For several decades, green treefrogs (Hyla cinerea) have been undergoing rapid range expansion northward and eastward in Illinois, Indiana, and Kentucky. While range expansion of green treefrogs in these states may be linked to climate change, a recent study suggested this expansion could be facilitated by parasites, given that expanded range populations of green treefrogs from Kentucky and Indiana exhibited significant decreases in helminth species diversity compared to those examined from historical locations of Kentucky. Because rapid range expansion may lead to hosts escaping their parasites (= parasite release), a reprieve from parasitic infection could allocate additional resources to growth and reproduction and thus facilitate the expansion. The present study compares patterns of helminth diversity for green treefrogs from historical and 2 types (early and late expansion) of expanded range locations of southern Illinois to test whether these range-expansion populations are also experiencing a reduction in parasitism due to parasite release. The results of this study did not find significant differences in helminth diversity when helminth communities of green treefrogs from their historical and expanded ranges were compared. These results appear to downplay the putative role of parasite release in the northward range expansion of H. cinerea in Illinois. Studies are underway to determine whether local factors, including abiotic conditions and amphibian host diversity, play a more prominent role in influencing helminth diversity of green treefrogs.

Apolocystis bosanqueti n. sp., a parasite of an important invasive earthworm in North America, Amynthas agrestis, is described from a site in northern Vermont. The earthworm host follows an annual life cycle in Vermont, so the entire life cycle of the parasite can be observed in 7 mo. In spring, the parasites were first seen in juvenile worms as paired gamonts (suggesting precocious association). These paired gamonts mature into gametocytes that form an opaque structure, with a thick gelatinous envelope (epicyst), that becomes full of zygotes. The resulting gametocyst becomes packed with ∼10⁵ fusiform oocysts. The mature orbicular gametocysts are large (∼1 mm in diameter) and visible to the naked eye through the body wall of the host's anterior segments. The new species most resembles Apolocystis herculea described from many lumbricid earthworm species in Europe but differs from that parasite because Ap. herculea infects the intestinal wall in the posterior of the host rather than the anterior segments. A survey of 9 other earthworm species sympatric with Am. agrestis revealed that only Amynthas tokioensis, also an invasive species, was infected with Ap. bosanqueti, albeit much less commonly. Diagnosis for the family Monocystidae is problematic because cardinal characters are lacking, and the commonly cited character, a trophozoite with no anterior differentiation, is violated in most genera placed in the family. For the first time, a molecular phylogeny is presented that includes 3 genera of monocystids with diverse cell morphology (including the new species) and supports the monophyly of the family. The only morphological character that may be used to diagnose the Monocystidae is the morphology of oocysts, which are fusiform with extended terminal tips. A comparison of oocysts from 7 parasites recovered from local earthworms, including from 3 monocystid species in the phylogeny, confirms the utility of this diagnostic trait. The 2 hosts of the new species were most likely introduced from Japan, so the range of Apolocystis likely extends into East Asia.

This study reports a new case of acanthocephalan (thorny-headed worm) eggs in a coprolite from Bonneville Estates Rockshelter in eastern Nevada and uses archaeological and ethnographic data to better understand long-term relationships between people and acanthocephalans. Acanthocephalans are parasitic worms that use arthropods as intermediate hosts in their multi-host life cycles. Though acanthocephaliasis is rare among humans today, cases have increased in the last decade, and the discovery of acanthocephalan eggs in coprolites from archaeological sites in the Great Basin suggests a deep, shared history. At Bonneville Estates Rockshelter, 9 acanthocephalan eggs were recovered using a modified rehydration-homogenization-micro-sieving protocol on a coprolite that was radiocarbon dated to 6,040 ± 60 ¹⁴C BP (7,160–6,730 cal BP), pushing back the oldest evidence of human acanthocephalan infection by 3 millennia. Researchers have proposed that the paleoepidemiology of acanthocephalans may relate to subsistence practices due to overlap in locations of infection and areas where insects are part of traditional foodways. This paper considers the paleoepidemiology of acanthocephalan infection through the first combined review of paleoparasitological, ethnographic, and archaeological records in western North America. Ethnographic and archaeological records support the hypothesis that archaeological cases of human acanthocephaliasis may be linked to entomophagy. Additional parasitological analyses are advised to determine whether this distribution is the result of dietary practices, host ecology, taphonomic issues, sampling biases, or a combination of factors.

The French grunt, Haemulon flavolineatum, is an abundant fish and a good model for studying parasite communities. Specimens were collected at 4 localities between the Campeche Bank (within the Gulf of Mexico) and the Mexican Caribbean Sea to describe and compare the differences and similarities between localities and regions in the communities of parasitic helminths. Thus, we calculated the Hill numbers associated with species richness (q = 0) and the dominance estimator (q = 2) using rarefaction and extrapolation curves to provide asymptotic estimators of diversity. A 2-way PERMANOVA was used to determine whether there was a significant difference in parasite assemblage structure between localities or regions. A total of 11 helminth taxa (species level) were recorded in 104 individuals of H. flavolineatum, consisting of 8 digenean trematodes species, 2 acanthocephalan species, and 1 nematode species. Our findings include new reports of 7 parasite taxa and new geographical records for some parasites in H. flavolineatum. The highest dissimilarities in parasite composition were observed between the most distant locations (Banco Chinchorro vs. Cayo Arcas) that were each located in different regions. Species richness was similar between regions, although the most dominant helminths were Postmonorchis orthopristis and Dollfustrema sp. in the Mexican Caribbean and Campeche Bank regions, respectively. Future studies should explore how patterns in parasite community structure are affected by currents running south to north by the Yucatan Current through the Yucatan Channel and easterly to Campeche Bank.

A new digenean species belonging in Encyclobrephus Sinha, 1949 is described, and the generic diagnosis is amended to accommodate variation in several features of the new species. Worms were collected from the intestines of 2 specimens of the Mekong snail-eating turtle, Malayemys subtrijuga (Schlegel and Müller, 1845). Permanent whole-mounted worms were studied using light microscopy, and ribosomal DNA (rDNA) sequences were generated from 3 worms. We investigated the phylogenetic relationship of the new species among some digenea using separate Bayesian inference analyses, 1 based on the 28S rDNA gene and rooted using a species from the Monorchioidea Odhner, 1911, and a second based on the internal transcribed spacer 1 region rooted by a species in the Microphalloidea Ward, 1901. Prior to the analyses, Encyclobrephus was classified in the Encyclometridae Mehra, 1931. Previous studies using rDNA from the type species for the family, Encyclometra colubrimurorum (Rudolphi, 1819) Baylis and Cannon, 1924, have demonstrated that En. colubrimurorum is closely related to species of Polylekithum Arnold, 1934 in the Gorgoderoidea Looss, 1901. Nevertheless, phylograms from both analyses indicated that the new species of Encyclobrephus belongs in the Plagiorchioidea Lühe, 1901, related to species in the families Cephalogonimidae Looss, 1899, Plagiorchiidae Lühe, 1901, Reniferidae Pratt, 1902, and Telorchiidae Looss, 1899. The present results suggest that Encyclobrephus is not closely related to En. colubrimurorum. Familial classification of Encyclobrephus is contingent on molecular data availability for the type species but it should be removed from the Encyclometridae and classified as incertae sedis within the Plagiorchioidea. Encyclometridae belongs in the Gorgoderoidea, not the Plagiorchioidea.

An undescribed species of Kannaphallus Unnithan, 1957 (Monogenoidea: Heteraxinidae) was collected from the gills of the golden trevally Gnathanodon speciosus (Forsskål) (Carangidae) from Moreton Bay, Queensland, during January 2016 and from Ningaloo Reef, Western Australia, during December 2021 and June 2022. The diagnosis for Kannaphallus was emended and the new species, Kannaphallus raphidium, was described. Kannaphallus virilis of Young, nec Unnithan was placed in synonymy with K. raphidium. The distal components of the male reproductive system and the arrangement of the clamp rows of the haptor occurred as mirror images among specimens of K. raphidium, suggesting that the respective antipodes of K. raphidium may have reproductive implications and function in the site selection of the parasite on the host's gills. A specimen of K. raphidium from Western Australia was sequenced for the cytochrome c oxidase subunit 1 (COI) mtDNA and ITS2 rDNA barcoding markers, and the phylogenetically informative 28S rDNA marker. Maximum likelihood and Bayesian inference analyses based on a partial 28S rDNA alignment, including all comparable heteraxinid sequence data available, resolved the Heteraxininae and Cemocotylinae as reciprocatively paraphyletic and provided evidence that Kannaphallus may be paraphyletic. No taxonomic changes concerning the subfamilies and genera of the Heteraxinidae were proposed. Finally, Kannaphallus univaginalis Ramalingam, 1960 and Cemocotylelloides univaginalis (Ramalingam, 1960) Nitta, Kondo, Ohtsuka, Kamarudin, and Ismail, 2022 are considered nomen nuda sensu the International Code of Zoological Nomenclature.

Both sexes of Catallagia appalachiensis n. sp. are described from high elevation spruce-fir forests in Sevier County, Tennessee and adjoining Swain County, North Carolina in the Great Smoky Mountains National Park. The type host of the new flea is the southern red-backed vole, Myodes gapperi (Vigors) (25 flea specimens), although small numbers of specimens were also collected from a sympatric northern short-tailed shrew, Blarina brevicauda (Say) (2 fleas), a red squirrel, Tamiasciurus hudsonicus (Erxleben) (1 flea), and a North American deer mouse, Peromyscus maniculatus (Wagner) (1 flea). Infestation prevalences for these hosts are provided. The new species is compared morphologically with other known species of Catallagia, in particular with Catallagia borealis, the only other described congeneric flea in eastern North America. This is the first new species of flea to be described from the eastern United States since 1980.

We herein resurrect and emend Plesiocreadium Winfield, 1929 (Digenea: Macroderoididae) and provide a supplemental description of its type species, Plesiocreadium typicum Winfield, 1929, based on adult specimens collected from the intestine of bowfins, Amia calva Linnaeus, 1766 (Amiiformes: Amiidae), captured in the L'Anguille River (Mississippi River Basin, Arkansas), Big Lake (Pascagoula River Basin, Mississippi), Chittenango Creek (Oneida Lake, New York), and Reelfoot Lake (Tennessee River Basin, Tennessee). Plesiocreadium spp. (Pl. typicum and Plesiocreadium flavum [Van Cleave and Mueller, 1932] n. comb.) differ from other macroderoidids by having a dorsoventrally flat forebody, ceca that extend posteriad beyond the testes and that do not form a cyclocoel, testes that are greater than one-half of maximum body width, a cirrus sac that is dorsal to the ventral sucker and arches dextrad or sinistrad, a uterine seminal receptacle, asymmetrical vitelline fields that remain separated anteriorly and posteriorly and that extend anteriad to the level of the ventral sucker, and an I-shaped excretory vesicle. Bayesian phylogenetic analyses (ITS2 and 28S) recovered monophyletic Plesiocreadium sensu stricto (as defined herein) sister to Macroderoides trilobatus Taylor, 1978 and that clade sister to the remaining macroderoidids, with sequences ascribed to species of Macroderoides Pearse, 1924 recovered as paraphyletic. We regard Macroderoides parvus (Hunter, 1932) Van Cleave and Mueller, 1934, M. trilobatus, and Rauschiella Babero, 1951 as incertae sedis. Arkansas, New York, and Tennessee comprise new locality records for Pl. typicum.

Pterobdella occidentalis n. sp. (Hirudinida: Piscicolidae) is described from the longjaw mudsucker, Gillichthys mirabilis Cooper, 1864, and the staghorn sculpin, Leptocottus armatus Girard, 1854, in the eastern Pacific, and the diagnosis of Pterobdella abditovesiculata (Moore, 1952) from the ‘o‘opu ‘akupa, Eleotris sandwicensis Vaillant and Sauvage, 1875, from Hawaii is amended. The morphology of both species conforms with the genus Pterobdella in possessing a spacious coelom, well-developed nephridial system, and 2 pairs of mycetomes. Originally described as Aestabdella abditovesiculata, P. occidentalis (present along the U.S. Pacific Coast), can be distinguished from most congeners by its metameric pigmentation pattern and diffuse pigmentation on the caudal sucker. Based on mitochondrial gene sequences, including cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit I (ND1), P. occidentalis forms a distinct polyphyletic clade with Pterobdella leiostomi from the western Atlantic. Based on COI, ND1, and the 18S rRNA genes, other leech species most closely related to P. occidentalis include Pterobdella arugamensis from Iran, Malaysia, and possibly Borneo, which likely represent distinct species, and Pterobdella abditovesiculata from Hawaii, one of only a few endemic fish parasites in Hawaii. Like P. abditovesiculata, P. arugamensis, and Petrobdella amara, P. occidentalis is often found in estuarine environments, frequently infecting hosts adapted to a wide range of salinity, temperature, and oxygen. The physiological plasticity of P. occidentalis and the longjaw mudsucker host, and the ease of raising P. occidentalis in the lab, make it an excellent candidate for the study of leech physiology, behavior, and possible bacterial symbionts.

Species of the family Reniferidae are trematodes found in the oral cavity and esophagus of snakes from Nearctic and Neotropical regions. Although Renifer heterocoelium has been reported in different snake species from South America, the snails involved in its transmission remain unknown. In this study, a xiphidiocercaria emerged from the physid snail Stenophysa marmorata from Brazil and was subjected to morphological and molecular study. The general morphology, including the shape of the stylet and arrangement of penetration glands, resembles that described for reniferid trematodes from North America. Phylogenetic analysis on the basis of nuclear sequences (28S ribosomal deoxyribonucleic acid gene [1,072 base pairs {bp}] and internal transcribed spacer region [ITS, 1,036 bp]) supports identifying this larva as a member of the family Reniferidae, very possibly a species of the genus Renifer. In the 28S analysis, low molecular divergences were found to Renifer aniarum (1.4%) and Renifer kansensis (0.6%), but also concerning other 2 reniferid species, i.e., Dasymetra nicolli (1.4%) and Lechriorchis tygarti (1.0%). Regarding ITS, the divergences between this Brazilian cercaria and R. aniarum or L. tygarti were 1.9% and 8.5%, respectively. In the case of the mitochondrial marker cytochrome oxidase subunit 1 (797 bp), our Reniferidae gen. sp. differs 8.6–9.6% from Paralechriorchis syntomentera, the only reniferid with sequences available for comparison. We discuss the probable conspecificity of the larval stages here reported with R. heterocoelium, the reniferid species reported in South America.