Morphological and molecular data on Pseudozoogonoides ugui Shimazu, 1974 (Digenea: Microphalloidea: Zoogonidae) ex Pseudaspius hakonensis (Günther, 1877) and taxonomic problems in Zoogoninae genera.

New morphological and molecular data were generated for trematodes recovered from the intestines of the fish Pseudaspius hakonensis from two locations in the south of the Russian Far East. Morphologically, these trematodes are identical to Pseudozoogonoides ugui (Microphalloidea: Zoogonidae) from Japan. According to results of phylogenetic analysis based on 28S rDNA sequence data, P. ugui was closely related to Zoogonoides viviparus, and P. subaequiporus appears as a sister taxon to these two species. Genetic distance values, calculated based on both 28S rDNA and ITS2 rDNA, between P. ugui and Z. viviparus represents an interspecific differentiation level. Our results have an ambiguous explanation, indicating that the implication of the presence of one or two compact vitellarial aggregations for the differentiation of Zoogonoides and Pseudozoogonoides should be reconsidered or that our results open up the question of the taxonomical status of trematodes previously denoted as Z. viviparus and P. subaequiporus.

Neodiplostomum cf. seoulense (Seo, Rim, Lee, 1964) sensu Pyo et al., 2014 (Trematoda: Diplostomidae Poirier, 1886): morphology, life cycle, and phylogenetic relationships.

Furcocercariae of the genus Neodiplostomum Railliet, 1919 (Diplostomidae Poirier, 1886) were found in freshwater snails Helicorbis sujfunensis Starobogatov, 1957 (Planorbidae Rafinesque, 1815) collected from three localities in the Russian southern Far East. For the trematodes from each locality, frogs played the role of the second intermediate host, and rats were the definitive host. Chickens were insusceptible to infection. The morphological and molecular data obtained for these trematodes indicated they were representatives of the same species. The experimentally-derived adult individuals were morphometrically similar to the East Asian Neodiplostomum seoulense (Seo, Rim, Lee, 1964), Neodiplostomum oriolinum Oschmarin, 1963, Neodiplostomum leei Chai and Shin, 2002, and Neodiplostomum boryongense Shin et al., 2008. Analysis of available data on the life cycle, developmental stage morphology, and molecular genetic characteristics of East Asian Neodiplostomum revealed a lack of information for objective assessment of the species status of neodiplostomula found in the East Asia region. Based on the considerations above and the data for the cox1 marker, we named the trematode Neodiplostomum cf. seoulense (Seo, Rim, Lee, 1964) sensu Pyo et al., 2014. In a phylogenetic reconstruction based on nuclear and mitochondrial markers, neodiplostomulas clustered into geographically related groups: South American, North American, European, and East Asian, with the former occupying an external position in the tree, which may indicate South America as a center of Neodiplostomum speciation.

New trematode species Lecithostaphylus halongi n. sp. (Zoogonidae, Microphalloidea) and Gymnotergestia strongyluri n. sp. (Fellodistomidae, Gymnophalloidea) from beloniform fishes in Vietnam.

In this study we described two new trematode species, Lecithostaphylus halongi n. sp. (Zoogonidae, Lecithostaphylinae) and Gymnotergestia strongyluri n. sp. (Fellodistomidae, Tergestiinae), on the basis of morphological and molecular data. Adult worms of these two species were collected from, respectively, Hemiramphus spp. (Hemiramphidae) and Strongylura strongylura (Belonidae) caught in the coastal waters of Vietnam. Adult worms of L. halongi n. sp. are morphologically close to Lecithostaphylus gibsoni Cribb, Bray & Barker, 1992 ex Abudefduf whitleyi from Heron Island and Lecithostaphylus depauperati Yamaguti, 1970 ex Hemiramphus depauperatus from Hawaii, but differ from these species in having a larger cirrus sac and a different arrangement of vitelline fields. They also differ from Lecithostaphylus brayi Cabañas-Granillo, Solórzano-García, Mendoza-Garfias & Pérez-Ponce de León, 2020 in the 28S ribosomal DNA (rDNA) sequence data at the interspecific level. Adult worms of G. strongyluri n. sp. ex S. strongylura are morphologically similar to Gymnotergestia chaetodipteri, the only previously known species of this genus, described from Chaetodipterus faber in Jamaica. The new species differs from G. chaetodipteri in body shape, testicular arrangement and the size of the pharynx and eggs. The 28S rDNA-based phylogenetic analysis indicates that G. strongyluri n. sp. is closely related to Tergestia spp., rendering Tergestia paraphyletic. Genetic divergence values between G. strongyluri n. sp. and Tergestia spp. are similar to those among species in the genera Tergestia, Steringophorus and Proctoeces. Our molecular results indicate that G. strongyluri n. sp. and Tergestia spp. may belong the same genus, but additional molecular data are needed for the final conclusion.

Stephanoprora amurensis sp. nov., Echinochasmus milvi Yamaguti, 1939 and E. suifunensis Besprozvannykh, 1991 from the Russian southern Far East and their phylogenetic relationships within the Echinochasmidae Odhner 1910.

Mature worms of Stephanoprora amurensis sp. nov. were obtained in an experimental study of its life cycle. In the Russian southern Far East, this trematode circulates using freshwater snails Parajuga subtegulata, freshwater fish and birds as the first, second intermediate and final hosts, respectively. Stephanoprora amurensis sp. nov. differs from the well-known representatives of Stephanoprora in a number of morphometric indicators of the developmental stages. The validity of the species was also confirmed by nuclear and mitochondrial DNA markers. In addition, new genetic data were obtained for Echinochasmus suifunensis and Echinochasmus milvi. An analysis of phylogenetic relationships within Echinochasmidae based on the 28S rRNA gene and ITS2 region identified two clusters, one of which combines species of Echinochasmus with 20-22 collar spines and short-tailed cercariae, and the other which includes Stephanoprora spp. and a number of representatives of Echinochasmus with 24 collar spines and long-tailed cercariae. The results of phylogenetic analysis based on ITS2 data show interfamily level of differences between the two clusters and intergeneric differentiation between the three subclusters uniting the species of Stephanoprora and Echinochasmus.

New species of Parasaccocoelium (Haploporidae) and new genus Pseudohaplosplanchnus (Haplosplanchnidae) from mullet fish in the Far East of Russia and Vietnam: morphological and molecular data.

A description and the molecular characterization of two new species in the Haploporidae and Haplosplanchnidae families are provided herein. Parasaccocoelium armatum n. sp. was collected from the intestine of a Mugil cephalus Linnaeus, 1758 from the Primorsky region, Russia, and Pseudohaplosplanchnus catbaensis n. g. n. sp. was collected from Moolgarda seheli (Forsskål, 1775) in the coastal waters of Cat Ba Island, Vietnam. The morphological features of P. armatum n. sp. closely resemble those of Parasaccocoelium polyovum, but these species differ from one another by hermaphroditic sac and vitellaria area length and by maximal egg size. The main difference between P. armatum n. sp. and P. polyovum is the presence of an armed hermaphroditic duct in the new species. Molecular data support the case for inclusion of the studied trematodes in P. armatum n. sp. Worms P. catbaensis n. g. n. sp. from the mullet from Vietnam are morphologically close to Haplosplanchnus (Haplosplosplanchninae). The only difference between P. catbaensis n. g. n. sp. and species of Haplosplanchnus is the presence of few (1-7) large eggs, measuring 135-142 × 92-104 µm, versus numerous small eggs with a maximal size of 75 × 50 µm. Phylogenetic analysis showed that there is a contradiction between the morphological similarity of the worms and their position in the Haplosplanchnidae system, based on the genetic data. Results of this study indicate that P. catbaensis n. g. n. sp. is genetically distant from other representatives of Haplosplanchnus, despite their morphological similarity. According to the molecular data, P. catbaensis n. g. n. sp. is close to Hymenocotta mulli Manter, 1961 (Hymenocottinae). However, these species are considerably different to each other morphologically. Molecular data argue for the possibility of establishing a new subfamily for P. catbaensis n. g. n. sp. However, considering earlier studies of Haplosplanchnidae, we support the view that creating new subfamilies within this family is unreasonable because of the lack of molecular data for most haplosplanchnid species, which are necessary to resolve the problematic systematics and phylogeny of this family.

Harmful Parasitoses on the Russian Southern Far East under Climatic and Demographic Changes.

Progressive expansion of the most hazardous human parasitoses caused by trematodes, cestodes and nematodes has been found on the south of the Russian Far East. Decelerating expansion of the trematode Clonorchis sinensis, an agent of clonorchiasis towards the southern Primorye Territory from the Amur River basin, that began 10-15 years ago, was revealed. A prognosis was made on the activation of the natural foci of clonorchiasis and paragonimiasis. Circulation possibilities are discussed of the highly pathogenic trematode Pagonimus heterotremusar in the South Asian regional ecosystems. Our experiments showed that the freshwater gastropods of the Parajuga genus from the Amur River basin and those of Stenothyra genus from Primorsky Territory were resistant to this trematode infection. Nevertheless, this does not exclude the possibility of this parasite penetration into the Far East region via infection of the local gastropods of other genera.

Description of Metagonimus pusillus sp. nov. (Trematoda: Heterophyidae): phylogenetic relationships within the genus.

As a result of experimental studies conducted in the Russian southern Far East, adult worms from the genus Metagonimus were obtained. A comparative analysis of the morphometry of these worms with other Metagonimus representatives showed that they are most similar to M. katsuradai Izumi, 1935 and M. otsurui Shimazu & Urabe, 2002 found in Japan, due to the ratio of suckers and the positions of the testicle, uterus and vitellaria. However, Russian worms differ from species in Japan by other metric characters: they differ from M. otsurui by the maximum size of most organs and from M. katsuradai by body width, pharynx length, and maximum size of testes and ovary. At the same time, they are identical to a trematode from the Russian southern Far East, which was previously identified as M. katsuradai. The validity of this species was also confirmed by genetic data. According to the 28S gene and the internal transcribed spacer 2 (ITS2) region of rDNA, as well as the cytochrome c oxidase I (cox1) gene of mtDNA, the Metagonimus specimens found in Russia differ from published genetic data for other members of this genus. However, both morphological similarity and molecular data showed that M. pusillus sp. nov., M. katsuradai and M. otsurui are most likely cryptic species. Furthermore, additional data based on a mitochondrial marker were provided for M. suifunensis Shumenko, Tatonova & Besprozvannykh, 2017 from Russia.

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.

Morphological and molecular data for species of Lecithaster Lühe, 1901 and Hysterolecithoides Yamaguti, 1934 (Digenea: Lecithasteridae) from fish of East Asia and phylogenetic relationships within the Hemiuroidea Looss, 1899.

Four representatives of the genus Lecithaster and one representative of the genus Hysterolecithoides were found during investigation of the trematode fauna of fish species in Vietnamese, Japanese and eastern coastal waters of the Russian Far East. Based on morphometric data, adult trematodes from Vietnamese Strongylura strongylura and Russian Acanthogobius flavimanus were identified as Lecithaster confusus, trematodes from Vietnamese Hemirhamphus marginatus as L. sayori and from osmerid fishes as L. salmonis. Further, a single specimen of Lecithaster sp. and representatives of Hysterolecithoides epinepheli were found in Vietnamese Siganus fuscescens. Morphological and molecular data, including 18S ribosomal DNA (rDNA) V4 fragment, 28S rDNA D1-D3 fragment, internal transcribed spacers (ITS) and a mitochondrial COI gene fragment were analysed for Lecithaster spp. The results revealed that L. sayori and L. salmonis are not synonyms of L. stellatus and L. gibbosus, respectively, but that Hysterolecithoides frontilatus and H. guangdongensis are junior synonyms of H. epinepheli. The 28S-rDNA-based phylogenetic tree of Hemiuroidea showed a distinct position for the genus Lecithaster with internal differentiation into three subclades, including L. confusus, L. sayori and Lecithaster sp. within the first subclade, L. mugilis and L. sudzuhensis within the second subclade and L. salmonis and L. gibbosus within the third subclade. Bayesian phylogenetic reconstructions of Hemiuroidea showed four clades for members of Hemiuridae and Lecithasteridae. The first clade consisted of Hemiuridae representatives and the second clade represented the genus Lecithaster. The third clade included genera Aponurus and Lecithophyllum (Lecithasteridae) and the fourth clade combined members of lecithasterid Quadrifoliovariinae and Hysterolecithinae and hemiurid Opisthadeninae and Bunocotylidae with high statistical support.

Diplodiscus Mehrai Pande, 1937 and D. Japonicus (): Morphology of Developmental Stages and Molecular Data.

Specimens of the snails Anisus centrifugops were infected with two types of cercariae relating to the genus Diplodiscus, differing from each other by body and organ sizes were found in a pond in the territory of Vladivostok (Primorsky region, Russia). Further study of their morphology and life cycles allowed us to establish that these flukes belong to Diplodiscus japonicus (Yamaguti, 1936) and D. mehrai Pande, 1937. Morphological and molecular data confirmed the validity of D. japonicus which had previously been synonymized with D. amphichrus Tubangui, 1933 and D. mehrai Pande, 1937.

Genetic divergence of human pathogens Nanophyetus spp. (Trematoda: Troglotrematidae) on the opposite sides of the Pacific Rim.

Human and animal nanophyetiasis is caused by intestinal flukes belonging to the genus Nanophyetus distributed on both North American and Eurasian coasts of Northern Pacific. In spite of the wide geographical distribution and medical and veterinary importance of these flukes, the intra-generic taxonomy of Nanophyetus spp. remains unresolved. The two most widely distributed nominal species, Nanophyetus salmincola and Nanophyetus schikhobalowi, both parasitizing humans and carnivorous mammals, were described from North America and eastern Eurasia, respectively. However, due to their high morphological similarity their interrelationships remained unclear and taxonomic status unstable. In this study, we explored genetic diversity of Nanophyetus spp. from the Southern Russian Far East in comparison with that of samples from North America based on the sequence variation of the nuclear ribosomal gene family (18S, internal transcribed spacers, ITS1-5·8S-ITS2 and 28S). High levels of genetic divergence in each rDNA region (nucleotide substitutions, indels, alterations in the secondary structures of the ITS1 and ITS2 transcripts) as well as results of phylogenetic analysis provided strong support for the status of N. salmincola and N. schikhobalowi as independent species.

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.

Morphometric and molecular analyses of two digenean species in mugilid fish: Lecithaster mugilis Yamaguti, 1970 from Vietnam and L. sudzuhensis n. sp. from southern Russian Far East.

Adult Lecithaster mugilis Yamaguti, 1970 were found in Moolgarda seheli, Valamugil engeli and Liza subviridis in the coastal waters of Cat Ba Island (Halong Bay, Vietnam). Specimens of Lecithaster sudzuhensis n. sp. were found in Mugil cephalus located in an estuary of the Kievka River in the Primorsky region of Russia. Studies have demonstrated that these species share significant morphometric similarities with each other and with specimens of L. helodes Overstreet, 1973 isolated from M. cephalus and Mugil curema from the Mississippi Sound and adjacent waters. These three species differ from one another in the size of the pharynx and ventral sucker and in the ratio of suckers, while they differ from other species in the genus by having a relatively elongated oesophagus. Molecular analysis, using the 18S rRNA and 28S rRNA genes, confirmed the validity of L. mugilis and L. sudzuhensis n. sp. and demonstrated that these species form a shared cluster with L. gibbosus (Rud, 1802).

Morphometric and molecular data of the two digenean species Lasiotocus lizae Liu, 2002 (Monorchiidae) and Paucivitellosus vietnamensis sp. n. (Bivesiculidae) from mullet fish in Tonkin Bay, Vietnam.

Adults of Lasiotocus lizae Liu, 2002 (Monorchiidae) were found in the mullet Liza longimanus (Günther) from Tonkin Bay, near Cat Ba Island, Vietnam. In this region, flukes belonging to the genus Paucivitellosus (Bivesiculudae) were found in Liza subviridis (Valenciennes), Liza engeli (Bleeker) and Valamugil seheli (Forskåi). Results of investigations showed that morphological features of L. lizae (like L. glebulentus Overstreet, 1971) do not meet the criteria of the genus Lasiotocus. In addition, L. lizae is highly differentiated from other species of Lasiotocus from which molecular data were obtained, including L. arrhichostoma Searle, Cutmore et Cribb, 2014 and L. typicum (Nicoll, 1912). Phylogenetic analyses revealed that L. lizae differs considerably from other species of the genus Lasiotocus presented in the GenBank database. We have identified a new species of the genus Paucivitellosus - P. vietnamensis sp. n. - from L. subviridis, which differs from P. fragilis Coil, Reid et Kuntz, 1965 by metrical and molecular (18S rRNA) data, and from P. hanumanthai Mani, 1989 by metric features. Our results also show considerable molecular differentiation between P. vietnamensis sp. n. and Paucivitellosus spp. recovered from L. engeli and V. seheli in Vietnam.

Morphometric and molecular analyses of two digenean species from the mullet: Haplosplanchnus pachysomus (Eysenhardt, 1892) from Vietnam and Provitellotrema crenimugilis Pan, 1984 from the Russian southern Far East.

Adults of Haplosplanchnus pachysomus (Eysenhardt, 1829) were found in the intestine of Liza engeli (Bleeker) from the coastal waters of Cat Ba Island, Ha Long Bay, northern Vietnam. Additionally, Provitellotrema crenimugilis Pan, 1984 was discovered in Liza haematocheila (Temminck & Schlegel) from Vostok Bay, Gulf of Peter the Great, southern Far-East Russia. Data concerning morphology, 18S rDNA and 28S rDNA of these worms were obtained.The molecular data confirmed the validity of these species and showed that specimens identified as H. pachysomus are closely related to specimens of H. pachysomus found in Spain, and that P. crenimugilis is closely related to Haplosplanchnus purii. Molecular differentiation of P. crenimugilis and H. purii was 0.92% by combined ribosomal gene sequences that confirmed species validity. Molecular differentiation between P. crenimugilis and H. purii, on the one hand, and H. pachysomus, on the other hand, was much higher, suggesting that the sequence for H. purii in GenBank is for a misidentified species of the genus Provitellotrema Pan, 1984.

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.

[Nosoareas of clonorchiasis in the Primorye Territory].

The mammalian liver parasite (Clonorchis sinensis flukes) has spread in the Primorye Territory. The areas of the first intermediate hosts for the parasite mollusks of the genus Parafossarulus have been found to recently become wider south-western predominantly due to lotus acclimatization, resulting in the expansion of a parasite habitation area. The intensity of newly formed foci of clonorchiasis is an order of magnitude greater than that of natural ones and they are a higher hazard since they have formed in the recreation areas used by the population for rest and fishing. The carp is the second intermediate host of trematodes. Patients' medical history data show that European and crucian carps (less frequently skygazer, rudd, gudgeon, minnow) have served as the main sources of human infection with trematodes.

[Life cycle of the trematode Echinochasmus spinosus Odhner, 1911 (Echinostomatidae) in the natural conditions of Primorye].

Life cycle and developmental stages of the trematode Echinochasmus spinosus Odhner, 1911 are described. As it was established experimentally, in the conditions of Primorsky Krai circulation of the trematode involves first intermediate host, mollusk Parafossarulus spiridonovi, and the second one, freshwater fishes. Adult worms were reared in chicken.

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.

[Life cycles of trematodes Echinochasmus japonicus Tanabe, 1926 and E. beleocephalus (Linstow, 1873) (Echinostomatidae) in Prymorye Region].

Life cycles of two species of echinostomes Echinochasmus japonicus Tanabe, 1926 and E. beleocephalus (Linstow, 1873) have been studied. In Primorye region the first intermediate hosts E. japonicus are snails of genus Boreoelona, E. beleocephalus develops in Parafossarulus. Second intermediate hosts are freshwater fish and tadpole of frog Rana dubowskii. Encysted cercariae of E. beleocephalus also were found in tissue of first intermediate hosts. Experimental definitive host for both species were Gallus gallus dom. chickens.