Red swamp crayfish Procambarus clarkii were collected from Cattail Marsh in Beaumont, Texas and necropsied. Eight (13%) of 62 crayfish collected were infected with metacercariae of Crepidostomum cornutum. Excysted metacercariae were stained and mounted for morphologic identification or preserved for molecular analysis. Morphometric values were consistent with those reported previously in the literature. Sequences of the 28S ribosomal RNA gene were aligned with the National Center for Biotechnology Information GenBank database. Blast analysis returned a result of 99% similarity for C. cornutum. This study provides the first report of C. cornutum metacercariae infecting P. clarkii in Texas substantiated by a voucher specimen and sequence data. Molecular data from this study should prove helpful in identification of adult stages from fish and cercariae from bivalves in future studies.

We elucidate the life cycle of Leuceruthrus stephanocauda (Faust, 1921) Womble and Bullard 2022, provide the first description of its adult, and redescribe its cercaria based on specimens infecting centrarchiform and perciform fishes and pleurocerid snails in the southeastern United States. Based on morphological and nucleotide-based (28S rRNA gene and internal transcribed spacer 2 [ITS2]) evidence, adults of L. stephanocauda infect the stomach of spotted bass, Micropterus punctulatus (Rafinesque, 1819), green sunfish, Lepomis cyanellus Rafinesque, 1819, and longear sunfish, Lepomis megalotis (Rafinesque, 1820) from Chewacla Creek (Tallapoosa River, Alabama) and mottled sculpin, Cottus bairdii Girard, 1850 (juvenile), from Raccoon Creek (Chattooga River, Georgia). The adult of L. stephanocauda differs from its congeners by having an elongated body and an asymmetrical vitellarium. The cercariae of L. stephanocauda shed from yellow elimia, Elimia flava (Lea, 1862) (Cerithioidea: Pleuroceridae) in Chewacla Creek and Moores Mill Creek (Tallapoosa River) and from Elimia caelatura georgiana (Lea, 1862) in Raccoon Creek. Naturally shed cercariae of L. stephanocauda are unique by having bilateral, discontinuous fields of black tail stem pigmentation posterior to the withdrawn distome and along the margins of the paired furcae, prominent subtriangular spines on the anterior end of the tail stem anterior and posterior to the distome, and broadly rounded to lanceolate furcae that are longer than wide and that bear numerous marginal and submarginal protuberances. Our 28S phylogenetic analysis recovered L. stephanocauda as a sister to Leuceruthrus micropteri Marshall and Gilbert, 1905, within monophyletic Leuceruthrinae Goldberger, 1911. No species of Leuceruthrus Marshall and Gilbert, 1905, has been reported previously from the Tallapoosa River.

Postharmostomum laruei McIntosh, 1934, utilizes terrestrial gastropods as first and second intermediate hosts. The flamed tigersnail, Anguispira alternata, is the only known first intermediate host. Among many reported second intermediate hosts, A. alternata is the most commonly reported and most heavily infected. The present investigation was undertaken to examine the breadth of second intermediate host use of P. laruei through experimental infections. Snails of 9 species were exposed to cercariae shed from infected A. alternata specimens in trials of varying durations. Developing worms were recovered from positive control A. alternata specimens, as well as members of 8 other species of terrestrial gastropods. Four of these (a succineid, Xolotrema fosteri, Oxychilus draparnaudi, and Neohelix albolabris) are new host records for P. laruei. The first record of incompatibility of P. laruei and potential second intermediate hosts is recorded, as members of the succineid and of X. fosteri were found to harbor dead worms at early stages of development. The ease with which P. laruei experimentally infects gastropods that are rarely found infected in the wild (e.g., N. albolabris, Webbhelix multilineata, Deroceras reticulatum), and even exotic snails (O. draparnaudi) combined with the seeming resistance to infection exhibited by other snails suggest that the specificity of host recognition is low, but also that both physiological incompatibility and ecological limitations restrict functional host use to A. alternata individuals in the wild.

The role of parasites as prey for nonhost species has received increasing attention over the last 3 decades as (1) such a reduction of infectious agents decreases disease transmission by reducing parasite numbers and (2) the importance of parasites in energy flow within aquatic food webs is acknowledged. Previous predation studies of digenetic trematode cercariae have assessed species in which large numbers of cercariae are released daily by individual snails. By contrast, the cercaria of the azygiid trematode Proterometra macrostoma averages less than 1 cercaria released per infected snail per day. The objective of this study was to evaluate the preference of crayfish (i.e., Procambarus spp. and Faxonius juvenilis) as predators of 3 different prey items of similar size and swimming ability including the comparatively large cercaria (i.e., 3–9 mm) of P. macrostoma. Four experiments were conducted, 2 with F. juvenilis and 2 with Procambarus spp. Each experiment consisted of 25 crayfish, which were individually exposed to 1 of 5 treatment levels consisting of a control (i.e., no prey), individual prey (i.e., cercariae, Daphnia magna, or Xenopus laevis tadpoles only), or a mixture of all 3 prey over a 7-hr exposure at 20°C and continuous light. In both the single-prey and mixed-prey experiments, cercariae were consumed at a similar or faster rate than tadpoles and D. magna, and these differences were most notable within the first hour postexposure. These results suggest that P. macrostoma cercariae are a legitimate component of the food web in freshwater habitats, and may play an important role in energy flow between trophic levels in such systems.

Eight helminth taxa, including an acanthocephalan (Centrorhynchus sp.) and 7 nematode species, were identified from material in held in the South Australian Museum Australian Helminthological Collection. All the specimens were collected from 3 individuals of Echymipera kalubu Fischer and a single Echymipera sp. at 25% prevalences, from Papua New Guinean localities. The nematodes were identified as follows: a heterakid Heterakis balamukensis Smales, 2023, known only from E. kalubu; a trichurid, most likely Trichuris peramelis Baylis, 1932; the trichostrongyloids Mackerrastrongylus peramelis (Johnston & Mawson, 1938) and Peramelostrongylus skedastos Mawson, 1960; and a seuratid, Linstowinema sp., likely Linstowinema latens Smales, 1997, the latter 4 species being also found in Australian bandicoots. The physalopterid Physaloptera echymipera n. sp. could be distinguished from all the physalopterids known from Australian and Indonesian hosts by a suite of characters including esophagus length, spicule length, vagina length, and egg size. The seuratid Owenema mikosi n. gen., n. sp. was distinguished by having, among other characters, longitudinal rows of tiny spines along the body, a buccal ring with 4 teeth, the proximal end of the esophagus ornamented, short spicules smaller than the gubernaculum, a simple ovejector, and 4 uteri. A comparison of the helminth community, albeit from a small host sample, with those known from Australian bandicoots indicated that the components of their communities were similar. Isoodon macrourus, primarily an Australian bandicoot, and E. kalubu, for example, frequent similar habitats in Papua New Guinea and share several helminth species.

Proterometra macrostoma is a digenetic trematode that is widely distributed in the eastern United States. The objective of this study was to assess how the cercariae of P. macrostoma within their redia in the infected intermediate snail host (Elimia semicarinata) respond during an initial 7-d exposure of their snail host to 20°C (mimicking a fall temperature), followed by a cold-water exposure of 7.5°C over a 28-d period (mimicking a winter temperature), and within a week after returning to warmer water at 20°C (mimicking a spring temperature). Specifically, we investigated whether cercarial development inside the redia ceases or continues during exposure of the snail host to a winter temperature, which was determined based on changes in the cercarial composition in each redia in the infected snails and the amount of cercarial shedding. Naturally infected snails (E. semicarinata) were collected from North Elkhorn Creek, Scott County, Kentucky, during June and July 2019. Baseline cercarial emergence was recorded over 7 d at 20°C for 55 snails with patent infections. Infected snails were then maintained at 7.5°C for 28 d and checked daily for any cercarial emergence followed by a post–cold treatment analysis of cercarial emergence over 7 d at 20°C. No cercariae were released during the 28-d cold treatment. Significantly more (mean ± SE) cercariae were released per snail during the 7 d following the cold treatment (4.60 ± 0.33) compared to the period prior to cold treatment (3.63 ± 0.35). At the termination of the experiment, 94.6% of infected snails were found to have living rediae with a mean ± SE infection intensity of 7.13 ± 0.51 rediae/snail (range 1–18). Additional sets of snails (pre–cold treatment = 4 snails; post–cold treatment = 5 snails) were dissected at the beginning of the pre– and post–cold treatment periods to observe individual cercarial populations within rediae. No significant differences were found in the average number of the 4 cercarial stages described within rediae pre– vs. post–cold treatment. These results suggest that additional cercariae within rediae mature during winter months, but this was not detectable by our staging criteria.