A new species of Intromugil (Digenea: Haploporidae) and redescription of Intromugil mugilicolus

The elucidation of the life cycle of Saccocoelioides nanii Szidat, 1954 (Digenea: Haploporidae) using molecular techniques

In South America, the knowledge of trematode diversity parasitizing freshwater fishes is still scarce, as less than 5% of the freshwater fish fauna has been examined for parasites. A similar situation applies to studies on digenean life cycles, which have become increasingly rare. Among the digenean families parasitizing freshwater fishes in the region, Haploporidae is considered the richest in species diversity. However, information about the developmental stages of haploporid life cycles remains fragmentary. Particularly, in Argentina, nine cercariae attributed to the family Haploporidae have been described using morphological analysis, and only two life cycles of this family have been completely elucidated. In this study a new type of cercaria, morphologically assigned to the family Haploporidae and collected from the snail Heleobia parchappii (Cochliopidae) in Los Padres shallow lake, Buenos Aires province, was identified using morphological and molecular techniques. The molecular analysis, based on 28S and ITS2 sequences, revealed that the cercariae were 100% identical to adult specimens of Saccocoelioides nanii (Haploporidae) parasitizing the fish Prochilodus lineatus (Prochilodontidae) from Los Talas, Buenos Aires province. Our results not only provide information about the life cycle of S.nanii but also show that a molecular and morphological approach can be extremely useful in identifying the developmental stages of digeneans and elucidating their life cycles.

Saccocoelioides kirchneri n. sp. (Digenea: Haploporidae) from the killifish Cnesterodon decemmaculatus (Cyprinodontiformes: Poeciliidae) from Argentina, morphological and molecular description

This paper presents a new haploporid digenean that expands the number of species of Saccoccoelioides to 27. The new species, Saccocoelioides kirchneri n. sp. was collected from the intestine of Cnesterodon decemmaculatus (Poeciliidae: Cyprinodontiformes) from Lago del Bosque, La Plata, Argentina. The new species possesses the diagnostic features for Saccocoelioides: a sac like ceca; the vitellarium confined in two irregular groups of follicles distributed between the ventral sucker and the anterior margin of the testis; and a uterus confined largely in the hind-body, but encroaching into the range of the ventral sucker. The new species is differentiated from the 26 congeners by the body size, pharynx size, ventral sucker size, posterior extent of ceca, posterior extent of uterus and egg size. S. kirchneri n. sp. also is supported by the molecular analysis.

Phyllodistomum vaili(Plagiorchiida: Gorgoderidae) infecting Parupeneus rubescens (Perciformes: Mullidae): morphology and phylogeny

Knowledge of the Arabian Gulf fish's parasite fauna is very poor. Until recently, only scattered reports from different locations are known for ecto- and endoparasites. Therefore, the present study aimed to investigate the digenean species that infects one of the most economically fish species in the Arabian Gulf, the rosy goatfish Parupeneus rubescens . One plagiorchiid species has been described, belonging to the Gorgoderidae family, and has been named as Phyllodistomum vaili Ho, Bray, Cutmore, Ward & Cribb, 2014 based on its morphological and morphometric characteristics. In order to accurately classify and characterize this plagiorchiid species, molecular analysis was carried out using both nuclear 18S and 28S rRNA gene regions and revealed that the present plagiorchiid species was associated with other species belonging to the Gorgoderidae family and deeply embedded in the Phyllodistomum genus, closely related to the previously described P. vaili (gb| KF013187.1, KF013173.1). The present study therefore revealed that the species Phyllodistomum is the first account as endoparasites from the rosy goatfish inhabiting the Arabian Gulf.

New species and new genus of Pseudohaploporinae (Digenea): Pseudohaploporus pusitestis sp. n. and Parahaploporus elegantus n. g., sp. n. (Digenea: Pseudohaploporinae) from Vietnamese mullet fish

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.

Population genetic analysis of trematode Parasaccocoelium mugili Zhukov, 1971 (Haploporidae Nicoll, 1914) from the Russian Far East and Vietnam based on ribosomal ITS and mitochondrial COI gene partial sequence data

Intraspecific variation of Parasaccocoelium mugili collected from mullet fish of the south of Russian Far East and Vietnam has previously been estimated on the basis of two molecular markers: ribosomal internal transcribed spacer 1 (ITS1) rDNA and mitochondrial cytochrome oxidase I (COI) gene sequences. In the present study, molecular identification of this species from the Kievka River, Primorye and from Vietnam was performed by analysis of 28S rDNA sequences. Analysis of ITS1 rDNA sequences variation revealed two highly differentiated main groups, representing trematode specimens from the two regions. Genetic variation within each region was relatively low. Mitochondrial COI gene sequence data analysis revealed fixed nucleotide and amino acid substitutions, and supported the existence of two genetically different groups associated with geographical origin. Analysis of the COI gene fragments showed extremely high variation within Russian and Vietnamese P. mugili samples. Our results for P. mugili most probably represent a case of initial step of allopotric speciation for this trematode, caused by living strategy of its definitive host at evolutionary scale. Mitochondrial DNA sequence data show that existence of gene flow between local populations of P. mugili in the Primorye Region caused by definitive hosts can be proposed.

A new subfamily, Pseudohaploporinae subfam. n. (Digenea: Haploporidae), with morphometric and molecular analyses of two new species: Pseudohaploporus vietnamensis n. g., sp. n. and Pseudohaploporus planilizum n. g., sp. n. from Vietnamese mullet

Adult specimens representing Pseudohaploporus vietnamensis n. g., sp. n., Pseudohaploporus planilizum n. g., sp. n., and Pseudohaploporus sp. were collected from the intestines of Osteomugil engeli (Bleeker, 1858), Moolgarda seheli (Forsskål, 1775), and Planiliza subviridis (Valenciennes, 1836) from Vietnam. The new genus Pseudohaploporus n. g. is similar to the genus Haploporus Looss, 1902 in morphology and host-specificity. Species of Pseudohaploporus and Haploporus both possess an elongated body, a long oesophagus, an intestinal bifurcation behind the ventral sucker, a large hermaphroditic bursa, vitellarium consisting of two compact accumulations, concretions in the excretory vesicle, and numerous small eggs that contain miracidia with a pigment eye, and both infect mullet. In contrast to Haploporus, both species of the genus Pseudohaploporus possess two testes. These species differ from each other morphometrically. Pseudohaploporus planilizum sp. n., in comparison with P. vietnamensis sp. n., possess a larger maximum and mean size for the body length, oral and ventral suckers, pharynx, oesophagus length, hermaphrodite bursa, and egg width. Molecular data (ITS and 28S rDNA sequences) support the validity of the new genus and the two new species and indicate the presence of another representative of this genus, Pseudohaploporus sp. Phylogenetic reconstructions show that Pseudohaploporus formed a well-supported clade within a large clade that represents the Haploporidae Nicoll, 1914. Based on morphological and molecular data for P. vietnamensis sp. n. and P. planilizum sp. n., we erected a new subfamily, Pseudohaploporinae subfam. n., which appears to be a sister taxon to Haploporinae Nicoll, 1914. Molecular data show that Pseudohaploporus differ from other haploporids at a level similar to that between other subfamilies.

Two New Species of Saccocoelioides (Digenea: Haploporidae) with Phylogenetic Analysis of the Family, Including Species of Saccocoelioides from North, Middle, and South America

Two cryptic species of haploporid digeneans belonging in Saccocoelioides are described from Costa Rica: one from a poeciliid fish, Poecilia gillii, and the other from a characid fish, Astyanax aeneus. Traditional morphological features are examined and found to be largely inefficient for differentiating among the new species and 20 New World congeners. Comparison of ribosomal DNA sequences among the 2 new species, 2 North American, 4 Middle American, and 3 South American species of Saccocoelioides, including the type-species Saccocoelioides nanii from Argentina and Saccocoelioides sogandaresi from Texas, is effective in differentiating among these species. A Bayesian inference analysis is conducted using a concatenated alignment of the same 2 ribosomal gene regions from 35 species belonging in the Haploporoidea and rooted by the atractotrematid Isorchis anomalus. The analysis provides stronger support for a close relationship between species in Saccocoelioides and Intromugil; thus, Intromugil is transferred from the Waretrematinae to the Chalcinotrematinae. Additionally, interrelationships among 11 species of Saccocoelioides are resolved and reveal a distinct genetic rift suggesting the presence of 2 distinct lineages within the genus, 1 containing the type-species and the other containing a group of species that more closely resemble other genera in the subfamily. Taxonomy of Saccocoelioides is discussed, and observations made during the present study justify taking several taxonomic actions: new combinations are proposed for Saccocoelioides tilapiae n. comb., formerly in the now-defunct Culuwiya, and Saccocoelioides ruedasueltensis n. comb., formerly in Chalcinotrema; Saccocoelioides guaporense nomen novem is proposed for Lecithobotrioides elongatus; Saccocoelioides papernai is considered a junior subjective synonym of Saccocoelioides overstreeti; Saccocoelioides godoyi is considered a junior subjective synonym of Saccocoelioides szidati; Saccocoelioides magnorchis and Saccocoelioides saccodontis are considered species inquirendae; and Saccocoelioides adelae is considered a nomen nudum. Four new hosts are reported for Saccocoelioides cichlidorum: Amphilophus lyonsi, Amatitlania nigrofasciatus, Amatitlania septemfasciatus, and Hypsophrys nicaraguensis. Molecular data call into question some existing species identifications in Saccocoelioides and reveal that molecular tools combined with traditional taxonomy are required for accurately identifying species in the genus. Twenty-two species of Saccocoelioides are formally accepted, but it is noted that as new molecular data become available, some of these species may be transferred to other genera in the subfamily.

Morphometric and molecular analyses of two digenean species from the mullet: Skrjabinolecithum spinosum n. sp. from the Russian southern Far East and Unisaccus tonkini n. sp. from Vietnam

Adults of Skrjabinolecithum spinosum n. sp. were discovered in Mugil cephalus from the Gulf of Peter the Great in southern Far-East Russia. Additionally, adults of Unisaccus tonkini n. sp. were found in the intestine of Moolgarda cunnesius and Moolgarda seheli from the coastal waters of Cat Ba Island, Tonkin Bay, northern Vietnam. Skrjabinolecithum spinosum n. sp. possesses a larger body, and ventral and oral sucker size in comparison with Skrjabinolecithum vitellosum, a smaller pharynx size and body length/width rate ratio in comparison to Skrjabinolecithum pyriforme, a smaller body length and prepharynx size in comparison to Skrjabinolecithum lobolecitum and a smaller pharynx length and egg size in comparison to Skrjabinolecithum indicum and S. lobolecitum. The new species also differs from S. indicum, S. lobolecitum and S. vitellosum by the form of the testis, and from the last two species by the presence of a two-branched intestine. The morphometric parameters of S. spinosum n. sp. are similar to those of Skrjabinolecithum spasskii. However, S. spinosum n. sp., unlike S. spasskii, has an armed hermaphroditic duct. Unisaccus tonkini n. sp. is similar to Unisaccus spinosus (Martin, 1973), Unisaccus brisbanensis (Martin, 1973) and Unisaccus overstreeti (Ahmad, 1987) in body size but differs in oral sucker, pharynx and hermaphroditic sac size from U. spinosus, and in ventral sucker and ovary size from U. brisbanensis and U. overstreeti. Bayesian phylogenetic analysis, based on combined data of internal transcribed spacer 2 (ITS2) and partial 28S rRNA gene sequences, confirmed the validity of S. spinosum n. sp. and U. tonkini n. sp. Analysis of interrelationships of the family Haploporidae, including molecular data on new species, showed that the Waretrematinae subfamily is more heterogeneous in comparison with Haploporinae and Forticulcitinae, and includes U. tonkini n. sp.

Filling the gaps in the classification of the Digenea Carus, 1863: systematic position of the Proterodiplostomidae Dubois, 1936 within the superfamily Diplostomoidea Poirier, 1886, inferred from nuclear and mitochondrial DNA sequences

The Diplostomida Olson, Cribb, Tkach, Bray & Littlewood, 2003 is the less diverse order of the two orders within the subclass Digenea Carus, 1863 and is currently classified into three superfamilies, i.e. Brachylaimoidea Joyeux & Foley, 1930, Diplostomoidea Poirier, 1886, and Schistosomatoidea Stiles & Hassall, 1898. Although the suprageneric-level relationships have been elucidated with the use of molecular markers, the lack of representation of some groups obscure the phylogenetic relationships among families, rendering the classification unstable. Here, we tested the phylogenetic position of the family Proterodiplostomidae Dubois, 1936 based on partial 28S rDNA and complete 18S rDNA sequences for Crocodilicola pseudostoma (Willemoes-Suhm, 1870), a crocodile parasite that has been found as a progenetic metacercaria parasitising the pale catfish Rhamdia guatemalensis (Günther) in Mexico and in other siluruforms in the Neotropics. We augmented the representation of the species, genera and families within the Diplostomida, including mostly representatives of the superfamily Diplostomoidea, and assembled a dataset that contains 49 species for the 28S rRNA gene, and 45 species for the 18S rRNA gene. Additionally, we explored the phylogenetic signal of the mitochondrial gene cox1 in reconstructing the phylogenetic relationships of selected members of the superfamily. Our analyses showed that the family Proterodiplostomidae is the sister taxon to the paraphyletic Diplostomidae Poirier, 1886 and Strigeidae Railliet, 1919, with Cyathocotylidae Mühling, 1898 + Brauninidae Wolf, 1903 as their sister group. Analysis of concatenated 18S + 28S sequences revealed the Liolopidae Odhner, 1912 as the basal group of the superfamily Diplostomoidea, although analyses of independent datasets showed that the position of this family remains uncertain. Analysis based on cox1 unequivocally resolved the Proterodiplostomidae as the sister taxon to the Diplostomidae and Strigeidae, although the Cyathocotylidae was nested in a different clade, along with brachylaimoids and schistosomatoids.

Morphometric and molecular analyses of Skrjabinolecithum pyriforme n. sp. (Digenea: Haploporidae) in mullet fish from the Primorsky Region, Russia

A new species of Skrjabinolecithum (Digenea: Waretrematinae), Skrjabinolecithum pyriforme n. sp., has been found in the intestines of Liza haematocheila and Mugil cephalus from the Primorsky Region, Russia. These worms differ from S. vitellosum and S. lobolecithum by the presence of two caeca, as do S. spasskii, S. indicum and S. bengalensis. These species differ morphologically from S. pyriforme n. sp. by a number of features, including body width, oral sucker, pharynx, eggs and ratio of length and width of the body. The most similar species to S. pyriforme n. sp. is Platydidymus flecterotestis (Zhukov, 1971) with some differences in maximal body length, testis and egg sizes. The results of molecular analysis confirmed that this new species belongs to Skrjabinolecithum on the basis of close relationships with S. spasskii-type species.

Description of three species of Isorchis (Digenea: Atractotrematidae) from Australia

Three species of Isorchis Durio and Manter, 1969 are described from Australian waters. Isorchis megas sp. nov. is described from the spotbanded scat, Selenotoca multifasciata (Richardson), off Western Australia (WA) and Northern Territory (NT); Isorchis currani sp. nov. is described from S. multifasciata off NT; and Isorchis anomalus sp. nov. is described from the milkfish, Chanos chanos Forsskål, off WA. Isorchis megas sp. nov. can be differentiated from the other species of Isorchis by possessing a single, large egg that is greater than 20% of the body length; having a shorter body (the largest specimen is less than 500 μm); and utilizing a scatophagid rather than a chanid host. Isorchis currani sp. nov. can be differentiated from species of Isorchis other than I. megas sp. nov. by utilizing a scatophagid rather than a chanid host; it is differentiated from I. megas sp. nov. in having eggs that are 11-15% of the body length. Isorchis anomalus sp. nov. can be differentiated from all other species of Isorchis in possessing an irregular shaped genital pore rather than one that is circular to oblong. A Bayesian inference analysis of partial 28S rDNA sequences of the three new species of Isorchis and 30 other haploporoids revealed 1) the monophyly of the Atractotrematidae Yamaguti, 1939, 2) the two species of Isorchis infecting S. multifasciata were each other's closest relative, and 3) that Isorchis was most closely related to Pseudomegasolena Machida and Komiya, 1976 rather than Atractotrema Goto and Ozaki, 1929 although sequence data are not yet available for a member of Pseudisorchis Ahmad, 1985.

Morphological and molecular analyses of a new species of Saccocoelioides Szidat, 1954 (Haploporidae Nicoll, 1914) in the fat sleeper Dormitator maculatus (Bloch) (Perciformes: Eleotridae) from the Gulf of Mexico

Saccocoelioides olmecae n. sp. is described from specimens recovered from the intestine of the fat sleeper Dormitator maculatus (Bloch) (Perciformes: Eleotridae) collected in six localities along the coast of the Gulf of Mexico. The new species is mainly distinguished from the other three described species of Saccocoelioides Szidat, 1954 from North and Middle America (i.e. S. sogandaresi Lumsden, 1963, S. chauhani Lamothe-Argumedo, 1974 and S. lamothei Aguirre-Macedo & Violante-González, 2008) by having an elongated body, a sac-like caecum, a uterus that extends to the first third of body and by having vitelline follicles longitudinally elongated reaching the posterior end of the body. Sequences of the large subunit (LSU) of the ribosomal DNA, including the domain D1–D3, and the internal transcribed spacer 2 (ITS2) were used independently and concatenated to corroborate the morphological distinction among S. olmecae n. sp., S. chauhani and S. lamothei from freshwater and brackish-water fish from Middle America. The genetic divergence estimated among the three species of Saccocoelioides was very low: 1% for LSU and from 1 to 4% for ITS2. Maximum likelihood and Bayesian inference analyses for each dataset and both datasets combined revealed that S. olmecae n. sp. represents an independent clade with moderate bootstrap support and posterior probabilities. This is the third species of Saccocoelioides described in Mexico, and the 17th species from the Americas.

Erection of the haploporid genus Litosaccus n. g. and its phylogenetic relationship within the Haploporidae Nicoll, 1914

Litosaccus n. g. is erected for Paralecithobotrys brisbanensis Martin, 1974 n. comb. for which an amended description is given. The new genus is morphologically similar to the haploporine Lecithobotrys Looss, 1902 but with a more elongate and cylindrical body; an infundibuliform oral sucker; a thin-walled hermaphroditic sac; a shallow genital atrium; and unequal, cylindrical and elongated caeca. It also resembles Pseudolecithobotrys Blasco-Costa, Gibson, Balbuena, Raga & Kostadinova, 2009, but the only member of that genus has a hermaphroditic sac that is twice the length of the ventral sucker, a hermaphroditic duct with intensely-staining cuboidal cells, an elongate testis, and single or paired caeca. A Bayesian inference analysis of partial 28S rDNA sequences of L. brisbanensis and 24 other haploporoids revealed that L. brisbanensis grouped with other haploporines and placed Intromugil Overstreet & Curran, 2005 in a clade with the chalcinotrematine Saccocoelioides Szidat, 1954 rather than the other seven tested waretrematine species. This analysis represents the first phylogenetic study of the Haploporidae Nicoll, 1914 that incorporates a haploporine from outside of the Mediterranean Sea.

Integrative taxonomy identifies a new species of Phyllodistomum (Digenea: Gorgoderidae) from the twospot livebearer, Heterandria bimaculata (Teleostei: Poeciliidae), in Central Veracruz, Mexico

Phyllodistomum inecoli n. sp. is described from the twospot livebearer, Heterandria bimaculata (Teleostei: Poeciliidae), collected in the Río La Antigua basin, Veracruz, Mexico. The new species is described and characterised by using a combination of morphology, scanning electron microscopy, and sequences of nuclear and mitochondrial genes. Diagnostic characters of the new species of Phyllodistomum include a genital pore opening at the level of the caecal bifurcation; oval vitellarium, situated just posterior to the ventral sucker and not extended laterally and anterior extracaecal uterine loops variable in extension (reaching the anterior, median or posterior margin of the ventral sucker). P. inecoli n. sp. most closely resembles P. brevicecum, a species described as a parasite of the central mudminnow, Umbra limi, in other parts of North America; however, the genital pore in P. brevicecum is situated between the caecal bifurcation and the ventral sucker, the ovary is larger, the vitellarium is lobed and extended laterally and the anterior portion of the uterus extends to the posterior margin of the ventral sucker. Comparison of about 1,500–2,200 nucleotides of cox1 and 28S rDNA and ITS1 strongly supports the status of P. inecoli as a new species. Bayesian inference analysis of combined datasets of 28S rDNA and cox1 sequences showed that P. inecoli n. sp. and the other species found in freshwater fishes of Mexico, including the species complex of P. lacustri, are not sister species. Phylogenetic analysis based on 28S rDNA sequences of several gorgoderid taxa revealed the close relationship of P. inecoli n. sp. with several species of Phyllodistomum, Gorgodera and Gorgoderina with cystocercous cercariae developing in sphaeriid bivalves. Dot-plot analysis of ITS1 sequences of P. inecoli n. sp. revealed the presence of eight repetitive elements with different length, which together represent almost half the length of ITS1.

Restoration of the genus Parasaccocoelium Zhukov, 1971 (Digenea: Haploporidae) and a description of two new species from mugilid fish in the Far East of Russia

New data relating to the fauna of Haploporidae (Digenea) in mugilid fish from Primorsky Region of the south of the Russian Far East are presented. In the most recent revision of the family Haploporidae Nicoll, 1914, Parasaccocoelium Zhukov, 1971 was synonymized with Pseudohapladena Yamaguti, 1952 (Overstreet & Curran, 2005). Here, we restore the genus Parasaccocoelium. The species described by Zhukov can be distinguished from the species Pseudohapladena sensu Yamaguti, 1952 using a combination of the following features: (1) diffuse or absent eye-spot pigment; (2) subterminal or terminal oral sucker; (3) present or absent genital atrium; and (4) vitellarium with two large and compact vitelline masses, or vitelline follicles tubular and divided into two groups. For the species of Pseudohapladena, i.e. P. scatophagi, Yamaguti noted that the vitelline follicles occupy almost the entire post-testicular region, but in the present specimens, the vitelline follicles do not occupy the post-testicular region. Based on the diagnosis of Pseudohapladena by Overstreet & Curran (2005), the genus Parasaccocoelium differs in the following features: (1) a single testis that is longitudinal, longitudinally oval, spherical, transversally oval, irregular, bilobed or V-shaped, or a testis that is subspherical to irregular to elongate; (2) the vitellarium in the lateral fields formed from large compact follicles that have an irregular form and extend between the anterior margin of the ventral sucker or pharynx and posterior margin of the testis, and the vitelline follicles do not occupy post-testicular regions; or the vitellarium consists of elongate groups of follicles that usually extend at least one-half of a body length and extend to the posterior end of the body in some and to the posterior margin of the testis in others; (3) the eggs are operculate, unembryonated and developed when laid, or the eggs in some cases are only operculate; and (4) a developed miracidium with or without an eye spot. New data have been added to the description of Parasaccocoelium mugili Zhukov, 1971 based on new material, and two new species of this genus, Pa. haematocheilum n. sp. from Liza haematocheila and Pa. polyovum n. sp. from L. haematocheila and Mugil cephalus, are described using morphological and molecular approaches. We support the taxonomic status of the genus Parasaccocoelium and its inclusion within the sub-family Waretrematinae, and we consider Pseudohapladena lizae Liu et Yang, 2002 to be a junior synonym of Parasaccocoelium mugili Zhukov, 1971.