A New Species of Cosmocerca Diesing, 1861 (Nematoda: Cosmocercidae) in Elachistocleis haroi Pereyra, Akmentins, Laufer, and Vaira, 2013 (Amphibia: Microhylidae) from South American Chaco.

PURPOSE: Cosmocercids are common nematodes that parasitize the digestive tract and lungs of amphibians and reptiles around the world. They are commonly found in leptodactylid and bufonid anurans in South America, primarily in Brazil and Argentina. This paper describes a new species of genus Cosmocerca based on specimens collected in a microhylid from the Dry Chaco ecoregion. METHODS: A total of 18 specimens of Elachistocleis haroi were collected in October 2011 in Chaco province and in December 2021 and March 2022 in Formosa province, Argentina, both areas of the Dry Chaco ecoregion. The morphology of the nematodes was studied in detail using light microscopy and scanning electron microscopy. RESULTS: One hundred and fifty-one nematodes were collected from the large intestines of E. haroi. Based on the morphology of the caudal papillae (rosette papillae and plectanes), the presence of two spicules and the absence of caudal alae in males, and the presence of two prodelphic ovaries in females, these specimens were allocated to the genus Cosmocerca. However, they presented unique characteristics that differentiate them from all known species. Cosmocerca wichiorum sp. nov. is similar to C. archeyi, C. australis, C. sardiniae, C. zugi, and C. leytensis by having four pairs of plectanes, but can be easily distinguished from all of them by the type, number, and arrangement of the precloacal (non-plectanes), adcloacal and postcloacal papillae, by the length of the spicules and by its different zoogeographical distribution. CONCLUSION: This is the 14th species of the genus Cosmocerca described in South America and the first one for the microhylid E. haroi from the Dry Chaco ecoregion.

DO ENVIRONMENTAL AND HOST VARIABLES INFLUENCE THE PARASITE COMMUNITY OF LEPTODACTYLUS FUSCUS (ANURA: LEPTODACTYLIDAE) IN THE AMAZON REGION?

Leptodactylus fuscus is a small-sized species widely distributed across South America. However, so far, no works have been addressed to analyze if biotic and abiotic factors may influence the parasite community in this species. Thus, the present work aims to describe the composition and structure of the parasite community and evaluate if biotic and environmental factors correlated to the distribution of the parasite community for this host. We collected 36 L. fuscus specimens from February 2018 to January 2019. The hosts were necropsied, and parasites were collected and identified. To test the effect of environmental variables (temperature, humidity, and precipitation) and morphological characters of the host (snout-vent length and body weight) on helminths of L. fuscus we used a multivariate distance matrix regression (MDMR). We found 10 helminth taxa: Aplectana sp., Aplectana membranosa, Cosmocercidae larvae, Mesocoelium sp., Mesocoelium aff. monas, Mesocoelium aff. sociale, Oswaldocruzia sp., Oxyascaris sp., Ortleppascaris sp. larvae, and Schrankiana formosula. In our study, the helminth community showed an aggregate pattern, and we did not observe a statistically significant correlation of body size and mass of the hosts regarding parasite abundance and richness. Thus, this study represents the first report of M. sociale, A. membranosa, and Ortleppascaris sp. larvae for L. fuscus and new locality reports. We conclude that there is no correlation between variables analyzed and the structure and composition of the parasite community of L. fuscus.

Oxyuricassis coronatus n. gen. n. sp. and O. hexaspinatus n. sp. (Oxyurida: Pharyngodonidae): Parasites of Lasiancistrus saetiger (Siluriformes: Loricariidae) in Freshwater Rivers of the Brazilian Amazon.

A new nematode genus is described from intestines of Lasiancistrus saetiger Ambruster from freshwater rivers in the Brazilian Amazon. Oxyuricassis n. gen. is characterized by a cephalic cone, small buccal cavity, long esophagus with a well-developed isthmus, and a conical tail with spines. Two new species are described: Oxyuricassis coronatus n. sp. is characterized by the absence of lateral alae, a conical tail with truncated extremity with spine-like sclerotized projections around the tail tip, and caudal alae in males expanded. Oxyuricassis hexaspinatus n. sp. is characterized by lateral alae, a conical tail with tapered extremity, with 2 pairs of proximal spines at the posterior extremity of the tail, 1 dorsal pair and 1 ventral pair, plus a pair of lateral spines that vary in position between sexes, and male of O. hexaspinatus has narrow caudal alae. Both species were found co-parasitizing all of the analyzed host specimens.

A new species of Mesocoelium (Digenea: Mesocoeliidae) found in Rhinella marina (Amphibia: Bufonidae) from Brazilian Amazonia.

Mesocoelium lanfrediae sp. nov. (Digenea: Mesocoeliidae) inhabits the small intestine of Rhinella marina (Amphibia: Bufonidae) and is described here, with illustrations provided by light, scanning electron microscopy and molecular approachs. M. lanfrediae sp. nov. presents the typical characteristics of the genus, but is morphometrically and morphologically different from the species described previously. The main diagnostic characteristics of M. lanfrediae sp. nov. are (i) seven pairs of regularly-distributed spherical papillae on the oral sucker, (ii) ventral sucker outlined by four pairs of papillae distributed in a uniform pattern and interspersed with numerous spines, which are larger at the posterior margin and (iii) small, rounded tegumentary papillae around the opening of the oral sucker, which are morphologically different from those of the oral sucker itself, some of which are randomly disposed in the ventrolateral tegumentary region of the anterior third of the body. Addionally, based on SSU rDNA, a phylogenetic analysis including Brachycoeliidae and Mesocoeliidae taxa available on GenBank established the close relationship between M. lanfrediae sp. nov. and Mesocoelium sp.

Liver histopathology in the cane toad, Rhinella marina (Amphibia: Bufonidae), induced by Ortleppascaris sp. larvae (Nematoda: Ascarididae).

Exposure to parasites is considered to be an important factor in the development of many diseases and histopathologies which are the result of the parasite-host interaction. The present study evaluated the impact of natural infection by larvae of Ortleppascaris sp. (Nematoda: Ascaridida) in the liver of the cane toad Rhinella marina (Linnaeus, 1758). Larvae were encysted in nodules delimited by collagenous fibers and fibroblasts or freely within the hepatic parenchyma, provoking a clear response from the host. The histological examination of the liver revealed viable larvae in a number of different developmental stages, as well as cysts filled with amorphous material and cell residues and surrounded by dense fibrotic tissue. The infection of the liver by these larvae induces a significant increase in the area occupied by melanomacrophages and a reduction or deficit in the vascularization of the liver, hypertrophy of the hepatocytes, vacuolar bodies, and cytoplasmatic granules. Focal concentrations of inflammatory infiltrates were observed enclosing the unencapsulated early-stage larvae. These results indicate that infection by Ortleppascaris sp. induces severe physiological problems and histopathological lesions in the liver of R. marina .

Morphological and molecular characterization of Ortleppascaris sp. larvae, parasites of the cane toad Rhinella marina from eastern Amazonia.

This study presents a new record for the occurrence of larval Ortleppascaris sp.(Sprent, 1978). The nematodes were collected from inside fibrous cysts found in the livers of cane toads, Rhinella marina (Linnaeus, 1758), captured in eastern Brazilian Amazonia. This is the first record of Ortleppascaris sp. larvae in both Brazil and this amphibian host, increasing its distribution in South America as well as expanding the number of helminths known to infect this toad. The detailed description of Ortleppascaris sp. provides new taxonomic data for these larvae, as well as sequences of the internal transcribed spacers and small subunit DNA segments, and the cytochrome oxidase I gene, which will, in time, contribute to a better understanding of the phylogeny of this group of parasites.

Morphological redescription of Dirofilaria immitis.

Morphological descriptions of Dirofilaria immitis are scarce. For this reason, we carried out morphological studies using both light and scanning electron microscopy for this filaroid species. Morphometric and morphological data were compatible with previous descriptions of D. immitis , but several anatomical structures are described by scanning electron microscopy for the first time, such as details of the cuticular striations, positioning of amphids, visualization of anal and vulvar opening, descriptions of deirids, lateral line, the pair of phasmids in the posterior end in females, and visualization of a small pair of latero-terminal papillae in the posterior end in males.