Gill parasites can negatively affect hosts by altering behavior or causing adverse effects to host physiology. Most unionid mussel larvae (glochidia) are obligate parasites requiring fish hosts, but much of the literature concerning how these parasites affect their hosts has been limited to only a few study species of salmonids and mussels. Here, we test the effects of natural glochidia infection levels on resting metabolic rate and hypoxia tolerance of bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides using glochidia of the southern fatmucket mussel Lampsilis straminea, a warm-water unionid. We quantified oxygen uptake, hypoxia tolerance, and ability to regulate metabolic rate via respiration rate, critical dissolved oxygen values (DO_crit), and a regulation index (RI), respectively, to compare the effects of glochidia infection between infected and uninfected fish over 11 wk after host inoculation. Hosts were infected with glochidia at levels similar to those seen in wild, naturally occurring infections. At these levels, we observed no effects of glochidia infection on metabolic rate, DO_crit, or RI of infected versus control fish of either species over our 11-wk experiment. Glochidia infection on fish gills at levels expected under field conditions may not always induce an organismal-level (i.e., individual organism) response or cause host respiratory stress. Preventing respiratory stress from infection would be beneficial for both host and parasite, given that glochidia survival and dispersal depend on host survival.

Vertebrates rely on their gut microbiome for digestion, and changes to gut microbial communities can impact host health. Past work, primarily in model organisms, has revealed that endoparasites disrupt the gut microbiome. Here, using wild-caught white-throated woodrats (Neotoma albigula), we tested whether naturally acquired parasite infections are associated with different microbiome structure and function. We surveyed wild N. albigula in eastern Utah for gastrointestinal parasites in the spring and fall of 2019, using traditional fecal float methods and testing a PCR-based approach to detect infection. We tested whether the host gut microbiome structure and function differed based on infection with the most prevalent parasite, the pinworm Lamotheoxyuris ackerti. In spring, infected and uninfected animals had significantly different microbiomes, but these differences were not detected in the fall. However, for both sampling periods, infection was associated with differences in particular microbial taxa determined by differential abundance analysis. As N. albigula rely on their microbiomes to digest both fiber and the plant defensive compound oxalate, we compared microbiome function by measuring dry matter digestibility and oxalate intake in infected and uninfected animals. Although we expected infected animals to have reduced fiber degradation and oxalate intake, we found no difference in microbiome function using these assays. This work suggests that parasite effects on the microbiome may be difficult to detect in complex natural systems, and more studies in wild organisms are warranted.

The acanthocephalan Neoechinorhynchus emydis has a complex life cycle and infects turtle, ostracod, and snail hosts. However, little information is available on the seasonal distribution or the effects of N. emydis on freshwater snail hosts. To address this, we examined the seasonal distribution and melanization of acanthocephalans in Planorbella cf. Planorbella trivolvis snails from a single location in north-central Oklahoma. Seasonally, prevalence of N. emydis was 0% during the winter, increased to 50% during the summer, and declined to 17% in the fall. Mean abundance exhibited more variation but generally followed a similar pattern as prevalence. More important, all acanthocephalans located within the head/foot region of snail hosts contained melaninlike pigment surrounding each worm, suggesting that snails were mounting an immunological reaction to infections with N. emydis. Snail shell diameter was greatest during the fall and decreased during the winter, indicating that larger or older snails were dying during the winter. However, because field-collected snails were commonly infected with trematodes, and snail size varied significantly with season, it was unclear whether the observed seasonal dynamics of acanthocephalan infections were a result of snail mortality resulting from snail age, parasitic infections, or a combination of factors. To control for these factors, we exposed laboratory-reared Planorbella cf. P. trivolvis snails to naturally infected ostracods in field cages for 5-wk intervals during the winter, spring, and summer. Data from snail-cage infections were consistent with the seasonal field survey such that N. emydis infections were highest in the summer (20%) and lowest (0%) in the winter, suggesting that snails were not ingesting infected ostracods during the winter. However, fewer of our laboratory-reared snails survived in field cages during winter than during spring and summer, suggesting that snails may die more often during harsh winter conditions. Finally, we conducted a laboratory survival experiment by testing the life span and egg production of field-collected snails of various sizes that were naturally infected with acanthocephalans or trematodes or both. Our snail-survival experiment indicated that snail size but not infection status with acanthocephalans or trematodes affected snail survival, with larger snails surviving a shorter amount of time than smaller snails. In addition, snails infected with trematodes laid significantly fewer eggs compared with uninfected snails or snails infected with acanthocephalans. However, we found no significant difference in the number of eggs laid by acanthocephalan-infected and uninfected snails. Although other abiotic factors still need evaluation, we suggest that the occurrence of acanthocephalans in snails throughout the year may be partially influenced by the abundance of infected ostracods that snails may be ingesting and snail population fluctuations during the year.

A new species of Alippistrongylus Digiani and Kinsella, 2014, was found in the intestines of the elegant rice rat, Euryoryzomys nitidus, collected in the Amazon rainforest. These mammals were preserved in alcohol and archived in the Colección Científica de Mamíferos del Museo de Historia Natural de la Universidad Mayor de San Marcos and accessed for the observation and investigation for the diversity of their endo-parasites. A total of 857 worms were recovered from the 3 individuals examined. Morphological investigations and comparisons with the only known species of the genus indicate that this is an undescribed species. These nematodes feature the diagnostic characteristic of the genus, being a bifurcated posterior end that consists of a tail and a conical appendage near the level of the vulva and uninterrupted ridges in the synlophe of unequal size. However, the orientation of this conical appendage on the female tail, features of the synlophe, and shape of the copulatory bursa warrant the proposal of an amended diagnosis to include character variability detected in the new species.

Phylogenetic relationships among the mammal-parasitic lungworms (Metastrongyloidea) were inferred using small- and large-subunit ribosomal DNA sequences together with 12S ribosomal mtDNA sequences. Maximum parsimony and Bayesian inference methods were used from optimal alignments and those filtered for alignment ambiguity. Analysis of 30 ingroup sequences using ribosomal DNA sequences yielded a single most parsimonious tree. Monophyly of the Metastrongyloidea was supported, but there was no support for monophyly of any of the 7 families as they have been traditionally defined. Parafilaroides decorus, an abursate lungworm of pinnipeds currently classified in the Filaroididae, was nested within a clade containing members of the Pseudaliidae, parasites of cetaceans. The tree also shows clades somewhat resembling the traditional familial divisions of the Metastrongyloidea, but in all groups, paraphyletic relationships were recovered. In a combined analysis of nuclear rDNA and 12S mtDNA, maximum parsimony and Bayesian analyses showed similar patterns to those observed with only nuclear rDNA sequences. Based on the phylogeny, the respiratory tract was inferred to be the ancestral predilection site for Metastrongyloidea, with multiple evolutionary invasions of extrapulmonary sites such as sinuses, circulatory system, and meninges. Similarly, the ancestral host was inferred to be a carnivore with subsequent colonization events into marsupial, rodent, artiodactyl, pinniped, and cetacean hosts.

The Diplostomidae Poirier, 1886 is a large family of digeneans within the superfamily Diplostomoidea Poirier, 1886. Members of the family are distributed worldwide and parasitize a diversity of tetrapod definitive hosts. Notably, only 2 mature diplostomids are known from crocodilians and both are suggested to be accidental infections. In this study, we use morphological and molecular data to describe Neofibricola n. gen. from a Nile crocodile Crocodylus niloticus collected in South Africa. We provide a description of adults and metacercariae of the type species, Neofibricola smiti n. sp., and metacercariae of a likely congeneric species. We generated partial 28S and internal transcribed spacer region ribosomal deoxyribonucleic acid (DNA) and cytochrome c oxidase 1 subunit mitochondrial DNA for both species and utilized the newly generated 28S sequences to examine phylogenetic affinities of these new taxa. In addition, we provide a new key to diplostomid genera, considering the substantial systematic changes and newly erected genera since the previously published key to diplostomid genera.

During October and November 2021, 33 creek chubs, Semotilus atromaculatus, were collected from 3 sites in Polk County, Arkansas (Ouachita River drainage), and their gills, gallbladder, fins, integument, musculature, and other major organs were examined for myxozoans. The gills of 9 (27%) were infected with a new myxozoan, Myxobolus fountainae n. sp. Qualitative and quantitative morphological data were from fresh and formalin-fixed preserved spores, while molecular data consisted of a 1918 base pair sequence of the partial small subunit ribosomal RNA gene. Phylogenetic analysis grouped M. fountainae n. sp. with the other leuciscid-infecting myxobolids from North America and within a larger clade of European myxozoans. In addition, histological information is provided on the infection. A previous record of Myxobolus muelleri Bütschli, 1882, from the gills and ureters of S. atromaculatus is considered invalid and represents an unknown species. Myxobolus fountainae n. sp. is the only named myxozoan known to infect the gill filaments of S. atromaculatus, whereas Myxobolus pendula (Guilford, 1967) infects the gill arches.

Herein, we reaffirm the validity of Coronoepimeritus and its junior synonym, Quadruspinospora, provide new combinations for existing species of Quadruspinospora, recognize Monospinospora n. gen. to receive Coronoepimeritus monospinus, and describe Coronoepimeritus otoensis n. sp. from the alimentary canal of the admirable grasshopper, Syrbula admirabilis (Orthoptera: Acrididae), from Nemaha County (40°45′69.49″N, 95°71′60.39″W) near Peru, Nebraska. Our specimens differ from all known species by differences in total gamont length (TL), oocyst length (OL), and oocyst spine length (OSL). Coronoepimeritus atractomorphii n. comb. is most like the new species on the basis of OL and OSL (10 µm and 33 µm, respectively, for both species), but the new species possesses gamonts whose TL is less than 60% of that reported for C. atractomorphii (average TL, 703 µm vs. 1,020 µm, respectively). Nucleotide sequences (18S) and phylogenetic analyses confirm the placement of the new species in Coronoepimeritus, and the K/Θ test (the ratio between the average distance separating 2 species-level clades and the genetic diversity of these clades) is consistent with a species distinct from the only other known sequence sample in the group, Coronoepimeritus mexicana n. comb.

The Lecanicephalidea represents one of 11 currently recognized elasmobranch-hosted tapeworm lineages. It is quite speciose, with nearly 100 validly recognized species to date. Yet spermatozoon features have been fully characterized for only a single species; spermatozoon characters for a second species were previously included in a data matrix used to infer phylogenetic relationships among cestode orders, but data are limited and no images were provided. Specimens of Tetragonocephalum sp. were collected from the whipray, Urogymnus asperrimus 1, from the Solomon Sea off the Solomon Islands. The mature spermatozoa of Tetragonocephalum sp. are distinctly different from the other lecanicephalidean species for which spermatozoon ultrastructure has been thoroughly investigated. Tetragonocephalum sp. spermatozoa represent the Type IV (sensu Levron, 2010) morphology possessing a single axoneme, crested bodies, cortical microtubules running parallel to the axoneme, and nucleus, which is helical to the axoneme. Although spermatozoa for both lecanicephalideans examined to date are of the Type IV spermatozoon morphology, they differ in the number of crested bodies and cortical microtubules, the relative size of the spermatozoon—specifically as it relates to the nuclear region—and the presence or absence of the anterior spiral structure. Significant spermatozoon character variation is present across these 2 representatives of 2 lecanicephalidean families, indicating that additional studies of representatives of the other families in the order are needed to better understand the extent of character variation present in the Lecanicephalidea. Overall, spermatozoon ultrastructure is understudied in elasmobranch-hosted tapeworm lineages compared to other vertebrate-hosted tapeworm orders at both the species and family levels.

Texas quail populations have declined over the past few decades. While habitat loss has been identified as the primary cause, it has been speculated that pathogens may also play a role in this decline. To help address this, we collected scaled quail, Callipepla squamata, Gambel's quail, Callipepla gambelii, and Montezuma quail, Cyrtonyx montezumae, from across the Trans-Pecos ecoregion of Texas via hunter-harvest. Quail samples were then necropsied to document pathogens not previously recorded in the host species. Pathogens were submitted to the Texas A&M University Veterinary Medicine Diagnostic Lab (TVMDL), where parasite identification and histopathological analyses were conducted. From this, we identified several parasites that had never been documented in the quails of the Trans-Pecos ecoregion of Texas. This study was the first to document Mycobacterium sp. and Sarcocystis sp. in scaled quail, Subulura sp. and Physaloptera sp. in Montezuma quail, and Oxyspirura petrowi and Aulonocephalus pennula in a Texas Gambel's quail.