Lepocreadiidae (Trematoda) associated with gelatinous zooplankton (Cnidaria and Ctenophora) and fishes in Australian and Japanese waters.

We examined gelatinous zooplankton from off eastern Australia for lepocreadiid trematode metacercariae. From 221 specimens of 17 species of cnidarian medusae and 218 specimens of four species of ctenophores, infections were found in seven cnidarian and two ctenophore species. Metacercariae were distinguished using cox1 mtDNA, ITS2 rDNA and morphology. We identified three species of Prodistomum Linton, 1910 [P. keyam Bray & Cribb, 1996, P. orientale (Layman, 1930), and Prodistomum Type 3], two species of Opechona Looss, 1907 [O. kahawai Bray & Cribb, 2003 and O. cf. olssoni], and Cephalolepidapedon saba Yamaguti, 1970. Two species were found in cnidarians and ctenophores, three only in cnidarians, and one only in a ctenophore. Three Australian fishes were identified as definitive hosts; four species were collected from Scomber australasicus and one each from Arripis trutta and Monodactylus argenteus. Transmission of trematodes to these fishes by ingestion of gelatinous zooplankton is plausible given their mid-water feeding habits, although such predation is rarely reported. Combined morphological and molecular analyses of adult trematodes identified two cox1 types for C. saba, three cox1 types and species of Opechona, and six cox1 types and five species of Prodistomum of which only two are identified to species. All three genera are widely distributed geographically and have unresolved taxonomic issues. Levels of distinction between the recognised species varied dramatically for morphology, the three molecular markers, and host distribution. Phylogenetic analysis of 28S rDNA data extends previous findings that species of Opechona and Prodistomum do not form monophyletic clades.

A new species, new host records and life cycle data for lepocreadiids (Digenea) of pomacentrid fishes from the Great Barrier Reef, Australia.

A new species of lepocreadiid, Opechonoides opisthoporus n. sp., is described infecting 12 pomacentrid fish species from the Great Barrier Reef, Australia, with Abudefduf whitleyi Allen & Robertson as the type-host. This taxon differs from the only other known member of the genus, Opechonoides gure Yamaguti, 1940, in the sucker width ratio, cirrus-sac length, position of the testes, position of the pore of Laurer's canal, and relative post-testicular distance. The new species exhibits stenoxenic host-specificity, infecting pomacentrids from seven genera: Abudefduf Forsskål, Amphiprion Bloch & Schneider, Neoglyphidodon Allen, Neopomacentrus Allen, Plectroglyphidodon Fowler & Ball, Pomacentrus Lacépède and Stegastes Jenyns. Phylogenetic analyses of 28S rDNA sequence data demonstrate that O. opisthoporus n. sp. forms a strongly supported clade with Prodistomum orientale (Layman, 1930) Bray & Gibson, 1990. The life cycle of this new species is partly elucidated on the basis of ITS2 rDNA sequence data; intermediate hosts are shown to be three species of Ctenophora. New host records and molecular data are reported for Lepocreadium oyabitcha Machida, 1984 and Lepotrema amblyglyphidodonis Bray, Cutmore & Cribb, 2018, and new molecular data are provided for Lepotrema acanthochromidis Bray, Cutmore & Cribb, 2018 and Lepotrema adlardi (Bray, Cribb & Barker, 1993) Bray & Cribb, 1996. Novel cox1 mtDNA sequence data showed intraspecific geographical structuring between Heron Island and Lizard Island for L. acanthochromidis but not for L. adlardi or O. opisthoporus n. sp.

Four new monorchiids from marine teleost fishes of Moreton Bay and the Great Barrier Reef, Australia, including the proposal of a new genus.

We report four new species of monorchiids infecting teleost fishes from Australian waters. Two new species of Paralasiotocus Wee, Cutmore, Pérez-del-Olmo & Cribb, 2020, Pa. abstrusus n. sp. and Pa. tectus n. sp., are described from haemulids of the Great Barrier Reef. The two species are morphologically cryptic and occur in sympatry but differ significantly in cox1 mtDNA and ITS2 rDNA sequence data. Paralasiotocus tectus n. sp. is found only in Plectorhinchus albovittatus (Rüppell) whereas Pa. abstrusus n. sp. infects Pl. albovittatus, Plectorhinchus flavomaculatus (Cuvier) and Plectorhinchus lineatus (Linnaeus). The two species differ from all known species of Paralasiotocus in the possession of a clear gap in the spines of the terminal organ. A new species is described from a mullid, Parupeneus spilurus (Bleeker), from off Heron Island and Moreton Bay. The new species is morphologically broadly consistent with the concept of Paralasiotocus in the possession of an unspined genital atrium, bipartite terminal organ, and lobed ovary. However, it possesses a highly lobed cirrus and is phylogenetically widely separated from the two species of Paralasiotocus characterized here, and thus we propose Lobucirruatus infloresco n. g., n. sp. Proctotrema prominens n. sp., is described from Pl. albovittatus. It is differentiated from all other species of Proctotrema in the combination of a prominent metraterm, slightly fusiform body, slightly funnel-shaped oral sucker, elongate cirrus-sac, unlobed ovary, and caeca that terminate in the post-testicular region.

Three new species of Helicometroides Yamaguti, 1934 from Japan and Australia, with new molecular evidence of a widespread species.

We report specimens of monorchiids infecting Haemulidae from the waters off Japan and Australia; these specimens represent five species of Helicometroides Yamaguti, 1934, three of which are unambiguously new. Helicometroides murakamii n. sp. infects Diagramma pictum pictum from off Minabe, Japan; Helicometroides gabrieli n. sp. infects Plectorhinchus chrysotaenia from off Lizard Island, Australia; and Helicometroides wardae n. sp. infects Plectorhinchus flavomaculatus and Plectorhinchus multivittatus from off Heron Island, Australia. Helicometroides murakamii n. sp. and H. gabrieli n. sp. conform to the most recent diagnosis of Helicometroides in lacking a terminal organ, but H. wardae n. sp. possesses a terminal organ with distinct, robust spines; despite this morphological distinction, the three form a strongly-supported clade in phylogenetic analyses. We also report specimens morphologically consistent with Helicometroides longicollis Yamaguti, 1934, from D. pictum pictum from off Minabe, Japan, and Diagramma pictum labiosum on the Great Barrier Reef, Australia. Genetic analyses of ITS2 rDNA, 28S rDNA and cox1 mtDNA sequence data for the Japanese specimens reveal the presence of two distinct genotypes. Specimens of the two genotypes were discovered in mixed infections and are morphologically indistinguishable; neither genotype can be associated definitively with H. longicollis as originally described. We thus identify them as H. longicollis lineage 1 and 2, pending study of further fresh material. Genetic analyses of specimens from the Great Barrier Reef are consistent with the presence of only H. longicollis lineage 1. This species thus has a range that incorporates at least Australia and Japan, localities separated by over 7000 km.

Genetic characterisation of Echinocephalus spp. (Nematoda: Gnathostomatidae) from marine hosts in Australia.

We genetically characterised larval and adult specimens of species of Echinocephalus Molin, 1858 (Gnathostomatidae) collected from various hosts found within Australian waters. Adult specimens of Echinocephalus were collected from a dasyatid stingray [Pastinachus ater (Macleay); n = 2] from Moreton Bay, Queensland and larvae from a hydrophiine sea snake [Hydrophis peronii (Duméril); n = 3] from Cape York Peninsula, Queensland, from an octopus (Octopus djinda Amor & Hart; n = 3) from Fremantle, Western Australia and from a lucinid bivalve [Codakia paytenorum (Iredale); n = 5] from Heron Island, Queensland Australia. All nematode samples were identified morphologically and genetically characterised using the small subunit nuclear ribosomal DNA (SSU). Some morphological differences were identified between previous studies of Echinocephalus spp. and those observed herein but the significance of these differences remains unresolved. Molecular phylogenetic analyses revealed that larval Echinocephalus sp. from H. peronii and C. paytenorum in Australia were very similar (with strong nodal support) to larval Echinocephalus sp. infecting two fish species from Egypt, Saurida undosquamis (Richardson) (Synodontidae) and Pagrus pagrus (Linnaeus) (Sparidae). The SSU sequences of larval Echinocephalus sp. from O. djinda and adults from P. ater formed a well-supported clade with that of adult E. overstreeti Deardorff and Ko, 1983 from the Port Jackson shark, Heterodontus portusjacksoni (Meyer), as well as that of the larval Echinocephalus sp., from the common carp (Cyprinus carpio Linnaeus) from Egypt. This study extends the intermediate host range of Echinocephalus larvae by including a sea snake for the first time. Findings of this study highlight the importance of genetic characterisation of larval and adult specimens of Echinocephalus spp. to resolve the current difficulties in the taxonomy of this genus.

Gastropod first intermediate hosts for two species of Monorchiidae Odhner, 1911 (Trematoda): I can't believe it's not bivalves!

The trematode superfamily Monorchioidea comprises three families of teleost parasites: the Monorchiidae Odhner, 1911, Lissorchiidae Magath, 1917, and Deropristidae Cable & Hunninen, 1942. All presently known lissorchiid and deropristid life cycles have gastropods as first intermediate hosts, whereas those of monorchiids involve bivalves. Here, we report an unexpected intermediate host for monorchiids; two species of Hurleytrematoides Yamaguti, 1954 use gastropods as first intermediate hosts. Sporocysts and cercariae were found infecting two species of the family Vermetidae, highly specialised sessile gastropods that form calcareous tubes, from two locations off the coast of Queensland, Australia. These intramolluscan infections broadly corresponded morphologically to those of known monorchiids in that the cercariae have a spinous tegument, oral and ventral suckers, a simple tail and distinct eye-spots. Given the simplified morphology of intramolluscan infections, genetic data provided a definitive identification. ITS2 rDNA and cox1 mtDNA sequence data from the gastropod infections were identical to two species of Hurleytrematoides, parasites of butterflyfishes (Chaetodontidae); Hurleytrematoides loi McNamara & Cribb, 2011 from Moreton Bay (south-eastern Queensland) and Heron Island (southern Great Barrier Reef) and Hurleytrematoides morandi McNamara & Cribb, 2011 from Heron Island. Notably, species of Hurleytrematoides are positioned relatively basal in the phylogeny of the Monorchiidae and are a sister lineage to that of species known to infect bivalves. Thus, the most parsimonious evolutionary hypothesis to explain infection of gastropods by these monorchiids is that basal monorchiids (in our analyses, species of Cableia Sogandares-Bernal, 1959, Helicometroides Yamaguti, 1934 and Hurleytrematoides) will all prove to infect gastropods, suggesting a single host switching event into bivalves for more derived monorchiids (17 other genera in our phylogenetic analyses). A less parsimonious hypothesis is that the infection of vermetids will prove to be restricted to species of Hurleytrematoides, as an isolated secondary recolonisation of gastropods from a bivalve-infecting lineage. Regardless of how their use arose, vermetids represent a dramatic host jump relative to the rest of the Monorchiidae, one potentially enabled by their specialised feeding biology.

Retroporomonorchis pansho n. g., n. sp., an unusual monorchiid trematode exploiting an atypical host.

The Monorchiidae Odhner, 1911 are well represented in tropical and subtropical marine fishes worldwide but rarely reported from the Lutjanidae, an important family of tropical fishes that prey mainly on demersal fishes, decapods and cephalopods. Here, we report the first monorchiid from a lutjanid in Australian waters, Retroporomonorchis pansho n. g., n. sp. in Lutjanus fulvus (Forster), off Lizard Island on the northern Great Barrier Reef. It is morphologically and phylogenetically distinct among known monorchiids, resolves within the Monorchiinae Odhner, 1911, and is characterised by a relatively large ventral sucker, a sinistral genital pore immediately posterior to the ventral sucker, unfilamented eggs, a single testis, and vitelline follicles restricted to the level of the gonads. We assessed all previous records of monorchiids from lutjanid fishes and found only one to be convincing, that of Infundiburictus overstreeti (Gupta & Gupta, 1990) Wee, Cutmore, Pérez-del-Olmo & Cribb, 2020 from Lutjanus monostigma (Cuvier) in the Bay of Bengal. Another, Monorcheides xishaensis Shen, 1985, from Lutjanus argentimaculatus (Forsskål) in the Paracel Islands, South China Sea, is here recognised as a cryptogonimid, and is synonymised with Siphoderina asiatica Gu & Shen, 1979. In the remaining reports, the identity of the host is either ambiguous or doubtful, or the identity of the worm is not supported with sufficient evidence.

Pseudohurleytrema yolandae n. sp., the first monorchiid trematode reported from the Triacanthidae (Tetraodontiformes).

Prior to the present study, species of the trematode family Monorchiidae Odhner, 1911 had been reported from four of the ten families of tetraodontiform fishes: the Balistidae, Monacanthidae, Ostraciidae and Tetraodontidae. Here we report the first monorchiid from the family Triacanthidae, Pseudohurleytrema yolandae n. sp. infecting Tripodichthys angustifrons (Hollard), from Moreton Bay, Queensland, Australia. The species conforms well to the morphological concept of the subfamily Hurleytrematinae Yamaguti, 1958, and the genus Pseudohurleytrema Yamaguti, 1954, in the possession of filamented eggs, a bipartite terminal organ, and a unipartite seminal vesicle. Relative to the other three recognised species of Pseudohurleytrema, the present species is distinctive in the size of the testis and eggs, position of the ovary, and the form of the vitellarium and excretory vesicle. We consider Pseudohurleytrema magnum Kaikabad & Bilqees in Bilqees, 1991 as a species inquirenda. Sequence data for the 28S ribosomal RNA gene and cox1 mitochondrial gene were generated for P. yolandae, providing the first molecular data for the genus. Phylogenetic analysis showed that P. yolandae does not form a clade with the other three hurleytrematine genera for which there are molecular data (Helicometroides Yamaguti, 1934, Hurleytrematoides Yamaguti, 1953 and Provitellus Dove & Cribb, 1998), forming a poorly-supported clade with Proctotrema addisoni Searle, Cutmore & Cribb, 2014 within the clade of the subfamily Monorchiinae Odhner, 1911. The four hurleytrematine genera resolved as four distinct clades, indicating that the current subfamilial classification requires comprehensive revision.

First steps to restructuring the problematic genus Lasiotocus Looss, 1907 (Digenea: Monorchiidae) with the proposal of four new genera.

Lasiotocus Looss, 1907 is the largest genus within the Monorchiidae Odhner, 1911, with 52 species currently considered valid. Species belonging to this genus exhibit wide morphological variation and it is likely that many of them belong in other genera; however, testing the validity of the group has been hampered by a lack of molecular sequence data, especially for the type-species. Here, we report the first DNA sequences for Lasiotocus mulli (Stossich, 1883) Odhner, 1911, the type-species of the genus, and only the sixth Lasiotocus species to be sequenced. Sequences were generated for three ribosomal DNA markers, the ITS2, 18S and 28S regions, and for one mitochondrial DNA marker, the cox1 region. Phylogenetic analyses show that the six sequenced species form four clearly distinct clades, each of which we argue require separate genera. On the basis of these relationships and review of the morphology of all species in the genus, we propose a system of six genera. Four genera, Lasiotocus, the resurrected concept of Ancylocoelium Nicoll, 1912, Infundiburictus n. gen., and Sinistroporomonorchis n. gen., represent the four molecular clades. Two genera, Paralasiotocus n. gen. and Alloinfundiburictus n. gen., are proposed on the basis of morphology only. Ancylocoelium is resurrected for Ancylocoelium typicum Nicoll, 1912, Infundiburictus is erected for Lasiotocus arrhichostoma Searle, Cutmore & Cribb, 2014, Sinistroporomonorchis is erected for Lasiotocus glebulentus Overstreet, 1971and Lasiotocus lizae Liu, 2002, Paralasiotocus is erected for Lasiotocus okinawaensis Machida, 2011, and Alloinfundiburictus is erected for Lasiotocus cacuminatus Nicoll, 1915. Of the 52 species presently recognised in Lasiotocus, 43 are distributed among these genera; nine are considered species inquirendae or are transferred to other genera. We think it likely that more genera will be required for the species reviewed here but more sequence data are essential to further refine the classification.

Four new monorchiids from the golden trevally, Gnathanodon speciosus (Forsskål) (Perciformes: Carangidae), in Moreton Bay, Australia.

Four new monorchiid trematodes are reported from Moreton Bay, Australia; three new species of Provitellus Dove & Cribb, 1998 and one species of Ovipusillus Dove & Cribb, 1998, are described from Gnathanodon speciosus (Forsskål) (Carangidae), the golden trevally. Provitellus chaometra n. sp., Provitellus infrequens n. sp. and Provitellus infibrova n. sp. differ significantly from the only other species of this genus, Provitellus turrum Dove & Cribb, 1998, in the structure of the eggs, vitelline follicles and terminal organ. The four species are united, however, in the possession of short caeca and a long genital atrium, a combination not reported previously. Ovipusillus geminus n. sp. strongly resembles its only congener, Ovipusillus mayu Dove & Cribb, 1998, but differs in the morphology of the diverticulum in the cirrus-sac and the shape of the pharynx. Complete ITS2 and partial 28S rDNA sequence data were generated for all four species, as well as for two known species of Hurleytrematoides Yamaguti, 1953, Hurleytrematoides galzini McNamara & Cribb, 2011 and Hurleytrematoides loi McNamara & Cribb, 2011. These sequences were analysed with those for other monorchiids available on GenBank, and phylogenetic analyses showed that the four species of Provitellus and two species of Ovipusillus each form strongly supported clades. As with previous monorchiid phylogenetic studies, however, the overall resolution of the phylogeny of the Monorchiidae is poor.

Two monorchiid species from the freckled goatfish, Upeneus tragula Richardson (Perciformes: Mullidae), in Moreton Bay, Australia, including a proposal of a new genus.

Two monorchiid species are reported from the freckled goatfish, Upeneus tragula Richardson, from Moreton Bay, Queensland, Australia. Specimens of a species new to science were most morphologically similar to species of the genus Timonia Bartoli & Prevot, 1966, but significant differences in the arrangement of the testes (symmetrical vs oblique) and morphology of the terminal organ (bipartite vs unipartite) necessitate the proposal of a new genus; Madhavia n. g. is proposed for M. fellaminutus n. sp. Specimens of the second species are identified as Parachrisomon delicatus (Manter & Pritchard, 1964) Madhavi, 2008, extending its known range from Hawaii to Australia. Complete ITS2 and partial 28S rDNA sequence data were generated for both species and analysed with those for other monorchiids available on GenBank. Phylogenetic analyses of the 28S rDNA dataset showed that both genera are distinct from other sequenced monorchiids, but overall the resolution between genera is poor and more sequence data are required to elucidate relationships within the family. We propose to transfer Timonia stunkardi (Ahmad, 1985) and Timonia vinodae (Ahmad, 1987) to the genus Neotimonia Madhavi, 2008, as Neotimonia stunkardi (Ahmad, 1985) n. comb. and Neotimonia vinodae (Ahmad, 1987) n. comb. Additionally, we were unable to locate any literature on Parachrisomon brotulidorum (Toman, 1973) Madhavi, 2008 and consider this species as nomen nudum.

Two new and one known species of Tergestia Stossich, 1899 (Trematoda: Fellodistomidae) with novel molecular characterisation for the genus.

Combined morphological and molecular analyses are employed to characterise three species of Tergestia Stossich, 1899 (Digenea: Fellodistomidae) from fishes of Moreton Bay, Queensland, Australia. Tergestia clonacantha Manter, 1963 is reported here for the first time from the halfbeak (Beloniformes: Hemiramphidae) species Arrhamphus sclerolepis krefftii (Steindachner), Hyporhamphus australis (Steindachner), H. quoyi (Valenciennes) and H. regularis ardelio (Whitley). Two new species, both infecting trevally (Perciformes: Carangidae) species, are described: T. maryae n. sp. from Alepes apercna Grant and T. henryi n. sp. from Pantolabus radiatus (MacLeay). Complete ITS2 and partial 28S ribosomal DNA data were generated for each of the new taxa. The three species differ from each other by 47-58 base pairs (bp) in the ITS2 rDNA region. Phylogenetic analysis of 28S rDNA supports Tergestia as a reliable generic concept, with our analyses showing that some species of the genus form a well-supported clade to the exclusion of all other fellodistomids for which sequence data are available.

Two known and one new species of Proctoeces from Australian teleosts: Variable host-specificity for closely related species identified through multi-locus molecular data.

Species of Proctoeces Odhner, 1911 (Trematoda: Fellodistomidae) have been reported from a wide range of marine animals globally. Members of the genus tend to lack strongly distinguishing morphological features for diagnosis, making identification difficult and the true number of species in the genus contentious. Combined morphological and molecular analyses were used to characterise three species of Proctoeces from Moreton Bay and the southern Great Barrier Reef. Data for two ribosomal regions and one mitochondrial region were generated for specimens collected from Australia. Three unique 18S-genotypes were identified which corresponded to subtle, but reliable, morphological differences. Two species of Proctoeces were identified from fishes of Moreton Bay, Proctoeces insolitus (Nicoll, 1915) Yamaguti, 1953 and P. major Yamaguti, 1934, and a third, P. choerodoni n. sp. from off Heron Island on the southern Great Barrier Reef. Phylogenetic analyses of partial 18S and partial 28S rDNA indicated that these three species differ from the four species reported outside of Australia for which sequence data are available. Phylogenetically, Proctoeces proved to be a reliable concept, with all species of Proctoeces that have been characterised genetically forming a well-supported clade in all analyses. Dramatically different patterns of host-specificity were identified for each of the three Australian species; P. insolitus apparently infects a single species of fish, P. choerodoni n. sp. infects multiple species of a single genus of fish, and P. major infects multiple species of two teleost orders.

A complex of Cardicola Short, 1953 (Digenea: Aporocotylidae) species infecting the milkfish Chanos chanos Forsskål (Gonorynchiformes), with descriptions of two new species.

Two new species of Cardicola Short, 1953 are described from the milkfish, Chanos chanos Forsskål (Gonorynchiformes: Chanidae), obtained from off Lizard Island on the northern Great Barrier Reef (GBR) and North Stradbroke Island in southeast Queensland. These are the first known blood flukes from this order of fishes. Cardicola suni n. sp. differs from all other Cardicola spp. by a combination of a large ovoid oral sucker surrounding a subterminal mouth, recurved tegumental spines up to 16 µm long, anterior caeca occupying 25.1-31.3% (28.7%) of total body length and a mostly-intercaecal ovary. Cardicola jiigurru n. sp. differs from C. suni n. sp. and all other species of Cardicola by a combination of a narrowly lanceolate body, weakly-muscularised and poorly-demarcated oral sucker, minute tegumental spines <1 µm in length, and anterior caeca occupying 15.9-22.0% (19.4%) of total body length, an almost entirely post-caecal ovary and the male genital pore terminal on a dorsolateral protuberance. A third species, closely resembling C. suni n. sp., was also discovered off Wangetti Beach, north Queensland, but is not described due to lack of material. Molecular phylogenetic analysis, based on both ITS2 and partial 28S rDNA regions, shows that these three species form a clade nested within that formed by existing species of Cardicola.