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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. [ABSTRACT FROM AUTHOR]

Keywords: Cercariae; Derogenes; fish parasites; Hemiuroidea; life cycles; Progonus; species recognition; Trematoda EN Cercariae Derogenes fish parasites Hemiuroidea life cycles Progonus species recognition Trematoda 1590 1606 17 11/08/22 20221001 NES 221001 Introduction The Digenea is the most species-rich group of the parasitic worms, however, their diversity is far from being well studied. The maritae identified as I Derogenes varicus i were found in 10 fish species from the White Sea and 3 fish species from the Barents Sea (Table 1). 24 Køie M. (1990. b) A new cystophorous cercaria in Lunatia pallida (Broderip & Sowerby) (Naticidae): possibly the cercaria of Hemiurus levinseni Odhner, 1905 (Digenea, Hemiuridae). Experimental data on DV2 cercariae are ambiguous: Køie (1990b) succeeded in infecting 3 copepod species by cystophorous cercariae from I E. pallida i , but those copepods did not survive for more than several weeks. [Extracted from the article]

The taxonomy of species of Bivesicula Yamaguti, 1934 is analysed for samples from holocentrid, muraenid and serranid fishes from Japan, Ningaloo Reef (Western Australia), the Great Barrier Reef (Queensland), New Caledonia and French Polynesia. Analysis of three genetic markers (cox1 mtDNA, ITS2 and 28S rDNA) identifies three strongly supported clades of species and suggests that Bivesicula as presently recognized is not monophyletic. On the basis of combined morphological, molecular and biological data, 10 species are distinguished of which five are proposed as new. Bivesicula Clade 1 comprises seven species of which three are effectively morphologically cryptic relative to each other; all seven infect serranids and four also infect holocentrids. Bivesicula Clade 2 comprises three species of which two are effectively morphologically cryptic relative to each other; all three infect serranids and one also infects a muraenid. Bivesicula Clade 3 comprises two known species from apogonids and a pomacentrid, and forms a clade with species of Paucivitellosus Coil, Reid & Kuntz, 1965 to the exclusion of other Bivesicula species. Taxonomy in this genus is made challenging by the combination of low resolving power of ribosomal markers, the existence of regional cox1 mtDNA populations, exceptional and unpredictable host-specificity and geographical distribution, and significant host-induced morphological variation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Enenteridae Yamaguti, 1958 and Gyliauchenidae Fukui, 1929 exhibit an interesting pattern of host partitioning in herbivorous fishes of the Indo-West Pacific. Enenterids are known almost exclusively from fishes of the family Kyphosidae, a group of herbivorous marine fishes common on tropical and temperate reefs. In contrast, gyliauchenids are found in most of the remaining lineages of marine herbivorous fishes, but until the present study, had never been known from kyphosids. Here we report on the first species of gyliauchenid known from a kyphosid. Endochortophagus protoporus gen. nov., sp. nov. was recovered from the Western buffalo bream, Kyphosus cornelii (Whitley, 1944), collected off Western Australia. Kyphosus cornelii also hosts an enenterid, Koseiria allanwilliamsi Bray & Cribb, 2002, and is thus the first fish known in which enenterids and gyliauchenids co-occur. Molecular phylogenetic analyses place the new species close to those of Affecauda Hall & Chambers, 1999 and Flagellotrema Ozaki, 1936, but there is sufficient morphological evidence, combined with the unusual host, to consider it distinct from these genera. We discuss factors which may have contributed to the host partitioning pattern observed between enenterids and gyliauchenids. [ABSTRACT FROM AUTHOR]

The taxonomy of trematodes of Great Barrier Reef (GBR) fishes has been studied in some detail for over 20 years. Understanding of the fauna has been informed iteratively by approaches to sampling, understanding of morphology, the advent of molecular methodology and a feed-back loop from the emergent understanding of host specificity. Here we analyse 658 host-parasite combinations for 290 trematode species, 152 genera and 28 families from GBR fishes. These are reported from 8 orders, 38 families, 117 genera and 243 species of fishes. Of the 290 species, only 4 (1·4%) have been reported from more than one order of fishes and just 23 (7·9%) infect more than one family; 77·9% of species are known from only one genus, and 60% from only one species of fish. Molecular studies have revealed several complexes of cryptic species and others are suspected; we conclude that no euryxenous host distribution should be accepted on the basis of morphology only. The occurrence of individual trematode species in potential hosts is patchy and difficult to predict reliably a priori or explain convincingly a posteriori. These observations point to the need for a vigorous iterative interaction between the accretion of host specificity data and its interpretation. [ABSTRACT FROM PUBLISHER]