Elevated corticosterone levels are associated with increased immunocompetence in male toads, both when calling and under experimental conditions

Circulating androgens can influence immune responses and sexual traits in male vertebrates. However, in the last 20 years, glucocorticoids have also been implicated as a possible source of variation in male sexual traits and immunocompetence. In this context, we studied the relations between male vocal mating display, immunity, androgens, and glucocorticoids in the explosive breeding toad Rhinella granulosa. In the field, males with high calling effort display either high- or low-corticosterone (CORT) plasma levels, but only males with both high calling effort and high CORT plasma levels showed high bacterial killing ability (BKA), suggesting that the acute CORT elevation can be immunostimulatory. CORT treatments increased BKA in laboratory experiments, confirming the functional relationship observed in the field. However, toads treated with a low dose of CORT increased BKA for 10 h after the treatment, while toads that received a high dose increased BKA for only 1 h after the treatment. These results indicate that different CORT doses can result in temporal differences in the immune response. We did not find any relationship between calling effort, immune response (BKA and PHA swelling response), and testosterone plasma levels in the field, or any effects of testosterone treatment on immunocompetence. Our results suggest a complex relationship between calling effort and immunity, mediated by CORT plasma levels.

Helminth Parasites of Three Anuran Species during Reproduction and Drought in the Brazilian Semiarid Caatinga Region

We investigated the mean abundance of helminths and analyzed helminth composition and structure at the infracommunity and component community levels for 3 anuran species (Pleurodema diplolister, Rhinella jimi, and Rhinella granulosa) from the Caatingas, a semiarid Brazilian region characterized by accentuated seasonality and unpredictability of rains. Data were collected during the reproductive period and during drought, when P. diplolister estivated buried underground but R. jimi and R. granulosa remained foraging actively. We expected higher parasitological parameters during the reproductive period when compared to drought for these 3 anurans. We also expected higher parasite infection in the Rhinella species and higher similarity between their helminth parasite communities when compared to the estivating species, P. diplolister. Contrary to our hypothesis, the season was not related to parasite community structure. As predicted, the Rhinella toads shared more similar species composition of parasite communities. These similarities in the composition of the parasite community between Rhinella species could be due to similar temporal/spatial patterns of activity and phylogenetic proximity. Pleurodema diplolister hosted a more restricted helminth fauna, a result that might be associated with estivation restricting the temporal window available to acquire parasites. This study also presents new helminth fauna records for R. jimi and P. diplolister, and the first helminth fauna record of R. granulosa from the Caatingas in semiarid Brazil.

Parasites of Gymnodactylus darwinii Gray, 1845 (Squamata, Phyllodactylidae) from an Atlantic Rainforest fragment

Gymnodactylus darwinii is an endemic lizard from Atlantic Rainforest. Ecological aspects of your parasitic fauna are still unknown. Therefore, the goal of the present study was to know the composition of parasitic fauna of G. darwinii in an Atlantic Rainforest fragment, as well to test the influence of the size, sex and seasonality on parasitological indices. The study was carried out in two conservation units: Mata do Camucim and Mata do Tapacurá, both located in the municipality of São Lourenço da Mata, Pernambuco state, northeast region of Brazil. Sixty-five specimens were collected, of which 39 (569%) were parasitized by cystacanths of Acanthocephala (prevalence 43%; mean intensity 4 ± 9.9; mean abundance 3.82 ± 7.87), Geckobia sp. (Acari, Pterygosomatidae) (prevalence 30.7%; mean intensity 4 ± 15.0; mean abundance 3.74 ± 9.54), Physaloptera sp. larvae (Nematoda, Physalopteridae) (prevalence 4.6%; mean intensity 1 ± 0.47; mean abundance 0.06 ± 0.47) and Paradistomum rabusculum (Trematoda, Dicrocoeliidae) (prevalence 1.2%; mean intensity 1; mean abundance 0.02). Acanthocephalans presented a significant relation with the animal length (r² = 0.31, p = 0.006, n = 28). Infestation by Geckobia sp. was more frequent during the dry season (BLM: p = 0.001), while the infection by Acanthocephalans was frequent in dry and rainy seasons, with no significant variation (BLM: p = 0.78). In addition, the most prevalent parasites showed no significant difference in relation to sex: males and females showed similar infestation intensity by Geckobia sp. (BLM: p = 0.31) and infection by Acanthocephala (BLM: p = 0.34). This is the first study about the parasitic ecology of G. darwinii, representing a significant contribution to the conservation of this species and the ecosystem in which they inhabit.

Did biogeographical processes shape the monogenean community of butterflyfishes in the tropical Indo-west Pacific region?

Geographical distribution of parasite species can provide insights into the evolution and diversity of parasitic communities. Biogeography of marine parasites is poorly known, especially because it requires an understanding of host-parasite interactions, information that is rare, especially over large spatial scales. Here, we have studied the biogeographical patterns of dactylogyrid parasites of chaetodontids, one of the most well-studied fish families, in the tropical Indo-west Pacific region. Dactylogyrid parasites were collected from gills of 34 butterflyfish species (n=560) at nine localities within an approximate area of 62millionkm². Thirteen dactylogyrid species were identified, with richness ranging from 6 to 12 species at individual localities. Most dactylogyrid communities were dominated by Haliotrema angelopterum or Haliotrema aurigae, for which relative abundance was negatively correlated (ρ=-0.59). Parasite richness and diversity were highest in French Polynesia and the Great Barrier Reef (Australia) and lowest in Palau. Three biogeographic regions were identified based on dactylogyrid dissimilarities: French Polynesia, characterised by the dominance of H. angelopterum, the western Pacific region dominated by H. aurigae, and Ningaloo Reef (Australia), dominated by Euryhaliotrema berenguelae. Structure of host assemblages was the main factor explaining the dissimilarity (turnover and nestedness components of the Bray-Curtis dissimilarity and overall Bray-Curtis dissimilarity) of parasite communities between localities, while environment was only significant in the turnover of parasite communities and overall dissimilarity. Spatial structure of localities explained only 10% of the turnover of parasite communities. The interaction of the three factors (host assemblages, environment and spatial structure), however, explained the highest amounts of variance of the dactylogyrid communities, indicating a strong colinearity between the factors. Our findings show that spatial arrangement of chaetodontid dactylogyrids in the tropical Indo-west Pacific is primarily characterised by the turnover of the main Haliotrema spp., which is mainly explained by the structure of host assemblages.

Living apart and having similar trouble: are frog helminth parasites determined by the host or by the habitat?

Sympatric hosts are exposed to similar ecological conditions, particularly if they are closely related phylogenetically and share some physiological and behavioral traits. We studied the sympatric frogs Leptodactylus chaquensis Cei, 1950 and Leptodactylus podicipinus (Cope, 1862) to investigate the extent to which the helminth parasite communities were influenced by host species’ characteristics or habitat location. We described and compared the helminth communities of 50 L. chaquensis and 40 L. podicipinus collected concurrently from two different study sites in Brazil’s Pantanal floodplain. Similarities in the prevalence and mean abundance of helminths were higher among allopatric populations of the same species than among sympatric populations of different species. The effects of host species, size, and habitat on helminth composition were significant. The amount of variance in the helminth community composition explained by host species and size was greater than that explained by host habitat. These results indicate that the main factors determining similarities in parasite species in this study system are the coevolutionary and biological constraints of the host species, which either limit or allow infection of the parasite species despite the host habitat.

Parasites as bioindicators of environmental degradation in Latin America: A meta-analysis

Unregulated economic growth in Latin America has resulted in environmental degradation, including the release of toxic compounds into the environment. One strategy to understand and prevent the outcomes of this harmful environmental degradation is the use of bioindicators. These are free-living or parasite species that respond to habitat alterations with changes in their numbers, physiology or chemical composition. The aim of this review was to determine whether there is evidence of a significant parasite response to environmental damage in Latin America. We collected 26 papers published between 2003 and 2015 and conducted a meta-analysis to test the null hypothesis that there is no significant overall effect of environmental insults on parasites. The meta-analysis showed a low but still significant negative mean overall effect (Hedges' g = -0.221; 95% CI: -0.241 to -0.200; P < 0.0001). However, the magnitudes and directions of the significant effects varied widely. These results suggest that different groups of parasites have distinct responses to various environmental insults and that the groups should be separately analysed after the accumulation of a sufficient number of studies. For future studies on this topic in Latin America, we suggest: (1) using field and experimental approaches to determine the response of parasites to environmental degradation; (2) using an interdisciplinary approach, including different types of biomarkers in both parasites and individual hosts to generate long-term datasets in polluted and reference areas; (3) conducting studies on parasites as accumulation bioindicators.

Helminth infracommunity structure of Leptodactylus melanonotus (Anura) in Tres Palos, Guerrero, and other records for this host species in Mexico

The amphibian genus Leptodactylus includes around 50 species, of which only 2 are distributed in Mexico; the helminth fauna of these 2 species is poorly known. As part of a research program on amphibian parasites in Mexico from 1997 to 2005, 281 sabinal frogs Leptodactylus melanonotus from 42 localities in 11 Mexican states were examined from a helminthological perspective. A total of 20 taxa of helminths-7 digeneans (5 adults, 2 larvae) and 13 nematodes (8 adults, 5 larvae)-was found to infect this amphibian host species. These data represent 105 new locality records, and 11 taxa are recorded in L. melanonotus for the first time. Infracommunity analyses of the sabinal frogs from Tres Palos indicated that these hosts are depauperate. The helminth community is dominated by specialist species, with Cosmocerca podicipinus the most common in almost 50% of the infracommunities. Percutaneous infection and predator-prey interactions were the 2 most common infection routes by helminths in frogs from Tres Palos, with 79% of the parasites recruited via skin penetration. Finally, our results show that the helminth fauna parasitizing L. melanonotus throughout Mexico has low similarity with the helminth fauna of leptodactylids studied comprehensively in South America, with only 2 digeneans and 3 nematodes being shared by hosts from both regions. As a result of our survey, the number of helminth species parasitizing L. melanonotus increased to 34. Considering its native distribution range, this number is now 36 with the inclusion of the nematodes Oswaldocruzia costaricensis and Cruzia empera in Costa Rica.

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.