Dicrocoeliid trematodes were detected in gallbladders and major bile ducts of 2 common marmosets. Their characteristics, including the broadly oval body shape with testes at the level of the anterior rim, ovary dorsal to the large acetabulum, and extracecal, multifollicular vitelline glands interrupted into 2 groups, are typical for a trematode belonging to the genus Euparadistomum. The morphology of the isolated trematodes is closest to the description of Euparadistomum thapari.

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.

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.

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.

One hundred eighty-three individuals of Glossogobius aureus, native to Lake Taal, Philippines, were collected in 2021–2022. Of these, 4 endohelminths were found and identified: Andracantha gravida (Acanthocephala: Polymorphidae), Schyzocotyle acheilognathi (Platyhelminthes: Bothriocephalidae), Azygia sp. (Platyhelminthes: Azygiidae), and Opegaster minima (Platyhelminthes: Opecoelidae). These helminths represent new host records for G. aureus and provide novel contributions to the recent Philippine parasite biodiversity listing. Among these 4 helminths, Azygia sp. was the most prevalent, had the highest percent dominance and mean intensity, and had a broader range followed by S. acheilognathi, A. gravida, and O. minima, respectively. These findings highlight the need to further explore Lake Taal's parasitofauna, especially with regard to the invasion of S. acheilognathi, and the transmission specificity of O. minima, which can be utilized as a keystone parasite biomarker and in return aid in the management and conservation efforts in Lake Taal.

Substitution rates in genes can provide information about their evolutionary dynamics and divergence among either species or protein groups. This work presents PANAS, a computational pipeline developed to facilitate the obtention of substitution rates in large amounts of genomic data from different taxa. We tested PANAS by analyzing the evolution of the mitochondrial protein-coding genes (PCGs) from 18 species of platyhelminths. Our results suggest that the cox1, cox2, cytb, and nad1 genes are under strong selection pressure at the nucleotide and protein level in platyhelminths.

Prosorhynchoides extenuatus n. sp. is described based on adult worms collected from the intestine of the chain pickerel, Esox niger Lesueur, 1818, from the Pascagoula River, Jackson County, Mississippi, U.S.A. Sequences of the ribosomal DNA from adult specimens (internal transcribed spacer region 2, and partial 28S ribosomal DNA gene) were identical to those of a cercaria developing in branched sporocysts within the Gulf wedge clam, Rangia cuneata (G. B. Sowerby I, 1832) and a metacercaria we collected from the threadfin shad, Dorosoma petenense (Günther, 1867) in the same river. The cercaria conforms to the description of bucephalid cercaria C Wardle, 1990, that was originally described from the same host in Texas, U.S.A. Novel sequence data are also provided for Prosorhynchoides potamoensis Curran & Overstreet, 2009, and Prosorhynchoides pusillus (Stafford, 1904) Margolis & Arthur, 1979. The 28S rDNA fragments from these species are aligned with bucephalid sequences available in GenBank and their relationships are analyzed using Bayesian inference analysis. The new species formed a branch within a clade of marine bucephalines, whereas P. potamoensis and P. pusillus branched within a clade of North American freshwater species currently classified in Bucephalinae and Paurorhynchinae. This study is the first to employ nucleotide-based evidence to demonstrate a 3-host life cycle from a North American bucephalid.

Nerocila fluviatilis Schiœdte and Meinert 1881 (Isopoda, Cymothoidea, Cymothoidae) is reported for the first time for a new host order of host, Mugil liza Valenciennes, 1836 (Actinopterygii, Mugiliformes, Mugilidae). Fish were collected in a coastal Atlantic lagoon in eastern Uruguay, Laguna de Rocha, and parasites were consistently restricted to the surface of caudal, anal, and paired fins. All stages of N. fluviatilis were found. Data on prevalence (6%), mean intensity of infestation (5.2), and size are provided for the first time for all stages of N. fluviatilis. An updated account of the geographic distribution and hosts of the isopod is given.