 27–33%) and greater ovary to testis distance (~17% vs. 4–9%) than G. graboides. Gorgocephalus graboides is easily distinguished from G. yaaji in having a far less dorsoventrally flattened body, and in having vitelline follicles restricted to the hindbody, rather than having them extend into the forebody. Gorgocephalus graboides also differs from G. yaaji morphometrically, namely in having, as a percentage of body length, a shorter forebody (21–26% vs. 31–42%), a shorter pharynx (3.0–4.3% vs. 6.0– 10.2%) and a longer testis to ventral sucker distance (36–44% vs. 22–32%). Gorgocephalus graboides also has a lesser pharynx length to oral sucker length ratio than G. yaaji (0.27–0.35 vs. 0.37–0.55). The inner and outer portions of the oral sucker tentacles of G. yaaji are approximately equal in length, rather than having the inner portion longer like in G. graboides and the tegument scales of G. yaaji have more posterior tendrils than those of G. graboides (up to 18 vs. up to 15). Lastly, the cirrus-sac of G. graboides is less robust than that of G. yaaji and does not have the anterior portion recurved. Gorgocephalus kyphosi and G. graboides share an intermediate host, Echinolittorina vidua, at Lizard Island, GBR, and other than the cercariae of G. graboides having a somewhat more fusiform body shape, we were unable to find any clear morphometric or qualitative differences between the intramolluscan stages of these two species. Thus, intramolluscan stages of G. kyphosi and G. graboides can only be distinguished on a molecular basis. The same subtle differences found between intramolluscan stages of G. kyphosi and G. yaaji apply when comparing G. graboides to G. yaaji. We obtained naturally emerged cercariae of G. graboides and did not observe the eyespot ‘lenses’ described for naturally emerged cercariae of G. yaaji (Huston et al., 2016). We also did not observe the posterior ‘protuberance’ in the rediae of G. graboides. However, as discussed above, these seem weak characters for species delineation.

GORGOCEPHALUS YAAJI BRAY & CRIBB, 2005 (FIGS 9D���F, 10; TABLES 3, 6) Synonym: ��� Gorgocephalus sp. Aus��� of O���Dwyer et al. (2015). Type host and locality: Kyphosus vaigiensis (Quoy & Gaimard, 1825) (Perciformes: Kyphosidae), brassy chub from off Lizard Island, Great Barrier Reef, Queensland, Australia (14��41���10������S, 145��28���15������E). Records: 1, Bray & Cribb (2005); 2, O���Dwyer et al. (2015); 3, Huston et al. (2016); 4, present study. Definitive hosts: Perciformes, Kyphosidae. Kyphosus cinerascens (Forssk��l, 1775), highfin chub (3, 4); Kyphosus elegans (W. K. H. Peters, 1869), Cortez sea chub (4); Kyphosus vaigiensis (Quoy & Gaimard, 1825) (1, 4). Intermediate hosts: Gastropoda, Littorinimorpha, Littorinidae. Austrolittorina unifasciata (Gray) (2, 3); Echinolittorina austrotrochoides Reid, 2007 (3); Echinolittorina cinerea (Pease, 1869) (4). Other localities: Gerringong, New South Wales, Australia (34��44���18������S, 150��49���29������E) (2); Kioloa, New South Wales, Australia (35��33���38������S, 150��22���27������E) (KI) (3); Shellharbour, New South Wales, Australia (34��34���59������S, 150��52���E) (2); Sydney, New South Wales, Australia (33��52���42������S, 151��12���34������E) (2); Ulladulla, New South Wales, Australia (35��21���17������S, 150��27���43������E) (2); off Rangiroa, Tuamotu Islands, French Polynesia (15�� 10��� 40������ S, 147 ��39��� 04������ W) (4); Sodwana Bay, KwaZulu-Natal, South Africa (27��32���24������S, 32��40���41������E) (SB) (4). Voucher material (adult): Ten whole-mount and three hologenophore specimens, ex K. vaigiensis from LI (QM G238592���G238604); six whole-mount and three hologenophore specimens ex K. cinerascens from RA (MNHN HEL1447���1455); one whole-mount specimen ex K. elegans from RA (MNHN HEL1456); three whole-mount and one hologenophore specimen ex K. cinerascens from SB (NMB 730); six whole-mount specimens ex K. vaigiensis from SB (NMB 731). Voucher material (intramolluscan): Eight slides of rediae and cercariae ex E. cinerea from RA (MNHN HEL1457���1464). Site in host: Upper intestine (definitive); gonad/ digestive gland (intermediate). Representative DNA sequences: Nineteen sequences (MW353650 ��� MW353668), using primers of Wee et al. (2017), and three sequences (MW350141 ��� MW350143), following O���Dwyer et al. (2016) (see methods) deposited for COI mtDNA; 17 sequences deposited for 5.8S-ITS2- partial 28S rDNA (MW353931 ��� MW353947); nine sequences deposited for partial 28S rDNA (MW353889 ��� MW353897); see Supporting Information, Table S2. Description of adult (Figs 9D ���F, 10 A ��� C, F: Measurements in Table 3). Description based upon all adult voucher material and SEM images of three adults. Body elongate-oval, somewhat dorsoventrally flattened, broadest in region of ventral sucker, tapering slightly posteriorly. Tegument armed with alternating rows of partially overlapping comb-like scales; distal portion of scales forming up to 18 distinct tendrils. Eyespot pigment sparsely scattered in forebody. Oral sucker terminal, partially retractable, infundibuliform, broadest in anterior region with distinct reduction in diameter about mid-length continuing through to posterior margin; margin of anterior portion bearing crown of 14 bifid tentacles; outer branch of tentacles broad, conoid; inner branch of tentacles approximately equal in length to outer, tendril-like, tapering distally. Ventral sucker in anterior third of body, round, smaller than oral sucker. Prepharynx short, distinct, sigmoid or looped. Pharynx ellipsoidal to dolioform, in line with oral sucker or rotated up to 45��. Oesophagus short, bifurcates just posterior to pharynx with proximal section reaching to ventral surface and opening as ���ventral anus���, and distal portion expanding to form caecum. Caecum single, broadest in anterior region, passes from mid-forebody to close to posterior extremity, terminates blindly; gastrodermis well developed. Testes two, ellipsoidal, tandem, contiguous, in midhindbody. Vasa deferentia narrow, passing relatively direct from testes to cirrus-sac. Cirrus-sac elongate, cylindrical, winding, reaching from anterior testis to level of ventral sucker; anterior portion curves back posteriorly from ventral sucker to genital atrium. Internal seminal vesicle tubular, bends slightly about mid-length, occupies about half length of cirrus-sac. Pars prostatica distinct, vesicular, approximately equal in length to internal seminal vesicle, lined with anuclear cell-like bodies. Ejaculatory duct long, occupies recurved portion of cirrus-sac. Genital atrium broad, dorsal and approximately equal in size to ventral sucker. Genital pore large, round to irregular, opening dorsodextrally at level of ventral sucker. Ovary pre-testicular, ellipsoidal to subglobular. Mehlis��� gland between ovary and anterior testis. Laurer���s canal opens dorsally posterior to ovary. Canalicular seminal vesicle saccular, contiguous with and dorsal to ovary. Uterus narrow, passes posteriorly from o��type to anterior testis, loops back, gently winding anteriorly, forming muscular metraterm about mid-level of pars prostatica, opening into genital atrium adjacent to ejaculatory duct. Eggs few, oval, operculate, large; length of eggs often exceeding that of ovary. Vitellarium follicular, in fore- and hindbody, fields reaching from pharyngoesophageal region to near posterior extremity; dorsal, lateral and ventral fields confluent, wrap around body from dorsal midline to ventrosinistral and ventrodextral regions anterior to testes, wrap entire body posterior to testes. Vitelline reservoir between ovary and anterior testis; collecting ducts indistinct. Excretory pore terminal; excretory vesicle Y-shaped, passes anteriorly, bifurcating in testicular region, ducts passing anteriorly sinistrally and dextrally, terminating as enlarged pyriform sacs on either side of cirrus-sac. Description of redia (Fig. 10D): Measurements in Table 6. Description based on voucher material. Body ellipsoidal, broadest posteriorly; distinctive protuberance arising from posterior extremity in most specimens. Cercarial embryos numerous, poorly developed. Mouth subterminal. Pharynx ellipsoidal. Intestine short, globular, immediately posterior and subequal in size to pharynx. Description of cercaria (Fig. 10E): Measurements in Table 6. Description based on voucher material. Oculate gymnocephalous cercariae. Body elongate, ellipsoidal. Eyespots two, in anterior forebody; eyespot lenses present in live naturally emerged specimens, not present in immature specimens. Oral sucker subterminal, infundibuliform. Ventral sucker post-equatorial, round. Prepharynx short, passes between eyespots. Pharynx ellipsoidal. Caecum single, terminating near anterior margin of ventral sucker. Tail bipartite; proximal portion bearing series of lateral projections; distal portion scaled, lacking lateral projections. Excretory vesicle Y-shaped; arms extending to ventral sucker, stem extending to near posterior extremity; posterior collecting duct visible to first few scales of distal portion of tail; anterior collecting ducts not visible beyond ventral sucker. Genital primordia darkly stained, dorsal to ventral sucker. Remarks: Gorgocephalus yaaji occurs across a wider geographic range than any other species of the family. Indeed, to our knowledge the finding of G. yaaji in French Polynesia, South Africa, and in between, is the first report, supported by molecular data, of naturally occurring populations of a single marine digenean species occurring across the whole breadth of the IWP. Although it has fewer definitive host records than G. kyphosi, three gastropod intermediate hosts are known for G. yaaji, the most for any species of the family. O���Dwyer et al. (2015) described the first gorgocephalid cercariae from the littorinid A. unifasciata, but did not connect these infections to an adult gorgocephalid, because their sequences did not match those of G. kyphosi from the study of Olson et al. (2003), the only sequences available for the family at that time. Huston et al. (2016) described the cercariae of G. yaaji from Echinolittorina austrotrochoides from Lizard Island, GBR, and determined that, based on the difference in host, molecular differences in the ITS2 and 28S rDNA gene-regions, and morphological differences, the infections characterized by O���Dwyer et al. (2015) were likely those of an undescribed species. However, by adding an additional molecular marker (COI) and performing expanded phylogenetic study of the family, we have demonstrated that the intramolluscan infections described by O���Dwyer et al. (2015) are best interpreted as representative of G. yaaji. The host, molecular and morphological differences reported by Huston et al. (2016) between their material and that of O���Dwyer et al. (2015) are clearly within the bounds of intraspecific variation for G. yaaji. Huston et al. (2016) noted that the morphological differences between their cercarial specimens of Gorgocephalus yaaji and those of O���Dwyer et al. (2015) may have been a result of differences between ���naturally emerged��� cercariae and cercariae excised from gastropods. O���Dwyer et al. (2015) studied live and fixed cercariae dissected from gastropods, whereas Huston et al. (2016) studied live and fixed naturally emerged cercariae. Naturally emerged cercariae are generally considered as ���mature���, whereas cercariae obtained from dissection of a gastropod may include mature and immature individuals. As stated above, the morphometric differences observed between G. yaaji cercariae appear due to normal intraspecific variation. However, one of the key morphological differences between the material of O���Dwyer et al. (2015) and Huston et al. (2016) was the observation of distinct ���lenses��� in the eyespots of the live cercariae from the latter study. O���Dwyer et al. (2015) studied live material from dissected gastropods and is unlikely to have missed such a distinctive feature if it was present. Huston et al. (2016) interpreted this lack of eyespot lenses as indicative of a species-level difference. However, we did not obtain naturally emerged cercariae of G. yaaji from Echinolittorina cinerea in French Polynesia, although we did study live material from dissected gastropods. We did not observe eyespot lenses in the French Polynesian cercariae. Thus, as all of these cercariae are conspecific, we interpret the presence of eyespot lenses in the cercariae from the study of Huston et al. (2016) as a feature that is likely present only in mature, naturally emerged cercariae. Five of the six known intermediate host records for gorgocephalids are attributable to Gorgocephalus kyphosi and G. yaaji. These two species have yet to be confirmed as having overlapping intermediate host ranges, but this remains possible. We obtained naturally emerged cercariae of G. kyphosi from an infected Echinolittorina vidua from Lizard Island, GBR, the same locality from which Huston et al. (2016) obtained naturally emerged cercariae of G. yaaji from E. austrotrochoides. Although there are no clear morphometric differences between the cercariae of G. kyphosi and G. yaaji, we did not observe eyespot lenses in the cercariae of G. kyphosi. However, as naturally emerged cercariae were studied from only a few infected gastropods, at present it is difficult to have confidence in the validity of this character for species differentiation. Additionally, Huston et al. (2016) described the rediae of G. yaaji from infected E. austrochoides from Lizard Island, GBR, with a strange posterior ���protuberance���. We observed the same feature in the rediae of G. yaaji from infected E. cinerea from Rangiroa, French Polynesia. This feature was not present in any of the rediae of G. kyphosi that we observed. We do note that this ���protuberance��� was not reported by O���Dwyer et al. (2015), so this would seem a somewhat tenuous feature for the differentiation of species. Despite repeated attempts, we were never able to obtain naturally emerged cercariae of G. kyphosi from Bembicium auratum. Considering the cryptic morphology of gorgocephalid cercariae, and the difficulty of obtaining naturally emerged specimens, use of molecular data for the identification of intramolluscan gorgocephalid infections will be required in most cases. As noted above, Bray & Cribb (2005) reported the number of oral sucker tentacles in G. yaaji as 14���17; based on our SEM images we believe that this species, and all known gorgocephalids, have only 14 bifid tentacles. Although Manter (1966) reported G. kyphosi from both the pyloric caeca and intestine of K. sydneyanus, Bray & Cribb (2005) found that in K. vaigiensis from Lizard Island, G. kyphosi was restricted to the pyloric caeca whereas G. yaaji was found in the intestine. Our observations agree. With the exception of G. yaaji, all species of Gorgocephalus we collected were found only in the pyloric caeca. We found G. yaaji in the upper intestine, just posterior to the pyloric caeca., Published as part of Huston, Daniel C., Cutmore, Scott C., Miller, Terrence L., Sasal, Pierre, Smit, Nico J. & Cribb, Thomas H., 2021, Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range, pp. 1416-1455 in Zoological Journal of the Linnean Society 193 (4) on pages 1438-1441, DOI: 10.1093/zoolinnean/zlab002, http://zenodo.org/record/5761768, {"references":["Bray RA, Cribb TH. 2005. Gorgocephalus yaaji n. sp. (Digenea: Gorgocephalidae) from the brassy chub Kyphosus vaigiensis (Perciformes: Kyphosidae) off Lizard Island, northern Great Barrier Reef and further records of G. kyphosi. Zootaxa 1068: 39 - 46.","O'Dwyer K, Faltynkova A, Georgieva S, Kostadinova A. 2015. An integrative taxonomic investigation of the diversity of digenean parasites infecting the intertidal snail Austrolittorina unifasciata Gray, 1826 (Gastropoda: Littorinidae) in Australia. Parasitology Research 114: 2381 - 2397.","Huston DC, Cutmore SC, Cribb TH. 2016. The life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 (Digenea: Gorgocephalidae) with a review of the first intermediate hosts for the superfamily Lepocreadioidea Odhner, 1905. Systematic Parasitology 93: 653 - 665.","Reid DG. 2007. The genus Echinolittorina Habe, 1956 (Gastropoda: Littorinidae) in the Indo-West Pacific Ocean. Zootaxa 1420: 1 - 161.","Wee NQ, Cribb TH, Bray RA, Cutmore SC. 2017. Two known and one new species of Proctoeces from Australian teleosts: Variable host-specificity for closely related species identified through multi-locus molecular data. Parasitology International 66: 16 - 26.","Olson PD, Cribb TH, Tkach VV, Bray RA, Littlewood DT. 2003. Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda). International Journal for Parasitology 33: 733 - 755.","Manter HW. 1966. A peculiar trematode, Gorgocephalus kyphosi gen. et sp. n. (Lepocreadiidae: Gorgocephalinae subfam. n.), from a marine fish of South Australia. Journal of Parasitology 52: 347 - 350."]}

GORGOCEPHALUS KYPHOSI MANTER, 1966 (FIGS 7���9; TABLES 2, 6) Type host and locality: Kyphosus sydneyanus (G��nther, 1886) (Perciformes: Kyphosidae), silver drummer, from near Port Noarlunga, South Australia (35��09���10������S, 138��27���49������E). Records: 1, Manter (1966); 2, Olson et al. (2003); 3, Bray (2005b). 4, Bray & Cribb (2005); 5, present study. Definitive hosts: Perciformes, Kyphosidae. Kyphosus cinerascens (Forssk��l, 1775), highfin chub (5); Kyphosus elegans (W. K. H. Peters, 1869), Cortez sea chub (5); Kyphosus sydneyanus (G��nther, 1886), silver drummer (1, 5). Kyphosus vaigiensis (Quoy & Gaimard, 1825), brassy chub (2, 3, 4, 5). The number in brackets refer to the ���records��� section directly preceding this - essentially a way to avoid having to list citations repeatedly. Intermediate hosts: Gastropoda, Littorinimorpha, Littorinidae. Bembicium auratum (Quoy & Gaimard, 1834) (5); Echinolittorina vidua (Gould, 1859) (5). Other localities: Off Point Riley, Yorke Peninsula, South Australia (33��52���49������S, 137��35���52������E) (PR) (5); off Amity Point, North Stradbroke Island, Moreton Bay, Queensland, Australia (27��23���53������S, 153��26���15������E) (AP) (5); off Dunwich, North Stradbroke Island, Moreton Bay, Queensland, Australia (27��29���46������S, 153��23���52������E) (DW) (5); off Lizard Island, Great Barrier Reef, Queensland, Australia (14��41���10������S, 145��28���15������E) (LI) (2, 3, 4, 5); off Moorea, Society Islands, French Polynesia (17��32���46������S, 149��49���47������E) (4); off Rangiroa, Tuamotu Islands, French Polynesia (15��10���40������S, 147��39���04������W) (RA) (5). The letters in brackets are an abbreviation for the locality. Voucher material (adult): Ten whole-mount and three hologenophore specimens, ex K. sydneyanus from PR (SAM AHC36801 ���36806); ten wholemount and three hologenophore specimens ex K. cinerascens from AP (QM G238552���G238564); two whole-mount specimens ex K. cinerascens from LI (QM G238571���G238572); 13 whole-mount and three hologenophore specimens ex K. vaigiensis from LI (QM G238573���G238588); nine whole-mount and three hologenophore specimens ex K. cinerascens from RA (MNHN HEL1431���1442); one whole-mount and three hologenophore specimens ex K. elegans from RA (MNHN HEL1433���1446). Voucher material (intramolluscan): Six slides of rediae and cercariae ex B. auratum from DW (QM G238565��� G238570); three slides of rediae and cercariae ex E. vidua from LI (QM G238589���G238591). Site in host: Pyloric caeca (definitive); gonad/digestive gland (intermediate). Representative DNA sequences: Twenty-one sequences deposited for COI mtDNA (MW353629 ��� MW353649); 21 sequences deposited for 5.8S-ITS2-partial 28S rDNA (MW353910 ��� MW353930); 12 sequences deposited for partial 28S rDNA (MW353877 ��� MW353888); see Supporting Information, Table S2. Description of adult (Figs 7A, B, E, 8, 9A���C): Measurements in Table 2. Description based on all adult voucher material plus SEM images of eight adult specimens. Body elongate, cylindrical, broadest in region anterior to ventral sucker, tapering slightly posteriorly. Tegument armed with alternating rows of partially overlapping comb-like scales; distal portion of scales forming up to 15 distinct tendrils. Eyespot pigment sparsely scattered in forebody. Oral sucker terminal, partially retractable, infundibuliform, broadest in anterior region with distinct reduction in diameter about mid-length continuing through to posterior margin; margin of anterior portion bearing crown of 14 bifid tentacles; outer branch of tentacles broad, conoid; inner branch of tentacles longer than outer branch, tendrillike, tapering distally. Ventral sucker in anterior third of body, round, far smaller than oral sucker. Prepharynx short, distinct, sigmoid or looped. Pharynx ellipsoidal to dolioform, in line with oral sucker or rotated up to 90��. Oesophagus short, bifurcates just posterior to pharynx with proximal section reaching to ventral surface and opening as ���ventral anus���, and distal portion expanding to form caecum. Caecum single, broadest in anterior region, passes from mid-forebody to close to posterior extremity, terminates blindly; gastrodermis well developed. Testes two, ellipsoidal, tandem, contiguous, in midhindbody. Vasa deferentia narrow, passing relatively direct from testes to cirrus-sac. Cirrus-sac elongate, cylindrical, winding, reaching from just anterior to ovary to level of ventral sucker. Internal seminal vesicle tubular, loops once about mid-length, occupies about half length of cirrus-sac. Pars prostatica distinct, vesicular, about half length of internal seminal vesicle, lined with anuclear, cell-like bodies. Ejaculatory duct short, curves back dorsally from pars prostatica to open into genital atrium. Genital atrium broad, dorsal to and larger than ventral sucker. Genital pore large, round to irregular, opening dorsally at level of ventral sucker. Ovary pre-testicular, pyriform, narrowing posteriorly toward union with o��type. Mehlis��� gland indistinct. Laurer���s canal opens dorsally at level of ovary. Canalicular seminal vesicle saccular, contiguous with and dorsal to ovary. Uterus narrow, passes posteriorly from o��type to anterior testis, loops back, gently winding anteriorly, forming muscular metraterm about mid-level of pars prostatica, opening into genital atrium adjacent to ejaculatory duct. Eggs few, oval, operculate, large; length often exceeding that of ovary. Vitellarium follicular, restricted to hindbody; fields reaching from about mid-cirrus-sac to near posterior extremity; dorsal, lateral and ventral fields confluent, wrap around body from dorsal midline to ventrosinistral and ventrodextral regions anterior to testes, wrap entire body posterior to testes. Vitelline reservoir between ovary and anterior testis; collecting ducts indistinct. Excretory pore terminal; excretory vesicle Y-shaped, passes anteriorly, bifurcating in testicular region, ducts passing anteriorly sinistrally and dextrally, terminating as enlarged pyriform sacs on either side of cirrus-sac. Description of redia (Fig. 7C): Measurements in Table 6. Description based on all voucher material. Body elongate, broadest anteriorly, tapering slightly posteriorly. Cercarial embryos numerous, poorly developed. Mouth subterminal. Pharynx cylindrical to hourglass-shaped. Intestine short, saclike, immediately posterior to pharynx. Description of cercaria (Fig 7D): Measurements in Table 6. Description based on all voucher material. Oculate gymnocephalous cercariae. Body elongate, ellipsoidal. Eyespots two, in anterior forebody; additional pigment dispersed in forebody. Oral sucker terminal, infundibuliform. Ventral sucker post-equatorial, round. Prepharynx short, passes between eyespots. Pharynx ellipsoidal. Caecum single, terminating in region dorsal to ventral sucker. Tail longer than body, bipartite; proximal portion bearing series of lateral projections; distal portion scaled, lacking lateral projections. Excretory vesicle Y-shaped, arms extending to anterior margin of ventral sucker, stem extending posterior to ventral sucker; posterior collecting duct visible to first few scales of distal potion of tail; anterior collecting ducts not visible beyond ventral sucker. Genital primordia dorsal to ventral sucker. Remarks: Gorgocephalus kyphosi has now been demonstrated to occur in four species of Kyphosus, the broadest definitive host range of any known member of the family. This species also occurs across a broad geographic range, from eastern and southern Australia to French Polynesia. Despite the discovery of two new species of gorgocephalid, which are morphologically similar to G. kyphosi, all previous records of this species subsequent to the type description have proven accurate. The previously available 28S rDNA sequence for G. kyphosi of Olson et al. (2003), generated from specimens from K. vaigiensis collected off Lizard Island, fell into a well-supported clade of specimens of this species from Lizard Island. Bray (2005b) and Bray & Cribb (2005) also reported G. kyphosi from Lizard Island, but again these specimens were all from K. vaigiensis; the morphologically similar G. graboides has only been recovered from K. cinerascens. No molecular data are available to confirm the identity of specimens reported from Moorea, French Polynesia (Bray & Cribb, 2005), but that report is again based on specimens recovered from K. vaigiensis. Off Rangiroa, Tuamotu Islands, French Polynesia, we obtained only G. kyphosi and G. yaaji, despite examination of specimens comprising three species of Kyphosus. Thus, we have little doubt that the specimens from Moorea represent G. kyphosi. Both Manter (1966), in the original type description, and Yamaguti (1971), in study of the same material, reported the number of oral sucker tentacles of Gorgocephalus kyphosi at 14���15. We find that, because of the bifid nature of these tentacles, the fact that they are often partially retracted and that they generally overlay one-another in slide-mounted specimens, it is difficult to be confident in the accuracy of counts of these tentacles obtained during light-microscopy. This difficulty was also noted by Bray & Cribb (2005), who reported the number of oral sucker tentacles in G. yaaji as 14���17. We obtained SEM images of the oral sucker of eight individual adult G. kyphosi, including specimens from three Australian localities and French Polynesia. Although not all tentacles were visible in some of these specimens, in all of those in which an accurate count was possible, the number of tentacles was determined to be 14. Furthermore, the number of oral sucker tentacles was determined to be 14 for all species studied here, and Zhukov (1983) reported the number of tentacles in G. manteri at 14. It appears that all presently recognized species of Gorgocephalus possess 14 oral sucker tentacles. Manter (1966) described the anterior region of the oesophagus as a ���dorsal sac��� from which the duct opening as the ventral anus arises. Yamaguti (1971) referred to these structures collectively as the ���post-pharyngeal vesicle���. Both of these authors also described these structures as separated from the oesophagus proper by a muscular sphincter. Bray & Cribb (2005) did not observe these features in specimens of G. yaaji or in serially sectioned specimens of G. kyphosi. We did not observe these features either, although we did not study any sectioned specimens. If such features are present, they are subtle and difficult to observe in whole-mounted specimens. Thus, we agree with Bray & Cribb (2005) that these features are unlikely to be useful for the differentiation of species. We have discovered two intermediate hosts for Gorgocephalus kyphosi, Bembicium auratum and Echinolittorina vidua, both gastropods of the family Littorinidae. The distribution of these two gastropods suggests that G. kyphosi utilizes additional intermediate host species throughout its range. Extant species of the genus Bembicium occur only on the coasts of mainland Australia, Tasmania, Lord Howe Island and Norfolk Island (Reid, 1988). Bembicium auratum ranges from South Australia to Lizard Island on the GBR (Reid, 1988), covering the Australian range of G. kyphosi. Echinolittorina vidua ranges throughout the central IWP, but not to French Polynesia (Reid, 2007). Thus, Polynesian populations of G. kyphosi must utilize an intermediate host different from those used by Australian populations, although this host will undoubtedly be a species of the Littorinidae. No morphological differences were found between the intramolluscan stages of Gorgocephalus kyphosi obtained from Bembicium auratum and Echinolittorina vidua. The cercariae of G. kyphosi are similar to those of the family described previously (O���Dwyer et al., 2015; Huston et al., 2016) and those of Gorgocephalus graboides described here. Although there are some subtle differences between intramolluscan gorgocephalids (see Remarks sections for G. yaaji and G. graboides), matching of these stages to adult forms using molecular markers is likely the best approach for future work elucidating life cycles in this family., Published as part of Huston, Daniel C., Cutmore, Scott C., Miller, Terrence L., Sasal, Pierre, Smit, Nico J. & Cribb, Thomas H., 2021, Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range, pp. 1416-1455 in Zoological Journal of the Linnean Society 193 (4) on pages 1432-1438, DOI: 10.1093/zoolinnean/zlab002, http://zenodo.org/record/5761768, {"references":["Manter HW. 1966. A peculiar trematode, Gorgocephalus kyphosi gen. et sp. n. (Lepocreadiidae: Gorgocephalinae subfam. n.), from a marine fish of South Australia. Journal of Parasitology 52: 347 - 350.","Olson PD, Cribb TH, Tkach VV, Bray RA, Littlewood DT. 2003. Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda). International Journal for Parasitology 33: 733 - 755.","Bray RA. 2005 b. Family gorgocephalidae manter, 1966. In: Jones A, Bray RA, Gibson DI, eds. Keys to the Trematoda, Vol. 2. Wallingford: CABI Publishing and the Natural History Museum, 663 - 664.","Bray RA, Cribb TH. 2005. Gorgocephalus yaaji n. sp. (Digenea: Gorgocephalidae) from the brassy chub Kyphosus vaigiensis (Perciformes: Kyphosidae) off Lizard Island, northern Great Barrier Reef and further records of G. kyphosi. Zootaxa 1068: 39 - 46.","Yamaguti S. 1971. Synopsis of digenetic trematodes of vertebrates. Tokyo: Keigaku Publishing Co.","Zhukov EV. 1983. New representatives of the fauna of trematodes from the fishes of the Gulf of Mexico. Parazitologiia 17: 112 - 117 [in Russian].","Reid DG. 1988. The genera Bembicium and Risellopsis (Gastropoda: Littorinidae) in Australia and New Zealand. Records of the Australian Museum 40: 91 - 150.","Reid DG. 2007. The genus Echinolittorina Habe, 1956 (Gastropoda: Littorinidae) in the Indo-West Pacific Ocean. Zootaxa 1420: 1 - 161.","O'Dwyer K, Faltynkova A, Georgieva S, Kostadinova A. 2015. An integrative taxonomic investigation of the diversity of digenean parasites infecting the intertidal snail Austrolittorina unifasciata Gray, 1826 (Gastropoda: Littorinidae) in Australia. Parasitology Research 114: 2381 - 2397.","Huston DC, Cutmore SC, Cribb TH. 2016. The life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 (Digenea: Gorgocephalidae) with a review of the first intermediate hosts for the superfamily Lepocreadioidea Odhner, 1905. Systematic Parasitology 93: 653 - 665."]}

Gorgocephalus yaaji This species was described by Bray & Cribb (2005) based on adult specimens obtained from Kyphosus vaigiensis, collected from off Lizard Island, GBR, Australia. Gorgocephalus yaaji is easily distinguished from all other species of the family, largely in having a more robust, dorsoventrally flattened body shape and in having the vitellarium extend into the forebody. Previously, Huston et al. (2016) generated ITS2 and 28S rDNA gene sequences from adult and intramolluscan specimens of G. yaaji from the type locality. In the present study, additional adult gorgocephalids morphologically consistent with G. yaaji were obtained from the type locality and from Rangiroa Atoll in French Polynesia and Sodwana Bay in South Africa (Fig. 1). Despite extensive investigation, including traditional morphometrics, PCA analyses and SEM imaging, we were unable to find any significant morphological differences between specimens from these three localities. Intramolluscan gorgocephalids from three Echinolittorina cinerea collected from Rangiroa Atoll, French Polynesia were molecularly matched to adults consistent with G. yaaji collected from the same locality. Furthermore, intramolluscan gorgocephalids have previously been collected from Austrolittorina unifasciata, from multiple locations along the coast of New South Wales, Australia (O���Dwyer et al., 2015; Huston et al., 2016), but they had not previously been connected to an adult form. BLAST analyses showed that the sequences generated from intramolluscan gorgocephalids collected from Kioloa, NSW, matched sequences of ��� Gorgocephalus sp. Aus��� from the study of O���Dwyer et al. (2015) with identity scores of 98���100%, demonstrating that gorgocephalids collected from A. unifasciata in the studies of O���Dwyer et al. (2015) and Huston et al. (2016) are conspecific. The present phylogenetic analyses (Figs 3���6) demonstrate that these infections are representative of G. yaaji. Despite adult gorgocephalids consistent with Gorgocephalus yaaji collected from across the IWP being morphologically indistinguishable, phylogenetic analyses of the ITS2 and 28S rDNA single-gene datasets did not recover a monophyletic G. yaaji clade (Figs 4, 5). In the ITS2 single-gene tree (Fig. 4), specimens morphologically consistent with G. yaaji were paraphyletic and formed three well-supported clades: specimens from Lizard Island (adults and intramolluscan stages), specimens from French Polynesia (adults and intramolluscan stages) + those from Kioloa, NSW, Australia (intramolluscan stages only), and those from South Africa (adults only). The first two of these clades were recovered in polytomy with the third + G. euryaleae + G. kyphosi, with G. graboides sister to all of these clades together. All ITS2 sequences for G. yaaji were identical for specimens within each locality and differed by 0���5 bp (0.0���1.1%) between localities (Table 5). In the 28S rDNA single-gene tree (Fig. 5), G. yaaji was also recovered as paraphyletic, but with the South African representatives resolving as basal to all clades. The 28S rDNA sequences of G. yaaji differed by 0���6 bp (0.0���0.6%) between localities. In contrast to analyses of ITS2 and 28S rDNA, those for the COI mtDNA single-gene dataset (Fig. 3) resolved all specimens morphologically consistent with Gorgocephalus yaaji as a monophyletic group, sister to the remaining lineages of the Gorgocephalidae, albeit without support in ML analysis. Sequences differed by only 0���3 bp (0.0���0.6%) within individual localities but differed by 12���62 bp (~3.0���13%) between localities. The largest difference (62 bp) was between specimens from French Polynesia and South Africa, representing opposite sides of the IWP marine region, although the South African specimens were also relatively divergent from those collected in Australia (50���58 bp or ~11���12%; Supporting Information, Table S5). The concatenated COI + ITS2 + 28S analyses (Fig. 6) also resolved representatives of G. yaaji in a monophyletic clade, with lower BI posterior probability support but higher ML bootstrap support. Similar to the pattern observed for Gorgocephalus kyphosi, COI and ITS 2 sequences of G. yaaji, generated from one Australian locality (Kioloa, NSW) were more similar to those from French Polynesia than to those from another Australian locality, Lizard Island, GBR (Supporting Information, Table S5). Such molecular variation coupled with the lack of monophyly in the ITS2 and 28S rDNA trees suggests the possibility of multiple species. However, in the ITS2 and 28S trees, sequences associated with specimens morphologically indistinguishable from G. yaaji, result in a paraphyletic, rather than a polyphyletic, G. yaaji (i.e. sequences are more, or at least, as related to one another as they are to other species represented). There are also no hostlevel distinctions to delineate additional species within the G. yaaji concept; the species appears to have a broad definitive and intermediate host range (within the confines of the Kyphosidae and Littorinidae). The issues with paraphyly in the ITS2 and 28S trees might be alleviated with sequences from additional specimens collected from localities between Australia and South Africa. However, without further evidence there appears no justification for splitting the G. yaaji clade into multiple morphologically cryptic species. Sequences of G. yaaji differ from the others species of the Gorgocephalidae recognized here by 66���88 bp (14���19%), 5���16 bp (1.1���3.5%) and 12���21 bp (1.2���2.1%) in the COI, ITS2 and 28S gene regions, respectively., Published as part of Huston, Daniel C., Cutmore, Scott C., Miller, Terrence L., Sasal, Pierre, Smit, Nico J. & Cribb, Thomas H., 2021, Gorgocephalidae (Digenea: Lepocreadioidea) in the Indo-West Pacific: new species, life-cycle data and perspectives on species delineation over geographic range, pp. 1416-1455 in Zoological Journal of the Linnean Society 193 (4) on pages 1425-1430, DOI: 10.1093/zoolinnean/zlab002, http://zenodo.org/record/5761768, {"references":["Bray RA, Cribb TH. 2005. Gorgocephalus yaaji n. sp. (Digenea: Gorgocephalidae) from the brassy chub Kyphosus vaigiensis (Perciformes: Kyphosidae) off Lizard Island, northern Great Barrier Reef and further records of G. kyphosi. Zootaxa 1068: 39 - 46.","Huston DC, Cutmore SC, Cribb TH. 2016. The life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 (Digenea: Gorgocephalidae) with a review of the first intermediate hosts for the superfamily Lepocreadioidea Odhner, 1905. Systematic Parasitology 93: 653 - 665.","O'Dwyer K, Faltynkova A, Georgieva S, Kostadinova A. 2015. An integrative taxonomic investigation of the diversity of digenean parasites infecting the intertidal snail Austrolittorina unifasciata Gray, 1826 (Gastropoda: Littorinidae) in Australia. Parasitology Research 114: 2381 - 2397."]}