Morphological and molecular characterization of Ceratomyxa binhthuanensis n. sp. (Myxosporea: Ceratomyxidae) from the gall bladder of blacktip grouper Epinephelus fasciatus (Perciformes: Serranidae) in the East Sea of Vietnam

A new myxozoan species, Ceratomyxa binhthuanensis n. sp. (Myxosporea: Ceratomyxidae), was found in the gall bladder of blacktip grouper Epinephelus fasciatus (Perciformes: Serranidae) in the East Sea of Vietnam. Myxospores were observed floating free in the gall bladder of 3 out of 20 fish examined (15%). Mature myxospores were elongate and slightly crescent-shaped and measured 12.2 ± 1.3 (10.8-16.0) μm in thickness and 5.8 ± 0.6 (4.8-6.9) μm in length, with two smooth equal shell valves. The two polar capsules were spherical and equal in size, measuring 2.6 ± 0.3 (2.3-2.9) μm in diameter. The posterior angle was slightly concave, 153.7° ± 5.6° (148.9°-166.0°). Molecular analysis of SSU rDNA sequence showed that Ceratomyxa binhthuanensis n. sp. differs from other Ceratomyxa spp. available in GenBank. Phylogenetic analysis indicated that C. binhthuanensis n. sp. was closely related to three species, Ceratomyxa nolani, Ceratomyxa yokoyamai, and Ceratomyxa cutmorei, which also infect fish hosts of the genus Epinephelus.

Description and Molecular Differentiation of a New Skrjabinoptera (Nematode: Physalopteridae) from Eutropis macularia (Sauria: Scincidae) in North-Central Vietnam

Skrjabinoptera vietnamensis n. sp. is described from specimens recovered from the stomach of Eutropis macularia in north-central Vietnam. The new species is characterized by the medium-sized male worms (6.7-8.7 mm in length and 154-182 μm in width) relative to known members of the genus, 2 pointed spicules of unequal length (87-112 μm and 56-72 μm in length), and 10 pairs of caudal papillae. Female worms are larger than male worms (10.7-18.4 mm in length and 264-411 μm in width), with the vulva situated in the anterior part, and embryonated, elliptical eggs, 35-46 μm long by 20-24 μm wide. Skrjabinoptera vietnamensis n. sp. represents the ninth species assigned to the genus and the first species recorded from the Oriental region. Partial sequences of the 18S ribosomal RNA gene (rDNA), and cytochrome c oxidase subunit 1 (COI) are provided for the new species. The molecular phylogenetic position of the genus Skrjabinoptera is briefly discussed.

Description and Molecular Differentiation of a New Falcaustra (Nematode: Kathlaniidae) from the Indochinese Water Dragon, Physignathus cocincinus (Squamata: Agamidae) in North-central Vietnam

Falcaustra vietnamensis n. sp. is described from the small intestine of Physignathus cocincinus from north-central Vietnam. The new species is characterized by the large male worms (20.2-28.8 mm in length and 557-724 μm in width) relative to known members of the genus, 2 sharply pointed alate spicules of equal length (1,128-1,256 μm in length), gubernaculum including 2 separate pieces, 1 ventral with a pointed distal end and 1 dorsal with a blunt distal end (164-192 μm and 155-172 μm in length, respectively), and 12 pairs of caudal papillae. Female worms are larger than male worms (24.2-34.1 mm in length and 532-735 μm in width), with the vulva situated in the posterior half of body, and elliptical eggs, 60-70 μm long by 42-47 μm wide. Falcaustra vietnamensis n. sp. represents the 38th species assigned to the genus and the third species recorded from a lizard host in the Oriental biogeographical region. Partial sequences of the 18S ribosomal RNA gene (rDNA), internal transcribed spacer regions (ITS), and cytochrome c oxidase subunit 1 (COI) are provided for the new species. The molecular phylogenetic position of the genus Falcaustra is briefly discussed.

Morphological and Molecular Description of Rhadinorhynchus hiansi Soota and Bhattacharya, 1981 (Acanthocephala: Rhadinorhynchidae) from Marine Fish off the Pacific Coast of Vietnam

Rhadinorhynchus hiansi Soota and Bhattacharya, 1981 , has remained unknown since its original incomplete description from 2 male specimens collected from the flat needlefish Ablennes hians Valenciennes (Belonidae) off Trivandrum, Kerala, India. Recent collections of fishes along the Pacific coast of Vietnam in 2016 and 2017 produced many specimens of the same species from the striped bonito Sarda orientalis Temminck and Schlegel (Scombridae) off the southern Pacific coast of Vietnam at Nha Trang. We describe females for the first time, assign a female allotype status, and provide an expanded description of males from a larger collection completing missing information on hooks and hook roots, receptacle, lemnisci, cement glands, Saefftigen's pouch, and trunk spines. Specimens of R. hiansi characteristically have no dorsal spines in the posterior field of trunk spines and a long proboscis with 36-48 dorso-ventrally differentiated proboscis hooks per row becoming progressively smaller posteriorly then increasing in size near the posterior end to a maximum at the posterior-most ring. Trunk, testes, and lemnisci in our specimens were considerably larger than those reported in the original description, but the proboscis was relatively smaller. The females had long reproductive system and corrugated elliptic eggs without polar prolongation of fertilization membrane. Energy Dispersive X-ray Analysis (EDXA) demonstrates high levels of calcium and phosphorus in large gallium cut hooks and high levels of sulfur in tip cuts of large and small hooks and in spines. This EDXA pattern is a characteristic fingerprint of R. hiansi. The molecular profile of R. hiansi is described from 18S rDNA and COI genes, and phylogenetic relationships with most closely related species are discussed.

Morphological and molecular description of Rhadinorhynchus laterospinosus Amin, Heckmann & Ha, 2011 (Acanthocephala, Rhadinorhynchidae) from marine fish off the Pacific coast of Vietnam

Rhadinorhynchus laterospinosus Amin, Heckmann & Ha, 2011 (Rhadinorhynchidae) was described from a single female collected from a trigger fish, Balistes sp. (Balistidae) from the northern Pacific coast of Vietnam in Halong Bay, Gulf of Tonkin. More recent collections of fishes in 2016 and 2017 revealed wider host and geographical distributions. We report this Acanthocephala from nine species of fish representing six families (including the original record from Balistes sp.) along the whole Pacific coast of Vietnam. The fish species are Alectis ciliaris (Carangidae), Auxis rochei (Scombridae), Auxis thazard (Scombridae), Leiognathus equulus (Leiognathidae), Lutjanus bitaeniatus (Lutjanidae), Megalaspis cordyla (Carangidae), Nuchequula flavaxilla (Leiognathidae), and Tylosurus sp. (Belonidae). We provide a complete description of males and females of R. laterospinosus, discuss its hook metal microanalysis using EDAX, and its micropores. Specimens of this species characteristically have lateral trunk spines bridging the anterior ring of spines with posterior field of ventral spines and a proboscis with 15–19 longitudinal alternating rows of 21–26 hooks each varying with host species. We demonstrate the effect of host species on the distribution and size of the trunk, proboscis, proboscis hooks, trunk spines, and reproductive structures. The molecular profile of this acanthocephalan, based on 18S rDNA and cox1 genes, groups with other Rhadinorhynchus species and further seems to confirm the paraphyly of the genus, which is discussed.

Descriptions of two new acanthocephalans (Rhadinorhynchidae) from marine fish off the Pacific coast of Vietnam

Two rhadinorhynchid acanthocephalans are described from marine fishes off the Pacific coast of Vietnam. Sclerocollum neorubrimaris n. sp. (Gorgorhynchinae Van Cleave & Lincicome, 1940) is described from the spine-foot rabbitfish Siganus guttatus (Bloch) (Siganidae) off Nha Trang. The new species is similar to the type-species, Sclerocollum rubrimaris Schmidt & Paperna, 1978 in most measurements and counts but has a posterior cephalic ganglion, a sub-ventral female gonopore, and one dorsal paravaginal filament bundle. In S. rubrimaris, the cephalic ganglion is near the middle of the receptacle, the female gonopore is terminal with two paravaginal filament bundles. The new species is distinguished from three other species of Sclerocollum Schmidt & Paperna, 1978 in proboscis hook formulas and the position of the female gonopore and cephalic ganglion. The issue of the importance of the position of the cephalic ganglion at the generic and sub-generic levels in the Acanthocephala is discussed. Females of Australorhynchus multispinosus n. sp. (Gorgorhynchinae) are described from the red cornetfish Fistularia petimba Lacépède off Nha Trang in the Pacific south. It is distinguished from the only other species of the genus, Australorhynchus tetramorphacanthus Lebedev, 1967, by having more trunk spines extending beyond the level of the proboscis receptacle and a smaller proboscis with considerably fewer hooks.

Descriptions of Acanthocephalus parallelcementglandatus (Echinorhynchidae) and Neoechinorhynchus (N.) pennahia (Neoechinorhynchidae) (Acanthocephala) from amphibians and fish in Central and Pacific coast of Vietnam, with notes on N. (N.) longnucleatus

Three species of acanthocephalans are described from fishes caught in the Pacific coast off eastern Vietnam and from amphibians in the midlands in 2016: (1) Acanthocephalus parallelcementglandatus Amin, Heckmann, Ha, 2014 (Echinorhynchidae), described from 1 male specimen is now fully described from males and females collected from 2 species of amphibians, the similar frog Hylarana attigua Inger, Orlov, Darevsky and the odorous frog Odorrana sp. Fei, Ye, Huang (Ranidae) in Huong Thuy, Hue City and Chu Yang Sin Park, central Vietnam, respectively, as well as from the needlefish Tylosurus sp. Cocco (Belonidae) in Binh Thuân in the Pacific South. The allotype female is designated. Neoechinorhynchus (N.) pennahia Amin, Ha, Ha, 2011 described from 1 female specimen is now fully described from males and females collected from the Toli shad (Chinese herring), Tenualosa toli (Valenciennes) (Clupeidae) in the Pacific north coast off Haiphong. The allotype male is designated. One specimen of Neoechinorhynchus (Neoechinorhynchus) longnucleatus Amin, Ha, Ha, 2011 is also reported from the common ponyfish, Leiognathus equulus (Forssskål) (Leiognathidae) in the Pacific south coast of Nha Trang and its ecology briefly discussed.

Descriptions of acanthocephalans, Cathayacanthus spinitruncatus (Rhadinorhynchidae) male and Pararhadinorhynchus magnus n. sp. (Diplosentidae), from marine fish of Vietnam, with notes on Heterosentis holospinus (Arhythmacanthidae)

Males of Cathayacanthus spinitruncatus Amin, Heckmann & Ha, 2014 (Rhadinorhynchinae Lühe, 1912) are described for the first time from Leiognathus equulus in Hai Phong and Nha Trang and from pony fish Nuchequula flavaxilla in Quang Ninh in the Pacific waters of Vietnam. The male allotype status is designated. Males of C. spinitruncatus are smaller and have fewer and smaller proboscis hooks and trunk spines than females. The male reproductive structures are in the posterior fifth of the trunk and with 6 club-shaped cement glands gradually merging into 6 independent cement gland ducts. The proboscis receptacle is more than half as long as the trunk and with a cephalic ganglion at its anterior end. In females, the receptacle is only about one fifth the length of the trunk. Specimens described as Cathayacanthus bagarii Moravec & Sey, 1989 were shown to have been wrongly assigned to Cathayacanthus. Pararhadinorhynchus magnus n. sp. (Diplosentidae) is described from Scatophagus argus off Hai Phong in the Gulf of Tonkin. It is the third species of the genus and is readily distinguished from the Australian species by having a considerably larger trunk and male reproductive structures, and more proboscis hooks. X-ray microanalysis (EDAX) of intact and gallium-cut hooks of P. magnus showed high calcium and phosphate mainly in the central core. Specimens of Heterosentis holospinus Amin, Heckmann & Ha, 2011 (Arhythmacanthidae) are also reported from L. equulus off Quang Binh, new host and locality records.

Descriptions of Neorhadinorhynchus nudum (Cavisomidae) and Heterosentis paraholospinus N. SP. (Arhythmacanthidae) (Acanthocephala) From Fish Along the Pacific Coast of Vietnam, With Notes On Biogeography

Two species of acanthocephalans are described from fishes caught along the Pacific coast off eastern Vietnam in 2016: (1) Neorhadinorhynchus nudum ( Harada, 1938 ) Yamaguti, 1939 (Cavisomidae) from the frigate tuna Auxis thazard (Lacépède) (Scombridae) in Nha Trang, Pacific south Vietnam, and (2) Heterosentis paraholospinus n. sp. (Arhythmacanthidae) from 3 species of fish: the common ponyfish Leiognathus equulus (Forsskål) (Leiognathidae) and the torpedo scad Megalaspis cordyla (Linn.) (Carangidae) off Nha Trang and Binh Thuân, respectively, and the yellowspotted ponyfish Nuchequula flavaxilla Kimura, Kimura, and Ikejima (Leiognathidae) at Quang Ninh in Pacific waters of Vietnam. Females of N. nudum are fully described for the first time in the Pacific Ocean. Heterosentis paraholospinus n. sp. is similar to Heterosentis holospinus Amin, Heckmann, and Ha, 2011, in having an unspined anterior trunk cone, nucleated pouch at the posterior end of the receptacle, and spines covering the entire trunk, but it differs in having a long cylindrical trunk, lemnisci much longer than the receptacle, more and different-sized proboscis hooks, and subterminal female gonopore. Biogeographical notes are discussed for both genera.

Phylogenetic relationships of Hemiuridae (Digenea: Hemiuroidea) with new morphometric and molecular data of Aphanurus mugilis Tang, 1981 (Aphanurinae) from mullet fish of Vietnam

Adult Aphanurus mugilis Tang, 1981 worms were detected in the intestine of Moolgarda engeli in the shallow waters off Cat Ba Island, Vietnam. Tang (1981) first described this species in Mugil cephalus off China. The worms in Vietnamese mullet were identical to Chinese specimens in a number of morphometric characteristics, with the exception of body and ovary size. In the present study, morphological characteristics, and the first molecular data for A. mugilis are provided. Additionally, molecular phylogenetic analysis of the family Hemiuridae was performed. The results of our molecular phylogenetic study indicate that the presence or absence of an ecsoma was not associated with molecular data for hemiurid subfamilies differentiation. The basal position of Bunocotylinae on the molecular-based phylogenetic tree indicated a primordial nature of ecsoma of hemiurid trematodes. Considerable molecular differentiation of Bunocotylinae from other hemiurids indicated the possibility of the recognition of the family Bunocotylidae Dollfus, 1950. Assuming that Machidatrema chilostoma is considered within the Bunocotylinae, the paraphyly of the Lecithasterinae was supported.

Real-time PCR detection and phylogenetic relationships of Neorickettsia spp. in digeneans from Egypt, Philippines, Thailand, Vietnam and the United States

Neorickettsia (Rickettsiales, Anaplasmataceae) is a genus of obligate intracellular bacterial endosymbionts of digeneans (Platyhelminthes, Digenea). Some Neorickettsia are able to invade cells of the digenean's vertebrate host and are known to cause diseases of domestic animals, wildlife, and humans. In this study we report the results of screening digenean samples for Neorickettsia collected from bats in Egypt and Mindoro Island, Philippines, snails and fishes from Thailand, and fishes from Vietnam and the USA. Neorickettsia were detected using a real-time PCR protocol targeting a 152bp fragment of the heat shock protein coding gene, GroEL, and verified with nested PCR and sequencing of a 1853bp long region of the GroESL operon and a 1371bp long region of 16S rRNA. Eight unique genotypes of Neorickettsia were obtained from digenean samples. Neorickettsia sp. 8 obtained from Lecithodendrium sp. from Egypt; Neorickettsia sp. 9 and 10 obtained from two species of Paralecithodendrium from Mindoro, Philippines; Neorickettsia sp. 11 from Lecithodendrium sp. and Neorickettsia sp. 4 (previously identified from Saccocoelioides lizae, from China) from Thailand; Neorickettsia sp. 12 from Dicrogaster sp. Florida, USA; Neorickettsia sp. 13 and SF agent from Vietnam. Sequence comparison and phylogenetic analysis demonstrated that the forms, provisionally named Neorickettsia sp. 8-13, represent new genotypes. We have for the first time detected Neorickettsia in a digenean from Egypt (and the African continent as a whole), the Philippines, Thailand and Vietnam based on PCR and sequencing evidence. Our findings suggest that further surveys from the African continent, SE Asia, and island countries are likely to reveal new Neorickettsia lineages as well as new digenean host associations.

[Molecular genetic characterization of the Far Eastern trematode Skrjabino lecithum spasskii Belous, 1954 (Digenea: Haploporidae)), a parasite of mullets]

Intraspecific genetic differentiation of the trematode Skrjabinolecithum spasskii and its phylogenetic relationships with other species of the family Haploporidae were studied by comparing the nucleotide sequences of a part of the 28S rRNA gene and the ITS1-5.8S-ITS2 rDNA region. Trematodes were isolated from so-iuy mullet Liza haematocheila fishes collected in rivers of Primorye and flathead grey mullet Mugil cephalus fishes collected in water bodies of Vietnam (27 fishes in total). A phylogenetic analysis showed that S. spasskii is close to species of the genus Capitimitta of the subfamily Waretrematinae. By intraspecific variation of rDNA sequences, trematodes were divided into three groups with tree different genotypes, which had fixed nucleotide substitutions. Genotype I was found in trematodes from fishes collected in Primorye. Genotype II was detected in trematodes from M. cephalus fishes collected in the Tonkin Bay, Cat Ba Island, Vietnam. Genotype III was found in five trematodes from L. haematocheila collected in the Kievka River, Primorye. The genetic distances between genotypes I and III from Primorye were 0.4 and 0.65% by 28S and ITS rDNA sequences, respectively. The lowest genetic distances were observed between genotypes II (Vietnam) and III (Primorye), 0.1 and 0.33% by 28S and ITS rDNA sequences, respectively. Possible causes of genetic differentiation of S. spasskii from different geographic locations and different definitive host species are discussed.

Current status of fish-borne zoonotic trematode infections in Gia Vien district, Ninh Binh province, Vietnam

BACKGROUND

Ninh Binh province is known as an endemic area of fish-borne zoonotic trematode (FZT) transmission in Vietnam. A cross-sectional study was conducted in Gia Minh and Gia Thinh communes of Gia Vien district, Ninh Binh province to investigate the infections with different stages of FZT in various host species.

METHODS

Faecal samples from 1,857 humans were examined for trematode eggs using the Kato-Katz method, while faecal samples from 104 dogs, 100 cats, and 100 pigs were examined using the Formalin-ethyl acetate concentration technique (FECT). A total of 483 specimens of freshwater fish, representing 9 species, were examined for metacercariae using the artificial digestion method. Three methods of cercarial detection (shedding, crushing and cutting) were applied for examination of 3,972 specimens of freshwater snails, representing 7 species. All relevant data e.g. location, sex, age group, animal species, and habitat were recorded for statistical analyses.

RESULTS

Helminth eggs were found in 65.5% of the human faecal samples, including 20.5% of faecal samples containing small trematode eggs. Infection with small trematodes differed among communes, age groups and sexes. Eggs of small trematodes were found in 32.7% of faecal samples from dogs, 49.0% from cats and 13.0% from pigs. The difference in prevalences and intensities were significant among species of animals but did not differ between the two communes. All fish species were infected with FZT, with an average prevalence of 56.1% and a mean intensity of 33.245 metacercariae per gram. Prevalence and intensity in fish differed significantly among cummunes and fish groups. Six species of zoonotic trematodes were identified. Metacercariae of the small liver fluke, Clonorchis sinensis, was only found in Hemiculter leucisculus. A total of 9 specimens from two snail species, Melanoides tuberculata and Bithynia fuchsiana, were infected with trematodes and four cercarial types were detected in the study sites.

CONCLUSIONS

We conclude that Gia Minh and Gia Thinh communes are continuing to be hot-spot endemic areas of FZT and other helminths infections where the habit of eating raw fish by the local people is still present.

Acanthocephalans from fishes and amphibians in Vietnam, with descriptions of five new species

Eight species of acanthocephalans are reported, and five are new. Specimens of Neoechinorhynchus (Hebesoma) manubrianus Amin, Ha & Ha, 2011 were similar to the original description. Neoechinorhynchus (Hebesoma) spiramuscularis n. sp. (Neoechinorhynchidae), from Xenocypris davidi, has a unique proboscis receptacle wrapped in a spiral muscular layer, and an undulating flask-shaped lemnisci, as well as double para-receptacle structures. Heterosentis mongcai n. sp. (Arhythmacanthidae), from Acreichthys sp., has a small fusiform trunk with an unarmed cone and anterior trunk spines, and a proboscis with two circles of rooted apical hooks and 3-4 circles of rooted posterior spines as well as a para-receptacle-like structure at the posterior end. The poorly known Filisoma indicum Van Cleave, 1928 is fully described and illustrated for the first time. Acanthocephalus parallelcementglandatus n. sp. (Echinorhynchidae), from Clarias batrachus, is distinguished from other species of Acanthocephalus by its small fusiform trunk and parallel tubular cement glands. Pseudoacanthocephalus coniformis n. sp. (Echinorhynchidae), from Hylarana sp., is distinguished from other species by having an anterior trunk collar and staggered prominent filiform cement glands, among other features. Cathayacanthus spinitruncatus n. sp. (Rhadinorhynchidae), from Leiognathus equulus, is distinguished from the only two known species of the genus by having a very long and slender proboscis with more than 50 hooks per row and a totally spined trunk. The generic diagnosis of Cathayacanthus Golvan, 1969 is emended. Rhadinorhynchus johnstoni Golvan, 1969 (Rhadinorhynchidae) perfectly fits the only complete description of that species from the Fiji Islands.

First report of Neoechinorhynchus (Acanthocephala: Neoechinorhynchidae) from marine fish of the eastern seaboard of Vietnam, with the description of six new species

The occurrence of acanthocephalans of the genus Neoechinorhynchus Stiles and Hassall, 1905 in Vietnamese waters is reported for the first time. Six new species are described from seven species of marine fish of the families Belonidae, Clupeidae, Megalopidae, Mugilidae, and Sciaenidae, collected in Halong Bay of the eastern seaboard of Vietnam in 2008 and 2009. These are Neoechinorhynchus (Neoechinorhynchus) plaquensis n. sp. characterized by dermal plaques covering the entire trunk; Neoechinorhynchus manubriensis n. sp. with very long anterior proboscis hooks having roots with prominent anterior manubria and very small and equal middle and posterior hooks, two pseudo-retractors in the receptacle, simple vagina, and terminal gonopore; Neoechinorhynchus pennahia n. sp. with equal anterior and middle proboscis and somewhat smaller posterior hooks, and terminal female gonopore; Neoechinorhynchus ampullata with many giant nuclei in the body wall and lemnisci and a parareceptacle structure complex which includes pumping ampullas reported for the first time; Neoechinorhynchus (Neoechinorhynchus) longinucleatus n. sp. with very long giant nuclei in the Lemnisci, anteriorly twisted vagina, and subterminal female gonopore. Neoechinorhynchus (Neoechinorhynchus) ascus n. sp. is the second species of Neoechinorhynchus found with the parareceptacle structure/ampulla complex. Neoechinorhynchus (Neoechinorhynchus) johnii Yamaguti, 1929 of Bilqees, 1972 is not N. johnii because of proboscis armature and other discrepancies with the Yamaguti material. Notes on host distribution and feeding habits are also included.