Anatomy and mechanisms of vocal production in harvest mice.

Characterizing mechanisms of vocal production provides important insight into the ecology of acoustic divergence. In this study, we characterized production mechanisms of two types of vocalizations emitted by western harvest mice (Reithrodontomys megalotis), a species uniquely positioned to inform trait evolution because it is a sister taxon to peromyscines (Peromyscus and Onychomys spp.), which use vocal fold vibrations to produce long-distance calls, but more ecologically and acoustically similar to baiomyines (Baiomys and Scotinomys spp.), which employ a whistle mechanism. We found that long-distance calls (∼10 kHz) were produced by airflow-induced vocal fold vibrations, whereas high-frequency quavers used in close-distance social interactions (∼80 kHz) were generated by a whistle mechanism. Both production mechanisms were facilitated by a characteristic laryngeal morphology. Our findings indicate that the use of vocal fold vibrations for long-distance communication is widespread in reithrodontomyines (Onychomys, Peromyscus, Reithrodontomys spp.) despite overlap in frequency content that characterizes baiomyine whistled vocalizations. The results illustrate how different production mechanisms shape acoustic variation in rodents and contribute to ecologically relevant communication distances.

Trematode parasites as indicators of an animal component in the diet of the Water Vole Arvicola amphibius.

The intestinal trematode fauna of the Water Vole Arvicola amphibius, (previously A. terrestris), was investigated to determine whether it might provide evidence of an animal component in the diet of this aquatic herbivorous small mammal. Interrogation of the electronic Host-Parasite Database of the Natural History Museum London revealed the presence of fourteen species of intestinal trematode in water voles, infection with each of which would require the ingestion of tissue from an animal intermediate host. The results obtained using these parasite indicators provide convincing evidence of animal components in the diet of A. amphibius and support anecdotal reports of water voles feeding on animal material in the field.

Lyme Disease Agent Reservoirs Peromyscus leucopus and P. maniculatus Have Natively Inactivated Genes for the High-Affinity Immunoglobulin Gamma Fc Receptor I (CD64).

The abundant and widely distributed deermice Peromyscus leucopus and P. maniculatus are important reservoirs for several different zoonotic agents in North America. For the pathogens they persistently harbor, these species are also examples of the phenomenon of infection tolerance. In the present study a prior observation of absent expression of the high-affinity Fc immunoglobulin gamma receptor I (FcγRI), or CD64, in P. leucopus was confirmed in an experimental infection with Borreliella burgdorferi, a Lyme disease agent. We demonstrate that the null phenotype is attributable to a long-standing inactivation of the Fcgr1 gene in both species by a deletion of the promoter and coding sequence for the signal peptide for FcγRI. The Fcgr1 pseudogene was also documented in the related species P. polionotus. Six other Peromyscus species, including P. californicus, have coding sequences for a full-length FcγRI, including a consensus signal peptide. An inference from reported phenotypes for null Fcgr1 mutations engineered in Mus musculus is that one consequence of pseudogenization of Fcgr1 is comparatively less inflammation during infection than in animals, including humans, with undisrupted, fully active genes.

Species delimitation and integrative taxonomy of the Reithrodontomys mexicanus (Rodentia: Cricetidae) cryptic complex.

Species boundaries are difficult to establish in groups with very similar morphology. As an alternative, it has been suggested to integrate multiple sources of data to clarify taxonomic problems in taxa where cryptic speciation processes have been reported. This is the case of the harvest mouse Reithrodontomys mexicanus, which has a problematic taxonomy history as it is considered a complex species. Here, we evaluate the cryptic diversity of R. mexicanus using an integrative taxonomy approach in order to detect candidate lineages at the species level. The molecular analysis used one mitochondrial (cytb) and two nuclear (Fgb-I7 and IRBP) genes. Species hypotheses were suggested based on three molecular delimitation methods (mPTP, bGMYC, and STACEY) and cytb genetic distance values. Skull and environmental space differences between the delimited species were also tested to complement the discrimination of candidate species. Based on the consensus across the delimitation methods and genetic distance values, four species were proposed, which were mostly supported by morphometric and ecological data: R. mexicanus clade I, R. mexicanus clade IIA, R. mexicanus clade IIIA, and R. mexicanus clade IIIB. In addition, the evolutionary relationships between the species that comprise the R. mexicanus group were discussed from a phylogenetic approach. Our findings present important taxonomic implications for Reithrodontomys, as the number of known species for this genus increases. Furthermore, we highlight the importance of the use of multiple sources of data in systematic studies to establish robust delimitations between species considered taxonomically complex.

Survey and Molecular Characterization of Sarcocystidae protozoa in Wild Cricetid Rodents from Central and Southern Chile.

In Chile, studies of parasites from the family Sarcocystidae (Apicomplexa) have mostly been related to domestic animals. We aimed to assess the presence of Sarcocystidae taxa in cricetid rodents from Central and Southern Chile. We studied 207 rodents, encompassing six species, from 13 localities. We isolated DNA from tissue samples, amplified the Sarcocystidae 18S rRNA gene with polymerase chain reaction, and performed phylogenetic analyses using maximum likelihood and Bayesian inferences. In addition, we examined blood smears and performed histological studies in organs from Sarcocystidae DNA-positive animals. Three specimens were DNA-positive and three genotypes were retrieved and named: Sarcocystis sp. P61, related to Sarcocystis strixi, was detected in two Abrothrix olivacea. Toxoplasmatinae gen. sp. P99 was retrieved from those same two specimens, and was related to Toxoplasma and other genera, although it branched independently. Besnoitia sp. R34 was detected in one Abrothrix hirta, and was clustered with congeneric species associated with rodents. No protozoa were found during microscopic studies; thus, it was not possible to confirm parasitic interactions rather than accidental encounters. However, the close relatedness of the retrieved genotypes to parasites of rodents supports the hypothesis of host-parasite associations. All three genotypes are suggested as potential new taxa, including a putative new genus.

Cross-reactivity of T cell-specific antibodies in the bank vole (Myodes glareolus).

The bank vole is a common Cricetidae rodent that is a reservoir of several zoonotic pathogens and an emerging model in eco-immunology. Here, we add to a developing immunological toolkit for this species by testing the cross-reactivity of commercially available monoclonal antibodies (mAbs) to the bank vole lymphocyte differentiation molecules and a transcription factor. We show that a combination of mAbs against CD4, CD3, and Foxp3 allows flow cytometric distinction of the main subsets of T cells: putative helper CD4+, cytotoxic CD8+ (as CD3+CD4-) and regulatory CD4+Foxp3+. We also provide a comparative analysis of amino acid sequences of CD4, CD8αß, CD3εγδ and Foxp3 molecules for a number of commonly studied Cricetidae rodents and discuss mAb cross-reactivity patterns reported so far in this rodent family. We found that in case of mAbs targeting the extracellular portions of commonly used T cell markers, sequence similarity is a poor prognostic of cross-reactivity. Use of more conserved, intracellular molecules or molecule fragments is a more reliable approach in non-model species, but the necessity of cell fixation limit its application in, e.g. functional studies.

Disentangling morphology and genetics in two voles (Microtus pennsylvanicus and M. ochrogaster) in a region of sympatry.

Species in recent, rapid radiations can be difficult to distinguish from one another due to incomplete sorting of traits, insufficient time for novel morphologies to evolve, and elevated rates of hybridization and gene flow. The vole genus Microtus (58 spp.) is one such system where all three factors are likely at play. In the central United States, the prairie vole, Microtus ochrogaster, and the eastern meadow vole, M. pennsylvanicus, occur in sympatry and can be distinguished on the basis of molar cusp patterns but are known to be exceptionally difficult to distinguish using external morphological characters. Using a combination of morphometrics, pelage color analyses, and phylogenetics, we explored which traits are most effective for species identification and whether these same traits can be used to identify the subspecies M. o. ohionensis. While we were able to identify six traits that differed significantly between M. ochrogaster and M. pennsylvanicus, we also found substantial measurement overlap which limits the utility of these traits for species identification. The subspecies M. o. ohionensis was particularly difficult to distinguish from M. p. pennsylvanicus, and we did not find any evidence that this subspecies forms a distinct genetic clade. Furthermore, the full species M. ochrogaster and M. pennsylvanicus did not form reciprocal clades in phylogenetic analyses. We discuss several possible reasons for these patterns, including unrecognized variation in molar cusp patterns and/or localized hybridization. Overall, our results provide useful information that will aid in the identification of these species and subspecies in the future, and provides a case study of how genetics, morphometrics, and fur color analyses can be used to disentangle signatures of evolutionary history and hybridization.

Helminth and protozoan parasites of subterranean rodents (Chordata, Mammalia, Rodentia) of the world.

Published studies and ten new unpublished records included herein reveal that approximately 174 species of endoparasites (helminths and protozoans) are known from 65 of 163 species of rodents that occupy the subterranean ecotope globally. Of those, 94 endoparasite species were originally described from these rodents. A total of 282 host-parasite associations are summarized from four major zoogeographic regions including Ethiopian, Palearctic/Oriental, Nearctic, and Neotropical. Thirty-four parasite records from the literature have been identified to only the level of the genus. In this summary, ten new records have been added, and the most current taxonomic status of each parasite species is noted. Interestingly, there are no data on endoparasites from more than 68% of described subterranean rodents, which indicates that discovery and documentation are at an early stage and must continue.

The First Record of Eothenomys (Arvicolinae, Cricetidae, Rodentia) from the Pleistocene of Vietnam.

The Oriental vole Eothenomys eleusis (Thomas, 1911) is identified from the Middle Pleistocene Tham Hai cave locality in northern Vietnam (Lang Son Province) based on isolated teeth. This is the first record of the Pleistocene Arvicolinae in Vietnam and the first fossil find of Eothenomys outside of China.

Andryoides gen. n. and morphological key features in cestodes of the family Anoplocephalidae sensu stricto (Cyclophyllidea) in mammals.

As presently defined, the tapeworm genus Andrya Railliet, 1895 (Cyclophyllidea: Anoplocephalidae sensu stricto) includes the type species A. rhopalocephala (Riehm, 1881) in hares of the genus Lepus Linnaeus (Leporidae) in western Eurasia and four species in cricetid (Neotominae, Sigmodontinae) and octodontid rodents in North and South America. The host range of Andrya is puzzling, because it is the only genus of anoplocephalid (s. s.) cestodes parasitising both rodents and lagomorphs. The present morphological analysis shows that the American species of Andrya share multiple consistent features, in which they differ from those of A. rhopalocephala and the morphologically related Neandrya cuniculi (Blanchard, 1891). The main differences concern the position of the uterus with respect to the longitudinal osmoregulatory canals and testes. Consequently, a new genus Andryoides gen. n. is proposed for the American species, resulting in the following combinations: Andryoides neotomae (Voge, 1946) comb. n. (type species), Andryoides octodonensis (Babero et Cattan, 1975) comb. n., Andryoides vesicula (Haverkost et Gardner, 2010) comb. n. and Andryoides boliviensis (Haverkost et Gardner, 2010) comb. n. However, A. boliviensis is regarded here as a junior synonym of A. vesicula (new synonymy). The present study also defines the morphological key features for all the valid genera of cestodes of the family Anoplocephalidae (s. s.), and discusses the phylogenetic affinities and historical biogeography of Andryoides and other endemic American anoplocephalid cestodes.

Mammals in Tawny Owl (Strixaluco) pellets from Kharkiv Region, Ukraine.

Background: The Tawny owl (Strixaluco) is a common owl species in Europe, demonstrating generalist diet strategy. Its main prey are small rodents and numerous studies show that the composition of its diet broadly reflects changes in prey species abundance in its habitats. Due to strictly sedentary habits of adult birds and their year-round territoriality, it is possible to locate habitats of their prey with a precision of several hundred metres. Analysis of owl pellets is a traditional method in faunistic studies to provide data on distribution of small mammals, especially cryptic species which are hard to be found using trapping. New information: Here, we present a dataset on mammals found in Tawny owl pellets collected during up to 13-year studies in the Kharkiv Region, Ukraine in three territories. Data from two territories were collected in a systematic way and allowed us to make analysis of seasonal, year-to-year and habitat variability in the Tawny owl diet and local mammal species composition.

New hosts for a snake's helminth: First report of intermediate and definitive hosts naturally infected by Ophidascaris arndti (Ascarididae) in the wild.

We wish to report the occurrence of adult nematodes Ophidascaris arndti (Ascarididae) naturally infecting a new definitive host, the Fonseca's lancehead Bothrops fonsecai (Viperidae), and third-stage larvae of O. arndti parasitizing a new intermediate host, the montane grass mouse Akodon montensis (Cricetidae), both found in the Atlantic Forest of the state of Rio de Janeiro, Brazil. We elucidated the morphological characteristics of both adults and larvae using light and scanning electron microscopy (SEM). Taxonomic affinities between larvae and adult worms were assessed using MT-CO1 gene sequences. Adult and larval gene sequences formed a well-supported clade and had low pairwise p-distances, suggesting that they are conspecific. Our phylogenies also supported the 'arndti', 'filaria', and 'obconica' groups as independent lineages and confirmed the allocation of Ophidascaris within the family Ascarididae, although as an early offshoot. This is the first report of natural infection of this helminth's larvae in a wild intermediate host.

No Evidence for the Presence of SARS-CoV-2 in Bank Voles and Other Rodents in Germany, 2020-2022.

Rodentia is the most speciose mammalian order, found across the globe, with some species occurring in close proximity to humans. Furthermore, rodents are known hosts for a variety of zoonotic pathogens. Among other animal species, rodents came into focus when the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) spread through human populations across the globe, initially as laboratory animals to study the viral pathogenesis and to test countermeasures. Under experimental conditions, some rodent species including several cricetid species are susceptible to SARS-CoV-2 infection and a few of them can transmit the virus to conspecifics. To investigate whether SARS-CoV-2 is also spreading in wild rodent populations in Germany, we serologically tested samples of free-ranging bank voles (Myodes glareolus, n = 694), common voles (Microtus arvalis, n = 2), house mice (Mus musculus, n = 27), brown or Norway rats (Rattus norvegicus, n = 97) and Apodemus species (n = 8) for antibodies against the virus. The samples were collected from 2020 to 2022 in seven German federal states. All but one sample tested negative by a multispecies ELISA based on the receptor-binding domain (RBD) of SARS-CoV-2. The remaining sample, from a common vole collected in 2021, was within the inconclusive range of the RBD-ELISA, but this result could not be confirmed by a surrogate virus neutralization test as the sample gave a negative result in this test. These results indicate that SARS-CoV-2 has not become highly prevalent in wild rodent populations in Germany.

Species limits and recent diversification of Cerradomys (Sigmodontinae: Oryzomyini) during the Pleistocene.

Cerradomys is a genus of the tribe Oryzomyini with eight species currently recognized, and a controversial taxonomy. These species are mainly distributed in the South America dry diagonal, but some species extend into Atlantic Forest, reaching the coastal sandy plains known as Restingas. This study aimed to address species limits and patterns of diversification of Cerradomys species. For this purpose, we performed cytogenetic and molecular analyses (phylogeny, coalescent species delimitation, barcoding, and divergence times estimation) using multiple mitochondrial and nuclear markers on a comprehensive sampling, representing all nominal taxa reported so far. Chromosomal information was a robust marker recognizing eight Cerradomys species. Reciprocal monophyly was recovered for all the species, except for C. subflavus. These results together with coalescent analyses recovered eight species as the most congruent species delimitation scenario for the genus (mean C tax : 0.72). Divergence time estimates revealed that Cerradomys' diversification occurred about 1.32 million years ago (Mya) during the Pleistocene. Although our results conservatively support the eight Cerradomys species described so far, different lines of evidence suggest that C. langguthi and C. subflavus could potentially be species-complexes. We discussed this scenario in the light of multiple evolutionary processes within and between species and populations, since Cerradomys comprises a species group with recent diversification affected by Pleistocene climatic changes and by the complex biogeographic history of South America dry diagonal. This work supports that the diversity of Cerradomys is underestimated and reiterates that interdisciplinary approaches are mandatory to identify small rodent species properly, and to unhide cryptic species.

Mechanisms of sound production in deer mice (Peromyscus spp.).

Rodent diversification is associated with a large diversity of species-specific social vocalizations generated by two distinct laryngeal sound production mechanisms: whistling and airflow-induced vocal fold vibration. Understanding the relative importance of each modality to context-dependent acoustic interactions requires comparative analyses among closely related species. In this study, we used light gas experiments, acoustic analyses and laryngeal morphometrics to identify the distribution of the two mechanisms among six species of deer mice (Peromyscus spp.). We found that high frequency vocalizations (simple and complex sweeps) produced in close-distance contexts were generated by a whistle mechanism. In contrast, lower frequency sustained vocalizations (SVs) used in longer distance communication were produced by airflow-induced vocal fold vibrations. Pup isolation calls, which resemble adult SVs, were also produced by airflow-induced vocal fold vibrations. Nonlinear phenomena (NLP) were common in adult SVs and pup isolation calls, suggesting irregular vocal fold vibration characteristics. Both vocal production mechanisms were facilitated by a characteristic laryngeal morphology, including a two-layered vocal fold lamina propria, small vocal membrane-like extensions on the free edge of the vocal fold, and a singular ventral laryngeal air pocket known as the ventral pouch. The size and composition of vocal folds (rather than total laryngeal size) appears to contribute to species-specific acoustic properties. Our findings suggest that dual modes of sound production are more widespread among rodents than previously appreciated. Additionally, the common occurrence of NLP highlights the nonlinearity of the vocal apparatus, whereby small changes in anatomy or physiology trigger large changes in behavior. Finally, consistency in mechanisms of sound production used by neonates and adults underscores the importance of considering vocal ontogeny in the diversification of species-specific acoustic signals.

Species limits and recent diversification of Cerradomys (Sigmodontinae: Oryzomyini) during the Pleistocene

Cerradomys is a genus of the tribe Oryzomyini with eight species currently recognized, and a controversial taxonomy. These species are mainly distributed in the South America dry diagonal, but some species extend into Atlantic Forest, reaching the coastal sandy plains known as Restingas. This study aimed to address species limits and patterns of diversification of Cerradomys species. For this purpose, we performed cytogenetic and molecular analyses (phylogeny, coalescent species delimitation, barcoding, and divergence times estimation) using multiple mitochondrial and nuclear markers on a comprehensive sampling, representing all nominal taxa reported so far. Chromosomal information was a robust marker recognizing eight Cerradomys species. Reciprocal monophyly was recovered for all the species, except for C. subflavus. These results together with coalescent analyses recovered eight species as the most congruent species delimitation scenario for the genus (mean Ctax: 0.72). Divergence time estimates revealed that Cerradomys’ diversification occurred about 1.32 million years ago (Mya) during the Pleistocene. Although our results conservatively support the eight Cerradomys species described so far, different lines of evidence suggest that C. langguthi and C. subflavus could potentially be species-complexes. We discussed this scenario in the light of multiple evolutionary processes within and between species and populations, since Cerradomys comprises a species group with recent diversification affected by Pleistocene climatic changes and by the complex biogeographic history of South America dry diagonal. This work supports that the diversity of Cerradomys is underestimated and reiterates that interdisciplinary approaches are mandatory to identify small rodent species properly, and to unhide cryptic species.

Variation and Selection in the Putative Sperm-Binding Region of ZP3 in Muroid Rodents: A Comparison between Cricetids and Murines.

In mammals, the zona pellucida glycoprotein 3 (ZP3) is considered a primary sperm receptor of the oocyte and is hypothesized to be involved in reproductive isolation. We investigated patterns of diversity and selection in the putative sperm-binding region (pSBR) of mouse ZP3 across Cricetidae and Murinae, two hyperdiverse taxonomic groups within muroid rodents. In murines, the pSBR is fairly conserved, in particular the serine-rich stretch containing the glycosylation sites proposed as essential for sperm binding. In contrast, cricetid amino acid sequences of the pSBR were much more variable and the serine-rich motif, typical of murines, was generally substantially modified. Overall, our results suggest a general lack of species specificity of the pSBR across the two muroid families. We document statistical evidence of positive selection acting on exons 6 and 7 of ZP3 and identified several amino acid sites that are likely targets of selection, with most positively selected sites falling within or adjacent to the pSBR.

Spermatogenesis in the Roborovski hamster (Phodopus roborovskii) and the Chinese hamster (Cricetulus griseus).

BACKGROUND: Spermatogenesis is an elaborately organized and tightly regulated differentiation process. The spermatogenesis duration is stable within a certain species but highly variable between species of the same family. OBJECTIVES: In this study, the spermatogenesis duration of the Roborovski hamster was measured for the first time, and the spermatogenesis duration of the Chinese hamster was re-assessed. MATERIALS AND METHODS: Stage classification and cycle length measurement were carried out by labeling the dividing cells with bromodeoxyuridine and an antibody-based chromogen as well as with the periodic acid-Schiff/hematoxylin stain. Analysis was conducted using reference calculation and linear regression. Morphological measurements completed our set of methods. RESULTS: The mean duration of one seminiferous epithelium cycle was 8.58 ± 0.34 days (mean ± SEM; Phodopus roborovskii) and 16.59 ± 0.47 days (Cricetulus griseus) based on the reference calculation. Slightly higher results were obtained using linear regression analysis: 9.72 ± 0.41 days for P. roborovskii and 17.64 ± 0.61 days for C. griseus. Additionally, a newly developed exemplary flowchart was proposed for the Roborovski hamster to facilitate spermatogenesis stage classification also in other species. The Chinese hamster presented an unexpectedly high paired epididymides weight of 1.701 ± 0.046 g (mean ± SEM) although having a body weight of only 40.5 ± 0.7 g. However, no significant correlation between the relative epididymis weight and spermatogenesis duration in mammals (Spearman rank correlation: r = -0.119, p = 0.607, n = 21) or rodents could be found (r = 0.045, p = 0.903, n = 11). CONCLUSION: Our data emphasize the stability of the spermatogenesis duration within species and its remarkable variability between species. Further research is needed to identify the principal mechanisms and selection drivers that are responsible for such stability within species and the variability between species.

Calling for a reassessment of rodent diversity in Colombia: description of a new species of Neacomys (Cricetidae: Oryzomyini) from the Magdalena Valley, with a new phylogenetic hypothesis for the genus and comments on its diversification.

Neacomys Thomas, 1900 is an oryzomyine genus comprising at least 17 lineages distributed from easternmost Panama to northern Bolivia. As is the case for other groups of the subfamily Sigmodontinae, Neacomys have experienced a substantial increase in the rate of species descriptions in the last two decades, prompted by the progressive generation of morphological, molecular and karyological data. Nevertheless, most of the studies related to the genus have focused on the assessment of Cis-Andean populations, so that the Trans-Andean ones have been relegated to the background. In more than a century, only two species have been described from that region, one of them present in Colombia (N. tenuipes Thomas, 1900). Here, a new species of Neacomys is named and described based on samples collected in montane ecosystems of the Serranía de los Yariguíes, an isolated massif in the Magdalena Valley (Trans-Andean Colombia). Its validity is supported by a unique combination of morphological and molecular characters: Neacomys sp. nov. can be distinguished from other congeners mainly by the presence of broad ochraceous-orange patches on the sides of the muzzle, a gray-based ochraceous buff ventral fur, a thick hamular process of the squamosal, an opened ectotympanic ring, and a narrow anterocone of M1. The species is recovered as a clearly divergent and well-supported monophyletic group in the phylogenies, which implies it is not closely related to any other species in the genus and probably represents an early radiation within it. The new species of Neacomys constitutes the only rodent described from Colombia in more than 50 years and brings the list of mammals of the country to 529 species. Its discovery evidences that Trans-Andean region could be an important source of hidden diversity for the genus, and in Colombia, for rodents in general. Thus, further inventories, especially into remote areas, are needed to unveil this diversity. The fact that the new species seems to be endemic to an isolated mountain range implies it merits attention in terms of conservation.

Description of a new species of Moniliformis (Acanthocephala: Moniliformidae) from Peromyscus hylocetes (Rodentia: Cricetidae) in Mexico.

Moniliformis ibunami n. sp., is described from the intestine of the transvolcanic deermouse Peromyscus hylocetes Merriam 1898 (Cricetidae) from Parque Nacional Nevado de Colima "El Floripondio", Jalisco, Mexico. The new species can be distinguished morphologically from the other 18 congeneric species of Moniliformis by a combination of morphological and molecular characters including the number of hooks on the proboscis (12 longitudinal rows, each one with six to eight transversally arranged unrooted hooks), the proboscis length (230-270 µm), the female trunk length (159-186 mm) and egg size (40-70 × 20-40). For molecular distinction, nearly complete sequences of the small subunit (SSU) and large subunit (LSU) of the nuclear ribosomal DNA and cytochrome oxidase subunit 1 (cox 1) of the mitochondrial DNA of the new species were obtained and compared with available sequences downloaded from GenBank. Phylogenetic analyses inferred with the three molecular markers consistently showed that Moniliformis ibunami n. sp. is sister to other congeneric species of Moniliformis. The genetic distance with cox 1 gene among Moniliformis ibunami n. sp., M. saudi, M. cryptosaudi, M. kalahariensis, M. necromysi and M. moniliformis ranged from 20 to 27%. Morphological evidence and high genetic distance, plus the phylogenetic analyses, indicate that acanthocephalans collected from the intestines of transvolcanic deer mice represent a new species which constitutes the seventh species of the genus Moniliformis in the Americas.