A new species of lungworm from the Atlantic Forest: Rhabdias megacephala n. sp. parasite of the endemic anuran Proceratophrys boiei.

Rhabdias are lung-dwelling parasites of anurans and some reptiles. Currently, 93 species are known to exist worldwide. The identification of Rhabdias species is based mainly on morphological traits of hermaphroditic females that generally have a very conserved morphology. However, different approaches, such as the combination of morphological, molecular, and ecological data, have provided advances in identifying and delimiting rhabdiasid species. Here, we describe a new species of Rhabdias from the south of Brazil, with morphological and molecular data. The new species is distinguished from its congeners by having an elongated body, evident cephalic dilation, larger buccal capsule, and large esophagus. In addition to morphological characteristics, we observed significant genetic divergence among the cytochrome oxidase subunit I (COI) sequence of the new species and the closest available sequence, Rhabdias fuelleborni (10.24%-10.87%). Furthermore, phylogenetic reconstructions based on the COI gene indicated that the new species represents a different lineage, constituting an outgroup of the species complexes Rhabdias cf. stenocephala and Rhabdias fuelleborni with Rhabdias sp. 4. Thus, Rhabdias megacephala is the 24th nominal species of the Neotropical region, the 14th Brazilian, and the fourth species described from south of Brazil.

Hidden in the frog: morphological and molecular characterization of Halipegus ovocaudatus (Platyhelminthes: Trematoda), type species of the genus Halipegus Looss, 1899.

The type species of the genus Halipegus Looss, 1899, Halipegus ovocaudatus (Vulpian, 1859) is a generalist parasite of different species of amphibians, mainly anurans. To date, the phylogenetic position of this species has not been established. Specimens of H. ovocaudatus, were collected from three species of water frogs, Pelophylax ridibundus (Pallas), P. esculentus (Linnaeus), and P. lessonae (Camerano) inhabiting the Middle Volga region (European Russia). In our study, we provide detailed morphological redescription of these digeneans and combine it with molecular phylogenetic analyses based on partial sequences of the 28S rDNA and coI mtDNA genes. The phylogenetic position of H. ovocaudatus among the derogenids has been established as a sister clade to other representatives of the Halipeginae. We compared pairwise distances based on partial sequences of coI mtDNA genes of H. ovocaudatus and other representatives of Derogenidae. It was shown, that adults of H. ovocaudatus from different hosts are representatives of the same species. Specimens parasitizing three frog hosts from several localities differ slightly in body shape and size, which probably reflects host-induced intraspecific variability.

GENETIC AND TRAIT VARIABILITY OF GYRINICOLA REVEALS THE EXISTENCE OF AT LEAST FOUR SPECIES WITHIN THE UNITED STATES.

The tadpole-dwelling pinworm, Gyrinicola batrachiensis (Walton, 1929) Adamson, 1981 was recognized as the sole representative of the genus across Canada and the United States. However, evaluation of the morphology of these parasites across their range revealed considerable morphological variability that suggested diagnosable morphotypes. These morphotypes were associated with different species of anurans, several of which occurred in sympatry. Herein we use an extensive geographic sampling across the United States to obtain the morphotypes, screen their genetic diversity, and analyze this information using an integrative approach. We reconstructed their phylogeny using nuclear ribosomal partial genes 18S and 28S, ITS1, 5.8S, and ITS2, as well as 5 mitochondrial genes generated with Next-Generation sequencing technology. This phylogeny reveals 3 well-resolved lineages, which upon the use of a statistical approach (bPTP [Bayesian implementation of the Poisson tree processes]) supports the delimitation of 4 distinct groups equivalent to species. These putative species groups were tested using morphological characteristics paired with a MANOVA and canonical variate analysis. Results suggest that at least 4 species of Gyrinicola are present within North America, resulting in the resurrection of G. armatus (Walton, 1933) and the description of 2 new species.

Baseline haematological parameters in three common Australian frog species.

Amphibians are experiencing declines globally, with emerging infectious diseases as one of the main causes. Haematological parameters present a useful method for determining the health status of animals and the effects of particular diseases, but the interpretation of differential cell counts relies on knowing the normal ranges for the species and factors that can affect these counts. However, there is very little data on either normal haematological parameters or guides for blood cell types for free-ranging frog species across the world. This study aims to 1) create a visual guide for three different Australian frog species: Litoria paraewingi, Limnodynastes dumerilii, and Crinia signifera, 2) determine the proportions of erythrocytes to leukocytes and 3) differential leukocytes within blood smears from these three species and 4) assess the association between parasites and differential counts. We collected blood samples from free-ranging frogs and analysed blood smears. We also looked for ectoparasites and tested for the fungal disease chytridiomycosis. Overall, we found that the differentials of erythrocytes to leukocytes were not affected by species, but the proportions of different leukocytes did vary across species. For example, while lymphocytes were the most common type of leukocyte across the three species, eosinophils were relatively common in Limnodynastes dumerilii but rarely present in the other two species. We noted chytridiomycosis infection as well as ectoparasites present in some individuals but found no effect of parasites on blood parameters. Our results add baseline haematological parameters for three Australian frog species and provide an example of how different frog species can vary in their differential blood cell counts. More information is needed on frog haematological data before these parameters can be used to determine the health status of wild or captive frogs.

Case report: Disseminated larval trematodiasis caused by Clinostomum marginatum in a green tree frog (Hyla cinerea).

Clinostomum spp. are common parasites of piscivorous birds. Metacercaria are typically observed in the muscles or just under the skin of fish and rarely amphibians. We describe an unusually severe case of Clinostomum marginatum infection in an adult female green tree frog (Hyla cinerea) from Georgia (USA). The frog was found in November 2015 with a high number (>250) of widely disseminated, raised, subcutaneous nodules. The frog died in December. At necropsy, it was emaciated, and the skin was covered in raised uniform, tan-green, subcutaneous, ∼2-3 mm diameter nodules. Each nodule contained 1-3 C. marginatum metacercariae. Microscopically, high numbers of trematodes were within subcutaneous tissues and in coelomic and oral cavities, lung, liver, kidney, ovary, orbit and calvarium. Small to large numbers of lymphocytes and melanomacrophages were in connective tissues and epidermis. A 732 bp region of COI was 98.8-99.8% similar to numerous sequences of C. marginatum and, phylogenetically it grouped with these C. marginatum sequences. The ITS-1 region was 100% similar to a C. marginatum sample from a great egret (Ardea alba) from Mississippi. This report represents a novel finding of severe trematodiasis in a free-ranging amphibian with C. marginatum infection.

Patterns in parasite diversity and interactions with anurans from the Atlantic Forest.

Knowledge of parasite-host interactions is essential for understanding factors associated with the ecology and evolution of both groups. Some aspects, such as host size and phylogeny, as well as parasite specificity, are significant predictors that help unveil the parasite-host relationship. Thus, the goals of this study were: (1) to describe parasite diversity in regions of the Atlantic Forest; (2) to analyze which host characteristics can influence parasite richness of anuran's parasite component community; and (3) to investigate if the prevalence of parasite infection is related to specificity metrics (ecological and phylogenetic), number of infected hosts and parasite's abundance. We identified 49 parasite taxa, classified into three phyla: Nematoda, Acanthocephala, and Platyhelminthes. Supporting the existing literature, our findings corroborate the positive relationship between host size and parasite richness, further emphasizing the significance of this predictor. Parasite prevalence in the host community is related to the number of infected host species and parasite abundance, but not to phylogenetic and ecological specificity indices. This shows that parasite prevalence is strongly associated with infection opportunity, host sampling effort, and high parasite abundance.

Proterodiplostomid no longer: Molecular phylogeny reveals the true position of Proalarioides (Digenea: Diplostomoidea).

Proalarioides Yamaguti, 1933 (Digenea Carus, 1863: Diplostomoidea Poirier, 1886) is a small genus of proterodiplostomids parasitic in the intestines of snakes in Asia. Only two species are considered valid: Proalarioides serpentis Yamaguti, 1933 and Proalarioides tropidonotis Vidyarthi, 1937. Unlike other proterodiplostomids, Proalarioides spp. possess pseudosuckers and lack the paraprostate, otherwise extremely characteristic of the Proterodiplostomidae Dubois, 1936. In the present study, we describe the morphology of progenetic metacercariae of a Proalarioides sp. from bicolored frog, Clinotarsus curtipes (Jerdon), collected in India and provide the first DNA sequences from any member of the genus. These specimens differ from previously described metacercariae and adults of P. serpentis and P. tropidonotis in several ways, including body and organ sizes, sucker ratios, and distribution of vitellarium. The newly generated partial large ribosomal subunit (28S) rRNA gene sequence was used to test the phylogenetic position of the genus among other major lineages of diplostomoideans. Our 28S phylogeny clearly demonstrated Proalarioides sp. to be well-separated from other members of the Proterodiplostomidae. Based on morphological and molecular evidence, we transfer Proalarioides out of the Proterodiplostomidae into the Diplostomidae Poirier, 1886.

Does the body size, sex, and reproductive modes of leaf litter anurans affect the diversity of parasites?

We describe the composition of endoparasites associated with leaf litter anurans from an Atlantic Forest area, in southeastern Brazil. We tested if body size, sex, and reproductive modes of anuran hosts influence endoparasite abundance and richness. We sampled 583 individuals from 11 anuran species and recorded 1,600 helminths from 14 taxa. The helminths that infected the greatest number of anuran host species were the nematodes Cosmocerca parva (8 spp.), Physaloptera sp. (8 spp.), and Cosmocerca brasiliense (7 spp.), and the most abundant helminth species were Physaloptera sp. (14.6%), Cosmocerca brasiliense (13.7%) and Cosmocerca parva (12.6%). Both helminth abundance and richness were positively affected by anuran body size and dependence on water for reproduction. Larger hosts can contain a higher abundance of parasites because they may provide more physical space than smaller ones, or it can simply be a function of age. Besides, parasite species richness can be highly correlated with the amount of time a host spends in association with aquatic habitats, a conservative aspect of both parasite and host natural history. Within host species, there was a positive and significant influence of body size on helminth abundance. Haddadus binotatus females had greater helminth abundance than males, probably due to sex-related differences in behavior and/or in physiology. Our data suggest that reproductive modes could also influence helminth infection parameters in other anuran communities and should be considered in detail in future analyses.

Subcutaneous occurrence of encysted Acanthocephala in an anuran amphibian from Brazil.

Acanthocephalans, in their adult stage, are obligatory parasites of many types of vertebrates, including anuran amphibians. Their complex life cycle always involves an arthropod intermediate host but may include non-obligatory strategies that could improve transmission success, such as paratenic infections. In paratenic hosts, these parasites are normally found loose in the body cavity or encysted in internal organs. Here, we present the first report of acanthocephalans found encysted under the skin of an amphibian (i.e., external to its body cavity). The specimen, a clay robber frog [Haddadus binotatus (Spix, 1824)], had been collected in an Atlantic Forest area in southeastern Brazil. Upon examination of the frog, we recovered two specimens of acanthocephalan (Order Echinorhynchida) encysted under the skin of its venter. Considering the host's relatively small size and its thin ventral musculature, we believe that the acanthocephalans may have accidentally trespassed the muscular tissue while attempting to encyst in the frog's internal body wall.

Centrorhynchus spp. (Acanthocephala) in South America: new anuran record and checklist of vertebrate hosts.

The aim of this study was to record Centrorhynchus sp. associated with the exotic species Aquarana catesbeiana (bullfrog) in southern Brazil and to present a checklist of vertebrate hosts in South America. Twenty-nine adults and juveniles of A. catesbeiana were collected in Capão do Leão, state of Rio Grande do Sul, Brazil, between October 2019 and December 2020. We found 275 specimens of Centrorhynchus sp. cystacanths in the stomach musculature and coelomic cavity of 55.1% of hosts (16). There was no significant differences in the prevalence and mean intensity of infection with cystacanths when compared males and females of A. catesbeiana. The prevalence was significantly higher in adults than in juveniles. The checklist presents 106 species of vertebrate hosts and 14 taxa of Centrorhynchus recorded in nine South American countries. Avian were the main definitive hosts of Centrorhynchus spp. and snakes Dipsadidae, anurans Hylidae and Leptodactylidae the main paratenic hosts in South America. This is the first record of Centrorhynchus cystacanths in A. catesbeiana in the South America. The study provides tools to help understand the parasitic relationships between species of Centrorhynchus and A. catesbeiana and other hosts in areas where bullfrog have been introduced.

Molecular phylogeny of the family Rhabdiasidae (Nematoda: Rhabditida), with morphology, genetic characterization and mitochondrial genomes of Rhabdias kafunata and R. bufonis.

BACKGROUND: The family Rhabdiasidae (Nematoda: Rhabditida) is a globally distributed group of nematode parasites, with over 110 species parasitic mainly in amphibians and reptiles. However, the systematic position of the family Rhabdiasidae in the order Rhabditida remains unsolved, and the evolutionary relationships among its genera are still unclear. Moreover, the present knowledge of the mitochondrial genomes of rhabdiasids remains limited. METHODS: Two rhabdiasid species: Rhabdias kafunata Sata, Takeuchi & Nakano, 2020 and R. bufonis (Schrank, 1788) collected from the Asiatic toad Bufo gargarizans Cantor (Amphibia: Anura) in China, were identified based on morphology (light and scanning electron microscopy) and molecular characterization (sequencing of the nuclear 28S and ITS regions and mitochondrial cox1 and 12S genes). The complete mitochondrial genomes of R. kafunata and R. bufonis were also sequenced and annotated for the first time. Moreover, phylogenetic analyses based on the amino acid sequences of 12 protein-coding genes (PCGs) of the mitochondrial genomes were performed to clarify the systematic position of the family Rhabdiasidae in the order Rhabditida using maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic analyses based on the 28S + ITS sequences, were also inferred to assess the evolutionary relationships among the genera within Rhabdiasidae. RESULTS: The detailed morphology of the cephalic structures, vulva and eggs in R. kafunata and R. bufonis was revealed using scanning electron microscopy (SEM) for the first time. The characterization of 28S and ITS regions of R. kafunata was reported for the first time. The mitogenomes of R. kafunata and R. bufonis are 15,437 bp and 15,128 bp long, respectively, and both contain 36 genes, including 12 PCGs (missing atp8). Comparative mitogenomics revealed that the gene arrangement of R. kafunata and R. bufonis is different from all of the currently available mitogenomes of nematodes. Phylogenetic analyses based on the ITS + 28S data showed Neoentomelas and Kurilonema as sister lineages, and supported the monophyly of Entomelas, Pneumonema, Serpentirhabdias and Rhabdias. Mitochondrial phylogenomic results supported Rhabdiasidae as a member of the superfamily Rhabditoidea in the suborder Rhabditina, and its occurrance as sister to the family Rhabditidae. CONCLUSIONS: The complete mitochondrial genome of R. kafunata and R. bufonis were reported for the first time, and two new gene arrangements of mitogenomes in Nematoda were revealed. Mitogenomic phylogenetic results indicated that the family Rhabdiasidae is a member of Rhabditoidea in Rhabditina, and is closely related to Rhabditidae. Molecular phylogenies based on the ITS + 28S sequence data supported the validity of Kurilonema, and showed that Kurilonema is sister to Neoentomelas. The present phylogenetic results also indicated that the ancestors of rhabdiasids seem to have initially infected reptiles, then spreading to amphibians.

Pattern of anuran infection by acanthocephalans from the Cerrado, Northeastern Brazil with a summary for South America.

In Brazil, acanthocephalans parasitise anurans in several biomes. In the present study, we performed an analysis of acanthocephalan infections across 175 anuran individuals from the Cerrado biome, belonging to ten species: Boana raniceps, Pithecopus hypochondrialis, Scinax fuscomarginatus, Scinax x-signatus, Leptodactylus pustulatus, Leptodactylus macrosternum, Leptodactylus vastus, Physalaemus cuvieri, Adenomera hylaedactyla, and Elachistocleis piauiensis. We also verified the specificity of the parasites using the STD* index. Additionally, we conducted a survey of acanthocephalan infection in anurans in South America. The studied assemblage in the Brazilian Cerrado presented 57 parasitised hosts of 175 specimens (overall prevalence: 32.6%). In total, 437 acanthocephalans cystacanths were recorded, among which 286 presented the same morphotype but could not be identified, 148 belonged to the genus Centrorhynchus, and three belonged to Oncicola. Unidentified acanthocephalans had a higher prevalence in L. vastus (53.85%) and the highest intensity was in L. pustulatus (17±16). The highest prevalence of Centrorhynchus sp. was in the species S. fuscomarginatus (28.57%), while the highest intensity was observed in L. vastus (111). The taxon Oncicola sp. it had a prevalence of 3.23% and an intensity of 3 only in S. x-signatus. The highest specificity was recorded for Oncicola sp. (STD*= 1), whereas the lowest was found in Centrorhynchus sp. (STD*= 2.21). Finally, according to the survey for South America, we found ten records of acanthocephalan taxa parasitizing 58 species of anurans distributed in seven countries (Brazil with the most records).

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.

A new species of Aplectana Railliet & Henry, 1916 (Nematoda: Cosmocercidae) in the Brazilian Amazon and the taxonomic status of Aplectana longa.

Nematodes of the genus Aplectana Railliet & Henry, 1916 are common parasites of the digestive tract of amphibians and reptiles in the Neotropical region. During a parasite survey on Boana boans (Linnaeus, 1758), we found specimens of nematodes with Aplectana characteristics. We observed a set of characteristics that differs the species of our study from its congeners, and the present study describes a new species of Aplectana parasite of B. boans using light microscopy and scanning electron microscopy. Aplectana pella n. sp. has lateral alae and somatic papillae in males and females; males have equal short spicules, and the gubernaculum is absent. The arrangement of pairs of caudal papillae also differs from other species (2 precloacal,1 adcloacal, and 5 postcloacal+1 unpaired). In females, the vulva is simple, with non-prominent lips, and equatorial. This is the first record of the genus Aplectana parasitizing B. boans and the 58th species described for this genus. Additionally, we added the precloacal papillae pattern of A. delirae, and based on morphological and morphometric characteristics, we propose the reallocation of Aplectana longa to the genus Oxyascaris.

Oswaldocruzia franciscoensis n. sp. (Nematoda: Molineidae) in Leptodactylus macrosternum Miranda-Ribeiro, 1926 (Anura: Leptodactylidae) from Caatinga morphoclimatic domain, Brazil: morphological and molecular characterisation.

A new species of Oswaldocruzia Travassos, 1917 (Nematoda, Molineidae), parasite of Leptodactylus macrosternum Miranda-Ribeiro, 1926 (Anura: Leptodactylidae), from Caatinga morphoclimatic domain, Brazil, is described based on morphological and molecular data. Oswaldocruzia franciscoensis n. sp. is characterised by an anterior extremity with a cephalic vesicle divided into two portions, a body covered by cuticular longitudinal ridges, and cervical alae. Males of the new species have caudal bursa of type I with a 2-1-2 pattern, spicules divided into a shoe, bifurcated fork, and blade with two unequal branches, in which the longer branch bifurcates at its distal portion end and the smaller branch with three distal processes, each with distal bifurcations. Females have didelphic and amphidelphic uteri, an ovijector divided into vestibule, anterior and posterior sphincters, and anterior and posterior infundibula. The new species differs from its Neotropical congeners that have caudal bursa of type I, based on the presence of cervical alae and by having a spicular blade distally divided into two unequal branches, with the longer branch bifurcating at its distal portion and smaller branch with three distal processes, each distally bifurcated. The partial 18S rDNA sequence generated for Oswaldocruzia franciscoensis n. sp. is the first of a representative belonging to this genus in the Neotropical region.

Putting infection on the map: Using heatmaps to characterise within- and between-host distributions of trematode metacercariae.

The location of parasites within individual hosts is often treated as a static trait, yet many parasite species can occur in multiple locations or organs within their hosts. Here, we apply distributional heat maps to study the within- and between-host infection patterns for four trematodes (Alaria marcianae, Cephalogonimus americanus, Echinostoma spp. and Ribeiroia ondatrae) within the amphibian hosts Pseudacris regilla and two species of Taricha. We developed heatmaps from 71 individual hosts from six locations in California, which illustrate stark differences among parasites both in their primary locations within amphibian hosts as well as their degree of location specificity. While metacercariae (i.e., cysts) of two parasites (C. americanus and A. marcianae) were relative generalists in habitat selection and often occurred throughout the host, two others (R. ondatrae and Echinostoma spp.) were highly localised to a specific organ or organ system. Comparing parasite distributions among these parasite taxa highlighted locations of overlap showing potential areas of interactions, such as the mandibular inner dermis region, chest and throat inner dermis and the tail reabsorption outer epidermis. Additionally, the within-host distribution of R. ondatrae differed between host species, with metacercariae aggregating in the anterior dermis areas of newts, compared with the posterior dermis area in frogs. The ability to measure fine-scale changes or alterations in parasite distributions has the potential to provide further insight about ecological questions concerning habitat preference, resource selection, host pathology and disease control.

Effect of altitude and spatial heterogeneity on the host-parasite relationship in anurans from a remnant humid forest in the brazilian semiarid.

In the present study, we investigated the effect of habitat heterogeneity, elevation gradient, and phylogenetic distance of host species on the abundance and richness of anuran endoparasites, assuming that parasites follow the distribution of their hosts independently of environmental variation. We collected 192 anurans distributed in three altitude ranges: 100-200 m, 400-500 m, and 700-800 m. We performed discriminant principal component analysis to analyze the interrelationships between environmental heterogeneity and the distribution of parasite and host species in the formation of species groups in each altitude range. We estimated the niche width and parasite overlap, using host species as a variable, and assessed whether parasite abundance is more influenced by historical (distance host phylogeny) or ecological effects in each altitude category and overall. Finally, we use network analyses to understand how interactions between parasites and hosts are formed along the altitude gradient. We found 22 parasite species, and the overall prevalence of infection was 74%. In our study, we did not identify environmental (altitude gradients and heterogeneity) or phylogenetic effects acting on the parasite species diversity. Overall, our results suggest that the parasites are distributed following the dispersal of their hosts and are dispersed among most anuran species.

A redescription of Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae), an endoparasite of the Titicaca water frog Telmatobius culeus (Garman, 1876) (Anura: Telmatobiidae), with comments on all other known Hedruris species in Peru.

Hedruris moniezi Ibáñez & Córdova, 1976 (Nematoda: Hedruridae) was described using light and scanning electron microscopy (SEM) based on specimens collected from the stomach of Telmatobius culeus (Anura: Telmatobiidae) in Peru. We observed some characteristics not reported previously, including sessile and pedunculated papillae and amphid on the pseudolabia, bifid deirids, morphology of the retractable chitinous hook, morphology and arrangement of the plates on ventral surface of the posterior end of the males, and arrangement of caudal papillae. Telmatobius culeus represents a new host of H. moniezi. In addition, H. basilichtensis Mateo, 1971 is considered to be a junior synonym of H. oriestae Moniez, 1889. A key to valid species of Hedruris in Peru is provided.

Top-down and bottom-up effects and relationships with local environmental factors in the water frog-helminth systems in Latvia.

Semi-aquatic European water frogs (Pelophylax spp.) harbour rich helminth infra-communities, whose effects on host population size in nature are poorly known. To study top-down and bottom-up effects, we conducted calling male water frog counts and parasitological investigations of helminths in waterbodies from different regions of Latvia, supplemented by descriptions of waterbody features and surrounding land use data. We performed a series of generalized linear model and zero-inflated negative binomial regressions to determine the best predictors for frog relative population size and helminth infra-communities. The highest-ranked (by Akaike information criterion correction, AICc) model explaining the water frog population size contained only waterbody variables, followed by the model containing only land use within 500 m, while the model containing helminth predictors had the lowest rank. Regarding helminth infection responses, the relative importance of the water frog population size varied from being non-significant (abundances of larval plagiorchiids and nematodes) to having a similar weight to waterbody features (abundances of larval diplostomids). In abundances of adult plagiorchiids and nematodes the best predictor was the host specimen size. Environmental factors had both direct effects from the habitat features (e.g., waterbody characteristics on frogs and diplostomids) and indirect effects through parasite-host interactions (impacts of anthropogenic habitats on frogs and helminths). Our study suggests the presence of synergy between top-down and bottom-up effects in the water frog-helminth system that creates a mutual dependence of frog and helminth population sizes and helps to balance helminth infections at a level that does not cause over-exploitation of the host resource.

Hematologic parameters and the effect of hemoparasites of wild anurans in Northern Sinaloa, Mexico.

BACKGROUND: Few hematologic profiles for free-ranging amphibians are available. Hematologic evaluation is a useful tool for determining the health of amphibian populations and providing further knowledge for conservation actions. OBJECTIVES: Hematologic variables and the presence and effect of hemoparasites in anuran species were evaluated in Northern Sinaloa, Mexico. METHODS: Blood samples were collected from wild anurans of eight species to perform blood cell counts, leukocyte differential counts, and serum protein concentrations using manual methods and refractometry. In addition, morphologic identification and quantification of the hemoparasites were performed on blood smears. RESULTS: Differences were observed by sex, age, and season for the hematologic values of Incilius alvarius (n = 23), Incilius mazatlanensis (n = 46), Rhinella horribilis (n = 64), Leptodactylus melanonotus (n = 46), Lithobates forreri (n = 135), Lithobates catesbeianus (n = 20), Smilisca fodiens (n = 42), and Scaphiopus couchii (n = 7). Intra- and extra-erythrocytic hemoparasites were found in 56.2% of amphibian hosts; the hemoparasite infection of R. horribilis and L. melanonotus was higher in the dry season, showing increases in erythroplastids and monocytes. For L. forreri, males were more infected than females, and increases in leukocytes were associated with infections of different types of hemoparasites species. CONCLUSIONS: Hematologic values, hemoparasite prevalence, and the response to hemoparasite infection vary among amphibian species, sex, and age, as well as on season and hemoparasite type. This highlights the importance of hematologic evaluations in wild amphibian populations to determine the subclinical effects of hemoparasite infections.