Revision of Podocotyloides Yamaguti, 1934 (Digenea: Opecoelidae), resurrection of Pedunculacetabulum Yamaguti, 1934 and the naming of a cryptic opecoelid species

Abstract

Despite morphological and ecological inconsistencies among species, all plagioporine opecoelids with a pedunculate ventral sucker are currently considered to belong in the genus Podocotyloides Yamaguti, 1934. We revise the genus based on combined morphological and phylogenetic analyses of novel material collected from haemulid fishes in Queensland waters that we interpret to represent species congeneric with the type-species, Pod. petalophallus Yamaguti, 1934, also known from a haemulid, off Japan. Our phylogenetic analysis demonstrates polyphyly of Podocotyloides; prompts us to resurrect Pedunculacetabulum Yamaguti, 1934; and suggests that Pod. brevis Andres & Overstreet, 2013, from a deep-sea congrid in the Caribbean, and Pod. parupenei (Manter, 1963) Pritchard, 1966 and Pod. stenometra Pritchard, 1966, from mullids and chaetodontids, respectively, on the Great Barrier Reef, may each represent a distinct genus awaiting recognition. Our revised concept of Podocotyloides requires a pedunculate ventral sucker, but also a uterine sphincter prior to the genital atrium, a petalloid cirrus appendage, restriction of the vitelline follicles to the hindbody, and for the excretory vesicle to reach to the level of the ventral sucker. Of about 20 nominal species, we recognise just three in Podocotyloides (sensu stricto): Pod. petalophallus, Pod. gracilis (Yamaguti, 1952) Pritchard, 1966 and Pod. magnatestes Aleshkina & Gaevskaya, 1985. We provide new records for Pod. gracilis, and propose two new species of Podocotyloides, Pod. australis n. sp. and Pod. brevivesiculatus n. sp., and one new Pedunculacetabulum species, Ped. inopinipugnus n. sp., all from haemulids. Podocotyloides australis is morphologically indistinguishable from Pod. gracilis, and exploits the same definitive host, but is genetically and biogeographically distinct. It is thus a cryptic species, the first such opecoelid to be formally named.

The Pseudoplagioporinae, a new subfamily in the Opecoelidae Ozaki, 1925 (Trematoda) for a small clade parasitizing mainly lethrinid fishes, with three new species

“…() and Martin, Cutmore, et al. (), which are expected to eventually be recognized at the subfamily level. The new taxa resolved as sister to clade C. The two analyses were essentially identical in topology, except in the position of the Opecoelinae.…”

“…However, most taxa which have been considered to belong to the Plagioporinae are marine. Already, many have been accommodated into new subfamily concepts, the Bathycreadiinae Martin, Huston, Cutmore, & Cribb, , Helicometrinae Bray, Cribb, Littlewood, & Waeschenbach, Opistholebetinae Fukui, 1929, Podocotylinae Dollfus, 1959, and Polypipapiliotrematinae Martin, Cutmore, & Cribb, , based on a combination of adult morphology, host usage, and phylogenetic distinctions (Bray et al., ; Martin, Crouch, Cutmore, & Cribb, ; Martin, Sasal, Cutmore, Ward, Aeby, & Cribb, ; Martin et al., ). Thus, the Opecoelidae is currently divided into nine subfamilies, although two sizeable clades of marine taxa (see Martin et al., ) remain without suitable subfamilial designation and the placement of multiple genera not yet represented by sequence data remains uncertain.…”

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

“…Genetic sequence data were generated for three ribosomal DNA (rDNA) markers: the second internal transcribed spacer region (ITS2 rDNA) and the small (18S) and large (28S) ribosomal subunit RNA coding regions. These markers were targeted for compatibility with existing opecoelid sequence data available in GenBank, especially those identified as relating to P. stenometra (Lucas et al, 2005;Martin et al, 2018c). Genomic DNA extraction, amplification and sequencing protocols, including primers, are detailed in Martin et al (2017).…”

“…Considering its potential significance as a pathogen of reef-building corals, P. stenometra is surprisingly poorly known. It has been reported from butterflyfishes in Hawaiian (Pritchard, 1966), French Polynesian (Martin et al, 2018c), Seychelloise (Toman, 1992) and Great Barrier Reef (Bray and Cribb, 1989;Lucas et al, 2005) waters. Additionally, cases of suspected Porites trematodiasis have been reported from Hawai'i (Aeby, 2006(Aeby, , 2007, French Polynesia (M. Rigby in Aeby, 2007), the Great Barrier Reef (Willis et al, 2001), Guam and Papua New Guinea (Aeby, 2007), the Ryuku Islands (Yamashiro, 2004), the Galapágos Archipelago (Vera and Banks, 2009) and the New Caledonian lagoon (Aeby et al, 2015).…”

“…In contrast to those species, P. stenometra lacks a uterine sphincter, a petalloid cirrus and a canalicular seminal receptacle, the latter a defining characteristic of not just Podocotyloides but also its nominal subfamily, the Plagioporinae Manter, 1947. Recent analyses of rDNA sequence data demonstrated that P. stenometra is distantly related to species of Podocotyloides (sensu stricto) and indeed is phylogenetically distinctive among all sequenced representatives of the Opecoelidae (Martin et al, 2018c). Those analyses suggested P. stenometra requires a new genus, but were based on sequence data generated from infections in Heniochus chrysostomus Cuvier (Perciformes: Chaetodonidae) collected off Moorea, French Polynesia (Martin et al, 2018c), whereas the type combination for P. stenometra is Chaetodon quadrimaculatus Gray (Chaetodontidae) from Hawaiian waters (Pritchard, 1966).…”