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Dirofilaria (Nochtiella) tenuis is a mosquito-borne subcutaneous parasite of raccoons, regarded as the causative agent of most human dirofilarial infections in North America. Despite the wide geographic range of raccoons in the Americas, the presence of this parasite has not been confirmed outside its known endemic areas in the Southern United States. Based on morphological and molecular data, we present the first record of D. (N.) tenuis in wild raccoons from the Yucatan Peninsula. Adult thread-like worms recovered from subcutaneous tissues of wild raccoons were analyzed with light microscopy, histology, scanning electron microscopy (SEM), and 18S rRNA, 28S rRNA and cox1 gene sequencing for identification and phylogenetic analysis. The collected nematodes were identified as D. (N.) tenuis based on their morphology. SEM analysis revealed details about different facial ornamentations in male worms, which had not been previously described. Molecular and phylogenetic analyses confirmed morphological observations by placing our specimens within clades of the Dirofilaria genus. Our findings represent the first molecular characterization for this nematode and extend the geographical range of this parasite to Mexico. Further studies are required for a more accurate picture of the epidemiology of this filarioid across Mexico and other areas overlapping the raccoon's range.

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Chelonoidis carbonarius is host to a great diversity of endoparasites. This research aimed to identify and taxonomically classify the parasitic forms of endoparasites found in the feces of C. carbonarius using coproparasitological methods. In total, 38 fecal samples were collected from animals captured in the municipalities of Cuiabá (n = 23) and Jataí (n = 15) in the Brazilian Ceraado. Fecal samples were submitted to at least one of the following techniques: Willis-Mollay flotation technique, zinc sulfate centrifugal flotation technique, and spontaneous sedimentation of Hoffman, and Pons, and Janer. Overall, 86.85% (33/38) of animals were positive in at least one of the diagnostic techniques. Of the 38 samples used, 50% of the animals were captive and 50% of the animals were free-living. Cysts, oocysts, and parasitic eggs were identified, as follows: Chapiniella spp. (65.78%; n = 24), Sauricola spp. (31.57%; n = 12), Ascaroidea (15.78%; n = 6), Oxyuridae (2.63%; n = 1), Trematoda (2.63%; n = 1), Acanthocephala (2.63%; n = 1), Balantidium spp. (39.47%; n = 15), Eimeria spp. (21.05%; n = 8), and Nyctotherus spp. (2.63%; n = 1). The study showed that both captive and free-living C. carbonarius are often parasitized by different endoparasite species, with nematode eggs being the most common.

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PURPOSE: This study describes the composition and infection patterns of macro endoparasites associated with the lizard Phyllopezus periosus. METHODS: We collected 115 P. periosus over 12 expeditions on the rocky cliffs of the Missão Velha waterfall canyon in northeastern Brazil. Specimens were collected by hand, during active searches conducted between 18:00 h and 23:30 h. The infection patterns were estimated using prevalence, total abundance, and mean intensity of infection for all parasites found. RESULTS: A total of 4256 parasites were collected from 104 hosts, resulting in an exceptionally high overall prevalence of 90.4%. No significant ontogenetic difference in the prevalence of infection was detected. Although juveniles exhibited a high parasite prevalence their parasite loads were significantly lower compared to adults. Six species of endoparasites were found; among these, the nematode Spauligodon oxkutzcabiensis was the most common endoparasite in the digestive tract, while the pentastomid Raillietiella mottae was the only species found in the respiratory tract. CONCLUSIONS: Infection rates in Gekkota species appear to correlate with body size, with larger individuals generally exhibiting a higher prevalence. This pattern was also observed across separate populations of P. periosus and other geckos from distinct ecological domains. The dominance of the monoxenous S. oxkutzcabiensis highlights potential transmission mechanisms, suggesting that behaviors such as limb licking after feeding may contribute to its prevalence. The occurrence of Physalopteroides venancioi, Oswaldocruzia sp., Parapharyngodon sp., Physaloptera sp., infecting P. periosus are new records for this host. These findings significantly contribute to the knowledge of host-parasite dynamics in geckos.

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The greater wax moth, Galleria mellonella, is a significant pest in apiculture and a well-established model organism for immunological and ecotoxicological studies. This investigation explores the individual and combined effects of the ectoparasite Bracon hebetor (B.h.) and the entomopathogenic nematode Steinernema carpocapsae (S.c.) on G. mellonella larvae. We evaluated the activity of oxidative stress enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), malondialdehyde (MDA) levels, cytochrome P450 activity, cell viability using Annexin V-FITC, DNA damage via comet assay, and larval morphology through scanning electron microscopy (SEM). Control larvae exhibited higher GPx and GST activities compared to those treated with B.h., S.c., or the B.h. + S.c. combination. Conversely, MDA levels displayed the opposite trend. SOD activity was reduced in the B.h. and S.c. groups but significantly higher in the combined treatment. Cytochrome P450 activity increased in response to parasitism by B. hebetor. The Annexin V-FITC assay revealed decreased cell viability in parasitized groups (B.h. 79.4%, S.c. 77.3%, B.h. + S.c. 70.1%) compared to controls. DNA damage analysis demonstrated significant differences between groups, and SEM observations confirmed severe cuticle abnormalities or malformations in G. mellonella larvae. These findings highlight the complex interactions between B. hebetor, S. carpocapsae, and their host, G. mellonella. Additionally, they illuminate the intricate physiological responses triggered within the host larvae.

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Background: The described dataset contains occurrence records of invertebrate specimens deposited at the State Museum of Natural History of the NAS of Ukraine, Lviv, Ukraine (SMNH NASU). It combines diverse taxonomic groups, mostly belonging to the class Insecta of the phylum Arthropoda, that were selected as prioritised for digitisation in war conditions. Selected specimens were ascertained as those being the most vulnerable to hostilities and requiring virtual preservation. Such virtual preservation is essential in the war realities as collection can be lost or damaged at any moment, resulting in a significant retrospective biodiversity data gap. At the same time, collection virtualisation and its deposition on the internet grant remote access to scientists who cannot visit it in person due to the war. Moreover, we believe that the mobilisation of the data from the Ukrainian collections and their publication online are essential for the integration of Ukrainian research facilities into a global scientific biodiversity pool. New information: A total of 3,660 occurrence records mobilised in 2023-2024 from the collection of invertebrates of the SMNH NASU, were published. This dynamic dataset will be continually supplied by new records during further digitisation work.

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The construction of dams and hydroelectric plants affects biodiversity in aquatic environments and can facilitate the invasion of species. Few studies assess the long-term response of parasite fauna under these events. The aim of this study was to investigate possible changes in the endoparasite composition of the invasive catfish Trachelyopterus galeatus (Linnaeus, 1766) in the floodplain of the upper Paraná River over a 27-year study period. A total of 79 fish were collected in period 1 (1993) and 31 in period 2 (2019/2020) at the same sampling points, and the endoparasites were located in the gastrointestinal system using a stereomicroscope. It was found that the development of the fish and the composition of their endoparasitic fauna changed over time. In the second period, the fish presented smaller values for mass (g) and standard length (cm) when compared to period 1. It was found that three species of endoparasites were found per period, but although the richness was the same, the composition differed, and only one digenean (Microrchis oligovitellum Lunaschi, 1987 (Trematoda: Paramphistomidae)) was shared. The Porto Primavera Dam was built upstream of the site between the sampling periods (1999) and caused a number of environmental changes, possibly being the main factor responsible for changes in components of the parasite community. Anthropic modification to an environment can cause loss of diversity and loss of ecological interactions. Through our results, we emphasize the importance of including parasite fauna in studies that assess environmental impacts.

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Among parasites of the digestive tract of the black-headed gull (Chroicocephalus ridibundus) in Poland, the best known are species of digenetic trematodes and cestodes. Nematodes of this bird species are not well known. Black-headed gulls, due to their varied diet, migration, life in a flock, and changes of habitat, can become infected with various species of helminths, and like synanthropic birds, they can spread the dispersal stages of parasites across urban and recreational areas. In the present study, an attempt was made to identify the helminth fauna of C. ridibundus from breeding colonies in north-central Poland. The aim of the study was to describe the taxonomic structure of parasites of the digestive tract of the black-headed gull and determine the quantitative parameters of their occurrence. A total of 43 black-headed gulls were examined post-mortem for gastrointestinal helminths, resulting in the identification of four cestodes (Paricterotaenia porosa, Lateriporus clerci, Anomotaenia micracantha, and Wardium fusum), three trematodes (Diplostomum pseudospathaceum, Plagiorchis laricola, and Apophallus muehlingi), and three nematodes (Eucoleus contortus, Cosmocephalus obvelatus, and Porrocaecum ensicaudatum). Lateriporus clerci (in adult form), C. obvelatus and P. ensicaudatum (in larval form) were recorded for the first time in the black-headed gull in Poland.

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The present paper comprises a systematic survey of helminths (trematodes, an acanthocephalan and nematodes) found in nine species of freshwater fishes in Ecuador collected in March 1999 and those (a trematode and acanthocephalans) collected from an amphibian and two species of freshwater fishes in Venezuela in 1992, 1996 and 2001. The following 17 helminth species were recorded: Trematoda: Prosthenhystera ornamentosa sp. n., P. obesa (Diesing, 1850), Crassicutis intermedius (Szidat, 1954), C. cichlasomae Manter, 1936 and Glypthelmins eleutherodactyli sp. n. Acanthocephala: Quadrigyrus torquatus Van Cleave, 1920, Gracilisentis variabilis (Diesing, 1851) and Neoechinorhynchus (Neoechinorhynchus) ecuadoris sp. n. Nematoda: Cosmoxynema vianai Travassos, 1949, Travnema travnema Pereira, 1938, Touzeta ecuadoris Petter, 1987, Sprentascaris hypostomi Petter et Cassone, 1984, Sprentascaris sp., Contracaecum sp. Type 1 larvae, Contracaecum sp. Type 2 larvae, Procamallanus (Procamallanus) peraccuratus Pinto, Noronha et Rolas, 1976 and Procamallanus (Spirocamallanus) sp. juv. Nearly all of these parasites are reported from Ecuador or Venezuela for the first time and many of these findings represent new host records. The new species P. ornamentosa sp. n. was collected from the gall-bladder of an unidentified anostomid (Anostomidae, Characiformes) in Ecuador, G. eleutherodactyli sp. n. from the digestive tract of the frog Eleutherodactylus sp. (Eleutherodactylidae, Anura) in Venezuela and N. (N.) ecuadoris sp. n. from the intestine of Lebiasina sp. (Lebiasinidae, Characiformes) in Ecuador. Most parasites are briefly described and illustrated and problems concerning their morphology, taxonomy, hosts and geographical distribution are discussed.

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Cuniculus paca, commonly known as the paca, is a rodent of the Cuniculidae family that is widely distributed throughout the Americas, including all Brazilian territories, and is abundant in the Amazon region. It is one of the most hunted species and faces significant predation in the extreme western Amazon region of Brazil because it constitutes a staple in the diet of local communities, for subsistence and commercial purposes. Understanding the helminthic fauna of these animals is of paramount importance, given that some nematodes have zoonotic potential and may pose risks to consumer health. This study aimed to contribute to the records of the nemtodes of this highly consumed species in the Amazon region, highlighting the occurrence of gastrointestinal parasites in free-living pacas intended for human subsistence consumption. The study was conducted in the Paranã da Floresta community, located in the municipality of Guajará, Amazonas from 2022 to 2023. The community members hunted this rodent for consumption and voluntarily provided the viscera for analysis. Nematodes were extracted from each organ. The organs were opened, and the contents were processed using a sieve (0.15 mm) and subsequently evaluated separately. In total, 10,157 nematodes were found in the 14 pacas. Based on morphological analyses, the nematodes were identified as Heligmostrongylus sedecimradiatus (n = 10,068), Trichuris sp. (n = 85), and Physaloptera sp. (n = 4). This study provides insights into the nematodes diversity of free-living pacas in the extreme Western Amazon region, emphasizing the importance of sanitary surveillance and public awareness of the risks associated with bushmeat consumption.

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In 2018, human anisakiasis caused by the ingestion of the skipjack tuna Katsuwonus pelamis occurred frequently in Japan. This may be attributable to a heavy infection of A. simplex (s.s.) in the host's muscle tissue. In this study, we investigate infection levels of anisakid L3 larvae in skipjack tuna captured in Japanese waters afterward (2019-2020) to contribute to predict and prevent the outbreak of human anisakiasis. A total of 476 larvae were detected from 78 out of 85 skipjack tuna captured at 14 stations of the Pacific and East China Sea. The present parasitological survey suggests that infection levels in 2019-2020 were low, comparing that in 2018; in total only seven larvae were found from the host's muscle tissue. The collected larvae were identified by molecular methods to Anisakis berlandi, A. pegreffii, A. simplex (s.s.), A. typica and Skrjabinisakis physeteris (s.l.). Not only larvae of A. simplex (s.s.) but also those of A. berlandi were found from the muscle tissue and thus the latter species may also be a causative agent of human anisakiasis. In addition, this study confirmed the geographic distribution pattern that A. simplex (s.s.) is abundant in the Pacific, while A. pegreffii is dominant in the East China Sea. Our results contribute to understanding the risk of food poisoning and stock delimitation of host animals.

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We describe the composition of endoparasites associated with leaf litter anurans from an Atlantic Forest area, in southeastern Brazil. We tested if body size, sex, and reproductive modes of anuran hosts influence endoparasite abundance and richness. We sampled 583 individuals from 11 anuran species and recorded 1,600 helminths from 14 taxa. The helminths that infected the greatest number of anuran host species were the nematodes Cosmocerca parva (8 spp.), Physaloptera sp. (8 spp.), and Cosmocerca brasiliense (7 spp.), and the most abundant helminth species were Physaloptera sp. (14.6%), Cosmocerca brasiliense (13.7%) and Cosmocerca parva (12.6%). Both helminth abundance and richness were positively affected by anuran body size and dependence on water for reproduction. Larger hosts can contain a higher abundance of parasites because they may provide more physical space than smaller ones, or it can simply be a function of age. Besides, parasite species richness can be highly correlated with the amount of time a host spends in association with aquatic habitats, a conservative aspect of both parasite and host natural history. Within host species, there was a positive and significant influence of body size on helminth abundance. Haddadus binotatus females had greater helminth abundance than males, probably due to sex-related differences in behavior and/or in physiology. Our data suggest that reproductive modes could also influence helminth infection parameters in other anuran communities and should be considered in detail in future analyses.

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Filariasis is recognised as a global public health threat, particularly in tropical and subtropical regions. It is caused by infection with a nematode parasite of the superfamily Filarioidea, including Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, and Onchocerca lupi. Three main types of filariasis have been classified: lymphatic filariasis, subcutaneous filariasis, and serous cavity filariasis. The symptoms exhibited by individuals afflicted with filariasis are diverse and contingent upon several variables, including the species of parasite, the host's health and immune response, and the stage of infection. While many classical parasitological techniques are considered indispensable tools for the diagnosis of parasitic infections in humans, alternative methods are being sought due to their limitations. Novel tests based on host-parasite interactions offer a rapid, simple, sensitive, and specific diagnostic tool in comparison to traditional parasitological methods. This article presents methods developed in the 21st century for the diagnosis of filariasis caused by invasion from W. bancrofti, B. malayi, O. volvulus, and O. lupi, as well as techniques that are currently in use. The development of modern diagnostic methods based on molecular biology constitutes a significant advancement in the fight against filariasis.

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Species of the genus Hysterothylacium are aquatic roundworms (nematodes) belonging to the family Raphidascarididae. Some species in this family are known to be associated with zoonotic diseases in humans after they consume their parasitic larvae in raw or undercooked fish. The aim of this research was to report the prevalence, morphology, and molecular characteristics of Hysterothylacium species in Pagellus erythrinus. A total of Two hundred fish were purchased from the fish market in Damanhour, Beheira Province, between December 2021 and November 2022 and subjected to examination. For molecular characterization, the internal transcribed spacer (ITS) region of nuclear ribosomal DNA and the mitochondrial cytochrome oxidase subunit 2 (COX-2) gene were used. Hysterothylacium species were morphologically described and identified from the intestine of Pagellus erythrinus in Beheira Province, Egypt. The PCR amplified 1087 bp and 629 bp of the target sequences of the ITS region and COX-2 gene, respectively. Sequence analysis revealed the Hysterothylacium thalassini species. The identified species provided novel biological data for the Hysterothylacium nematode in Pagellus erythrinus. The prevalence of Hysterothylacium species recovered from the intestine was 55%. The highest prevalence of 72% has been reported in summer compared to the lowest prevalence of 38% in the winter. Females had a higher prevalence of 61.8% than males, with 44.2%. The first detection, prevalence, and molecular characterization of H. thalassini in Pagellus erythrinus from Beheira Province, Egypt, was presented in this study.

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Mastophorus muris (Gmelin, 1790) is a globally distributed parasitic nematode of broad range mammals. The taxonomy within the genus Mastophorus and the cryptic diversity among the genus are controversial among taxonomists. This study provides a detailed morphological description of M. muris from Mus musculus combined with a molecular phylogenetic approach. Moreover, descriptions and molecular data of M. muris from non-Mus rodents and wildcats complement our findings and together provide new insights into their taxonomy. The analysis of M. muris was based on light microscopy and scanning electron microscopy. The morphological description focused on the dentition pattern of the two trilobed pseudolabia. Additionally, we described the position of the vulva, arrangement of caudal pairs of papillae, spicules and measured specimens from both sexes and the eggs. For the molecular phylogenetic approach, we amplified the small subunit ribosomal RNA gene and the internal transcribed spacer, and the cytochrome c oxidase subunit 1. Mastophorus morphotypes based on dentition patterns and phylogenetic clustering indicate a subdivision of the genus in agreement with their host. We recognize two groups without a change to formal taxonomy: One group including those specimens infecting Mus musculus, and the second group including organisms infecting non-Mus rodents. Our genetic and morphological data shed light into the cryptic diversity within the genus Mastopohorus. We identified two host-associated groups of M. muris. The described morphotypes and genotypes of M. muris allow a consistent distinction between host-associated parasites.

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Information about parasites of cetaceans in Australia is scarce and mostly opportunistic. The morphology of specimens of the metastrongyloid Stenurus globicephalae Baylis & Daubney, 1925 (Nematoda: Pseudaliidae), collected from the blowhole of a pilot whale Globicephala macrorhynchus Gray, 1846 (Cetacea: Delphinidae) off northern Tasmania, Australia, were studied. Light and scanning electron microscopical examinations enabled a detailed redescription of this nematode species, including corrections of some inaccuracies in previous species descriptions, particularly those concerning cephalic and caudal structures. The presence of numerous ventrolateral oblique muscle bands, characteristic of the males of S. globicephalae, is reported for the first time. This is the second finding of this nematode parasite, in a different host species, in Tasmania.

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PURPOSE: This study aimed to examine the species diversity and structure of the strongylid community in domestic horses in Eastern Slovakia. Also, an analysis of the impact of age, sex, and collection location factors on the strongyid communities was performed. METHODS: Twenty-seven horses 1.5-21 years old from two farms in eastern Slovakia with different horse-management conditions were studied. Strongylids were collected after horse treatments with Noromectin (0.2 mg ivermectin); 66,170 specimens were collected and identified. Faecal egg count reduction test (FECRT) was performed following fenbendazole (FBZ) and ivermectin (IVM) treatments. RESULTS: Twenty-four strongylid species were found; horses were infected with 6 to 16 (average = 11.7) species. Six cyathostomin species (Cylicocyclus nassatus, Cyathostomum catinatum, C. pateratum, Cylicostephanus longibursatus, C. goldi, C. calicatus) were the most prevalent; C. catinatum was the dominant species in both farms (Berger-Parker index 0.34 and 0.42). The structure of the strongylid community was multimodal with dominant, subdominant, background, and rare species. The Mantel test showed that horse age and sex did not significantly affect the nematode infracommunity composition (p > 0.05), while the impact of the collection location (farm) was significant (p = 0.03). Additionally, C. longibursatus was identified as the species contributing significantly to the observed farm differences. Strong resistance to FBZ was documented on both farms (FECRT was 36.4% and 22.7%); IVM resistance was not observed (FECRT = 100%). CONCLUSION: This study presents the first report on the strongylids parasitizing domestic horses in Eastern Slovakia and gives basic information for further studies of horse parasites and their control in the region.

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The organic enrichment effects on the meiofauna and nematofauna were assessed for field sediment and other experimental ones enriched with organic matters conducted in the laboratory for 4 weeks. Also, dissolved oxygen (DO) and pH were monitored for each one. The abundance and diversity of meiofaunal groups and nematofauna varied. Strong significant correlations were found between DO and the studied items. Nematoda was the most abundant group in the field sediment and other experimental ones; their counts increased with the increase in organic enrichments and were dominated by deposit feeders. Amphipoda, Ostracoda and predator/omnivore nematodes disappeared in highly organic-enriched sediments. Changes in DO and organic enrichments might be the more attributable reasons for the alteration of the meiobenthic assemblages. The generic compositions of Nematoda provide a good indicator for environmental alterations.

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Six species of freshwater turtles dominate the Chaco-Pampa Plain in southern South America and their parasites have been relatively understudied, with most records concentrated in Brazil. Particularly in Argentina, there are only scattered records of parasites for most of the turtles that inhabit the region, leaving a large knowledge gap. The purpose of the present contribution is to increase the knowledge of the internal parasites of six species of freshwater turtles from Argentina, after 15 years of fieldwork, by providing new hosts and additional geographic records for many host-parasite relationships. Some molecular sequences of the studied parasites were provided as a tool for better species identification. We processed 433 stomach and fecal samples from live individuals and visceral and soft tissue samples from 54 dissected turtles collected from a wide range and different ecoregions. We found 6230 helminths belonging to 18 taxa (one cestode, 11 digeneans and six nematodes). Fourteen new parasite-host associations are reported here, and for the first time parasites are recorded for Phrynops williamsi. This work contributes significantly to the knowledge of the parasitofauna in freshwater turtles in Argentina, providing a detailed list of parasites present in each turtle species and reporting molecular characters for future studies.

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A general limitation of ecological investigations based on nematodes is related to the difficult and time-consuming taxonomic identification of species. Therefore, nematologists are investing many efforts to develop alternative approaches as proxies applicable in biomonitoring assessment. Recently, an alternative method that combines morpho-functional traits was proposed for detecting assemblage changes of marine nematodes. In view of the promising results, it was tested the same approach to document taxonomic structure changes of soil free-living and plant parasitic nematodes. Specifically, this attempt was carried out using three data sets that include studies from various European regions and different types of ecosystems: forests, grasslands and maize crops. Multivariate statistical analysis revealed that the simple combination of the four traits (i.e., buccal cavity cuticularization occurrence, amphideal fovea size and shape, morphology of the cuticle and pharynx) in a single code number perfectly mirrors the taxonomic structure trends of the nematode assemblage at genus level. Therefore, we predict that similar results can be also obtained by directly encoding nematode specimens with the selected traits and we point to new important advances if this procedure can be coupled with advanced machine learning.

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BACKGROUND: The family Rhabdiasidae (Nematoda: Rhabditida) is a globally distributed group of nematode parasites, with over 110 species parasitic mainly in amphibians and reptiles. However, the systematic position of the family Rhabdiasidae in the order Rhabditida remains unsolved, and the evolutionary relationships among its genera are still unclear. Moreover, the present knowledge of the mitochondrial genomes of rhabdiasids remains limited. METHODS: Two rhabdiasid species: Rhabdias kafunata Sata, Takeuchi & Nakano, 2020 and R. bufonis (Schrank, 1788) collected from the Asiatic toad Bufo gargarizans Cantor (Amphibia: Anura) in China, were identified based on morphology (light and scanning electron microscopy) and molecular characterization (sequencing of the nuclear 28S and ITS regions and mitochondrial cox1 and 12S genes). The complete mitochondrial genomes of R. kafunata and R. bufonis were also sequenced and annotated for the first time. Moreover, phylogenetic analyses based on the amino acid sequences of 12 protein-coding genes (PCGs) of the mitochondrial genomes were performed to clarify the systematic position of the family Rhabdiasidae in the order Rhabditida using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic analyses based on the 28S + ITS sequences, were also inferred to assess the evolutionary relationships among the genera within Rhabdiasidae. RESULTS: The detailed morphology of the cephalic structures, vulva and eggs in R. kafunata and R. bufonis was revealed using scanning electron microscopy (SEM) for the first time. The characterization of 28S and ITS regions of R. kafunata was reported for the first time. The mitogenomes of R. kafunata and R. bufonis are 15,437 bp and 15,128 bp long, respectively, and both contain 36 genes, including 12 PCGs (missing atp8). Comparative mitogenomics revealed that the gene arrangement of R. kafunata and R. bufonis is different from all of the currently available mitogenomes of nematodes. Phylogenetic analyses based on the ITS + 28S data showed Neoentomelas and Kurilonema as sister lineages, and supported the monophyly of Entomelas, Pneumonema, Serpentirhabdias and Rhabdias. Mitochondrial phylogenomic results supported Rhabdiasidae as a member of the superfamily Rhabditoidea in the suborder Rhabditina, and its occurrance as sister to the family Rhabditidae. CONCLUSIONS: The complete mitochondrial genome of R. kafunata and R. bufonis were reported for the first time, and two new gene arrangements of mitogenomes in Nematoda were revealed. Mitogenomic phylogenetic results indicated that the family Rhabdiasidae is a member of Rhabditoidea in Rhabditina, and is closely related to Rhabditidae. Molecular phylogenies based on the ITS + 28S sequence data supported the validity of Kurilonema, and showed that Kurilonema is sister to Neoentomelas. The present phylogenetic results also indicated that the ancestors of rhabdiasids seem to have initially infected reptiles, then spreading to amphibians.

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