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The atractid nematode Cyrtosomum penneri is an autoinfective parasite of several lizard species. Intraspecific transmission between hosts appears to occur exclusively through sexual copulation, yet it is unclear how worms are transferred between different host species. Our research aims to test the possibility of oral transmission of C. penneri using experimental infections. The lizards Anolis sagrei, Leiocephalus carinatus, Hemidactylus mabouia, and Agama picticauda were experimentally exposed to C. penneri in 1 of these groups: (1) oral infection using a feces and saline slurry to approximate host coprophagy, (2) oral infection with a large meal to approximate host predation, and (3) venereal infection using a pipette to confirm sexual transmission. Experimental infections to test venereal transmission were successful in A. sagrei, A. picticauda, and H. mabouia, but were unable to establish infections in L. carinatus. In the predation exposures, A. picticauda, A. sagrei, and H. mabouia hosted infections, whereas L. carinatus were uninfected. Finally, coprophagy experimental infections did not result in infections for any species of host. Our study corroborates venereal transmission of C. penneri in multiple species of lizards and establishes predation as an alternative route of infection. Predation as an oral route of transmission may provide C. penneri an opportunity for interspecific transmission that would otherwise be unlikely during host copulation., (© American Society of Parasitologists 2024.)

Gyrinicola Yamaguti, 1938, includes 6 species of oxyurid found within the intestinal tract of numerous, larval, anuran species in Europe, Asia, South America, and North America. The systematic placement and hierarchical treatment of the genus has shifted at least 5 times since its discovery; the group was first considered as its own family (Gyrinicolidae), then treated as a subfamily (Gyrinicolinae) of Cosmocercidae, then as a member of the Pharyngodonidae, followed by movement back to the Cosmocercidae, and finally a recent proposal suggested the resurrection of the Gyrinicolidae. Species in the genus vary widely in the morphology of the uterine tract, a characteristic often used to indicate membership in the genus, as it is tied to the reproductive mode. However, until recently very few genetic data were available to aid in the placement of this unique group of worms, and before this study to the best of our knowledge none existed for the North American species. To examine the monophyly and placement of the Gyrinicola we sampled populations of Gyrinicola batrachiensis across North America and screened them for genetic diversity using nuclear markers 18S and 28S. Phylogenies suggest at least 3 clades exist among the nematodes from North America and that these clades, alongside Gyrinicola japonica, form a well-supported group within Oxyuroidea. Further representation of Pharyngodonidae from other vertebrate classes may help clarify the relationship of this historical grouping to other members of the Oxyuroidea., (© American Society of Parasitologists 2023.)

Morpholino Oligonucleotides (MOs), an uncharged DNA analogue, are functionalized with an acrylamide moiety and incorporated into polymer hydrogels as responsive cross-links for microRNA sequence detection. The MO cross-links can be selectively cleaved by a short target analyte single-stranded DNA (ssDNA) sequence based on microRNA, inducing a distinct swelling response measured optically. The MO cross-links offer significant improvement over DNA based systems through improved thermal stability, no salt requirement and 1000-fold improved sensitivity over a comparative biosensor, facilitating a wider range of sensing conditions. Analysis was also achieved using a mobile phone camera, demonstrating portability.

Phenotypic plasticity is a process in which multiple phenotypes arise from 1 genotype because of environmental selection pressures. Gyrinicola batrachiensis has a heterogeneous reproductive strategy such that females reproduce either via parthogenesis with thick-shelled eggs in a single uterus or sexual reproduction with thick- and thin-shelled eggs in separate uterine horns. No evidence exists that strains of G. batrachiensis are able to switch between parthenogenetic and sexual reproduction. Thin-shelled eggs are autoinfective, and thick-shelled eggs act as transmission agents once shed into the aquatic environment. Our primary goal was to determine whether dioecious, didelphic pinworms that infect Rana sphenocephala, a slow-developing tadpole, and Osteopilus septentrionalis, a quick-developing tadpole, display reproductive plasticity with concern to thick- and thin-egg development. We performed experimental cross-infections in aquatic mesocosms to determine if dioecious, didelphic worms vary (based on tadpole host) in their ability to produce thin-shelled eggs: O. septentrionalis (hylid) egg masses were exposed to infected R. sphenocephala (ranid) tadpoles, ranid egg masses to infected hylid tadpoles, and a fully crossed infection that exposed ranid and hylid egg masses to infected tadpoles of both anuran families. Results indicated that worms reproduced via didelphic haplodiploidy in experimental ranid and hylid hosts, but that worms from hylids produced only thick-shelled eggs, which supports an intermediate reproductive strategy in O. septentrionalis. There was a significant difference in the mean intensities of ranid and hylid hosts, supporting our assertion that females infecting ranids are capable of producing autoinfective, thin-shelled eggs, and females infecting hylids do not produce such thin-shelled, autoinfective eggs because of the host microenvironment.

The lungworm Rhabdias joaquinensis (Nematoda: Rhabdiasidae) is a common parasite of anurans in eastern Nebraska, yet absent from the same hosts in western Nebraska. This study investigated the ecology of the lungworm's free-living stages that reside in host feces and surrounding soils to establish the worm's free-living niche in eastern Nebraska. Using a comparative method, this study also investigated the absence of lungworms in western Nebraska's Sandhills. Soil composition, moisture, and temperature were experimentally varied in the laboratory to assess their effects on juvenile development and survival. Field mesocosm and host defecation experiments were used to determine where in nature lungworms survive and eventually infect frogs and toads and to discover if vegetation facilitates lungworm transmission to hosts. The results found loam soils were amenable to lungworm development, whereas soils with high clay or sand content produced few infective lungworms. Soil moisture <50 % did not support lungworm development. Infective juveniles successfully developed between 5 and 35 °C, albeit at different rates, whereas only a limited number of non-infective worms developed at 40 °C. Field studies found that shoreline environments supported lungworm development, and the majority of lungworm infections appear to occur within a zone of infection adjacent to shorelines in eastern Nebraska. The prevalence in vegetation mesocosms was 100 %, and a significantly higher mean abundance was found in toads from containers with vegetation than without. Overall, these experiments suggest that the spatial distribution of R. joaquinensis in Nebraska is constrained by the worm's ability to survive and reproduce in a soil matrix.

Given their ubiquitous nature, it is surprising that more oligochaete annelid worms (Annelida: Clitellata) have not adopted an endoparasitic lifestyle. Exceptions, however, are the understudied members of the genus Dero (Allodero) that parasitize the ureters of tree frogs and toads. This study experimentally explores the life cycle and host specificity of Allodero hylae, the worm's use of chemical cues in host searching, and its seasonal prevalence and abundance over a year-long collection period on the Florida Southern College campus. A total of 2,005 A. hylae was collected from the ureter, urinary bladder, or expressed urine of wild Osteopilus septentrionalis ; a significant positive correlation was found between host snout-vent length and parasite intensity for female but not male hosts. Monthly prevalence of A. hylae reached a peak of 58% in April, but never dropped below 20% in any month; mean abundance peaked March-May, whereas few worms were recovered in December and January. Confirming a parasitic lifestyle, wild-collected hosts with intense infections, typically >40 worms, showed obvious dilatation of the ureter wall, and some young-of-the-year O. septentrionalis exposed to A. hylae in the laboratory were killed by the apparent rupture of the host's ureter. The worm has a direct life cycle: worms expelled in the host's urine are capable of locating and re-infecting other hosts within aquatic microhabitats such as bromeliad tanks, and worms can survive for weeks in a free-living environment, even undergoing a morphological change. Further, chemotaxis assays found a positive response to a tree frog attractant for worms recently removed from hosts. Overall, this study provides the first multifaceted investigation on the life history and ecology of any Allodero spp., which offers new insights into an understudied endoparasitic oligochaete.

Species of Haematoloechus and Rhabdias both are ubiquitous lung parasites of frogs, yet surprisingly little research has been conducted on the interactions between these worms. In a small Nebraska stream, 256 Rhabdias joaquinensis and 225 Haematoloechus complexus were found in the lungs of Lithobates (=Rana) blairi. Thirty-six of the 44 (82%) frogs were co-infected with H. complexus and R. joaquinensis whereas 5 (11%) frogs were infected with only 1 species and 3 (7%) frogs were uninfected. Tests for association between H. complexus and R. joaquinensis found a significant positive relationship between the 2 parasites. Significant positive relationships in intensity of infection were found when both lungs were combined but not when lungs were considered individually. Tests for association between H. complexus and R. joaquinensis found no relationship between the worms in the anterior and posterior portions of the lungs. These data suggest that H. complexus and R. joaquinensis do not competitively exclude each other from the lungs of L. blairi in southeastern Nebraska.

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.

Experimental infections and field-collected lizards were used to investigate issues of transmission, host specificity, and seasonal occurrence in the nematode Cyrtosomum penneri (Cosmocercoidea: Atractidae). Anolis sagrei (87 males, 42 females) were captured from the Florida Southern College campus, Polk County, Florida, from October 2010 to September 2011, and 8,803 C. penneri were collected from their intestines. During the breeding season all sexually mature (SVL ≥ 34 mm) A. sagrei were infected, whereas juvenile lizards (SVL <34 mm) were never infected. Experimental infections, using A. sagrei , found that worms were transferred to new hosts venereally, but not during oral exposures. Mating trials confirmed that worms were consistently transferred between hosts during copulation under natural conditions. Experimental exposures found that land snails and crickets do not serve as transport or intermediate hosts, which supports the idea that C. penneri is transferred only during host copulation. Experimental infections to test host specificity in C. penneri successfully infected A. sagrei , Hemidactylus turcicus , and Sceloporus undulatus , but not Anolis carolinensis or Plestiodon inexpectatus. Overall, this is the first study to fully elucidate the life cycle of any atractid nematode, and we suggest a venereal route of transmission for all atractid worms that infect reptilian hosts. Our findings also have implications for the host's reproductive and behavioral biology, e.g., support for covert or satellite males in the A. sagrei mating system.

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 following new gregarine taxa are described from larvae of flour beetles (Coleoptera: Tenebrionidae): Awrygregarina billmani, n. gen., n. sp., from Tribolium brevicornis; Gregarina cloptoni, n. sp., from Tribolium freemani; Gregarina confusa, n. sp., from Tribolilum confusum; and Gregarina palori, n. sp., from Palorus subdepressus. In addition, the description of Gregarina minuta Ishii, 1914, from Tribolium castaneum, is emended. Scanning electron micrograph studies of these species' oocysts reveal differences in surface architecture. The Gregarina species have oocysts with longitudinal ridges, visible with SEM, whereas Awrygregarina billmani oocysts have fine circumferential striations; surface architecture is the main feature distinguishing the 2 gregarine genera. Although parasites from adult beetles are not included in the descriptions, adults of all host species can be infected experimentally using oocysts from the new taxa.

The surface architecture of oocysts produced by Gregarina niphandrodes (Eugregarinorida) from Tenebrio molitor adults (Coleoptera: Tenebrionidae) as revealed by scanning electron microscopy is reported. Gametocysts were allowed to dehisce on 15-mm, round cover glasses; the cover glasses with their oocysts chains were then mounted on stubs without further processing, and sputter-coated with 20-nm gold palladium. Scanning electron microscopy was performed at 10-15 kV with a Hitachi 3000N SEM. Oocysts retained their characteristic shapes as reported in the original species description but showed longitudinal ridges of relatively uniform height, width, and spacing, in separate fields on either side of a central equatorial bulge in the oocysts. There was no ultrastructural evidence of an enclosing external sheath holding the oocysts in a chain. Oocyst ends were flared slightly, and the chain itself was twisted, with adjacent oocysts offset slightly from one another. This article now provides an additional set of structural characters potentially useful in gregarine systematics.