Diversity of Acanthocephala parasites in Neotropical amphibians.

Acanthocephalans constitute a small taxonomic group related to rotifers and specialized in a parasitic lifestyle. Anurans act as paratenic and definitive hosts and infections always occur trophically. Our objective is to describe and summarize the richness of acanthocephalans in Neotropical anurans. We conducted a literature review in the main research databases, compiling data published until August 2021. We identified 66 articles with records of acanthocephalan-anuran association, 53.03% were carried out in Brazil. We detected 108 species of anurans from 11 families parasitized by acanthocephalans. With the exception of Bufonidae, Hylidae and Leptodactylidae, which are relatively well-studied families, interaction with acanthocephalans remains largely unexplored for most anuran species. We found six families of acanthocephalans: Centrorhynchidae, Echinorhynchidae, Oligacanthorhynchidae, Cavisomidae, Neoechinorhynchidae and Plagiorhynchidae. Centrorhynchidae and Echinorhynchidae presented the largest number of taxa associated with anurans. The largest number of records corresponded to acanthocephalans in the larval stage (cystacanths), for which anurans act as paratenic hosts. We observed a lack of specific taxonomic resolution in the identifications of most reports, because a large part of the records in the larval stage make morphological identification difficult. Brazil, Mexico, Paraguay, Argentina, Ecuador and Peru are the countries with the most records, while Costa Rica, Venezuela, Colombia, Chile and Uruguay exhibited the lowest publication numbers, resulting in gaps in the distribution of acanthocephalans. We expanded the known number of anuran species parasitized by acanthocephalans, compared to the last published review. Overall, we aim to contribute to the understanding of diversity within this intriguing but understudied group.

Rich but random: parasite communities of snouted treefrog, Scinax fuscovarius (Anura: Hylidae), in Bodoquena Mountains, western Brazil.

Hosts represent discrete habitats that contain finite parasite communities, and individual hosts can be used as replicates in parasitism studies, such as investigations of the processes that mediate the formation of parasite communities. However, within a single host population, there may be singularities among individuals that affect parasite contact rates. Accordingly, the goals of the present study were to document the parasites associated with the small treefrog Scinax fuscovarius, to verify possible variation and co-occurrences in parasite infracommunities, and to assess the effects of host characteristics (size and sex) on infracommunity structure. Treefrog specimens (n = 75) were collected from the Bodoquena Mountains in Mato Grosso do Sul, Brazil. After collection, the specimens were transported to the laboratory, and examined for parasitic. The parasites found were removed, fixed, and identified. Patterns in parasite infracommunity organization were analyzed using the checkerboard score index, which was calculated using a presence-absence matrix. The matrix was randomized under the null hypothesis that the infracommunities independently represent the component community. Forty-two (56%) of the individuals harbored at least one parasite, and a total of 500 metazoan parasites were recovered, with a particularly rich composite community of 18 taxa, including 13 nematodes, two trematodes, one cestode, one oligochaete, and one mite larvae. The parasite species were randomly distributed among the infracommunities, with no evidence of co-occurrence, segregation, or aggregation. However, both body size and sex influenced infection, with larger hosts harboring more parasites and parasites were more abundant in male specimens and more species rich in female specimens. These results suggest that the parasite infracommunities of S. fuscovarius are shaped by both random factors and individual host characteristics.

Biological drivers of individual-based anuran-parasite networks under contrasting environmental conditions.

Understanding the mechanisms driving host-parasite interactions has important ecological and epidemiological implications. Traditionally, most studies dealing with host-parasite interaction networks have focused on species relationship patterns, and intra-population variation in such networks has been widely overlooked. In this study, we tested whether the composition of parasite communities of five anuran species (Leptodactylus chaquensis, Leptodactylus fuscus, Leptodactylus podicipinus, Pseudis paradoxa and Pithecopus azureus) vary across a pasture pond and a natural reserve site in south-eastern Pantanal, Brazil. We analysed the structure of individual-based networks of these five anuran species, assessed the species roles in the networks and the contribution of host species and body size to interaction strength in the networks, and tested if network ecological attributes varied between the two sites. We observed a total of 17 parasite morphospecies in 151 individual anurans and found that the abundance of parasite species tends to vary, with host species being the main filter driving parasite community structure. The composition of core parasite species remained similar between study sites, and network structure (i.e. parasite richness, interaction diversity, specialization, nestedness and modularity) did not change between pasture and natural reserve. Individual traits of hosts influenced network descriptors since larger hosts presented greater interaction strength independent of the study site. In short, we found that the occurrence of highly connected parasite taxa in both the pasture and the reserve sites may have promoted similarity in network structures, and host body size was the best predictor of associations with parasites in both study sites.

Anuran helminth communities from contrasting nature reserve and pasture sites in the Pantanal wetland, Brazil.

Studies of amphibian macroparasites are relevant for the investigation of parasite community ecology and disease dynamics. Here, the parasite communities of five anuran species (Hypsiboas raniceps, Phyllomeduza azurea, Pseudis paradoxa, Leptodactylus fuscus and Leptodactylus podicipinus) are described from two habitats with different levels of preservation (pasture versus nature reserve). Specifically, we used mixed-effect models to test whether helminth species richness, prevalence and abundance differ between the two host collection sites. A total of 120 anuran individuals and 25 helminth parasite taxa were collected. Helminth communities differed between collection sites and among host species. In general, helminth species richness, prevalence and abundance were higher in hosts collected in the pond from the nature reserve. In all, these data help fill the gap in parasite biodiversity knowledge in a changing area, within a sensitive group of vertebrate hosts.

Diversity and patterns of interaction of an anuran-parasite network in a neotropical wetland.

We describe the diversity and structure of a host-parasite network of 11 anuran species and their helminth parasites in the Pantanal wetland, Brazil. Specifically, we investigate how the heterogeneous use of space by hosts changes parasite community diversity, and how the local pool of parasites exploits sympatric host species of different habits. We examined 229 anuran specimens, interacting with 32 helminth parasite taxa. Mixed effect models indicated the influence of anuran body size, but not habit, as a determinant of parasite species richness. Variation in parasite taxonomic diversity, however, was not significantly correlated with host size or habit. Parasite community composition was not correlated with host phylogeny, indicating no strong effect of the evolutionary relationships among anurans on the similarities in their parasite communities. Host-parasite network showed a nested and non-modular pattern of interaction, which is probably a result of the low host specificity observed for most helminths in this study. Overall, we found host body size was important in determining parasite community richness, whereas low parasite specificity was important to network structure.

Helminth parasite communities of allopatric populations of the frog Leptodactylus podicipinus from Pantanal, Brazil.

Several factors may influence the structure of parasite communities in amphibian hosts. In this study, we describe the helminth parasites of three allopatric populations of the frog Leptodactylus podicipinus and test whether host size and sex were determinants of the structure and composition of the helminth communities. One hundred and twenty-three anurans were collected from three different study sites within the Pantanal wetlands and surveyed for helminth parasites. We found 14 helminth taxa: 7 species of nematodes, 4 species of trematodes, 1 species of cestodes, 1 species of acanthocephalan and one unidentified cyst. Host sex and size did not cause significant differences in helminth abundance or richness. The structure of helminth communities from the three study sites varied in terms of species composition, abundance and diversity. Six out of 14 helminth taxa were found in the three localities. Among those, the nematodes Cosmocerca podicipinus and Rhabdias sp., the trematode Catadiscus propinquus and the helminth cyst showed significant differences in mean abundances. We suggest that such differences found among the three component communities are driven by biotic and abiotic factors operating locally. Moreover, these differences stress the importance of local conditions, such as hydrologic characteristics and landscape composition, on helminth community structure.

Helminth parasites of Leptodactylus podicipinus (Anura: Leptodactylidae) from south-eastern Pantanal, State of Mato Grosso do Sul, Brazil.

Forty-three specimens of Leptodactylus podicipinus (Anura: Leptodactylidae) were collected in the south-eastern Pantanal, municipality of Corumbá, State of Mato Grosso do Sul, Brazil in February and July 2007, and examined for endoparasites. Forty (93%) specimens were infected with at least one helminth species. The predominant parasites were nematodes (Aplectana sp., Cosmocerca podicipinus, Oswaldocruzia lopesi, Physalopteroides venancioi, Rhabdias sp.), but the trematode Catadiscus propinquus also showed high prevalence. The trematodes Infidum infidum and Travtrema stenocotyle were also found, but in only one specimen. Adult frogs showed higher parasite diversity than subadults. Leptodactylus podicipinus was preferentially infected by direct life-cycle parasites and was reported as a new host record for seven helminth species.