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(A) Isorchis cannoni n. sp., ventral view, holotype, from Siganus lineatus, Heron Island, Great Barrier Reef. (B) Isorchis cannoni n. sp., ventral view, hermaphroditic sac and ovarian complex, paratype, from Siganus fuscescens, Heron Island. Scale bars: (A) 200 μm; (B) 100 μm.
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We describe Isorchis cannoni n. sp. from the rabbitfishes Siganus fuscescens (Houttuyn) and Siganus lineatus (Valenciennes) (Siganidae) collected off Heron Island, southern Great Barrier Reef, Australia and, using molecular data, demonstrate that ‘ Cercariae queenslandae II’ of Cannon (1978) from the gastropod Clypeomorus batillariaeformis Habe & K...
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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 sp...
Citations
... Presumably they penetrate invertebrates living among algae which are incidentally ingested by the definitive fish hosts, but it is also possible that they have secondarily adopted a 2-host life cycle with direct encystment of metacercariae onto algae or the substrate. This strategy is known for other trematode families specializing in herbivorous fishes such as the Atractotrematidae (Huston et al., 2018), Gorgocephalidae (Huston et al., 2016), Gyliauchenidae (Al-Jahdali and Hassanine, 2012), Haplosplanchnidae (see the Haplosplanchnata chapter for more information), and Microscaphidiidae (Hassanine et al., 2016). Intriguingly, the cercaria has been described for one of the species of Choerodonicola and, unlike most other opecoelid cercariae, it lacks a stylet, the specialized organ used to penetrate the second intermediate host (Martin et al., 2018a). ...
... In light of the derived position of the haplosplanchnids in the overall phylogeny of the Digenea Littlewood et al., 2015), this form of metacercarial encystment suggests there was no second intermediate host in the evolution of the haplosplanchnid lineage . External encystment has been demonstrated in multiple digenean lineages which exploit herbivorous fishes as definitive hosts, for example, the Atractotrematidae, Gorgocephalidae, Gyliauchenidae, and Microscaphidiidae (Al-Jahdali and Hassanine, 2012;Hassanine et al., 2016;Huston et al., 2016;2018b). ...
... Sequence data have proven to be invaluable in elucidating the life cycles of digeneans, which typically exhibit an indirect life cycle. The use of genetic information, such as DNA sequencing of specific regions like 28S rRNA, ITS1, and CoxI, has provided crucial insights into the complex life cycles of these parasitic flatworms (Huston et al. 2018;Rochat et al. 2020;Shamsi et al. 2021a;Shamsi et al. 2021b;Shamsi et al. 2023, Barton et al. 2022Choudhary et al. 2022). Cribb (1987) highlighted that the proper identification of Phyllodistomum spp. is challenging due to significant intra-specific morphological variations and inadequate descriptions of several species. ...
Phyllodistomum is the large digenean group of fish parasites, with 25 species described so far in the Indian subcontinent. Here, we redescribed two adult species of Phyllodistomum (P. srivastava Rai 1964 and P. parorchium Jaiswal 1957) collected from freshwater fish Heteropneustes fossilis Bloch, 1974 and Glossogobius giuris Ham, 1822, respectively, and an unknown Phyllodistomum metacercaria from shrimp (Macrobrachium dayanum Henderson, 1893). These parasites were genetically characterized using 28S and first and second internal transcribed spacers (ITS1 and ITS2) regions of the nuclear ribosomal DNA and CoxI region of the mitochondrial (mt) DNA to establish the link between metacercaria and adult. Morphologically, both the unknown metacercaria in shrimp and adult Phyllodistomum srivastava in fish, resembled in terms of crenulated margin of hind body, arrangement of diagonal testes, bipartite seminal vesicle, and compact paired vitelline masses. The two adult parasite species, P. srivastava from P. parorchium, were different in terms of shape and size of the body, ratio of suckers, the absence of crenulated margin of hind body, a single chambered seminal vesicle, and deeply lobed paired vitelline masses, in the former species. Comparison of the 28S, ITS, and mtCoxI sequence data suggested P. srivastava and Phyllodistomum metacercaria belong to the same species, and supported the distinction between P. srivastava and P. parorchium. Exploring the potential impact of Phyllodistomum infection on host behaviour and health would be prospective areas for future research.
... These species thereby infect their herbivorous fish host through its consumption of specific algal taxa, a trait typical of digeneans infecting herbivorous fishes (Al-Jahdali & Hassanine, 2012;Hassanine et al., 2016;Huston et al., 2018). Although further research is required to determine the infection pathways of these endoparasites, and whether these, or similar parasite assemblages, are shared by other fish species with similar feeding ecologies, differences in diet may have contributed to the observed differences in endoparasite communities of these three species. ...
Parasites are important, diverse, and abundant components of natural ecosystems and can influence the behaviour and health of their hosts, inter‐ and intraspecific interactions, and ultimately community structure. Coral reefs are one of the world's most biodiverse ecosystems, yet our understanding of the abundance, diversity, and composition of parasite communities of coral reef fishes is limited. Here, the authors aimed to compare the abundance, richness and composition of parasite communities among three co‐occurring herbivorous coral reef fishes (the barred rabbitfish Siganus doliatus, Ward's damsel Pomacentrus wardi and the obscure damsel Pomacentrus adelus) from an inshore reef of the Great Barrier Reef (GBR). In total, 3978 parasites (3869 endoparasites and 109 ectoparasites) from 17 families were recovered from 30 individuals of each of the three fish species (mean = 44 ± 22 s.e. parasites per fish; range = 0–1947 parasites per fish). The parasite communities of P. wardi and P. adelus were characterised by pennellid copepods, derogenid and lecithasterid digeneans and were distinct from those of S. doliatus that were characterised by a higher abundance of atractotrematid and gyliauchenid digeneans. The abundance and family richness of all parasites were greatest in S. doliatus (abundance: 22.1 ± 5.0 parasites per fish; richness: 3.2 ± 0.3 families per fish), intermediate in P. wardi (abundance: 4.8 ± 1.1 parasites per fish; richness: 2.3 ± 0.3 families per fish) and lowest in P. adelus (abundance: 1.4 ± 0.4 parasites per fish; richness: 0.9 ± 0.2 families per fish). Similarly, the abundance of endoparasites was greatest in S. doliatus (19.7 ± 5.1 endoparasites per fish), intermediate in P. wardi (2.6 ± 0.7 endoparasites per fish) and lowest in P. adelus (1.2 ± 0.4 endoparasites per fish). Ectoparasite abundances were also lowest for P. adelus (0.2 ± 0.1 ectoparasites per fish), and S. doliatus and P. wardi had comparable abundances of ectoparasites (1.3 ± 0.3 and 2.1 ± 0.5 parasites per fish, respectively). Similarities between the parasite assemblages of the two pomacentrids may be related to their similar behaviours and/or diets vs. those of the larger‐bodied and more mobile rabbitfish. Investigating the causes and consequences of variation in parasite communities across a broader range of fish species will be critical to understand the potential role of parasites in coral reef ecosystems.
... rDNA and 28S rDNA of Brachycladium goliath (van Beneden, 1858) from GenBank were used as the outgroup. The authors of these and other sequences from GenBank [3][4][5][6][7][8][9][10][11][21][22][23][24][25][26][27][28][29][30][31] and their accession numbers are given in Table 1. Etymology: species name associated with trematode body form. ...
We restore the genus Paraunisaccoides (Haploporidae), synonymised earlier with the genus Skrjabinolecithum. Adult worms, detected in Vietnamese mullet fish, were highly similar to trematodes described as P. lobolecithum via digestive and genital system structures and relative organ arrangement. Differences are expressed as absence and presence of pads on the hermaphrodite duct, respectively, and the disjunction of some metric parameter values, namely body, ovary and eggs. Ribosomal DNA sequences, based on the phylogenetic analysis of Haploporidae, indicates that new worms represent a sister clade to Unisaccus tonkini. Genetic divergence between new worms and Skrjabinolecithum species can be interpreted as intergeneric. Based on morphological and molecular data, we recognise Paraunisaccoides as a valid genus within Waretrematinae and worms from Vietnam as a new species of this genus, P. elegans n. sp. Other worms detected in Vietnamese mugilids are morphologically similar to representatives of Paraunisaccoides и Skrjabinolecithum. However, molecular-based phylogenetic analysis showed that these trematodes are closely related to Unisaccus tonkini; the genetic divergence between them is at the interspecific level, despite considerable differences in vitellarium structure as intergeneric character. Accepting the priority of molecular results, we include these new worms into the genus Unisaccus as new species, Unisaccus halongi n. sp.
... The last 50 years has seen substantial progress in the understanding of marine trematode life cycles. By our reckoning, representatives of six significantly or entirely marine families have had their first cycles reported: Atractotrematidae (Huston et al., 2018), Brachycladiidae , Gorgocephalidae (O'Dwyer et al., 2015;Huston et al., 2016), Gyliauchenidae (Al-Jahdali and Hassanine, 2012), Lepidapedidae (Køie, 1985), and Microscaphidiidae (Lotz and Corkum, 1984;Hassanine et al., 2016). Life cycles for the Atractotrematidae, Gorgocephalidae, Gyliauchenidae and Lepidapedidae relate to trematodes of fishes, Microscaphidiidae relate to infections of fishes and turtles and Brachycladiidae relate to those of marine mammals. ...
Trematodes are the richest class of platyhelminths in the marine environment, infecting all classes of marine vertebrates as sexual adults and many phyla of marine invertebrates as part of their life cycles. Despite the cryptic nature of their existence (almost all marine trematodes are internal parasites), they have been the focus of study for almost 250 years, with the first species described in 1774. Here we review progress in the study of the “biodiversity” of these parasites, contrasting the progress made in the last 50 years (post-1971) to that in the almost 200 years before it (pre-1972). We consider an understanding of biodiversity to require knowledge of the species present in the system, an understanding of their evolutionary relationships (which informs higher classification), and, specifically for trematodes, an understanding of their complex life cycles. The fauna is now large, comprising well over 5,000 species. Although species description continues, we see evidence of a slow-down in all aspects of discovery. There has been only one completely new family identified since 1984 and the proposal of new genera is in decline as is the description of new species, especially for those of tetrapods. However, the extent to which this slow-down reflects an approach to the richness asymptote is made uncertain by changes in the field; reduced effort and difficulty of study may be important components of the effect. Regardless of how close we are to a complete description of the fauna, we infer that the outline is well-understood although the details are not. Adoption of molecular methodologies over the last 40 years have complemented morphometric analyses to facilitate objective recognition of species; however, despite these objective data, there is still inconsistency between authors on species delimitation. Molecular methodologies have also completely revolutionised inference of relationships at all levels, from within genera to between orders, and underpinned elucidation of novel life cycles. We expect the next 50 years to produce further dividends from technological innovations. The backdrop to the field will be global environmental concerns and the growing problem of funding for basic biodiversity studies.
... Furthermore, a number of studies of other IWP trematode lineages (e.g. Trieu et al., 2015;Bray et al., 2018b;Huston et al., 2018a) have reported fewer bp differences in sequences between well-defined species than we have observed within Gorgocephalus kyphosi and G. yaaji. Inclusion of COI sequences in the present study augmented patterns revealed by ITS2 and 28S rDNA gene sequences and improved our ability to recognize intraspecific variation, which we might previously have interpreted as interspecific variation. ...
The digenetic trematode family Gorgocephalidae comprises just a few species, and the literature devoted to the lineage consists of only a handful of reports. With one exception, all reports have been based on material collected in the Indo-West Pacific, an expansive marine ecoregion stretching from the east coast of Africa to Easter Island, Hawaii and French Polynesia. We collected adult and intramolluscan gorgocephalids from kyphosid fishes and littorinid gastropods from several Australian localities, and from South Africa and French Polynesia. Specimens of Gorgocephalus kyphosi and G. yaaji were collected from, or near, their type-localities, providing new morphological and molecular (COI, ITS2 and 28S) data needed for a revised understanding of species boundaries in the family. Two new species are recognized: Gorgocephalus euryaleae sp. nov. and Gorgocephalus graboides sp. nov. New definitive host records are provided for described species and three new intermediate hosts are identified. These new records are all associated with Kyphosus fishes and littorinid gastropods, reaffirming the restriction of gorgocephalids to these hosts. Most significantly, we provide evidence that G. yaaji is distributed from South Africa to French Polynesia, spanning the breadth of the Indo-West Pacific. Our findings have significant relevance regarding digenean species delineation over geographic range.
... rDNA and 28S rDNA of Paragonimus westermani (Braun, 1899), Brachycladium goliath (van Beneden, 1858), and Hurleytrematoides chaetodoni (Manter, 1942) Yamaguti, 1954 from GenBank were used as the outgroup. Authors of these and other sequences from GenBank [1,5,[11][12][13][14][15][16][17][18][19][20][21][22][23] and their accession numbers are given in Table 1. Adult worm ( Table 2, Fig. 1 a, b). ...
Two new species of Pseudohaploporinae, Pseudohaploporus pusitestis sp. n. and Parahaploporus elegantus n. g., sp. n., are described from intestines of the Vietnamese mullet fish Moolgarda seheli and Osteomugil cunnesius, respectively. Pseudohaploporus pusitestis sp. n. differs from two known Pseudohaploporus species, P. vietnamensis and P. planiliza, by the absence of a diverticulate hermaphroditic duct and muscular sphincters at the proximal end of the hermaphroditic sac. Metrically, P. pusitestis sp. n. is close to P. vietnamensis and differs from this species and from P. planilizum by lower maximum sizes of most parameters. Parahaploporus elegantus n. g., sp. differs from representatives of Pseudohaploporus by the presence of a single testis and the armament of hermaphroditic duct and is morphologically close to trematodes of the genus Haploporus. However, P. elegantus n. g differs from all known Haploporus species from mugilids of the Indo-West Pacific by the structure of the armament of the hermaphroditic duct and also by size of body, organs and eggs. The validity of designating two new species and a new genus of trematodes is supported by ITS and 28S rDNA sequence data. Phylogenetic reconstructions showed that the new trematodes belong to the Pseudohaploporinae, which formed a well-supported cluster within the monophyletic Haploporidae.
... The significance of the phylogenetic relationships was estimated using posterior probabilities (Huelsenbeck et al. 2001). Accession numbers, authority and supporting information about rDNA sequences from Gene Bank, used for phylogenetic analyses, were provided in Table 1 (Blasco-Costa et al. 2009;Andres et al. 2014Andres et al. , 2015Andres et al. , 2018Atopkin et al. 2015;Besprozvannykh et al. 2015b;Briscoe et al. 2016;Besprozvannykh et al. 2017;Curran et al. 2018;Huston et al. 2018;Atopkin et al. 2019). Brachyphallus goliath was used as an outgroup (authors of these data and accession numbers are given in the Table 1). ...
Adult worms that belong to Carassotrema Park 1938 and Elonginurus Lu, 1955 were found in the intestine of Carassius gibelio Bloch, 1782 from the southern Russian Far East and Mugil cephalus Linnaeus, 1758 from northern Vietnam, respectively. Morphometric parameters, geographic location and host species composition of these worms correspond to Carassotrema koreanum Park 1938, which is a known parasite of cyprinid fish in Korea, Japan and China, and Elonginurus mugilus Lu, 1955, first described from M. cephalus in China. The validity of Carassotrema ginezinskajae Kulakova, Ha Ky, 1976, a synonym of C. koreanum, first described from Spinibarbichthys denticulatus Oshima, 1926 in Vietnam, supported the morphometric data. Phylogenetic analysis based on combined ITS2 ribosomal DNA (rDNA) and 28S rRNA indicated that C. koreanum and E. mugilus belong to the subfamily Waretrematinae and are closely related to the genera Skrjabinolecithum and Parasaccocoelium, respectively. Species similarity, revealed through molecular analysis, agreed with the generic diagnoses for Parasaccocoelium and Elonginurus, as well as for Carassotrema and Skrjabinolecithum.
... Such external encystment is the typical life-cycle strategy for digeneans which exploit herbivorous fishes, e.g. species of the Atractotrematidae Yamaguti, 1939, Gorgocephalidae Manter, 1966, Haplosplanchnidae Poche, 1926and Microscaphidiidae Looss, 1900(Cable, 1954Hassanine et al., 2016;Huston et al., 2016Huston et al., , 2018. ...
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.
