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L. stephanocauda are unique by having bilateral, discontinuous fields of black tail stem pigmentation posterior to the withdrawn distome and along the margins of the paired furcae, prominent subtriangular spines on the anterior end of the tail stem anterior and posterior to the distome,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.