New collections of blood flukes (Aporocotylidae) from fishes of the tropical Indo-west Pacific, including a new genus, two new species and molecular evidence that Elaphrobates chaetodontis (Yamaguti, 1970) is widespread in the region

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.

Molecular species delimitation of marine trematodes over wide geographical ranges: Schikhobalotrema spp. (Digenea: Haplosplanchnidae) in needlefishes (Belonidae) from the Pacific Ocean and Gulf of Mexico

Geographical distribution plays a major role in our understanding of marine biodiversity. Some marine fish trematodes have been shown to have highly restricted geographical distributions, while some are known to occur over very wide ranges; however, very few of these wide distributions have been demonstrated genetically. Here, we analyse species of the genus Schikhobalotrema (Haplosplanchnidae) parasitizing beloniforms from the tropical west Pacific, the eastern Pacific and the Gulf of Mexico (GoM). We test the boundaries of these trematodes by integrating molecular and morphological data, host association, habitat of the hosts and geographical distribution, following a recently proposed and standardized delineation method for the recognition of marine trematode species. Based on the new collections, Schikhobalotrema huffmani is here synonymized with the type-species of the genus, Schikhobalotrema acutum; Sch. acutum is now considered to be widely distributed, from the GoM to the western Pacific. Additionally, we describe a new species, Schikhobalotrema minutum n. sp., from Strongylura notata and Strongylura marina (Belonidae) from La Carbonera coastal lagoon, northern Yucatán, GoM. We briefly discuss the role of host association and historical biogeography of the hosts as drivers of species diversification of Schikhobalotrema infecting beloniforms.

Morphological constraint obscures richness: a mitochondrial exploration of cryptic richness in Transversotrema (Trematoda: Transversotrematidae)

Species of Transversotrema Witenberg, 1944 (Transversotrematidae) occupy a unique ecological niche for the Trematoda, living externally under the scales of their teleost hosts. Previous studies of the genus have been impeded partly by limited variation in ribosomal DNA sequence data between closely related species and partly by a lack of morphometrically informative characters. Here, we assess richness of the tropical Indo-west Pacific species through parallel phylogenetic and morphometric analyses, generating cytochrome c oxidase subunit 1 mitochondrial sequence data and morphometric data for hologenophore specimens from Australia, French Polynesia, Japan and Palau. These analyses demonstrate that molecular data provide the only reliable basis for species identification; host distribution, and to a lesser extent morphology, are useful for identifying just a few species of Transversotrema. We infer that a combination of morphological simplicity and infection site constraint has led to the group displaying exceptionally low morphological diversification. Phylogenetic analyses of the mitochondrial data broadly support previous systematic interpretations based on ribosomal data, but also demonstrate the presence of several morphologically and ecologically cryptic species. Ten new species are described, eight from the Great Barrier Reef, Australia (Transversotrema chrysallis n. sp., Transversotrema daphnidis n. sp., Transversotrema enceladi n. sp., Transversotrema hyperionis n. sp., Transversotrema iapeti n. sp., Transversotrema rheae n. sp., Transversotrema tethyos n. sp., and Transversotrema titanis n. sp.) and two from off Japan (Transversotrema methones n. sp. and Transversotrema panos n. sp.). There are now 26 Transversotrema species known from Australian marine fishes, making it the richest trematode genus for the fauna.

SYSTEMATIC REVISION OF THE FISH BLOOD FLUKES WITH DIAGNOSES OF CHIMAEROHEMECIDAE YAMAGUTI, 1971, ACIPENSERICOLIDAE N. FAM., SANGUINICOLIDAE POCHE, 1926, ELOPICOLIDAE N. FAM., AND APOROCOTYLIDAE ODHNER, 1912

We herein morphologically diagnose the 5 natural groups of fish blood flukes and name them. Species of Chimaerohemecidae Yamaguti, 1971 infect chimeras, sharks, and rays (Chondrichthyes) and have C-shaped lateral tegumental spines and a non-sinusoidal testis or lack spines and have a sinusoidal testis. Species of Acipensericolidae n. fam. infect sturgeons and paddlefish (Acipenseriformes) and have a robust, bowl-shaped, pedunculate anterior sucker, lateral tegumental spines that are spike-like (not C shaped), an inverse U-shaped intestine (anterior ceca absent) with posterior ceca terminating near the excretory bladder, 6 testes (inter-cecal ovoid or oblong, lacking deep lobes; including 1 post-ovarian testis), a Laurer's canal, and a dextral common genital pore. Species of Sanguinicolidae Poche, 1926 infect primarily later-branching freshwater ray-finned fishes (Teleostei) and have a diminutive anterior sucker, a medial esophageal swelling (pouch), short, radial ceca of approximately equal length or short anterior ceca plus an elongate, dendritic posterior cecum, testis with appendix-like lateral lobes, no Laurer's canal, and separate or common genital pores. Species of Elopicolidae n. fam. infect ladyfishes, tarpons, and catadromous eels (Elopomorpha) and have a robust, bowl-shaped, pedunculate anterior sucker, lateral tegumental spines that are spike-like (can be lost in adult), short or indistinct anterior ceca, posterior ceca that terminate at level of the testis(es), a single testis or 2 testes, a Laurer's canal present or absent, and a sinistral common genital pore and atrium. Species of Aporocotylidae Odhner, 1912 primarily infect later-branching marine and estuarine ray-finned fishes (Teleostei) and have a spheroid anterior sucker with concentric rows of circumferential spines or the spheroid anterior sucker is lost in adults or adults have a diminutive anterior sucker, a sinuous esophagus lacking a pouch, an X- or H-shaped intestine having 4 ceca, long anterior ceca (or secondarily lost), smooth posterior ceca that extend posteriad in parallel with respective body margin and terminate near the posterior body end, testis(es) that lack appendix-like lateral lobes, no Laurer's canal, and a sinistral common genital pore or separate genital pores that are sinistral. Our 28S phylogeny recovered the fish blood flukes as monophyletic and each of the morphologically diagnosed families as monophyletic and sister to the remaining blood flukes infecting turtles and homeotherms. Acipensericolidae was recovered sister to the clade comprising Chimaerohemecidae + Sanguinicolidae and Elopicolidae + Aporocotylidae. The branching order and interrelationships of these families remains unsettled perhaps because of low taxon sampling among non-aporocotylids and extinction of intermediate taxa.

Rich but morphologically problematic: an integrative approach to taxonomic resolution of the genus Neospirorchis (Trematoda: Schistosomatoidea)

Neospirorchis Price, 1934 is a genus of blood flukes that infect the cardiovascular system, including vessels surrounding the nervous systems of marine turtles. Although the genus comprises just two named species, the available molecular data suggest substantial richness which has not yet been formally described. The lack of description of species of Neospirorchis is probably explained by their small, slender, elongate bodies, which allow them to infect numerous organs and vessels in their hosts, such as the heart and peripheral vessels of nervous system, endocrine organs, thymus, mesenteric vessels, and gastrointestinal submucosa. This morphology and site of infection means that collecting good quality, intact specimens is generally difficult, ultimately hampering the formal description of species. Here we supplement limited morphological samples with multi-locus genetic data to formally describe four new species of Neospirorchis infecting marine turtles from Queensland, Australia and Florida, USA; Neospirorchis goodmanorum n. sp. and Neospirorchis deburonae n. sp. are described from Chelonia mydas, Neospirorchis stacyi n. sp. is described from Caretta caretta, and Neospirorchis chapmanae n. sp. from Ch. mydas and Ca. caretta. The four new species are delineated from each other and the two known species based on the arrangement of the male and female reproductive organs, on the basis of cytochrome c oxidase subunit 1 (cox1), internal transcribed spacer 2 (ITS2), and 28S ribosomal DNA (rDNA) molecular data, site of infection, and host species. Molecular evidence for three further putative, presently undescribable, species is also reported. We propose that this integrated characterisation of species of Neospirorchis, based on careful consideration of host, molecular and key morphological data, offers a valuable solution to the slow rate of descriptions for this important genus. We provide the first known life cycle data for Neospirorchis in Australian waters, from Moreton Bay, Queensland; consistent with reports from the Atlantic, sporocysts were collected from a terebellid polychaete and genetically matched to an unnamed species of Neospirorchis infecting Ch. mydas from Queensland and Florida.

Proposal of a new genus, Doorochen (Digenea: Lepocreadioidea), for reef-inhabiting members of the genus Postlepidapedon Zdzitowiecki, 1993

A new genus, Doorochen n. gen., is erected for four species of Postlepidapedon Zdzitowiecki, 1993, all of which inhabit members of the labroid genus Choerodon Bleeker, the tuskfishes, and which molecular phylogenies have indicated are not congeneric with the type-species, P. opisthobifurcatum (Zdzitowiecki, 1990) Zdzitowiecki, 1993. Doorochen secundum (Durio & Manter, 1968) n. comb. from Choerodon graphicus (De Vis), the Graphic tuskfish, from the Great Barrier Reef (GBR) and New Caledonia is designated the type-species of the new genus. Other species recognised are Doorochen spissum (Bray, Cribb & Barker, 1997) n. comb. from C. venustus (De Vis), the Venus tuskfish, C. cyanodus (Richardson), the Blue tuskfish, and C. graphicus from the GBR; D. uberis (Bray, Cribb & Barker, 1997) n. comb. from C. schoenleinii (Valenciennes), the Blackspot tuskfish, and C. venustus from the GBR and Moreton Bay; and D. philippinense (Machida, 2004) n. comb. from C. anchorago (Bloch), the Orange-dotted tuskfish, from Philippine waters. In addition to these four species, two new species are described: D. zdzitowieckii n. sp. from C. fasciatus (Günther), the Harlequin tuskfish, and C. graphicus from the GBR; and D. goorchana n. sp. from C. anchorago from the GBR and Palau. The genus Postlepidapedon is now considered to comprise just two species, P. opisthobifurcatum and P. quintum Bray & Cribb, 2001. The relationships of Doorochen, Postlepidapedon, Myzoxenus Manter, 1934 and Intusatrium Durio & Manter, 1968 in the family Lepidapedidae Yamaguti, 1958 are discussed.

Evidence that a lineage of teleost-infecting blood flukes (Aporocotylidae) infects bivalves as intermediate hosts

The family Aporocotylidae is recognized as having the widest intermediate host usage in the Digenea. Currently, intermediate host groups are clearly correlated with definitive host groups; all known life cycles of marine teleost-infecting aporocotylids involve polychaetes, those of freshwater teleost-infecting aporocotylids involve gastropods, and those of chondrichthyan-infecting aporocotylids involve bivalves. Here we report the life cycle for a marine elopomorph-infecting species, Elopicola bristowi Orélis-Ribeiro & Bullard in Orélis-Ribeiro, Halanych, Dang, Bakenhaster, Arias & Bullard, 2017, as infecting a bivalve, Anadara trapezia (Deshayes) (Arcidae), as the intermediate host in Moreton Bay, Queensland, Australia. The cercaria of E. bristowi has a prominent finfold, distinct anterior and posterior widenings of the oesophagus, a tail with symmetrical furcae with finfolds, and develops in elongate to oval sporocysts. We also report molecular data for an unmatched aporocotylid cercaria from another bivalve, Megapitaria squalida (G. B. Sowerby I) (Veneridae), from the Gulf of California, Mexico, and six unmatched cercariae from a gastropod, Posticobia brazieri (E. A. Smith) (Tateidae), from freshwater systems of south-east Queensland, Australia. Phylogenetic analyses demonstrate the presence of six strongly-supported lineages within the Aporocotylidae, including one of elopomorph-infecting genera, Elopicola Bullard, 2014 and Paracardicoloides Martin, 1974, now shown to use both gastropods and bivalves as intermediate hosts. Of a likely 14 aporocotylid species reported from bivalves, six are now genetically characterised. The cercarial morphology of these six species demonstrates a clear distinction between those that infect chondrichthyans and those that infect elopomorphs; chondrichthyan-infecting aporocotylids have cercariae with asymmetrical furcae that lack finfolds and develop in spherical sporocysts whereas those of elopomorph-infecting aporocotylids have symmetrical furcae with finfolds and develop in elongate sporocysts. This morphological correlation allows predictions of the host-based lineage to which the unsequenced species belong. The Aporocotylidae is proving exceptional in is propensity for major switches in intermediate host use, with the most parsimonious interpretation of intermediate host distribution implying a minimum of three host switches within the family.