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Two new species of lung-dwelling nematodes are described from North American frogs: Rhabdias aurorae n. sp. from Rana aurora and Rhabdias conni n. sp. from Rana clamitans and Rana catesbeiana from Arkansas; the latter species was also found in Oklahoma and Georgia. Rhabdias aurorae n. sp. differs from other Nearctic congeners in the combination of the following characteristics: buccal capsule 22-25 μm wide, elongated tail covered with inflated cuticle, esophagus with prominent dilatation in anterior part and 6 small circumoral lips. Rhabdias conni n. sp. is morphologically closest to Rhabdias ranae Walton, 1929 and Rhabdias joaquinensisIngles, 1936; it differs from them in the shape of lateral pseudolabia, the dimensions of the body, and the egg size. Both new species were found to be significantly different from the Nearctic congeners in the nucleotide sequences of nuclear ribosomal DNA (18S-ITS-28S region), 12S, and CO1 mitochondrial genes. The 2 new species differ from other currently sequenced Nearctic congeners by 1.1-2.7% of nucleotide positions in the nuclear rDNA region, 1.3-3.4% in the 12S gene, and 3.4-9.4% in CO1 gene. Molecular phylogenetic analysis based on nuclear ribosomal DNA sequences placed both new species into the clade consisting of Nearctic and Neotropical Rhabdias spp. The position of Rh. aurorae n. sp. within the clade is uncertain because of a polytomy, but Rh. conni n. sp. is nested within the "Rh. joaquinensis complex" related to Rh. ranae and Rhabdias tarichaeKuzmin, Tkach, and Snyder, 2003. The phylogenetic analysis based on nuclear ribosomal DNA sequences has revealed 3 evolutionary host-switching events from anuran to caudatan hosts among Rhabdias spp. that occurred in the Nearctic and Palearctic. The molecular phylogeny also suggests that Rhabdias may have originally evolved in what is now Africa., (© American Society of Parasitologists 2024.)

One Gram-negative, rod-shaped bacterial strain, isolated from an undescribed Heterorhabditis entomopathogenic nematode species was characterized to determine its taxonomic position. The 16S rRNA gene sequences indicate that it belongs to the class Gammaproteobacteria, to the family Morganellaceae, to the genus Photorhabdus, and likely represents a novel bacterial species. This strain, designated here as CRI-LC T , was therefore molecularly, biochemically, and morphologically characterized to describe the novel bacterial species. Phylogenetic reconstructions using 16S rRNA gene sequences show that CRI-LC T is closely related to P. laumondii subsp. laumondii TT01 T and to P. laumondii subsp. clarkei BOJ-47 T . The 16rRNA gene sequences between CRI-LC T and P. laumondii subsp. laumondii TT01 T are 99.1% identical, and between CRI-LC T and P. laumondii subsp. clarkei BOJ-47 T are 99.2% identical. Phylogenetic reconstructions using whole genome sequences show that CRI-LC T is closely related to P. laumondii subsp. laumondii TT01 T and to P. laumondii subsp. clarkei BOJ-47 T . Moreover, digital DNA-DNA hybridization (dDDH) values between CRI-LC T and its two relative species P. laumondii subsp. laumondii TT01 T and P. laumondii subsp. clarkei BOJ-47 T are 65% and 63%, respectively. In addition, we observed that average nucleotide identity (ANI) values between CRI-LC T and its two relative species P. laumondii subsp. laumondii TT01 T and P. laumondii subsp. clarkei BOJ-47 T are 95.8% and 95.5%, respectively. These values are below the 70% dDDH and the 95-96% ANI divergence thresholds that delimits prokaryotic species. Based on these genomic divergence values, and the phylogenomic separation, we conclude that CRI-LC T represents a novel bacterial species, for which we propose the name Photorhabdus africana sp. nov. with CRI-LC T (= CCM 9390 T  = CCOS 2112 T ) as the type strain. The following biochemical tests allow to differentiate P. africana sp. nov. CRI-LC T from other species of the genus, including its more closely related taxa: β-Galactosidase, citrate utilization, urease and tryptophan deaminase activities, indole and acetoin production, and glucose and inositol oxidation. Our study contributes to a better understanding of the taxonomy and biodiversity of this important bacterial group with great biotechnological and agricultural potential., (© 2024. The Author(s).)

Species of the genus Rhabdias Stiles & Hassall, 1905 are common parasitic nematodes occurring in the lungs of amphibians and reptiles worldwide. In the present study, Rhabdias macrocephalum n. sp. is described using integrated morphological methods (light and scanning electron microscopy) and molecular approaches (sequencing of the nuclear 28S and ITS regions, and mitochondrial cox1, cox2, and 12S genes) based on specimens collected from the green striped tree dragon Diploderma splendidum (Barbour & Dunn) (Reptilia: Agamidae) in China. The complete mitochondrial genome of R. macrocephalum n. sp. was sequenced and annotated: it is 14,819 bp in length, including 12 protein coding genes (missing atp8), 22 tRNA genes, 2 rRNA genes and three non-coding regions. The gene arrangement of R. macrocephalum n. sp. is different from all of the currently available mitogenomes of nematodes and represents a novel type of mitochondrial gene arrangement reported in Nematoda. Molecular phylogenetic results based on the ITS + 28S data support the monophyly of Entomelas, Pneumonema, Serpentirhabdias, and Rhabdias, and showed R. macrocephalum n. sp. forming a most basal lineage in Rhabdias., (© J. Zeng et al., published by EDP Sciences, 2024.)

Serpentirhabdias mamlambo n. sp. is described from the lung of the herald snake, Crotaphopeltis hotamboeia (Laurenti) in KwaZulu-Natal Province, South Africa. The new species is characterised by the small lips, the absence of the buccal capsule, the large excretory glands (1.5-2.3 times longer than the oesophagus), and the numerous eggs in uteri. Serpentirhabdias mamlambo n. sp. differs from other Serpentirhabdias spp. in the presence of M-shaped cuticular folds on dorsal and ventral sides of apical surface, the eye-shaped internal labial papillae, and the distinct dilatation of the oesophagus at its mid-length. Morphological differentiation of S. mamlambo n. sp. from its congeners is supported by molecular evidence based on cox1 mitochondrial gene, and ITS and partial 28S region of nuclear rDNA. Serpentirhabdias mamlambo n. sp. is the first species of the genus Serpentirhabdias described from the Afrotropical Realm., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Rhabdias pocoto n. sp. is herein described from the lungs of the swamp frog Pseudopaludicola pocoto Magalhães, Loebmann, Nogueira, Kokubum, Baptista, Haddad & Garda, 2014, from the Caatinga biome in the state of Ceará, in north-eastern Brazil. The new species is characterized by a body that dilates posteriorly, six small lips (protuberances) and two rounded lateral expansions of cuticular inflation on the anterior end, each containing an amorphous gland-like structure inside and a short and conical tail. Additionally, molecular analysis and comparison of the partial mitochondrial cytochrome c oxidase I sequence of R. pocoto n. sp. revealed genetic divergence between the new species and the sequences of Rhabdias spp. previously deposited in GenBank. Phylogenetic analysis grouped the new taxon into the R. pseudosphaerocephala species complex + R. glaurungi clade. The new discovery represents the 19th species of Rhabdias spp. described in the Neotropical region, the ninth in Brazil and the first species of Rhabdias found parasitizing South American frogs of the genus Pseudopaludicola, as well as the first Caatinga biome species of Rhabdias.

Serpentirhabdias mussuranae n. sp. is described from the lungs of the mussurana, Clelia clelia (Daudin, 1803), from vicinities of Lábrea, Amazonas State, Brazil. The species is characterized by the triangular oral opening, the presence of teeth (onchia) in the oesophastome, the excretory glands longer than the oesophagus and the tail abruptly narrowing in its anterior half and gradually tapering in posterior half. Among the Neotropical representatives of the genus, three species are known to possess the onchia in the oesophastome: S. atroxi, S. moi and S. viperidicus. Serpentirhabdias mussuranae n. sp. differs from S. atroxi and S. viperidicus by its triangular shape of the oral opening and the oesophastome in apical view, vs. round in the latter two congeners. Additionally, S. viperidicus has a larger oesophastome, 13-22 micrometers wide and 13-23 micrometers deep. The new species has relatively longer excretory glands than S. moi. The new species is morphologically and genetically close to S. atroxi, S. moi and S. viperidicus, all parasitic in Brazilian snakes, based on the presence of onchia and the comparison of nucleotide sequences of nuclear ribosomal DNA and mitochondrial cox1 gene (differences varied between 3.8% and 7.1%). Data on the life cycle of S. mussuranae n. sp. is provided, and the life cycle is typical of the genus Serpentirhabdias, with the combination of direct development and heterogony. Free-living larval stages and the adults of amphimictic free-living generation are described. The results of molecular phylogenetic analysis based on nuclear ribosomal internal transcribed spacer (ITS) + partial 28S region and partial mitochondrial cox1 gene are provided.

The genus Rhabdias Stiles & Hassal, 1905 includes about 83 species of nematodes parasitic in amphibians and reptiles worldwide. Herein, we describe Rhabdias glaurungi sp. nov. from the hylid frog Scinax gr. ruber (Laurenti, 1768) in the Gunma Ecological Park, Santa Bárbara municipality, state of Pará, Brazil. This species has six small lips, an inflated cuticle along the entire body and a cup-shaped buccal capsule with smooth internal surface of its anterior part and irregularly folded internal surface of its posterior part in apical view. From the 17 valid species recognized in the Neotropical realm, the new species can be distinguished by the number of lips, the morphology and size of its buccal capsule, as well as the extent and shape of its cuticular inflation; in addition, there are molecular differences. Sequences of the mitochondrial Cytochrome c Oxidase subunit I gene strongly support the status of this form as a separate species. Molecular phylogenetic analysis shows R. glaurungi sp. nov. nested within the R. pseudosphaerocephala Kuzmin, Tkach & Brooks, 2007 species complex. Rhabdias glaurungi sp. nov. is the second species of the genus described from hosts of the family Hylidae in the Neotropical realm. We conclude that the diversity of Rhabdias within the Neotropics is likely largely underestimated.

Coexistence of highly similar species is at odds with ecological theory of competition; coexistence, then, requires stabilizing mechanisms such as differences in ecological niche. In the bacterivore nematode Litoditis marina species complex, which occurs associated with macro-algae, four cryptic lineages (Pm I-IV) co-occur in the field along the south-western coast and estuaries of The Netherlands. Here we investigate the temporal and/or spatial niche differentiation in their natural environment using a qPCR-based detection and relative quantification method. We collected different algal species (i.e. two Fucus species and Ulva sp.) and separated algal structures (i.e. receptacula, thalli, non-fertile tips and bladders) at different sampling months and times (i.e. twice per sampling month), to examine differences in microhabitat use between coexisting L. marina species. Results demonstrate that the cryptic species composition varied among different algal species and algal structures, which was also subject to temporal shifts. Pm I dominated on Fucus spp., Pm II showed dominance on Ulva sp., while Pm III overall had the lowest frequencies. Microhabitat partitioning was most pronounced between the two cryptic species which had similar microbiomes (Pm I and Pm II), and less so between the two species which had significantly different microbiomes (Pm I and Pm III), suggesting that species which share the same microhabitats may avoid competition through resource partitioning. The interplay of microhabitat differentiation and temporal dynamics among the cryptic species of L. marina implies that there is a complex interaction between biotic components and abiotic factors which contributes to their coexistence in the field., Competing Interests: The authors have declared that no competing interests exist.

Entomopathogenic nematodes (EPN) belonging to the Heterorhabditidae family are lethal parasites of soil-dwelling insects. Two species were reported in Argentina: Heterorhabditis argentinensis and Heterorhabditis bacteriophora characterized mainly by morphometric features. In this work a comparative and phylogenetic study between five Heterorhabditis populations from Argentina was conducted to analyze the variability between strains and to evaluate the taxonomic position of Heterorhabditis argentinensis. The PCA analyses of morphometric characters separated the larger juvenile, female and male H. argentinensis from H. bacteriophora populations. The juvenile (IJs) stage provided the clearest separation of Heterorhabditis populations presenting the least variability between strains. The variable L and MBW were highly related to H. argentinensis IJs. Three groups were separated by this stage considering PC1 and PC2: one formed by H. bacteriophora OLI, RIV and RN strains, (isolates from Córdoba and Río Negro province), one for H. bacteriophora VELI strain (Buenos Aires province) and one for H. argentinensis (Santa Fe province). Heterorhabditis bacteriophora VELI and H. argentinensis isolated from regions with more rainfalls and humidity presented larger values for morphometric features. Molecular analyses showed the Argentinian populations (H. bacteriophora VELI strain and H. argentinensis), forming a same clade, with six other H. bacteriophora populations (not from Argentina) with a genetic similarity between them of 99%. Heterorhabditis argentinensis presented one unique nucleotide that was not present in any of the other species of the clade. Considering the results of this study H. argentinensis would be conspecific to H. bacteriophora, constituting a strain with a great morphometric variation where the host and climatic conditions could have influenced on the measurements.

Serpentirhabdias viperidicus n. sp. (Nematoda: Rhabdiasidae) is described from the lungs of the 'Brazilian lancehead' Bothrops moojeni (Hoge, 1966) from the savannah in São Paulo State, Brazil. The new species is the eighth species of Serpentirhabdias described in the Neotropical region, and differs from other species mainly by a combination of characters: lips slightly notable, presence of fine striations at posterior ends, presence of two parallel lines with intercalated pores, a pore-shaped phasmid situated at the level of the anal aperture and another two in the posterior half of the tail. It is the first species of Serpentirhabdias reported in this snake host and the second species of this genus found parasitizing South American viperidian snakes. Molecular phylogenetic analysis using ribosomal (ITS and 28S partial) genes confirms Serpentirhabdias viperidicus n. sp. as a new species that clustered in the Serpentirhabdias clade, sister taxon to Serpentirhabdias fuscovenosa and Serpentirhabdias elaphe. This is the first description of Serpentirhabdias species from Brazil using molecular approaches and morphological characters to confirm the monophyly of this recent genus.

A new entomopathogenic nematode species of Heterorhabditis, described as H. pakistanense n. sp., was isolated from soil samples around the roots of grass at Malir, Karachi, Sindh, Pakistan. The new species is characterized morphologically by features of males: body size 819 μm (720-1013 μm), D% ((distance from anterior end to excretory pore divided by pharynx length) × 100) 119 (110-126), SW% ((spicule length divided by anal body diameter) × 100) 156 (144-191), GS% ((gubernaculum length divided by spicule length) × 100) 58 (48-65) and variations in the number of bursal papillae of the terminal group: 8th and 9th papillae sometimes absent on both sides, sometimes eight papillae present on the right side whereas six papillae present on the left side. On the right side the arrangement of papillae is 1 + 2 + 3 + 2 whereas on the left side it is 1 + 2 + 3. The hermaphrodite has a prominent post-anal swelling and a conoid tail 82 μm (64-95 μm) long with a pointed terminus. Hermaphrodites of H. pakistanense n. sp. can be distinguished from all species of Heterorhabditis except H. downesi by having a mucronate tail. Infective juveniles have a medium-sized body (581 μm (558-624 μm)), long pharynx (117 μm (113-125 μm)), ensheathed tail (99 μm (95-110 μm)) and E% ((distance from anterior end to excretory pore divided by tail length) × 100) 100 (95-107). The new species can be distinguished from all species of Heterorhabditis by the absence of the 7th, 8th and 9th bursal papillae. Heterorhabditis pakistanense is further characterized by the internal transcribed spacer (ITS) and the D2D3 region of the 28S rDNA gene. The closest species H. indica, H. gerrardi, H. amazonensis and H. noenieputensis being separated by 9, 7, 66 and 15 bp, respectively, in the ITS region. Molecular phylogenetic trees based on sequences of ITS rDNA, D2D3 regions and the mitochondrial 12S rRNA gene support the description of H. pakistanense as a new species.

Angiostoma norvegicum n. sp. (Angiostomatidae) is described from the oesophagus, crop and the buccal mass of five species of slugs of the family Arionidae, Arion vulgaris (Moquin-Tandon), Arion ater (L.), Arion fasciatus (Nilsson), Arion fuscus (Müller) and Arion rufus/Arion ater hybrid), collected throughout Norway. Angiostoma norvegicum n. sp. was found parasitising arionids at seven of the 30 sample sites examined (23.3%), and 9.9% of all Arion spp. were infected with this nematode. The new species is characterised by its large size (4.0-8.6 mm long) and in having: lateral alae; 6 + 6 papillae at the cephalic end; a large circular mouth aperture; a spacious stoma; a pharyngeal basal bulb without valvular apparatus; an excretory pore near the base of bulb; a distal part of posterior ovary always outstretched; an anterior ovary distally nearly always outstretched; a vulva situated anterior to mid-body; long, nearly straight spicules and a small gubernaculum; three circumcloacal papillae and caudal genital papillae (GP) arranged in a pattern 1+2/3+3 with GP 5 and GP 8 opened on dorsal side of narrow bursa not reaching tail tip; short conical tails in both sexes with tips supplied by 4 short, unequal denticles. Morphologically, A. norvegicum n. sp. is similar to Angiostoma limacis Dujardin, 1845, which diagnostic characteristics are given based on examination of specimens from Norway and the UK. Conversely, the phylogenetic analyses based on D2D3 large subunit (LSU) rRNA gene sequences performed in the present study did not support the morphological affinity of these two species. Phylogenetic analyses demonstrated that although Angiostoma spp. cluster together, A. norvegicum n. sp. forms a tight monophyletic clade with the milacid nematode parasites Angiostoma margaretae Ross, Malan & Ivanova, 2011 and Angiostoma milacis Ivanova & Wilson, 2009., Competing Interests: The authors declare that they have no conflict of interest. Ethical approval All applicable institutional, national and international guidelines for the care and use of animals were followed.

Phasmarhabditis bonaquaense n. sp. is described and illustrated from the body of Malacolimax tenellus, from the locality of České Švýcary near the village of Dobrá Voda, the Czech Republic. Females are characterized by a body length of 2349 (1878-2626) µm and a cupola shaped tail with a long hyaline hair-like tail tip. Extremely prominent papilla-like phasmids present. Males 1829 (1414-2121) µm long. Peloderan bursa with nine pairs of rays (papillae), 1/1/1/2/1/3. One non-paired apparent papilla-like structure located near the ventral appendage anterior to the cloaca. Prominent papilla-like phasmids located close to the tail tip. Small subunit (18S), ITS, and D2-D3 expansion segments of the large subunit of ribosomal DNA were used to analyze the phylogenetic relationships of sequenced species in the genus Phasmarhabditis and other closely related species. Phasmarhabditis bonaquaense n. sp. varied from other related nematodes both in morphological characterizations and phylogenetic analysis. The life cycle of the newly described species is not well known but it is probably a facultative, mollusc-parasitic nematode able to survive permanently in the saprobic phase on decaying organic matter.

Two new lung-dwelling nematode species of the genus Rhabdias Stiles et Hassall, 1905 were discovered in Caxiuanã National Forest, Pará state, Brazil. Rhabdias galactonoti sp. n. was found in a dendrobatid frog Adelphobates galactonotus (Steindachner). The species is characterised by the regularly folded inner surface of the anterior part of the buccal capsule seen in apical view, flask-shaped oesophageal bulb and narrow, elongated tail. Rhabdias stenocephala sp. n. from two species of leptodactylid frogs, Leptodactylus pentadactylus (Laurenti) (type host) and L. paraensis (Heyer), is characterised by a narrow anterior end that is separated from the remaining body by a constriction. Both species possess six small but distinct lips, a cuticle that is inflated along the whole body, a doliiform buccal capsule separated into a longer anterior and a shallow, ring-shaped posterior part, lateral pores in the body cuticle and zones of spermatogenesis in the syngonia. Rhabdias galactonoti sp. n. is the first species of the genus found in Dendrobatidae; R. stenocephala sp. n. is the second species described from Leptodactylidae in eastern Amazonia.

A new lung-dwelling nematode species is described from the common lancehead Bothrops atrox (Linnaeus) in the Brazilian Amazon Region. The species is assigned to the genus Serpentirhabdias Tkach, Kuzmin & Snyder, 2014 based on the presence of six lips arranged in two lateral groups, the absence of prominent cuticular inflations, and lung parasitism in snakes. Serpentirhabdias atroxi n. sp. differs from other species of the genus mainly by details of the morphology of the anterior end: cuticularised ring surrounding the anterior part of the buccal cavity and six minute onchia present in the oesophastome. Serpentirhabdias atroxi n. sp. is the seventh species of the genus known from the Neotropical Realm and the second species described from viperid snakes.

The genus Phasmarhabditis is an economically important group of rhabditid nematodes, to which the well-known slug-parasite P. hermaphrodita belongs. Despite the commercial use of Phasmarhabditis species as an attractive and promising approach for pest control, the taxonomy and systematics of this group of rhabditids are poorly understood, largely because of the lack of diagnostic morphological features and DNA sequences for distinguishing species or inferring phylogenetic relationship. During a nematode sampling effort for identifying free-living relatives of Caenorhabditis elegans in Huizhou City, Guangdong, China, a novel species belonging to the genus Phasmarhabditis was isolated from rotting leaves. Detailed morphology of the gonochoristic P. huizhouensis sp. nov. was described and illustrated. The adult female has a robust body, a relatively short and wide buccal capsule conjoined by a rhabditiform pharynx. Females are characterized by a short cupola-shaped tail end bearing a slender pointed tip, with the junction flanked by a pair of 'rod-like' phasmids. Males have an open peloderan bursa that is supported by 9 pairs of genital papillae and 1 terminal pair of phasmids. P. huizhouensis sp. nov. is morphologically very similar to the type species Phasmarhabditis papillosa but is distinguishable by its male caudal traits. The new species is readily differentiated from other taxa in the genus by its female tail shape. Molecular phylogenetic inferences based on small subunit (SSU) and the D2-D3 domain of large subunit (LSU) ribosomal DNA genes reveal that P. huizhouensis sp. nov. forms a unique branch in both phylogenies which is genetically related to P. hermaphrodita and other parasites such as Angiostoma spp. The host associations of P. huizhouensis sp. nov. and its ability to parasitize slugs are unknown.

An entomopathogenic nematode, Heterorhabditis H39, was found in Darwin, Australia. Based on morphological and morphometric similarities, and molecular characterisation, it is an isolate of Heterorhabditis bacteriophora. Males, hermaphrodites, females and juveniles showed important similarities on most characters that define H. bacteriophora. The morphometrics of the infective juvenile of Heterorhabditis H39 are similar to those of H. bacteriophora, including average body length (562 (537-587) vs 570 (520-600) µm), maximum body width (21 (19-22) vs 24 (21-31) µm), distance from the anterior end to the EP (96 (87-104) vs 104 (94-109) µm) and tail length (101 (94-111) vs 91 (83-99) µm). The morphology of the spicules and gubernaculum of male Heterorhabditis H39 are indistinguishable from those of H. bacteriophora. The biology and life cycle of Heterorhabditis H39 are similar to those of other Heterorhabditis species. The Neighbour-Joining Tree based on 475 nucleotides of the SSU rRNA gene showed that Heterorhabditis H39 formed a monophyletic group with other H. bacteriophora isolates with a bootstrap value of 100. Thus, phylogenetic study of SSU sequence data provided strong evidence that Heterorhabditis H39 is an isolate of H. bacteriophora. This is the first record of H. bacteriophora in northern Australia.

A new entomopathogenic nematode in the genus Heterorhabditis is described from South Africa, from two singular isolates found 1000 km from each other, from beneath a fig tree and in a citrus orchard, respectively. Morphological and molecular studies indicate both isolates to be the same and a new undescribed Heterorhabditis species. Comparison of sequences of the internal transcribed spacer (ITS) rDNA and the D2D3 region of the 28S rDNA gene with available sequences of other described species within the genus, indicate the two isolates as a new species. Phylogenetic analysis of the sequence data concerned placed the new species, H. noenieputensis n. sp., closest to H. indica and H. gerrardi in the indica-group. The new species, H. noenieputensis n. sp., is distinguished from other species in the genus by a combination of several morphological traits of the males and the infective juveniles (IJs). The new species differs from all other species previously described, as regards the body length of the IJs, except for H. indica and H. taysearae, in which the IJ is smaller. The IJ also differs from that of H. indica in the length of the oesophagus, the body diameter, the length of the tail and the E%. In addition, males of H. noenieputensis n. sp. differ from their closest relative, H. indica, in the position of the excretory pore, SW% and D%; and from H. gerrardi in the length of the oesophagus and SW%. The seventh pair of genital papillae of H. noenieputensis n. sp. are normally developed, while for H. indica they are often branched or swollen at the base, while 8 and 9 are usually absent in both species.

Rhabdiasidae Railliet, 1915 is a globally distributed group of up to 100 known species of nematodes parasitic in amphibians and reptiles. This work presents the results of a molecular phylogenetic analysis of 36 species of Rhabdiasidae from reptiles and amphibians from six continents. New DNA sequences encompassing partial 18S rDNA, ITS1, 5.8S rDNA, ITS2 and partial 28S rDNA regions of nuclear ribosomal DNA were obtained from 27 species and pre-existing sequences for nine species were incorporated. The broad taxonomic, host and geographical coverage of the specimens allowed us to address long-standing questions in rhabdiasid systematics, evolution, geographic distribution, and patterns of host association. Our analysis demonstrated that rhabdiasids parasitic in snakes are an independent genus sister to the rest of the Rhabdiasidae, a status supported by life cycle data. Based on the combined evidence of molecular phylogeny, morphology and life cycle characteristics, a new genus Serpentirhabdias gen. nov. with the type species Serpentirhabdias elaphe (Sharpilo, 1976) comb. nov. is established. The phylogeny supports the monophyly of Entomelas Travassos, 1930, Pneumonema Johnston, 1916 and the largest genus of the family, Rhabdias Stiles and Hassall, 1905. DNA sequence comparisons demonstrate the presence of more than one species in the previously monotypic Pneumonema from Australian scincid lizards. The distribution of some morphological characters in the genus Rhabdias shows little consistency within the phylogenetic tree topology, in particular the apical structures widely used in rhabdiasid systematics. Our data suggest that some of the characters, while valuable for species differentiation, are not appropriate for differentiation among higher taxa and are of limited phylogenetic utility. Rhabdias is the only genus with a cosmopolitan distribution, but some of the lineages within Rhabdias are distributed on a single continent or a group of adjacent zoogeographical regions. Serpentirhabdias, Entomelas and Pneumonema show rather strict specificity to their host groups. The evolution of the Rhabdiasidae clearly included multiple host switching events among different orders and families of amphibians as well as switching between amphibians and squamatan reptiles. Only a few smaller lineages of Rhabdias demonstrate relatively strict associations with a certain group of hosts., (Copyright © 2014 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

The genus Entomelas Travassos, 1930 currently includes nine species of rhabdiasid nematodes, eight of them parasitic in lizards and only one, Entomelas sylvestris Baker, 1982, parasitic in amphibians. Entomelas sylvestris was originally described from the Forest Rain Frog Breviceps sylvestris FitzSimons in South Africa and was not reported since. It was placed in the genus Entomelas without any specific arguments for this taxonomic decision, presumably mainly based on details of the buccal capsule morphology. We have found this species in the same host in Limpopo province, South Africa. Molecular phylogenetic analysis based on the newly-obtained sequence of complete ITS region and partial nuclear large ribosomal subunit (28S) gene of E. sylvestris and previously published sequences of a variety of other rhabdiasid taxa, has convincingly demonstrated that this species does not belong in Entomelas. Instead, it clustered together with the members of Rhabdias Stiles & Hassall, 1905 from amphibian hosts. Therefore, we transfer E. sylvestris into Rhabdias as Rhabdias sylvestris (Baker, 1982) n. comb. In our analysis E. sylvestris appears, albeit with weak support, as a basal/sister taxon to the rest of Rhabdias spp. which explains to some extent the differences in the buccal capsule morphology between this species and other Rhabdias spp.

The helminth parasite fauna of the hylid frog Pseudacris hypochondriaca in several localities along the Baja California Peninsula in northwestern Mexico is presented. The helminth fauna consists of 4 species of nematodes (Oswaldocruzia pipiens, a larval form of an Ascaridid, 2 new species belonging to the genera Rhabdias and Cosmocercoides), and 1 species of digenean ( Gorgoderina sp.). The new species of Rhabdias represents the 88th species assigned to the genus and the third species described from Mexican anurans. Also, the species of Cosmocercoides represents the 20th species assigned to the genus and the first representative of this genus described from Mexico.

Nematodes of the genus Rhabdias Stiles & Hassall, 1905 (Rhabditoidea: Rhabdiasidae) have a dioecious free-living stage and a hermaphroditic stage that parasitises the lungs of amphibians and reptiles. Approximately 94 species of Rhabdias have been described. Because the similar morphological characteristics such as the labial structures, the location of the vulva and the shape of the tail of Rhabdias spp. hinder their identification, molecular biology techniques and scanning electron microscopy have been employed to diagnose species of this genus. This study describes Rhabdias breviensis n. sp., parasitic in the lungs of two Neotropical frog species Leptodactylus petersii Steindachner and Leptodactylus macrosternum Miranda-Ribeiro. The description of this species integrates classical taxonomy, scanning electron microscopy and a molecular analysis of the mitochondrial COI gene. The new species differs from all other Rhabdias species parasitic in Neotropical hosts in certain morphometric parameters, the position of the vulva, the host group and the cephalic characters.

Rhabdias himalayanus n. sp. from the lungs of Duttaphrynus himalayanus and Rhabdias dehradunensis n. sp. from the lungs of Nanorana minica from Dehradun, India are described and figured. Of the 3 previously described Indian species, Rhabdias himalayanus n. sp. is most similar to Rhabdias shortii in having a cylindrical corpus, inflated cuticle, and conical tail; it differs from R. shortii in having greater body measurements, longer esophagus, larger eggs, and a different pattern of cuticle inflation at the vulva and tail region. Rhabdias dehradunensis n. sp. is most similar to Rhabdias bulbicauda in that both possess a swollen posterior end; it differs from R. bulbicauda by having a subterminal anus, a prominent tail, and a postequatorial vulva.

Lungworms of the cosmopolitan genus Rhabdias are among the most common parasites of amphibians and squamate reptiles. The present study used experimental infections, field studies, and a molecular phylogeny to determine the host specificity of 6 Rhabdias spp. that infect snakes and anurans from North America. The molecular phylogeny suggests Rhabdias ranae from Nebraska and Mississippi may represent separate, cryptic species. In addition, the phylogeny strongly supports separate clades for anuran and snake lungworms. Field studies and experimental infections indicate that snake lungworms are generalist snake parasites; however, laboratory experiments also suggest that lizards can be infected under some environmental conditions. Lungworms from anurans were found not to infect salamanders or reptiles, in nature or in the laboratory; anuran lungworm species ranged from strict host specificity, e.g., R. ranae from Nebraska, to relative generalist, e.g., Rhabdias joaquinensis from Nebraska. Overall, host specificity for species of Rhabdias does not provide support for the evolution of progressive specialization over time. For most species of lungworms, host specificity in nature appears to be limited by both ecological and physiological factors, which vary between species and their hosts. Furthermore, some lungworms, e.g., Rhabdias bakeri from Missouri, appear to be tracking host resources instead of host phylogenies, an example of ecological fitting.

Organisms that live in close association with other organisms make up a large part of the world's diversity. One driver of this diversity is the evolution of host-species specificity, which can occur via reproductive isolation following a host-switch or, given the correct circumstances, via cospeciation. In this study, we explored the diversity and evolutionary history of Acrostichus nematodes that are associated with halictid bees in North America. First, we conducted surveys of bees in Virginia, and found six halictid species that host Acrostichus. To test the hypothesis of cospeciation, we constructed phylogenetic hypotheses of Acrostichus based on three genes. We found Acrostichus puri and Acrostichus halicti to be species complexes comprising cryptic, host-specific species. Although several nodes in the host and symbiont phylogenies were congruent and tests for cospeciation were significant, the host's biogeography, the apparent patchiness of the association across the host's phylogeny, and the amount of evolution in the nematode sequence suggested a mixture of cospeciation, host switching, and extinction events instead of strict cospeciation. Cospeciation can explain the relationships between Ac. puri and its augochlorine hosts, but colonization of Halictus hosts is more likely than cospeciation. The nematodes are vertically transmitted, but sexual transmission is also likely. Both of these transmission modes may explain host-species specificity and congruent bee and nematode phylogenies. Additionally, all halictid hosts come from eusocial or socially polymorphic lineages, suggesting that sociality may be a factor in the suitability of hosts for Acrostichus., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The review deals with the species of Rhabdiasidae Railliet, 1915 occurring in the Holarctic. Descriptions of 26 species from the genera Rhabdias Stiles et Hassal, 1905 (21 species), Entomelas Travassos, 1930 (4 species), and KurolonemaSzczerbak et Sharpilo, 1969 (1 species) are presented. Additionally, 5 species of Rhabdias are listed as species inquirenda, and 4 species are included into the review, since they have been reported close to south-eastern border of Palaearctic (the exact distribution is unknown). Keys to the Holarctic species and diagnoses of the genera are provided. An overview of the information on the biology, morphology and taxonomy of Rhabdiasidae is also presented, as well as the host-parasite list of Holarctic Rhabdiasidae.

Invasive species may carry with them parasites from their native range, differing from parasite taxa found in the invaded range. Host switching by parasites (either from the invader to native fauna or from native fauna to the invader) may have important consequences for the viability of either type of host (e.g., their survivorship, fecundity, dispersal ability, or geographic distribution). Rhabdias pseudosphaerocephala (Nematoda) is a common parasite of cane toads (Rhinella marina) in the toad's native range (South and Central America) and also in its introduced Australian range. This lungworm can depress host viability and is capable of infecting Australian frogs in laboratory trials. Despite syntopy between toads and frogs for up to 75 yr, our analyses, based on DNA sequence data of lungworms from 80 frogs and 56 toads, collected from 2008 to 2011, did not reveal any cases of host switching in nature: toads and native frogs retain entirely different lungworm faunas. All lungworms in cane toads were the South and Central American species Rhabdias pseudosphaerocephala, whereas Australian frogs contained at least four taxa (mostly undescribed and currently lumped under the name Rhabdias cf. hylae). General patterns of prevalence and intensity, based on the dissection of 1,315 frogs collected between 1989 and 2011 across the toads' Australian range, show that these Australian endemic Rhabdias spp. are widely distributed geographically and across host taxa but are more common in some frog species (especially, large-bodied species) than they are in others.

Rhabdias odilebaini n. sp. is described on the basis of specimens found in the lungs of 2 species of agamid lizards: the Philippine flying lizard Draco spilopterus and the marbled bloodsucker Bronchocela marmorata . Specimens were collected in Aurora Province, Luzon Island, Philippines. The new species of Rhabdias is characterized by presence of 4 submedian lips, inconspicuous lateral lips, rounded cross-shaped oral opening, and tail end bent dorsally. This species is morphologically distinct from other Rhabdias spp. that parasitize reptilian and amphibian hosts, including 3 other species known to parasitize lizards of the Agamidae.

A new taxon, Rhabdias esculentarum n. sp., is described based on DNA sequence analysis at multiple loci (i.e. mtDNA cox-1, 12S rRNA, ITS-1 and partial ITS-2 regions of the nuclear rDNA) and morphometric analysis carried out on specimens collected from the green frogs of the Rana esculenta species complex in Italy (i.e. R. lessonae Camerano and R. esculenta Linnaeus, identified genetically by diagnostic allozyme loci). Rhabdias esculentarum n. sp. was differentiated genetically, at both mitochondrial and nuclear levels, from Rh. bufonis (Schrank, 1788) (sensu Hartwich, 1972) and Rh. sphaerocephala Goodey, 1924 recovered from the toad Bufo bufo Linnaeus collected sympatrically with the specimens of Rana lessonae and R. esculenta examined in the present study. Moreover, the new taxon proved to be different from the other species of Rhabdias from anurans, which had previously been sequenced using the same genes and deposited in GeneBank. Phylogenetic analyses (MP and ML) inferred from mitochondrial (mtDNA cox-1 and 12S ribosomal RNA) and nuclear (ITS-1 and ITS-2 of the rDNA regions) sequences datasets were congruent in depicting Rh. esculentarum n. sp. as forming a highly supported clade distinct from the sympatric species Rh. bufonis, as well as from Rh. sphaerocephala, characterised on the basis of the same loci. Morphometric analysis and the differential diagnosis of genetically characterised specimens of the new species have revealed differences in several features in comparison with the type-species, Rh. bufonis. Material of the latter species included voucher specimens from Germany deposited by Hartwich (1972) and other specimens collected from B. bufo in Italy. Among the diagnostic characters, the particular cup-shaped buccal capsule characterising Rh. esculentarum is clearly different from the tear-shaped buccal capsule observed in material of R. bufonis obtained from Berlin Museum and collected in the same geographical area as the green frogs under study. Rh. esculentarum was also found to differ in some measurements and allometric characters from Rh. bufonis (sensu Moravec et al., 1997). The data so far collected appear to indicate a host-preference of Rh. esculentarum for Rana lessonae and R. esculenta, which belong to the R. esculenta hybridogenetic species complex in Italy.

Rhabdias singaporensis n. sp. (Rhabditida: Rhabdiasidae) from the lungs of Calotes versicolor (Squamata: Agamidae) from Singapore is described and illustrated. Rhabdias singaporensis n. sp. represents the 77th species assigned to the genus, the eighth of the Asian region, and the second from Singapore. The distinguishing characteristic of the new species is the location of the excretory pore. In all species of Rhabdias for which excretory pore location data are available, the excretory pore is situated just posterior to the level of the nerve ring; in R. singaporensis , it lies near the esophageointestinal junction.

A new Heterorhabditis species of entomopathogenic nematode was isolated from soil of the Atacama Desert in Chile. The new species is characterized by morphometrics of the infective juvenile (IJ) with length (L) = 611 (578-666) μm, head to excretory pore length (EP) = 115 (101-126) μm, tail = 69 (62-79) μm long, (EP/tail) × 100 (E%) = 165 (149-182) and L/maximum body diameter (ratio a) = 28 (25-31). The male has spicules 45 (40-49) μm long, gubernaculum 20 (17-22) μm long and (spicule length/anal body diameter) × 100 (SW%) = 205 (179-249). The hermaphroditic adult has shallow cuticular folds immediately anterior and posterior to the vulva, a slight post-anal swelling and a finely rounded tail terminus. Morphologically, H. atacamensis n. sp. resembles H. safricana, H. marelatus, H. downesi and H. amazonensis, but can be distinguished by characters of adult and IJ stages. In particular, for adult males, H. atacamensis n. sp. differs from H. amazonensis by the number and orientation of the genital papillae and from H. downesi by the position of the excretory pore; by the shape of the female tail terminus from H. downesi and by the position of the IJ hemizonid from H. marelatus. Heterorhabditis atacamensis n. sp. is further characterized by internal transcribed spacer (ITS) and D2D3 rDNA sequences, the closest species, H. safricana, being separated by 13 bp across 730 bp of the ITS (incorporating ITS1 (partial sequence), 5.8S (complete sequence), ITS2 (complete sequence)) and 5 bp across 592 bp of the partial 28S (incorporating D2D3) sequence. The morphological and molecular data confirm that H. atacamensis n. sp. is a valid species.

Kurilonema browni n. sp. is described on the basis of specimens found in the lungs of the scincid lizard Sphenomorphus abdictus aquilonius from Aurora Province, Luzon Island, Philippines. The new species differs from Kurilonema markovi, the only previously known species in the genus, by the presence of 2 prominent lateral pseudolabia, larger body size, shorter tail length relative to total body length, and more numerous eggs in the uteri, containing fully developed larvae. The inner surface of the buccal capsule in the new species is densely covered with rounded scales that have not been observed in K. markovi or any other rhabdiasid species. This is the first record of the genus from the Philippines.

Rhabdias filicaudalis n. sp. (Nematoda: Rhabdiasidae) from the lung of Spilotes pullatus (Serpentes: Colubridae) is described. The host snake was captured in the municipality of Avaré, São Paulo State, Brazil. Rhabdias filicaudalis n. sp. differs from all other species by the combination of the following characters: straight body, truncated anterior end, six weakly developed lips arranged in two opposite groups of three, pre-equatorial vulva, oesophagus length/body length ratio (%) 4.9-7.5 (5.8 +/- 0.6), nerve ring distance from anterior end/oesophagus length ratio (%) 36.9-61.1 (49.8 +/- 6.4), tail length/body length ratio (%) 3.0-5.5 (4.0 +/- 0.5), vulva distance from anterior end/body length ratio (%) 39.9-51.7 (45.9 +/- 3.5), and a cuticular filiform tail tip.

The nematode Angiostoma glandicola sp. n. found parasitizing Megaustenia sp. snails (Pulmonata: Helicarionidae) collected in Dong Nai Province, Vietnam, is described and illustrated. The new species is characterized by its unusual host location (the digestive gland) and in having: two circles of cephalic probolae, six lips each bearing two prominent papillae, amphids situated at posterior of lips, the presence of lateral alae, an enlarged stoma, a club-shaped pharynx with cuticularized valves in the bulb, the nerve ring situated on the junction of the corpus and isthmus and the excretory pore opposite the bulb. Oviparous females have a mid-body vulva position, long reflexed ovaries and short divergent uteri, and a conical tail with a slightly triangular tip. Males have long, curved, not distinctly cephalate spicules and a small gubernaculum, nine pairs of pedunculate genital papillae (GP) incorporated into the bursa (three precloacal, six postcloacal in two groups: GP 4-7 closely behind the cloaca and GP 8-9 distanced), of which GP 5 and 8 terminate on dorsal edge of the bursa and GP 8 and 9 are fused at the base, the bursa nearly reaches the tail tip, unpaired precloacal GP and a pair of ventral circumcloacal GP not incorporated into bursa. It clearly differs from other species of the genus by having cephalic probolae vs. no cephalic probolae and the specific number and disposition of male GP. A partial sequence of D2D3 large subunit (LSU) rDNA was obtained and subjected to phylogenetic analyses. Relationships within the Angiostoma genus are discussed.

A new nematode species, Rhabdias lacertae n. sp. (Rhabdiasidae), is described from the body-cavity of the common lizard Lacerta vivipara Jacquin (Lacertidae) from the Ridge of Malá Fatra (Sokolie Hill), north-western Slovakia. The new species differs from its congeners mainly in possessing 3 min cuticular spikes at the tail tip and some other features. This is the first species of Rhabdias Stiles & Hassall, 1905 described from lizards in Europe and the first species of this genus parasitising hosts belonging to the Lacertidae.

Two new species of Angiostoma Dujardin, 1845 taken from the intestines of terrestrial molluscs (Gastropoda: Stylommatophora) collected in the UK are described and illustrated. Angiostoma milacis n. sp. is parasitic in milacid and agriolimacid slugs and is closely related to A. asamati Spiridonov, 1985. Angiostoma zonitidis n. sp. was found in a zonitid snail and is most closely related to A. kimmeriense Korol & Spiridonov, 1992 (emend.), a species also from zonitid snails. An amended generic diagnosis is proposed. The distribution of A. limacis and A. milacis sp. n. in hosts is discussed and a key to the species of Angiostoma is presented.

The present study used experimental infections to compare the life cycles and life histories of 6 Rhabdias spp. infecting snakes and anurans. Free-living development of anuran lungworms was primarily limited to heterogonic reproduction, and females utilized matricidal endotoky exclusively, whereas snake lungworms primarily reproduced homogonically and, when heterogonic reproduction occurred, females used a combination of releasing eggs and matricidal endotoky. Infective snake lungworms survived for longer periods in fresh water compared to anuran worms. Infective anuran lungworms penetrated into the skin of frogs and toads; few infections resulted from per os infections. In contrast, snake lungworms were unable to penetrate skin; instead, infective juveniles penetrated into snake esophageal tissue during per os infections. Despite separate points of entry, anuran and snake lungworms both migrated and developed in the fascia, eventually penetrating into the body cavity of the host. Worms molted to adulthood inside the body cavity and subsequently penetrated into the host's lungs, where they fed on blood while becoming gravid. Adult lungworm survival varied among lungworm species, but, in general, snake lungworms were longer lived than anuran worms. Anuran lungworms were poorly suited for transmission via transport hosts, whereas snake lungworms were consistently capable of establishing infections using transport hosts. Overall, these observations suggest that snake and anuran lungworms have discrepant life cycles and life history strategies.

The occurrence of Heterorhabditis brevicaudis (Rhabditida: Heterorhabditidae) and its symbiotic bacteria, Photorhabdus luminescens subsp. akhurstii in Taiwan were recorded for the first time. H. brevicaudis was described by Liu in 1994, but it was unavailable and no molecular data has ever been published for it ever since. The native entomopathogenic nematode (EPN), H. brevicaudis TG01 was recovered from sandy coastal soils in moist bamboo forest, as observed in this article. The bacterial symbiont was isolated from H. brevicaudis for the first time. On the basis of biochemical tests and 16S rDNA it was identified as P. luminescens subsp. akhurstii. This is also the first report of novel nucleotide sequences of the internal transcribed spacer (ITS) from H. brevicaudis. The phylogenetic relationships of ITS sequences were established using Neighbor-Joining, Maximum Parsimony, and Maximum Likelihood methods. The inferred trees strongly support that H. brevicaudis TG01 is specifically related to H. indica and H. hawaiiensis. But the tail length of the infective juveniles (IJ) of H. brevicaudis TG01 in our study, which was less than 80 microm, shorter than that of other species indeed, fall within the original description for H. brevicaudis. Moreover, comparing with morphometrics of IJ and male of H. brevicaudis and H. indica, we recognize that the H. brevicaudis TG01 does not represent variation among populations of H. indica and H. hawaiiensis. This article will answer questions regarding the status of H. brevicaudis and would also provide this species for further investigation.

Pinpointing processes that structure the geographical distribution of genetic diversity of marine species and lead to speciation is challenging because of the lack of obvious dispersal barriers and the likelihood of substantial (passive) dispersal in oceans. In addition, cryptic radiations with sympatric distributions abound in marine species, challenging the allopatric speciation mechanism. Here, we present a phylogeographical study of the marine nematode species complex Rhabditis (Pellioditis) marina to investigate processes shaping genetic structure and speciation. Rhabditis (P.) marina lives on decaying macroalgae in the intertidal, and may therefore disperse over considerable distances. Rhabditis (P.) marina consists of several cryptic species sympatrically distributed at a local scale. Genetic variation in the COI gene was screened in 1362 specimens from 45 locations around the world. Two nuclear DNA genes (ITS and D2D3) were sequenced to infer phylogenetic species. We found evidence for ten sympatrically distributed cryptic species, seven of which show a strong genetic structuring. A historical signature showed evidence for restricted gene flow with occasional long-distance dispersal and range expansions pre-dating the last glacial maximum. Our data also point to a genetic break around the British Isles and a contact zone in the Southern Bight of the North Sea. We provide evidence for the transoceanic distribution of at least one cryptic species (PmIII) and discuss the dispersal capacity of marine nematodes. The allopatric distribution of some intraspecific phylogroups and of closely related cryptic species points to the potential for allopatric speciation in R. (P.) marina.

Fifty (26 males, 21 female and 3 juvenile) Lyciasalamandra luschani (Luschan's salamander) collected in Antalya, were examined for helminths during 1997-2001. In this study, 3 helminth species, Aplectana acuminata, Cosmocerca longicauda and Angiostoma aspersae (Nematoda) were found. This study is the first helminthological research of Luschan's salamander in the world. This is the first time that Luschan's salamander has been shown to be the host of these parasites.

Rhabdias kuzmini n. sp., a parasite of the lungs of Bufo occidentalis, is described and illustrated. This Mexican taxon differs from the related species in the genus by the possession of 4 lips (2 subdorsal and 2 subventral) and 2 lateral pseudolabia, corpus not inflated, a larger barrel-shaped buccal capsule, equatorial vulva, and the presence of a slightly swollen cuticle in the anterior and posterior ends of the body. This is the 16th species described in the Neotropical Realm and the first species of Rhabdias described from endemic anurans in México.

Rhabdias nicaraguensis n. sp. (Rhabditida: Rhabditidae) from the lungs of Norops capito (Sauria: Polychrotidae) is described and illustrated. Rhabdias nicaraguensis n. sp. represents the 54th species assigned to the genus and the 12th from the Neotropical realm. Of the 12 Neotropical Rhabdias species, nicaraguensis is most similar to tobagoensis and vellardi. These 3 species have equatorial placement of the vulva, inflated cuticle, and 6 small circumoral lips. Rhabdias nicaraguensis is easily separated from R. tobagoensis by the shape of the buccal cavity and from R. vellardi by body size and shape of the tail. Rhabdias nicaraguensis differs from both species by host preference, the amount of inflated cuticle covering the body, and the phasmids situated posterior to the midpoint of the tail.

Two new Rhabdias species are described from the lungs of the cane toad Bufo marinus (L.) from Costa Rica and Nicaragua. Rhabdias alabialis n. sp. differs from other known species of the genus by the remarkable morphology of its head end, i.e., the absence of lips or pseudolabia, the slitlike oral opening, and the triangular shape of the buccal capsule in apical view. Rhabdias pseudosphaerocephala n. sp. is identified as a form previously known in Central and South America as Rhabdias sphaerocephala Goodey, 1924, a species initially described from toads in Europe. The new species is differentiated from R. sphaerocephala based on head-end morphology and sequences of nuclear rDNA.

Rhabdias leonae n. sp., a parasite of the lungs of Norops megapholidotus, is described and illustrated. The Mexican taxon differs from the other species in the genus by a combination of characters: possession of 4 lips, corpus slightly inflated, slightly postequatorial vulva, and presence of swollen cuticle of anterior and posterior ends. This is the 12th species described in the Neotropical realm and the first species of Rhabdias described from an endemic Mexican lizard.

Entomelas duellmani n. sp. (Rhabditida: Rhabdiasidae) from the lungs and Skrjabinodon cortagoensis n. sp. (Oxyurida: Pharyngodonidae) from the intestines of Mesaspis monticola (Sauria: Anguidae) are described and illustrated. E. duellmani is the sixth species assigned to the genus and is the third species described from the Western Hemisphere. It is easily separated from other neotropical species in the genus by pre-equatorial position of its vulva. Skrjabinodon cartagoensis is the 24th species assigned to the genus and differs from other neotropical species in the genus by female tail morphology.

Oscheius tipulae is a common soil nematode of the same family as C. elegans (Rhabditidae), which presents the same hermaphroditic mode of reproduction and is easily cultured in the same conditions. Oscheius tipulae has been used as a developmental genetic model system to study vulva formation. Compared to C. elegans, it has a simpler vulval cell lineage, a reduced competence group and a different mechanism of vulval cell fate patterning. The spectrum of vulval phenotypes obtained in genetic screens differs from that found in C. elegans. Its easy isolation from soil and the availability of numerous wild isolates of O. tipulae from all over the world facilitate population genetic and microevolutionary studies, especially of the evolution of cell lineage. The Oscheius genus also presents many species with interesting evolutionary changes in mode of reproduction, gonad development, body size, etc.

We studied variation in isozyme patterns of 8 metabolic enzymes in 5 species of Heterorhabditis (H. bacteriophora, H. indica, H. marelata, H. megidis, and H. zealandica) comprising 18 isolates. Isozyme banding patterns of all the 8 enzymes were species specific; however, 3 enzymes, i.e., arginine kinase, fumarate hydratase, and malate dehydrogenase, displayed distinct patterns among all the 18 isolates. Phylogenetic analysis of the isozyme patterns produced dendrograms depicting a high degree of genetic variation among Heterorhabditis species, with the average pairwise distance of 0.2000. Trees constructed using different phylogenetic methods showed a relatively close genetic relationship between H. megidis and H. zealandica and between H. bacteriophora and H. indica. Also, H. bacteriophora HP88 was the most distant species from H. megidis (UK isolate), H. marelatus (Oregon isolate), and H. zealandica (X1 isolate) with pairwise distance of 0.1957, 0.2228, and 0.2120, respectively. Phylogenetic analysis also revealed genetic variation among H. bacteriophora isolates with the average pairwise distance of 0.1507. GPS2 and GPS3 were the most closely related isolates with the average distance of only 0.0870, followed by GPS1 and GPS2 with average distance of 0.1087. In contrast, KMD19 and HP88, OH25, and HP88, and OH25 and Acows isolates were the most divergent populations with a pairwise distance of 0.2011 and 37 character differences. Pairwise distance analysis also revealed that genetic divergence among populations of H. bacteriophora is relatively independent of geographic distance. Overall, these results demonstrate strong subspecies structuring in H. bacteriophora.

Rhabdias bakeri n. sp. is described from specimens found in lungs of the wood frog, Rana sylvatica, from North Dakota. The new species has previously been mistakenly identified as Rhabdias ranae Walton, 1929, a common parasite of the leopard frog, Rana pipiens. The new species differs from R. ranae and Rhabdias joaquinensis Ingles, 1935 by the shape and size of pseudolabia, shape and size of buccal capsule, and wider esophageal bulb. Molecular analysis based on the partial sequences of nuclear 18S rDNA gene, complete sequences of internal transcribed spacer region, and partial sequences of 28S gene demonstrates clear differences between Rhabdias from Ra. sylvatica and Ra. pipiens, and supports the status of R. bakeri as a new species.

Rhabdias kongmongthaensis sp. n. is described based on specimens found in the lungs of the tree frog Polypedates leucomystax (Gravenhorst) (Amphibia: Rhacophoridae) from Kanchanaburi Province, western Thailand. The new species is similar to two North-American species, Rhabdias ranae and R. americanus, by presence of two lateral pseudolabia, each with two inner submedian protuberances. R. kongmongthaensis differs from both species by relative length and shape of the tail, and by its distribution and host specificity. Presence of lateral pseudolabia distinguishes the new species from the geographically closest Rhabdias species as well as from those parasitizing other rhacophorid frogs.

Chabirenia cayennensis n. g., n. sp. (Nematoda: Rhabdiasidae) is described from the teiid lizard Ameiva ameiva. A total of 139 worms were recovered, all females, from the mucous glands of the buccal cavity. The worm has a free-living phase in a homogonic life-cycle. Infective larvae are enclosed in a sheath with chequered ornamentation and composed of two exuviae. The new genus is distinct from the five known genera of the family, Pneumonema Johnston, 1916, Acanthorhabdias Pereira, 1927, Entomelas Travassos, 1930, Rhabdias Stiles and Hassall, 1905 and Neoentomelas Hasagawa, 1989, in the following characters: helical habitus, longitudinal cuticular crests, very tiny buccal cavity without thick walls and three oesophageal onchia. Several characters of this new rhabdiasid suggest the Strongylida.