New genus of opecoelid trematode from Pristipomoides aquilonaris (Perciformes: Lutjanidae) and its phylogenetic affinity within the family Opecoelidae

Molecular characterisation of three species of Coitocaecum (Digenea: Opecoelidae) infecting Clinus superciliosus (Clinidae) in South Africa, with description of Coitocaecum brayi sp. n

The genus Coitocaecum Nicoll, 1915 is part of the most speciose digenean family, the Opecoelidae Ozaki, 1925, which is found globally in both freshwater and marine fishes. Fifteen opecoelid species have been reported from marine fishes in South Africa, yet only one species of Coitocaecum has been described from this region: Coitocaecum capense Bray, 1987. During an explorative study of the digeneans of the endemic, intertidal fish Clinus superciliosus (Linnaeus) from the Saldanha Bay area, Cape Town harbour, Hermanus, the Tsitsikamma section of the Garden Route National Park and Chintsa East in South Africa, a total of three distinct species of Coitocaecum were identified based on morphological and molecular (28S rDNA, ITS1-5.8S-ITS2 rDNA and COI mtDNA) data: the previously mentioned C. capense, Coitocaecum brayi sp. n. and a third, unnamed species. We provide the first molecular characterisation of species of Coitocaecum from South Africa, accompanied by detailed morphological descriptions. This study illustrates the importance of an integrated taxonomic approach, especially when studying species with similar morphology. These findings further emphasise the lack of information on the true diversity and molecular data for trematodes of marine fishes in South Africa, creating a great capacity for future explorative taxonomic studies and highlighting the use of intertidal areas for conducting such research.

Allopodocotyle palmi sp. nov. and Prosorhynchus maternus Bray & Justine, 2006 (Digenea: Opecoelidae & Bucephalidae) from the Orange-Spotted Grouper Epinephelus coioides (Hamilton, 1822) off Bali, Indonesia, Described Using Modern Techniques

BACKGROUND

The most convincing species of Allopodocotyle Pritchard, 1966 (Digenea: Opecoelidae) are known overwhelmingly from groupers (Serranidae: Epinephelinae). Six species of Allopodocotyle have been reported, collectively, from species of Cromileptes Swainson, 1839, Epinephelus Bloch, 1793 and Plectropomus Oken, 1817. These are A. epinepheli (Yamaguti, 1942), A. heronensis Downie & Cribb, 2011, A. manteri (Saoud & Ramadan, 1984), A. mecopera (Manter, 1940), A. plectropomi (Manter, 1963) and A. serrani (Yamaguti, 1952). In addition, a not yet fully described and unnamed seventh species, morphologically and phylogenetically close to A. epinepheli, was isolated from the orange-spotted grouper Epinephelus coioides (Hamilton, 1822) off Bali, Indonesia in 2016. An eighth species, again from E. coioides off Bali is described herein.

METHODS

Morphological and phylogenetic analyses justify the recognition of A. palmi sp. nov., which is also genetically different from the as yet unnamed congener from the same host and locality. For the first time, 3D confocal laser scanning microscopy was applied to study and distinguish Digenea taxonomically. We introduce the 'Palm pattern', a new simplified way to visualise morphometric differences of related digenean taxa.

RESULTS

Allopodocotyle palmi sp. nov. is distinguished from its congeners that infect groupers by its elongate body with a size > 2.7 mm and diagonal testes. The ovary is located mainly, and the anterior testis completely, in the posterior half of the body; the uterine coils are in the fourth eighth of the body. The cirrus-sac is 0.75-1.4 (1.1) mm long, its posterior extremity is well separated from the anterior extent of the vitelline fields, just reaching the anterior border of uterine coils. In addition, Prosorhynchus maternus Bray & Justine, 2006 (Bucephalidae) was isolated from E. coioides, representing the first record in Indonesia and the third record for this fish species.

CONCLUSION

The biodiversity research in Indonesia is enhanced with a new species description based on modern and newly applied techniques.

Phylogenetic position of deep-sea opecoelid digenean Tellervotrema beringi (Mamaev, 1965) (Trematoda: Opecoelidae) based on novel genetic data

Adult opecoelid digeneans consistent with Tellervotrema beringi (Mamaev, 1965) were found in the intestine of the deep-water fish Antimora microlepis Bean collected off the northern Kuril Islands (Russia). Earlier, T. beringi was recorded only in macrourid fish. This is the first record of a species of Tellervotrema Gibson & Bray, 1982 from fishes of the family Moridae (Gadiformes). A partial 28S rRNA gene sequence was obtained for this species and was compared with the available sequences on GenBank from other opecoelids. The phylogenetic analysis did not support the current taxonomic hypothesis that the genus Tellervotrema belongs to the subfamily Podocotylinae Dollfus, 1959. Our results demonstrated that species of this genus formed a clade with those of the genera Mesobathylebouria Martin, Huston, Cutmore & Cribb, 2019 and Abyssopedunculus Martin, Huston, Cutmore & Cribb, 2019. The morphological synapomorphies of the Tellervotrema + (Mesobathylebouria + Abyssopedunculus) clade are currently unclear, and this group does not have an adequate subfamilial classification.

A new subfamily for a clade of opecoelids (Trematoda: Digenea) exploiting marine fishes as second-intermediate hosts, with the first report of opecoelid metacercariae from an elasmobranch

Metacercariae of trematodes belonging to the family Opecoelidae were collected from small fishes of the Great Barrier Reef: a blenniid, two gobiids, two labrids, three pomacentrids, a monacanthid, an ostraciid and the epaulette shark, Hemiscyllium ocellatum. Sequences of the second internal transcribed spacer region (ITS2) of ribosomal DNA were generated from these metacercariae in an attempt to match them with adult worms. Three species of Allopodocotyle (Allopodocotyle epinepheli, Allopodocotyle heronensis and an unidentified species), two unidentified species of Hamacreadium and Pacificreadium serrani were detected. Among the Opecoelidae, these species all resolve to a single, phylogenetically and somewhat morphologically distinct clade. Species of this clade are the only known marine opecoelids to exploit fishes as second-intermediate hosts. The clade is proposed to warrant a new subfamily, the Hamacreadiinae subfam. nov. It includes Allopodocotyle, Bentholebouria, Cainocreadium, Choanotrema, Hamacreadium, Pacificreadium, Paraplagioporus, Pedunculacetabulum and Podocotyloides.

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

Podocotyloides stenometra Pritchard, 1966 (Digenea: Opecoelidae) is the only trematode known to infect anthozoan corals. It causes disease in coral polyps of the genus Porites Link (Scleractinia: Poritidae) and its life-cycle depends on ingestion of these polyps by butterflyfishes (Perciformes: Chaetodontidae). This species has been reported throughout the Indo-Pacific, from the Seychelles to the Galápagos, but no study has investigated whether multiple species are involved. Here, we recollect P. stenometra from its type-host and type-locality, in Hawaiian waters, and describe four new species from examination of 768 butterflyfishes from French Polynesia. On the basis of morphology, phylogeny and life-history, we propose Polypipapiliotrema Martin, Cutmore & Cribb n. gen. and the Polypipapiliotrematinae Martin, Cutmore & Cribb n. subf., for P. stenometra (Pritchard) n. comb., P. citerovarium Martin, Cutmore & Cribb n. sp., P. hadrometra Martin, Cutmore & Cribb n. sp., P. heniochi Martin, Cutmore & Cribb n. sp., and P. ovatheculum Martin, Cutmore & Cribb n. sp. Given the diversity uncovered here and the ubiquity, abundance and diversity of butterflyfishes on coral reefs, we predict that Polypipapiliotrema will prove to comprise a rich complex of species causing disease in corals across the Indo-Pacific. The unique life-cycle of these taxa is consistent with phylogenetic distinction of the group and provides evidence for a broader basis of diversification among the family. We argue that life-cycle specialisation, in terms of adoption of disparate second intermediate host groups, has been a key driver of the diversification and richness of the Opecoelidae, the largest of all trematode families and the group most frequently encountered in coral reef fishes.

Records of opecoeline species Pseudopecoelus cf. vulgaris and Anomalotrema koiae Gibson & Bray, 1984 (Trematoda, Opecoelidae, Opecoelinae) from fish of the North Pacific, with notes on the phylogeny of the family Opecoelidae

Opecoelid species Pseudopecoelus cf. vulgaris and Anomalotrema koiae Gibson & Bray, 1984 were found in fish collected in the boreal waters of the North Pacific. Pseudopecoelus cf. vulgaris differs from Pseudopecoelus vulgaris (Manter, 1934) in terms of the egg size. This is the first record of A. koiae in the North Pacific, and the second of Pseudopecoelus cf. vulgaris. Previously, A. koiae was recorded only in North Atlantic fish. Partial sequences of 28S rDNA obtained for these two species and six other previously unsequenced representatives of the family Opecoelidae were analysed together with data from GenBank. Phylogenetic analysis supports the allocation of the six clades of opecoelids - Helicometrinae, Opecoelinae, Opistholebetinae, 'freshwater Plagioporinae', 'marine Plagioporinae B' and 'marine Plagioporinae C', and confirms the paraphyly of the group 'deep-sea Plagioporinae'. Our phylogeny does not support previous hypotheses about the monophyly of opecoelines with a uroproct.

The phylogenetic position of Choerodonicola Cribb, 2005 (Digenea: Opecoelidae) with a partial life-cycle for a new species from the blue-barred parrotfish Scarus ghobban Forsskål (Scaridae) in Moreton Bay, Australia

Choerodonicola Cribb, 2005 is a minor genus of opecoelid trematodes defined for species with exceptionally small eggs but otherwise generalised morphology. Four species are currently recognised, all from fishes collected in Japanese waters but each from different perciform families: a labrid, a scarid, a sparid and pinguipeds. We report on a new species, Choerodonicola arothokoros n. sp., from the blue-barred parrotfish Scarus ghobban Forsskål (Scaridae) collected in subtropical waters of Moreton Bay, south-east Queensland, Australia. Using genetic sequence data for the ITS2 rDNA marker, we matched adult C. arothokoros to intramollsucan stages discovered in an intertidal gastropod Herpetopoma atratum (Gmelin) (Vetigastropoda: Chilodontidae) collected in close proximity to the fish hosts. Notably, the cercariae lack a penetration stylet and are among the smallest known in the Opecoelidae. We provide the first assessment of the phylogenetic position of Choerodonicola based on sequence data generated for the phylogenetically informative 18S and 28S rRNA coding regions, for C. arothokoros and also C. renko Machida, 2014, which we recollected from the yellowback seabream Dentex hypselosomus Bleeker from the fish market in Minabe, Wakayama Prefecture, Japan. In our analyses, species of Choerodonicola resolved to neither of the major marine Plagioporinae (sensu lato) clades, clustering instead with Trilobovarium parvvatis Martin, Cutmore & Cribb, 2017, Podocotyloides parupenei (Manter, 1963) Pritchard, 1966 and Macvicaria magellanica Laskowski, Jeżewski & Zdzitowiecki, 2013. This clade is phylogenetically distinctive such that it has the potential to be recognised as a new opecoelid subfamily, but further investigation is required to establish the bounds for such a grouping and to determine the morphological and/or life-history patterns reflected by the phylogeny. Finally, we propose C. interruptus (Manter 1954) n. comb. for a species previously recognised in Plagioporus Stafford, 1904 and known only from Pseudolabrus miles (Schneider & Forster), a labrid endemic to New Zealand.

Two New Species of Plagioporus (Digenea: Opecoelidae) from the Ouachita Madtom, Noturus lachneri, and the Banded Sculpin, Cottus carolinae, from Arkansas

Plagioporus ictaluri n. sp. and Plagioporus carolini n. sp. are described from the intestines of the Ouachita Madtom, Noturus lachneri, and the Banded Sculpin, Cottus carolinae, respectively, from adjacent drainages in Arkansas. The new species are morphologically most similar to one another and in turn similar to Plagioporus sinitsini, Plagioporus chiliticorum, Plagioporus serratus, and Plagioporus hypentelii, but they can be distinguished from these congeners in possession of an excretory vesicle that extends anteriorly to the level of the anterior testis as opposed to 1 reaching only the posterior testis ( P. hypentelii) or 1 confined to the posttesticular space ( P. sinitsini, P. serratus, and P. chiliticorum), a feature that necessitates altering the generic diagnosis for the genus. Plagioporus ictaluri n. sp. is distinguished from Plagioporus carolini n. sp. in having tandem vs. oblique testes, a submedian to median ovary as opposed to 1 that is dextral, a ventral sucker occupying 53-71% of the body width (BW) vs. 80-92% of the BW, an oral sucker occupying 36-47% of the BW as opposed to 49-58% of the BW, and a pharynx occupying 21-26% of the BW compared to 28-36% of the BW. A Bayesian inference analysis of partial 28S rDNA sequences of the 2 new species and those of 34 opecoelids obtained from GenBank found that P. ictaluri and P. carolini formed a highly supported clade that was sister to P. chiliticorum and in turn to P. sinitsini. These 4 species are notably the only Nearctic plagioporids included in the analysis without a uterus extending to the posterior end that lack a confluent vitelline field in the posttesticular space. This study includes the first species of Plagioporus to be described from an ictalurid host and the first species in the genus to be described from a cottid east of the Rocky Mountains.

Phylogenetic position of the family Orientocreadiidae within the superfamily Plagiorchioidea (Trematoda) based on partial 28S rDNA sequence

Trematodes of the family Orientocreadiidae are mostly parasites of freshwater fishes. Here, the phylogenetic position of this family is inferred based on the partial 28S rDNA sequence from a representative of the genus Orientocreadium s. str.-О. pseudobagri Yamaguti, 1934. Sequences were analysed by maximum likelihood and Bayesian inference algorithms. Both approaches placed the Orientocreadiidae within a clade corresponding to the superfamily Plagiorchioidea and supported the family Leptophallidae as a sister taxon.

Hamacreadium cribbi n. sp. (Digenea: Opecoelidae) from Lethrinus miniatus (Forster) (Perciformes: Lethrinidae) from New Caledonian waters

A new species of Hamacreadium Linton, 1910, H. cribbi n. sp. is described from Lethrinus miniatus (Forster) from the waters off New Caledonia. It is compared with the other species of Hamacreadium reported from lethrinids and is characterised by the size of its eggs which tend to be larger [72-93 (84) vs 54-81 (56) µm long] than those of other species. Other characteristics, such as body size and shape and internal ratios, differentiate H. cribbi from other species; these differences are discussed in detail.

New species of Plagioporus Stafford, 1904 (Digenea: Opecoelidae) from California, with an amendment of the genus and a phylogeny of freshwater plagioporines of the Holarctic

Plagioporus hageli n. sp. is described from the intestine of Oncorhynchus mykiss (Walbaum) collected from the River Yuba, California, USA. Of the accepted, nominal species of Plagioporus Stafford, 1904 from the Nearctic, the new species is morphologically similar to three intestinal species from the western USA parasitising diadromous fishes, including Plagioporus shawi (McIntosh, 1939), Plagioporus kolipinskii Tracey, Choudhury, Cheng & Ghosh, 2009 and Plagioporus siliculus Sinitsin, 1931, and is also similar to Plagioporus serotinus Stafford, 1904 from catostomids from eastern Canada. Plagioporus hageli n. sp. is distinguished from the former three species in lacking a dorsal vitelline field and from the latter species in having a consistent interruption in the distribution of the vitellarium at the level of the ventral sucker. The new species is also morphologically similar to an unnamed species of Plagioporus and a species misidentified as 'Plagioporus angusticolle' that were collected from California, but it is easily distinguished from both in its shorter body length. To estimate the placement of the new species within Plagioporus and within the Opecoelidae Ozaki, 1925, we conducted a Bayesian inference (BI) analysis of partial 28S rDNA sequence data that included sequences from Plagioporus hageli n. sp., five other species of Plagioporus, three species of Neoplagioporus Shimazu, 1990, including the type-species, Neoplagioporus zacconis (Yamaguti, 1934), two species of Urorchis Ozaki, 1927 (including the type-species, Urorchis goro Ozaki, 1927) and sequences of 42 opecoelid species obtained from GenBank. Our phylogenetic analysis revealed (i) plagioporines parasitising freshwater hosts form a monophyletic group; (ii) Plagiocirrus loboides Curran, Overstreet & Tkach, 2007 nested within the rest of the members of Plagioporus; (iii) the new species was closer to Plagiocirrus loboides than to Plagioporus shawi, the other salmonid parasite included in our analysis; (iv) P. shawi was the poorly supported sister to its congeners; (v) Neoplagioporus elongatus (Goto & Ozaki, 1930) Shimazu, 1990 was closer to the two species of Urorchis than to the other two species of Neoplagioporus; and (vi) the paraphyly of the Plagioporinae Manter, 1947 was reinforced. Based on 28S rDNA sequence data and our BI analysis, we propose Plagioporus loboides (Curran, Overstreet & Tkach, 2007) n. comb., and amend Plagioporus accordingly. This analysis represents the first phylogenetic study of the opecoelids that estimates the interrelationships of the Plagioporinae that includes a member of Plagioporus.

The molecular phylogeny of the digenean family Opecoelidae Ozaki, 1925 and the value of morphological characters, with the erection of a new subfamily

Large and small rDNA sequences of 41 species of the family Opecoelidae are utilised to produce phylogenetic inference trees, using brachycladioids and lepocreadioids as outgroups. Sequences were newly generated for 13 species. The resulting Bayesian trees show a monophyletic Opecoelidae. The earliest divergent group is the Stenakrinae, based on two species which are not of the type-genus. The next well-supported clade to diverge is constituted of three species of Helicometra Odhner, 1902. Based on this tree and the characters of the egg and uterus, a new subfamily, the Helicometrinae, is erected and defined to include the genera Helicometra, Helicometrina Linton, 1910 and Neohelicometra Siddiqi et Cable, 1960. The subfamily Opecoelinae is found to be monophyletic, but the Plagioporinae is paraphyletic. The single representative of the Opecoelininae (not of the type genus) is nested within a group of deep-sea 'plagioporines'. The two representatives of the Opistholebetidae are embedded within a group of shallow-water 'plagioporine' species. The Opistholebetidae is reduced to subfamily status pro tem as its morphological and biological characteristics are distinctive. This implies that as opecoelid systematics develops with more molecular evidence, several further subfamilies will be recognised. Many of the morphological characters were found to be homoplasious, but the characters defining the Helicometrinae and Opecoelinae, such as filamented eggs, reduced cirrus-sac and uterine seminal receptacle, are closely correlated with the inferred phylogeny.

Dollfustrema durum n. sp. and Heterobucephalopsis perardua n. sp. (Digenea: Bucephalidae) from the giant moray eel, Gymnothorax javanicus (Bleeker) (Anguilliformes: Muraenidae), and proposal of the Heterobucephalopsinae n. subfam

Two new species of bucephalid trematode (Platyhelminthes: Digenea) are described from the giant moray eel, Gymnothorax javanicus (Anguilliformes: Muraenidae), from off Lizard Island, Australia. We used a combined morphological and molecular-based approach targeting the internal transcribed spacer 2 (ITS2) of the ribosomal DNA (rDNA) and the D1-D3 region of the large subunit (28S) of rDNA to circumscribe the species. Dollfustrema durum n. sp. is distinguished from seven congeners in having 5-6 rows of enlarged body spines circling the anterior portion of the rhynchus. From the remaining 10 species, D. durum n. sp. differs in body length, and in having a caecum that terminates posteriorly to the confluent arc formed by the vitelline follicles, gonads predominantly anterior to the pharynx, testes in tandem, an anterior testis positioned posteriorly to the vitelline follicles, and the pre-vitelline field 23-40% of the body length. Heterobucephalopsis perardua n. sp. differs from Heterobucephalopsis gymnothoracis, the type- and only other reported species, in being two to three times smaller. Heterobucephalopsis, currently considered a genus inquirendum, is confirmed as valid and is rediagnosed. Bayesian inference analysis of 28S rDNA sequences representing 28 species from nine genera and four subfamilies of bucephalid, indicates that i) subfamily classifications previously based on morphological characters are broadly robust, ii) the sequence representing H. perardua n. sp. is resolved as distinct, and basal, to sequences representing the Bucephalinae, the Prosorhynchinae, the Paurorhynchinae, and the Dolichoenterinae, iii) the Dolichoenterinae and the Prosorhynchinae are monophyletic sister clades, basal to the Bucephalinae and the Paurorhynchinae, iv) sequences representing Grammatorcynicola, Prosorhynchus, and Dollfustrema are also monophyletic, v) the Bucephalinae is paraphyletic relative to the Paurorhynchinae, and vi) the bucephaline genera Prosorhynchoides, Rhipidocotyle, and Bucephalus are each polyphyletic. The morphological and molecular differences observed among the four previously recognised subfamilies in this study lead us to propose Heterobucephalopsinae n. subfam. to accommodate the genus Heterobucephalopsis.