Morphological and molecular characterization of Paraleptus chiloscyllii Yin & Zhang, 1983 (Nematoda: Physalopteridae) from the brownbanded bambooshark Chiloscyllium punctatum Müller & Henle (Elasmobranchii: Orectolobiformes).

Paraleptus (Spirurida: Physalopteridae) is a small genus of nematodes, parasitic in fishes, most species of which are inadequately described. Genetic data for these congeners have not been reported. The detailed morphology of P. chiloscyllii was studied using light and scanning electron microscopy, based on newly collected specimens from the brownbanded bambooshark C. punctatum Müller & Henle (Elasmobranchii: Orectolobiformes) in the Taiwan Strait. Some previously unreported morphological features of taxonomic significance were observed, i.e., pseudolabium with two sublateral rows of 6-7 small spines, 7-8 small spines on each lower rim between pseudolabia, deirids not distally bifurcated, vulva with remarkable protruding lip, presence of 1 pair medio-ventral precloacal papillae and 1 pair of discoid protrusions of postcloacal lip in male. The specimens described by González-Solís & Ali's (2015) as P. chiloscyllii from the Arabian carpetshark C. arabicum off Iraq are considered a new species, for which the name P. moraveci n. sp. is proposed. The genetic characterization of the partial small (18S) and large (28S) ribosomal DNA, and the partial mitochondrial cytochrome c oxidase subunit 1 (cox1) of P. chiloscyllii are provided for the first time. There was no intraspecific nucleotide divergence detected in the 18S and 28S regions among different individuals of P. chiloscyllii, but a low level of intraspecific genetic variation was found in the cox1 (0.62-0.92%). The present genetic data is very important for molecular identification, and will be valuable for further invertigantions on the population genetics and phylogeny of this group.

RICTULARIA JIYEONI N. SP. (NEMATODA: RICTULARIIDAE) FROM THE STRIPED FIELD MOUSE, APODEMUS AGRARIUS, IN KOREA.

Rictularia jiyeoni n. sp. from the small intestine of the striped field mouse, Apodemus agrarius, in Korea, is described and illustrated. Specimens were studied using light and scanning electron microscopies. This rictulariid nematode is closest to the Rictularia species that have a reduced number of combs and spines. However, the new species can be differentiated from the other species of Rictularia by having 36-58 perioral denticles, a buccal capsule with a single esophageal tooth, and 37-44 pairs of combs and spines of which 32-37 are prevulvar and 5-11 are postvulvar.

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.

Molecular Phylogeny of Thelastomatoidea (Nematoda) with the Description of a New Genus and Two New Species of Hystrignathidae Associated with Bess Beetles (Coleoptera: Passalidae) from Oaxaca, Mexico.

Bess beetles (Passalidae) display important roles in forestall ecosystems, particularly in energy extraction from dead wood. These organisms maintain complex biological interactions with their gut symbiotic communities, including bacteria, protists, and metazoans. Very little is known about symbionts since most of the species of Passalidae haven't been studied from a parasitological point of view. Here we describe a new genus and 2 new species of nematodes of the family Hystrignathidae associated with 2 beetle species of the tribe Proculini collected in the State of Oaxaca, Mexico. Tuhmai garciaprietoi n. gen., n. sp., found in Vindex agnoscendus is characterized by the presence of an unarmed cervical cuticle, a subcylindrical procorpus and a conspicuous isthmus, a monodelphic-prodelphic reproductive system, and a short subulate tail. Urbanonema osorioi n. sp., found in Verres hageni mainly differs from other species of Urbanonema by the number and disposition of cervical spines, as well as by a subulate tail. For each new taxon, we describe the external and internal morphology, and we generated molecular data (nuclear ribosomal DNA) to place the new taxa in a phylogenetic context.

Morphology and Molecular Characterization of Parabronema smithii (Cobbold, 1882) (Nematoda: Habronematidae) from Wild Asian Elephant (Elephas maximus maximus) of Sri Lanka.

PURPOSE: The aim of the present study was to carry out a detailed study of morphological features and to determine the phylogenetic position of Parabronema smithii (Cobbold, 1882) found in wild elephants in Sri Lanka. METHODS: Adult worms were collected from stomach ulcers at postmortem examination of wild elephants in the Udawalawe National Park, Sri Lanka. The detailed morphology of P. smithii was studied using light microscopy and, for the first time, scanning electron microscopy. Fifteen morphological characteristics were investigated. The phylogenetic analysis was conducted using the second internal transcribed spacer region (ITS2), and portions of the large subunit ribosomal DNA (28S) and cytochrome c oxidase subunit 1 (cox1). Furthermore, the present study provides a comparison of morphology and morphometrics of Parabronema species that occur in different hosts. CONCLUSION: Parabronema smithii isolated from wild elephants exhibited the key morphological features. Phylogenetic analysis of selected genes revealed that P. smithii is closely associated with P. skrjabini and Habronema spp. Findings of the present study enhance our understanding of the biology and taxonomy of P. smithii in wild elephant in Sri Lanka and will contribute to future phylogeographic studies.

A New Species of Triumphalisnema (Nematoda: Coronostomatoidea) Parasite of Proculejus hirtus (Coleoptera: Passalidae) from Mexico, and the Position of the Family in the Oxyuridomorpha.

A new species of the nematode Triumphalisnema Kloss, 1962 (Oxyuridomorpha), is described from the wood beetle Proculejus hirtus Truqui from the mountain mesophilic forest in Hidalgo State, Mexico. Triumphalisnema zuuei n. sp. is distinguished from the other 4 congeners species by the presence of an expanded cervical ring, well-developed lateral alae, an obtuse cauda with a short and bifurcated caudal appendage, series of cuticular folds at ventral and dorsal body surface from excretory pore level to anal region, and ellipsoidal eggs ornamented with numerous small mushroom-like structures over the surface. The phylogenetic position of the new species is inferred based on a Maximum Likelihood and Bayesian Inference analysis of partial sequences of 18S SSU rRNA. The phylogenetic analysis showed that Triumphalisnema zuuei n. sp., the only representative of the Traklosiidae in our study, is closely related to Coynema poeyi and species of Longior, Hystrignathus, and Lepidonema, all of them members of Hystrignathidae. These relationships are supported by high support values. The present study increases to 5 the number of species assigned to Triumphalisnema, all of them parasites of Passalidae. Additionally, a taxonomic key to the species of the genus is provided.

Additional Morphological Features and Molecular Data of Paracamallanus cyathopharynx (Nematoda: Camallanidae) Infecting Clarias gariepinus (Actinopterygii: Clariidae) in Kenya.

This study provides additional taxonomic features based on scanning electron microscopy (SEM) and molecular data for Paracamallanus cyathopharynx ( Baylis, 1923 ) (Nematoda: Camallanidae). Parasites were collected from the posterior end of the intestine of cultured freshwater Sharptooth catfish Clarias gariepinus (Burchell, 1822) from Kibos fish farm, Kisumu County, Kenya, from December 2017 to March 2018. Additional taxonomic features recorded for P. cyathopharynx include the occurrence of 4-5 equal length digitate processes on the caudal end of the female, 4 processes (2 smaller and 2 larger) on the male caudal end, and a description of the shape of the distal tip of the right spicule. The study provides SEM images of the exposed sclerotized buccal capsule. This gives more information on the tridents, the sclerotized plate that extends laterally from the buccal capsule, and the narrow isthmus separating the anterior buccal capsule from the posterior. The prevalence, intensity, mean intensity, and mean abundance was 52.91%, 2-38, 12.37 and 6.54, respectively. 18S rDNA fragments were amplified, sequenced, and compared to other camallanid taxa, and 18S data confirmed the identity of the newly obtained sequences (MN396556) as that of P. cyathopharynx, being identical to sequence DQ813445 from Tanzania. This represents the first geographical record of P. cyathopharynx in Kenya.

First record of the nematode Echinocephalus pseudouncinatus (Gnathostomatidae, Spirurida) in an edible, commercial host, the pen shell Atrina maura (Bivalvia: Pinnidae).

We describe a nematode infestation of the Atrina maura, the most valuable pen shell fished in Mexico, for the first time. Observations by Mexican authorities indicated that parasites were found encysted in pen shell gonads. The aims of this study included: (i) to identify the parasite morphologically; (ii) to quantify the infestation in different tissues of the pen shell; and (iii) to establish the seasonal variation in gonadal development. During 2015, 10 to 40 pen shells were randomly collected each month from the same commercial bed, and gonads were preserved and processed histologically to establish the seasonal and monthly frequency of infested gonads. A subsample of 35 pen shells was used to identify the parasite and to characterize the infestation of the muscle, mantle, gonad, and digestive gland tissue components. All tissues were dissected, and parasites were collected, photographed, quantified, and adequately preserved for species identification using scanning electron microscopy. Prevalence, intensity of infestation, abundance and crowding data were analyzed by Quantitative Parasitology software and compared monthly and seasonally using a chi test and analysis of means. Results indicated that all parasites were juvenile (second stage) nematodes, Echinocephalus pseudouncinatus. Parasites were found only in muscle and gonad tissues in both male and female pen shells. Hyperpigmentation was observed in the muscle and atretic oocytes with phagocytosis in the gonads. The frequency of infested gonads was significantly higher during winter but was not related to shell size or sex (p > 0.05). A greater number of pen shells were observed to be infested during December and August and during pen shell spawning and development stages. The highest frequency of infested gonads (40%) occurred in December when the lowest temperature and chlorophyll a concentration were recorded. The effects of the biotic and abiotic parameters on this host-pathogen relationship need further research. This nematode species is related to species that are causal agents of gnathostomiasis, which may constitute a health hazard for raw muscle consumers and could affect the reproductive activity of pen shell.

Redescription of Dichelyne ( Cucullanellus) Dichelyneformis (Nematoda: Cucullanidae) and Description of a New Congeneric Species in Eleginops maclovinus (Pisces: Eleginopsidae) Collected in the Bay of Corral, Chile.

Dichelyne ( Cucullanellus) dichelyneformis ( Szidat, 1950 ) Petter, 1974 , was collected in the intestine of the rock cod, Eleginops maclovinus, in the Bay of Corral, Chile, and redescribed based on light and scanning electron microscopy. The correct arrangement of caudal papillae and post deirids, the shape of gubernaculum, and the morphology and number of denticles surrounding the oral opening are described for the first time. These characteristics along with the excretory pore position, size of spicules, and presence of a nodular thickening near the distal end of the spicules differentiate D. ( C.) dichelyneformis from the other congeners reported in South America and in the Antarctic. The new congeneric species found in E. maclovinus differs from D. ( C.) dichelyneformis based on the larger males, larger and more numerous denticles with a smooth surface, weakly developed sclerotized plates in esophastome, excretory pore and deirids posterior to nerve ring, shorter gubernaculum and spicules with no thickening on their distal region, lower spicules/body length ratio (10.4-15.1%), and a papilla-like phasmids closer to pairs 8 and 10.

A new species of Orientatractis (Nematoda: Atractidae) from the tortoise Indotestudo elongata (Blyth) in China.

A new species of nematode, Orientatractis longicaudata n. sp. is described from the intestine of Indotestudo elongata (Blyth) (Testudinidae) from Zoo of Tianjin, Tianjin, China. The new species can be easily distinguished from its congers by having longer tail, by the length of gubernaculum and left spicule, and by the numbers of caudal papillae. This is first species of Orientatractis Petter, 1966 reported in China. A key to the species of Orientatractis is provided.

Redescription of Dichelyne (Cucullanellus) jialaris (Nematoda: Cucullanidae), a parasite of seabreams (Perciformes: Sparidae) in East Asia.

An insufficiently known nematode species Dichelyne (Cucullanellus) jialaris Luo, Guo, Fang et Huang, 2004 (Cucullanidae), originally described from the red seabream Pagrus major (Temminck et Schlegel) (Sparidae) in the Taiwan Strait, off China, is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the intestine of three species of sparid fishes, Acanthopagrus schlegelii (Bleeker), Evynnis tumifrons (Temminck et Schlegel) and P. major, in Hiroshima Bay, Japan. The present redescription provides exact data on the cephalic structure, character of cephalic papillae and amphids, location of the excretory pore, deirids and phasmids, and the number and distribution of caudal papillae in the male; the presence of the dorsal postdeirid in this species is reported for the first time. The SEM study revealed that the anterior cloacal lip has a median lobe-like elevation bearing two minute papillae, whereas the posterior cloacal lip is somewhat depressed, with a median longitudinal rod-like elevation probably serving to direct the movement of spicules. The size of eggs is reported for the first time. Dichelyne (C.) jialaris differs from the morphologically similar D. (C.) pleuronectidis (Yamaguti, 1935) mainly in the shape of the oesophagus. The present finding of D. (C.) jialaris represents the first record of this nematode from fishes in Japanese waters and A. schlegelii and E. tumifrons are its new host records.

A New Rictulariid (Nematoda: Spirurida) in Xenarthrans from Argentina and New Morphological Data of Pterygodermatites ( Paucipectines) Chaetophracti.

Pterygodermatites is a cosmopolitan genus of nematodes from mammals, and it is frequently encountered in the parasite fauna of armadillos (Mammalia, Xenarthra, Cingulata). In this work, a new species, Pterygodermatites ( Paucipectines) argentinensis, is described, and new morphometric data, new host records, and the geographical distribution of Pterygodermatites ( Paucipectines) chaetophracti are provided. We examined 109 hosts belonging to Chaetophractus vellerosus, Chaetophractus villosus, Cabassous chacoensis, Dasypus hybridus, Tolypeutes matacus, and Zaedyus pichiy, from several regions of Argentina. Pterygodermatites ( Paucipectines) argentinensis can be distinguished from P. ( P.) chaetophracti by the morphology and size of esophageal teeth of both sexes, by subequal and longer spicules, by having only 1 precloacal cuticular semicircular fan in males, and by a greater number of cuticular processes in females. Cabassous chacoensis and Zaedyus pichiy are new hosts for Pterygodermatites ( P.) chaetophracti.

Morphological and molecular characterisation of Heliconema hainanensis sp. nov. (Spirurina: Physalopteridae) from congers in the South China Sea, with a key to the species of Heliconema.

Heliconema hainanensis sp. nov. collected from Uroconger lepturus (Richardson) (Anguilliformes: Congridae), Muraenesox cinereus (Forsskål) and Congresox talabonoides (Bleeker) (Anguilliformes: Muraenesocidae) in the South China Sea was described using light and scanning electron microscopy. The new species differs from its congeners by the following morphology: pseudolabia, the number and arrangement of caudal papillae (4 pairs of pedunculate precloacal papillae arranged in 2 groups of 2 and 2 pairs and 6 pairs of pedunculate postcloacal papillae arranged in 4 groups of 1, 2, 1 and 2 pairs), the length of spicules [left spicule 0.51-0.69 mm, right spicule 0.20-0.27 mm, spicule (right:left) ratio 1:2.20-2.69] and the morphology of the female tail tip. In addition, specimens of the new species collected from the three different hosts and specimens of an unidentified species of Heliconema collected from U. lepturus were characterised using molecular methods by sequencing the internal transcribed spacer (ITS) of ribosomal DNA. Analyses and comparison of the ITS sequence of H. hainanensis sp. nov. with Heliconema sp. support the validity of the new species based on morphological observations. An identification key to the species of Heliconema is also provided.

Morphological and molecular characterisation of Heliconema hainanensis sp. nov. (Spirurina: Physalopteridae) from congers in the South China Sea, with a key to the species of Heliconema

Heliconema hainanensis sp. nov. collected from Uroconger lepturus (Richardson) (Anguilliformes: Congridae), Muraenesox cinereus (Forsskål) and Congresox talabonoides (Bleeker) (Anguilliformes: Muraenesocidae) in the South China Sea was described using light and scanning electron microscopy. The new species differs from its congeners by the following morphology: pseudolabia, the number and arrangement of caudal papillae (4 pairs of pedunculate precloacal papillae arranged in 2 groups of 2 and 2 pairs and 6 pairs of pedunculate postcloacal papillae arranged in 4 groups of 1, 2, 1 and 2 pairs), the length of spicules [left spicule 0.51-0.69 mm, right spicule 0.20-0.27 mm, spicule (right:left) ratio 1:2.20-2.69] and the morphology of the female tail tip. In addition, specimens of the new species collected from the three different hosts and specimens of an unidentified species of Heliconema collected from U. lepturus were characterised using molecular methods by sequencing the internal transcribed spacer (ITS) of ribosomal DNA. Analyses and comparison of the ITS sequence of H. hainanensis sp. nov. with Heliconema sp. support the validity of the new species based on morphological observations. An identification key to the species of Heliconema is also provided.

Echinocephalus janzeni n. sp. (Nematoda: Gnathostomatidae) in Himantura pacifica (Chondrichthyes: Myliobatiformes) from the Pacific coast of Costa Rica and Mexico, with historical biogeographic analysis of the genus.

Echinocephalus janzeni n. sp. in the stingray, Himantura pacifica, is described from the eastern Pacific Ocean off the coasts of Costa Rica and southern Mexico. On the basis of the presence of 6 postanal caudal papillae, and modified annules anterior to the caudal alae in males, E. janzeni is most similar to Echinocephalus daileyi and Echinocephalus diazi. Specimens of E. janzeni are distinguished from those of E. daileyi by bilobed caudal alae and long cervical sacs that extend up to 65% of the length of the esophagus; E. janzeni is differentiated from E. diazi by the number of rows of cephalic spines (30-38 vs. 26-27), arrangement of the postanal caudal papillae, 3 rather than 2 preanal papillae, relative position and distance between the anus and vulva (395-460 microm vs. 70 microm), the digitiform female tail with a terminal cuticular fold, and the length of the female tail (450-480 microm vs. 270 microm). Cladistic analysis of the 10 Echinocephalus spp. resulted in a single most parsimonious tree (consistency index=0.893) and placed E. janzeni in a highly derived subclade where E. daileyi is the sister species of E. diazi + E. janzeni. Historical biogeographic analysis of hosts and parasites provides support for origins in the Pacific rather than the Atlantic for the potamotrygonid stingrays.