Molecular characterization of Neoechinorhynchus cylindratus Van Cleave, 1913 (Acanthocephala: Neoechinorhynchidae), a parasite of the largemouth bass ( Micropterus salmoides ) in northern Mexico

Helminth parasites of terrestrial and freshwater chelonians in the Neotropical region: Biogeographic distribution and new record for Phrynops geoffroanus (Schweigger, 1812) (Testudines: Chelidae) in the Brazilian semi-arid region

The Neotropical region is considered a biodiversity hotspot for reptiles, with eight families of terrestrial and freshwater chelonians. Parasites are of great importance to aquatic ecosystems and are essential to host communities. They help understand the patterns and phylogenetic relationships of their hosts and act to control populations. A literature survey on helminth parasites of chelonians in the Neotropical region was conducted, examining the most commonly found groups of helminths, the most parasitized hosts, compiling their biogeographical and political distribution and recording the parasite fauna of Phrynops geoffroanus in the state of Paraíba, northeastern Brazil. Considering the literature from 1850 to 2024, 202 helminth taxa were recorded. The Mesoamerican dominion had the highest number of helminth taxa, and Brazil was the political unit that recorded the most helminth taxa, followed by Mexico. Nematoda was the group with the highest number of taxa and occurred in all biogeographical units, with the species Spiroxys contortus being the most commonly found, followed by Trematoda, represented by the most commonly found species, Nematophila grandis. Hosts from the Chelidae family had the highest number of helminth taxa, followed by the Kinosternidae family. The most parasitized host species were Chelonoidis denticulatus and Phrynops hilarii. For the host Phrynops geoffroanus, the first occurrence of the nematode helminth Spiroxys contortus was recorded. This is the first study to include all parasitic helminths of terrestrial and freshwater chelonians in the Neotropical region, including a new occurrence in a chelonian host in the hinterland of Paraíba, Brazil.

ADULT THORNY-HEADED WORM (ACANTHOCEPHALA) PARASITES OF NORTH AMERICAN HERPETOFAUNA: CHECKLIST OF SPECIES AND IDENTIFICATION KEY TO FAMILIES AND GENERA

An updated checklist of adult thorny-headed worms (Acanthocephala) that parasitize wild North American amphibians and reptiles is presented: A total of 21 species grouped in 4 genera, 4 families, 2 orders, and 2 classes are registered; these infect a total of 19 species of reptiles and 17 species of amphibians in the region. An illustrated identification key for the families and genera listed is proposed.

First molecular description of Neorhadinorhynchus nudus (Acanthocephala: Cavisomidae) from fish in the pacific coast of Vietnam, with notes on biogeography

Neorhadinorhynchus nudus (Harada, 1938) Yamaguti, 1939 (Cavisomidae) was morphologically described from the frigate tuna Auxis thazard (Lacépède) (Scombridae) in Nha Trang, Pacific south Vietnam. Females of N. nudus were fully described for the first time in the Pacific. Its original inadequate description as Rhadinorhynchus nudus (Harada, 1938) was corrected in material from Fiji Island, the Red Sea and Pacific Vietnam and errors in the text and line drawings of Harada were repeated in subsequent major publications where it underwent considerable nomenclature changes. New descriptive and biogeographical notes are included. We also provided here the molecular characterization of the nuclear gene (18S) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) sequence data of N. nudus. Furthermore, to elucidate the phylogenetic relationship of N. nudus within the family Cavisomidae and with other isolates were performed incorporating nuclear (18S) and mitochondrial (cox1) sequence data using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic results showed that N. nudus has a relationship with other isolates of the same species and the median-joining network showed the pattern of haplotypes that reflected the structure of the populations.

Phenotypic plasticity, genetic structure, and systematic position of Neoechinorhynchus emyditoides Fisher, 1960 (Acanthocephala: Neoechinorhynchidae) a parasite of emydid turtles from the Nearctic and Neotropical regions

The taxonomy of the 10 recognized Neoechinorhynchus species associated with emydid turtles is complex due to the morphological conservatism. In the present study, specimens of N. emyditoides from northern and southeastern Mexico exhibit great phenotypic plasticity on its diagnostic characteristics. We sequenced three molecular markers: the internal transcribed spacers ITS1, ITS2 and 5.8S gene, the D2 + D3 domains of the large subunit from nuclear DNA and cytochrome c oxidase subunit I (cox1 ) from mitochondrial DNA. Sequences of the nuclear molecular markers were aligned and compared with other congeneric species associated with emydids available in GenBank. Phylogenetic analyses supported the polyphyly of Neoechinorhynchus . The species from emydids formed a clade, which was subdivided into five subclades that correspond with each species analysed (N. pseudemydis , N. chrysemydis , N. emydis , N. schmidti and N. emyditoides ). To understand better the genetic structure of N. emyditoides a haplotype network was inferred with 29 cox1 sequences, revealing the presence of 13 haplotypes, two of which were shared and 11 were unique. The high values of fixation index, F st (0.4227–0.8925) detected between the two populations from southeastern and the two from northern Mexico indicated low genetic flow among the populations. Our data suggest that the Neoechinorhynchus species associated with emydid turtles diversified in the eastern USA and that of N. emyditoides expanded its distribution range reached southeastern Mexico.

Molecular characterisation and updated description of Neoechinorhynchus aldrichettae Edmonds, 1971 (Acanthocephala: Neoechinorhynchidae), based on material from Aldrichetta forsteri (Valenciennes) collected in Tasmania, Australia

We report on Neoechinorhynchus aldrichettae Edmonds, 1971 (Acanthocephala: Neoechinorhynchidae), obtained from yellow-eye mullet Aldrichetta forsteri (Valenciennes) (Mugiliformes: Mugilidae) from the Huon River, Tasmania, Australia. We provide new 18S and 28S rDNA gene sequence data for N. aldrichettae, assess its phylogenetic position relative to other species of Neoechinorhynchus and provide an updated morphological account of this species including detail of features omitted in the type-description, specifically of the apical organ, a collar at the base of the neck and a para-receptacle structure associated with the proboscis receptacle. We determine that eggs in this species are ovoid, without polar prolongations of fertilisation membrane, which permits assignment of N. aldrichettae to the subgenus Neoechinorhynchus. Our phylogenetic analyses place N. (N.) aldrichettae in a clade with other species of Neoechinorhynchus which parasitise mullets in marine and estuarine waters. We find that, in terms of monophyletic clades, the current subgeneric classification system for Neoechinorhynchus is not reflected in our phylogenetic analyses.

An Unusual Type of Neoechinorhynchus cylindratus (Acanthocephala: Neoechinorhynchidae) from Gambusia affinis in Peru, with Notes on Introductions

BACKGROUND

Neoechinorhynchus cylindratus Van Cleave (Zoo Anz 43: 177-1990, 1913) Van Cleave (Ill Natl Hist Surv Bull 13:225-257, 1919) is a North American acanthocephalan originally described from Micropterus salmoides (Lacépède) in Pelican Lake, Minnesota. It is common in Centrarchids but also not infrequent in fishes of other families.

PURPOSE

A unique population of N. cylindratus was discovered in Peru. It needed to be described and its introduction into Peru investigated.

METHODS

Standard processing of specimens and staining in Borax carmine and fast green for creating whole mounts were employed. Literature sources were available from the OMA personal collection.

RESULTS

The descriptive accounts of N. cylindratus have been rather stable over the years since its original description. It has been, however, oddly identified from Gambusia affinis (Baird and Girard) in Peru. Females of the Peruvian specimens were, however, not typical in having a terminal-near terminal gonopore at odds with the sub-ventral position characteristic of the usual populations of N. cylindratus in North America. We describe the Peruvian material and outline the distinct morphological variations from the North American populations in the position of the female gonopore, among other characters. We also explain its introduction into Peru and the translocation of the position of female gonopore to the terminal position.

CONCLUSIONS

The translocation to the terminal position of the female gonopore in the Peruvian material is attributed to host related developmental factors. The route of introduction of N. cylindratus into Peru through the introduction of G. affinis from the United States has been accounted for. It may be comparable to the introduction of the same acanthocephalan species into northern Mexico via the documented introduction of its primary host, M. salmoides, also from the United States into Mexico in 1930. The introduction of Acanthocephalus dirus Van Cleave (Ill Natl Hist Surv Bull 13:225-257, 1919) (Van Cleave and Townsend, 1936) into Mexico is also discussed.

MOLECULAR IDENTIFICATION OF JUVENILE NEOECHINORHYNCHUS SPP. (PHYLUM: ACANTHOCEPHALA) INFECTING OSTRACOD AND SNAIL HOSTS PROVIDES INSIGHT INTO ACANTHOCEPHALAN HOST USE

The role of invertebrates in some acanthocephalan life cycles is unclear because juvenile acanthocephalans are difficult to identify to species using morphology. Most reports suggest acanthocephalans from turtle definitive hosts use ostracods as intermediate hosts and snails as paratenic hosts. However, laboratory studies of the life cycle suggest that ostracods and snails are both required hosts in the life cycle. To elucidate the role of ostracods and snails in acanthocephalan life cycles better, we collected 558 freshwater snails of 2 species, including Planorbella cf. Planorbella trivolvis and Physa acuta, from 23 wetlands in Oklahoma, U.S.A., and examined them for acanthocephalan infections. Additionally, we examined 37,208 ostracods of 4 species, Physocypria sp. (morphotype 1), Cypridopsis sp., Stenocypris sp., and Physocypria sp. (morphotype 2) for juvenile acanthocephalans from 2 wetlands in Oklahoma. Juvenile acanthocephalans were morphologically characterized, and the complete internal transcribed spacer (ITS) region of nuclear rDNA was sequenced from acanthocephalans infecting 11 ostracod and 13 snail hosts. We also sampled 10 red-eared slider turtles, Trachemys scripta elegans, and 1 common map turtle, Graptemys geographica, collected from Oklahoma, Arkansas, and Texas and recovered 1,854 adult acanthocephalans of 4 species. The ITS of 17 adult acanthocephalans of 4 species from turtle hosts were sequenced and compared to juvenile acanthocephalan sequences from ostracod and snail hosts from this study and GenBank to determine conspecificity. Of the 23 locations sampled for snails, 7 (30%) were positive for juvenile acanthocephalans in the genus Neoechinorhynchus. The overall prevalence and mean intensity of acanthocephalans in Planorbella cf. P. trivolvis and P. acuta were 20% and 2 (1-6) and 2% and 1 (1), respectively. In contrast, only 1 of 4 species of ostracods, Physocypria sp. (morphotype 1), was infected with larval/juvenile Neoechinorhynchus spp. with an overall prevalence of 0.1% and a mean intensity of 1 (1-2). Although 4 species of acanthocephalans infected turtle definitive hosts, including Neoechinorhynchus chrysemydis, Neoechinorhynchus emydis, Neoechinorhynchus emyditoides, and Neoechinorhynchus pseudemydis, all the ITS sequences from cystacanths infecting snail hosts were conspecific with N. emydis. In contrast, the ITS sequences from larval/juvenile acanthocephalans from ostracods were conspecific with 2 species of acanthocephalans from turtles (N. emydis and N. pseudemydis) and 1 species of acanthocephalan from fish (Neoechinorhynchus cylindratus). These results indicate that N. emydis infects freshwater snails, whereas other species of Neoechinorhynchus appear not to infect snail hosts. We document new ostracod and snail hosts for Neoechinorhynchus species, including the first report of an ostracod host for N. pseudemydis, and we provide novel molecular barcodes that can be used to determine larva, juvenile, and adult conspecificity of Neoechinorhynchus species.

Morphological and molecular characterization of Neoechinorhynchus (N.) cephali n. sp. (Acanthocephala: Neoechinorhynchidae) Stiles and Hassall 1905 infecting the flathead grey mullet Mugil cephalus (Linnaeus, 1758) from the southwest coast of India

The present paper describes Neoechinorhynchus (Neoechinorhynchus) cephali n. sp., an acanthocephalan parasite infecting the intestine of the flathead grey mullet Mugil cephalus from the southwest coast of India. The parasite exhibited a prevalence of 7.40%, mean intensity of 18.5 and abundance of 18-19 worms/infected host. Morphologically, N. (N.) cephali n. sp. is sexually dimorphic, small, cylindrical, slightly curved and creamy white in colour. Females are larger than males, measured 8.87 × 0.88 mm and 5.65 × 0.66 mm, respectively. Proboscis is armed with three circles of six hooks each, which progressively decreases in size posteriorly. Hooks are backwardly curved and robust and tapering with a sharp, pointed tip, striations on the surface and a manubrium at its base. The body is aspinose, trunk surface with micropores and pits and proboscis surface with papilliform structures. The body wall is with five dorsal and two ventral hypodermal nuclei, along with lacunar canals connected by circular anastomoses. Lemnisci are subequal, small lemnisci are uninucleated, and large ones are binucleated. The cement gland is oval, with four giant nuclei; bursa is with many sensory cells. Eggs are elliptical, with concentric shells, and polar prolongation is absent. In the molecular and phylogenetic analyses based on the 18S ribosomal DNA region, the present species stands out with a high bootstrap value and is positioned as a sister branch of N. (N.) dimorphospinus. Based on the differences in morphology, morphometry and molecular and phylogenetic analyses, the present species of acanthocephalan infecting M. cephalus is considered as new, and the name Neoechinorhynchus (Neoechinorhynchus) cephali n. sp. is proposed.

The Molecular Profile of Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha 2011 (Acanthocephala: Rhadinorhynchidae) from Vietnam

Of the 46 known species of Rhadinorhynchus Lühe, 1911, only 6 species, including Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha, 2011, have dorsal and ventral, as well as lateral, trunk spines in the posterior field of trunk spines. The other 5 species are Rhadinorhynchus erumei Gupta and Fatima, 1981, Rhadinorhynchus adenati (Golvan and Houin, 1964) Golvan, 1969, Rhadinorhynchus lintoni Cable and Linderoth, 1963, Rhadinorhynchus pacificus Amin, Rubtsova, and Ha, 2019, and Rhadinorhynchus multispinosus Amin, Rubtsova, and Ha, 2019. These 5 species are distinguished from R. dorsoventrospinosus by differences in proboscis hook armature, trunk spine organization, and egg size. The distinction of R. dorsoventrospinosus is further demonstrated by its molecular description. We amplified the 18S and ITS1+5.8S+ITS2 rDNA region and cytochrome c oxidase subunit 1 (COI) gene for this study. Unfortunately, no ITS1+5.8S+ITS2 gene sequences are available for comparison with other species of the genus Rhadinorhynchus. Therefore, phylogenetic trees generated from sequences of the 18S nuclear region and COI gene were analyzed for the phylogenetic position of isolates of R. dorsoventrospinosus. Rhadinorhynchus dorsoventrospinosus has been validated as a species based on comparisons of morphological (original description) and molecular features (this paper). The additional genetic data will be useful as more species are described and as more genetic material becomes available to improve taxon sampling in the genetic analysis.

Molecular characterisation of acanthocephalans from Australian marine teleosts: proposal of a new family, synonymy of another and transfer of taxa between orders

We provide molecular data (cox1, 18S rDNA and 28S rDNA) for 17 acanthocephalan species and 20 host-parasite combinations from Australian marine teleosts collected from off Queensland, Australia. Fourteen of these acanthocephalans are characterised with molecular data for the first time and we provide the first molecular data for a species of each of the genera Heterosentis Van Cleave, 1931, Pyriproboscis Amin, Abdullah & Mhaisen, 2003 and Sclerocollum Schmidt & Paperna, 1978. Using 18S and 28S rDNA sequences, the phylogenetic position of each newly sequenced species is assessed with both single-gene and concatenated 18S+28S maximum likelihood and Bayesian inference analyses. Additional phylogenetic analyses focusing on the genus Rhadinorhynchus Lühe, 1912 and related lineages are included. Our phylogenetic results are broadly consistent with previous analyses, recovering previously identified inconsistencies but also providing new insights and necessitating taxonomic action. We do not find sufficient evidence to recognise the Gymnorhadinorhynchidae Braicovich, Lanfranchi, Farber, Marvaldi, Luque & Timi, 2014 as distinct from the Rhadinorhynchidae Lühe, 1912. The family Gymnorhadinorhynchidae and its sole genus, Gymnorhadinorhynchus Braicovich, Lanfranchi, Farber, Marvaldi, Luque & Timi, 2014, are here recognised as junior synonyms of Rhadinorhynchidae and Rhadinorhynchus, respectively. The two species currently assigned to Gymnorhadinorhynchus are recombined as Rhadinorhynchus decapteri (Braicovich, Lanfranchi, Farber, Marvaldi, Luque & Timi, 2014) n. comb. and Rhadinorhynchus mariserpentis (Steinauer, Garcia-Vedrenne, Weinstein & Kuris, 2019) n. comb. In all of our analyses, Rhadinorhynchus biformis Smales, 2014 is found basal to the Rhadinorhynchidae + Transvenidae Pichelin & Cribb, 2001, thus resulting in a paraphyletic Rhadinorhynchidae. It appears that R. biformis may require a new genus and family; however, morphological data for this species are currently insufficient to adequately distinguish it from related lineages, thus we defer the proposal of any new higher-rank names for this species. Species of the genus Sclerocollum, currently assigned to the Cavisomidae Meyer, 1932, are found nested within the family Transvenidae. We transfer the genus Sclerocollum to the Transvenidae and amend the diagnosis of the family accordingly. The genera Gorgorhynchoides Cable & Linderoth, 1963 and Serrasentis Van Cleave, 1923, currently assigned to the Rhadinorhynchidae, are supported as sister taxa and form a clade in the Polymorphida. We transfer these genera and Golvanorhynchus Noronha, Fabio & Pinto, 1978 to an emended concept of the Isthomosacanthidae Smales, 2012 and transfer this family to the Polymorphida. Lastly, Pyriproboscis heronensis (Pichelin, 1997) Amin, Abdullah & Mhaisen, 2003, currently assigned to the Pomphorhynchidae Yamaguti, 1939, falls under the Polymorphida in our analyses with some support for a sister relationship with the Centrorhynchidae Van Cleave, 1916. As this species clearly does not belong in the Pomphorhynchidae and is morphologically and molecularly distinct from the lineages of the Polymorphida, we propose the Pyriprobosicidae n. fam. to accommodate it.

Redescription and molecular analysis of Neoechinorhynchus (Neoechinorhynchus) johnii Yamaguti, 1939 (Acanthocephala, Neoechinorhynchidae) from the Pacific Ocean off Vietnam

Neoechinorhynchus (Neoechinorhynchus) johnii Yamaguti, 1939 is redescribed from Eleutheronema tetradactylum (Polynemidae), Johnius carouna (Sciaenidae), Johnius sp., and Otolithes ruber (Sciaenidae) along the north and south coasts of Vietnam. Our description completes missing and inadequate information in the original descriptions and line drawings from Johnius goma in Japan and from Pseudosciaena diacanthus in the Indian Ocean. We add new information documented by scanning electron microscopy (SEM) and photomicroscopy, and explore the wide morphological diversity attributed to host species. The redescription includes: worms cylindrical with round proboscis with prominent apical organ, and large anterior hooks distant from small middle and posterior hooks; neck longer than the proboscis, nucleated lemnisci subequal, and receptacle with large basal triangulate cephalic ganglion and attached para-receptacle structure (PRS); male reproductive system in posterior half of trunk; adult females with introvert genital vestibule; and eggs spherical or rectangular. Gallium cuts and X-ray scans of hooks show high concentrations of sulfur on edge layer aiding in forming hardened calcium phosphate apatite of that layer with calcium and phosphorus in higher concentration in central part of hook. Molecular results consistently yielded a strongly supported distinct clade for the Neoechinorhynchus species from Vietnam for both 18S gene and the ITS1-5.8S-ITS2 region of ribosomal RNA. Phylogenetic analysis demonstrated that N. johnii occupies a separate position in the trees, probably indicating an Asian origin of this species.