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Parapharyngodon spp. are nematodes parasites of amphibian and reptiles worldwide distributed. Of 55 valid species, only 11 are known for the Neotropical realm, and six were found parasitizing hylid frogs in the world. In the present work, we describe a new species of Parapharyngodon from the large intestine of Osteocephalus taurinus from Reserva de Desenvolvimento Mamirauá, Amazonas, Brazil, using light and scanning electron microscopy. Parapharyngodon curupira n. sp. is allocated to the group of species with three pairs of cloacal papillae. However, it shows a set of different morphological characters compared to its congeners. In the new species, males have gubernaculum and smooth cloacal lip, females have pre-bulbar ovaries, and we also observed some morphometric differences. Among Parapharyngodon spp. from the Neotropical realm, the new taxon resembles P. alverangai and P. politoedi. The last species was described from the same host and biome (Amazon); however, they can be easily distinguished from new species by the presence of gubernaculum and v-shape structure at the lower caudal lip. Thus, we characterize and propose a new species of Parapharyngodon from the western amazon., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

The Proterodiplostomidae Dubois, 1936 is a relatively small family of diplostomoidean digeneans parasitising the intestines of reptilian hosts associated with freshwater environments in tropical and subtropical regions. The greatest diversity of proterodiplostomids is found in crocodilians, although some parasitise snakes and turtles. According to the most recent revision, the Proterodiplostomidae included 17 genera within 5 subfamilies. Despite the complex taxonomic structure of the family, availability of testable morphology-based phylogenetic hypotheses and ancient hosts, molecular phylogenetic analyses of the group were practically lacking. Herein, we use novel DNA sequence data of the nuclear lsrRNA gene and mitochondrial cox1 gene from a broad range of proterodiplostomid taxa obtained from crocodilian, fish, and snake hosts on four continents to test the monophyly of the family and evaluate the present morphology-based classification system of the Proterodiplostomidae in comparison with the molecular phylogeny. This first detailed phylogeny for the Proterodiplostomidae challenges the current systematic framework. Combination of molecular phylogenetic data with examination of freshly collected quality specimens and re-evaluation of morphological criteria resulted in a number of systematic and nomenclatural changes along with a new phylogeny-based classification of the Proterodiplostomidae. As the result of our molecular and morphological analyses: (i) the current subfamily structure of the Proterodiplostomidae is abolished; (ii) three new genera, Paraproterodiplostomum n. g., Neocrocodilicola n. g. and Proteroduboisia n. g., are described and Pseudoneodiplostomoides Yamaguti, 1954 is restored and elevated from subgenus to genus level; (iii) two new species, Paraproterodiplostomum currani n. g., n. sp. and Archaeodiplostomum overstreeti n. sp., are described from the American alligator in Mississippi, USA. Comparison of the structure of terminal ducts of the reproductive system in all proterodiplostomid genera did not support the use of these structures for differentiation among subfamilies (or major clades) within the family, although they proved to be useful for distinguishing among genera and species. Our study includes the first report of proterodiplostomids from Australia and the first evidence of a snake acting as a paratenic host for a proterodiplostomid. A key to proterodiplostomid genera is provided. Questions of proterodiplostomid-host associations parasitic in crocodilians are discussed in connection with their historical biogeography. Our molecular phylogeny of the Proterodiplostomidae closely matches the current molecular phylogeny of crocodilians. Directions for future studies of the Proterodiplostomidae are outlined.

Metadelphis tkachi n. sp. is described based on material from the gall-bladder of Molossus molossus (Pallas) (Chiroptera: Molossidae) in the Brazilian eastern Amazon. The main differentiating characters of the new species include lobed, tandem testes and elongated clusters of vitelline follicles commencing at the level of the seminal receptacle. The new species can be distinguished from Metadelphis lenti (Santos & Gibson, 1998) and Metadelphis apharyngotrema (Marshall & Miller, 1979) by the shape and position of the testes; from Metadelphis evandroi Travassos, 1944 by having tandem, lobed testes and shorter clusters of vitelline follicles; from Metadelphis compactus Travassos, 1955 by having tandem testes and more elongated clusters of vitelline follicles, and from Metadelphis alverangai Travassos, 1955 by having smaller testes and body, and vitellarium with large follicles. New morphological data are reported for M. lenti based on light and scanning electron microscopy; intraspecific variation was observed.

Leptodactylus paraensis Heyer, is a Neotropical anuran species that inhabits Rainforest habitats in the eastern Amazon, but because it has only been recently separated from the Leptodactylus pentadactylus (Laurenti) species group, little is known about its helminth fauna. This study describes a new species of Oswaldocruzia Travassos, 1917 and records the first occurrence of this genus parasitising L. paraensis and the second species for the Caxiuanã National Forest in the eastern Amazon, Brazil. Oswaldocruzia lanfrediae n. sp. is characterised by having an anterior extremity with a smooth cephalic vesicle divided into two portions, a claviform oesophagus, well-developed cuticular longitudinal ridges and lateral alae. Females have a well-developed ovojector, with didelphic and amphidelphic uteri. Males show complex robust spicules divided into a slightly curved shoe, a bifurcated fork and a blade terminating in 2-3 processes. The new species differs from its congeners especially regarding the lateral alae and the morphology of the spicules, in addition to morphometric characters such as body size, oesophagus length, deirid position, nerve-ring position and relative position of the vulva in females.

Neocosmocercella fisherae n. sp. is the first nematode species found parasitising Phyllomedusa bicolor from the Brazilian Amazon Region. The new species has a triangular oral opening, with bi-lobed lips, and is distinguished from N. bakeri (triangular oral opening with simple lips), and from N. paraguayensis (hexagonal oral opening with bi-lobed lips). Additionally, the new species has ciliated cephalic papillae, which are absent in the other species of the genus. The reduced uterine sac and the presence of a single egg in the uterus in females are the main morphological characters that differentiate the new species from its congeners N. bakeri (8-10 eggs) and N. paraguayensis (10 eggs, based on the allotype). Additionally, the new species differs from the other two species of the genus by morphometric characters such as the size of spicules and gubernaculum in males and the vagina in females. Until now, phyllomedusid anurans are the only known hosts for the nematodes of this genus. The present work describes the third species of the genus and the first species of nematode parasitising P. bicolor.