Search Results (121)

Memory is a fundamental neurological function, essential for animal survival. Over the course of vertebrate evolution, elaborations in the forebrain telencephalon create new memory mechanisms, meaning basal vertebrates such as amphibians must have a less sophisticated system of memory acquisition, storage, and retrieval than the well-known hippocampal-based circuitry of mammals. Personality also appears to be a fundamental vertebrate trait and is generally defined as consistent individual behavior over time and across life history stages. In anuran amphibians (frogs), personality studies generally ask whether adult frogs retain the personality of their tadpole stage or whether personality shifts with metamorphosis, an idea behavioral ecologists term adaptive decoupling. Using a multidisciplinary perspective and recognizing there are ~7843 species of frogs, each with some molecular, morphological, physiological, or behavioral feature that makes it unique, we review, clarify, and provide perspective on what we collectively know about memory and personality and their mechanisms in anuran amphibians. We propose four working hypotheses: (1) as tadpoles grow, new telencephalic neurons become integrated into functional networks, producing behaviors that become more sophisticated with age; (2) since carnivores tend to be more bold/aggressive than herbivores, carnivorous anuran adults will be more aggressive than herbivorous tadpoles; (3) each amphibian species, and perhaps life history stage, will have a set point on the Shy–Bold Continuum; and (4) around this set point there will be a range of individual responses. We also suggest that several factors are slowing our understanding of the variety and depth of memory and personality possibilities in anurans. These include the scala natura approach to comparative studies (i.e., the idea that one frog represents all frogs); the assumption that amphibians are no more than simple reflex machines; that study species tend to be chosen more for convenience than taxonomic representation; and that studies are designed to prove or disprove a construct. This latter factor is a particular hindrance because what we are really seeking as scientists is not the confirmation or refutation of ideas, but rather what those ideas are intended to produce, which is understanding. Full article

Emerging infectious diseases such as chytridiomycosis and ranavirosis, caused by Batrachochytrium dendrobatidis (Bd) and ranavirus (RV), respectively, are major contributors to global amphibian declines. Despite their significance, comprehensive data on the spatial epidemiology of these pathogens in South Korea remain limited. This study aimed to assess the nationwide co-occurrence and prevalence of Bd and RV across four anuran species in five administrative regions. Infection rates were analyzed in relation to host species, sex, and life history stage. Results indicated distinct prevalence patterns driven by ecological traits. Bd was predominantly detected in mountainous and coastal habitats, whereas RV was more common in flat inland areas. Both pathogens exhibited peak occurrence in central regions, likely reflecting seasonal transmission dynamics rather than stable endemic hotspots. The observed spatial heterogeneity appears to be influenced by pathogen-specific thermal tolerance and host ecology. These findings underscore the importance of understanding host–pathogen–environment interactions for effective disease surveillance and management. Continuous monitoring and integrative ecological approaches are essential to mitigate pathogen-induced biodiversity loss and to inform amphibian conservation strategies in East Asia. Full article

Horizontal gene transfer (HGT), the non-Mendelian transfer of genetic material between organisms, is relatively frequent in prokaryotes, whereas its extent among eukaryotes remains unclear. Here, we raise the hypothesis of a possible cross-phylum HGT event involving 5S ribosomal DNA (rDNA). A specific type of 5S rDNA sequence from the anuran Xenopus laevis was highly similar to a 5S rDNA sequence of the genome of its flatworm parasite Protopolystoma xenopodis. A maximum likelihood analysis revealed phylogenetic incongruence between the gene tree and the species trees, as the 5S rDNA sequence from Pr. xenopodis was grouped along with the sequences from the anurans. Sequence divergence analyses of the gene region and non-transcribed spacer also agree with an HGT event from Xenopus to Pr. xenopodis. Additionally, we examined whether contamination of the Pr. xenopodis genome assembly with frog DNA could explain our findings but found no evidence to support this hypothesis. These findings highlight the possible contribution of HGT to the high diversity observed in the 5S rDNA family. Full article

Anurans, commonly known as frogs and toads, comprise a diverse group of amphibians distributed across all continents except Antarctica. This manuscript provides a detailed overview of the global anuran fauna, emphasizing their biology, remarkable adaptations, and ecological importance. A particular focus is placed on their specialized cutaneous glands, which are crucial for defense, communication, and survival. These glands secrete a diverse array of bioactive compounds, including peptides, alkaloids, and other secondary metabolites, shaped by evolutionary pressures. Among these compounds, toxins with potent antimicrobial properties stand out due to their ability to combat a broad spectrum of microbial pathogens. We explore the chemical diversity of these secretions, analyzing their modes of action and their potential applications in combating antibiotic-resistant bacteria and other pathogens. By integrating knowledge, this study underscores the importance of anurans as both ecological keystones and a valuable resource for biotechnological innovations. Furthermore, it highlights the urgent need to conserve anuran biodiversity for harnessing their potential in the development of novel antimicrobial agents to address global health challenges. Full article

Microorganisms play a dual role in human health, serving as both essential allies and serious threats. Their association with infections led to the development of antimicrobials like penicillin, which revolutionized medicine. However, the emergence of antimicrobial resistance (AMR) has created a global health crisis, rendering many treatments ineffective due to pathogen mutations and acquired resistance mechanisms, particularly among ESKAPE pathogens. This resistance increases morbidity, mortality, and healthcare costs, exacerbated by antibiotic overuse and globalization. Biofilms and sepsis further complicate treatment. Addressing AMR requires new therapies, rational antibiotic use, and innovative approaches for drug discovery. Coordinated global action is essential to ensure future access to effective treatments. Antimicrobial peptides (AMPs) derived from Boana species (Anura, Hylidae) represent a promising alternative in the fight against AMR. These peptides exhibit activity against multidrug-resistant pathogens. Unlike conventional antibiotics, Boana peptides act through a broad mechanism that limits resistance development. Their ability to disrupt bacterial membranes and modulate immune responses makes them ideal candidates for the development of new treatments. These peptides may offer valuable alternatives for treating resistant infections and addressing the global AMR crisis. Full article

Satellite DNAs (satDNAs) play a crucial role in understanding chromosomal evolution and the differentiation of sex chromosomes across diverse taxa, particularly when high karyotypic diversity occurs. The Physalaemus cuvieri–Physalaemus ephippifer species complex comprises at least seven divergent lineages, each exhibiting specific karyotypic signatures. The group composed of Ph. ephippifer, Lineage 1B of ‘Ph. cuvieri’ (L1B), and a lineage resulting from their secondary contact is especially intriguing due to varying degrees of sex chromosome heteromorphism. In this study, we characterized the satellitome of Ph. ephippifer in order to identify novel satDNAs that may provide insights into chromosomal evolution, particularly concerning sex chromosomes. We identified 62 satDNAs in Ph. ephippifer, collectively accounting for approximately 10% of the genome. Notably, nine satDNA families were shared with species from distantly related clades, raising questions about their potential roles in anurans genomes. Among the seven satDNAs mapped via fluorescent in situ hybridization, PepSat3 emerged as a strong candidate for the centromeric sequence in this group. Additionally, PepSat11 and PepSat24 provided evidence supporting a translocation involving both arms of the W chromosome in Ph. ephippifer. Furthermore, a syntenic block composed of PepSat3, PcP190, and PepSat11 suggested an inversion event during the divergence of Ph. ephippifer and L1B. The variation in signal patterns of satDNAs associated with nucleolar organizer regions (NORs) highlights the complexity of NOR evolution in this species complex, which exhibits substantial diversity in this genomic region. Additionally, our findings for PepSat30-350 emphasize the importance of validating the sex-biased abundance of satDNAs. Full article

The intestinal microbiota is vital for host immunity and metabolism, and its changes are associated with the development stage of hosts. However, little is known regarding how growth and development of anurans affect the diversity of their microbiota, which has a complex life cycle. The Tibetan toad (Bufo tibetanus) is a wild population in the high-altitude area of southwest China, which has special adaptability to the environment. Here, the microbial community of the Tibetan toad at six developmental stages (from the tadpole at Gosner stage 18 to the 8-year-old adult) was assessed using high-throughput 16S rRNA sequencing. The alpha diversity index analysis showed that the Chao, Ace, and Shannon indices were highest at Gosner stage 32 and decreased as development progressed, and their alpha diversity remained unchanged over time in adult stages. Beta diversity revealed that the gut microbiota structure differed significantly from Gosner stages 18 to 31, and it became similar to adult toads from Gosner stages 45 to 46 and in juvenile groups. At the phylum level, Firmicutes, Proteobacteria, and Actinobacteria were dominant phyla in tadpoles and adults. The relative abundance of Firmicutes and Proteobacteria in the adult group was significantly higher and lower than that of tadpoles, respectively. The linear discriminant analysis effect size (LEfSe) analysis identified seven phyla exhibiting significant differences during life stages: Verrucomicrobiota, Bacteroidota, and Proteobacteria (Gosner 18 to 31), Cyanobateria and Chloroflexi (Gosner 32 to 41), Actinobacteriota (Gosner 45 to 46), Desulfobacterota (juvenile group), and Firmicutes (adult group). A pathway enrichment analysis revealed that the metabolism and biosynthesis of secondary metabolites were significantly enriched across all developmental stages. This research unveiled variations in the intestinal microbiota composition during development in anurans. Factors such as developmental stage, habitat type and feeding habit jointly affected the gut microbial diversity and community composition in the Tibetan toad. The findings of this study can provide information for understanding the influence of historical developments on the intestinal microbiota and provide protection information for anurans. Full article

Trichomitus batrachorum is a species of trichomonad that has gained attention due to its ecological importance and potential interactions with various hosts, such as amphibians (anurans) and reptiles (lizards and chelonians), where it has been recorded in the gastrointestinal tract of these vertebrates, specifically in their feces. Molecular studies have placed this flagellated protist within the Metamonada clade. Unlike parabasalids that inhabit endothermic mammals in relatively stable temperature conditions, protists associated with ectothermic reptiles are subject to significant temperature fluctuations. The ability of T. batrachorum to thrive in the variable temperatures encountered by reptiles suggests that its parasitism may remain largely unaffected by climate change. In our study, we detected and characterized T. batrachorum from the liver tissue of the lizard species Ameiva ameiva, collected in Presidente Figueiredo Municipality, Amazonas State, Brazil. The identification of T. batrachorum was confirmed by cultivation technique, light microscopy, scanning electron microscopy and transmission electron microscopy for ultrastructural analyses, and sequencing the 5.8S rDNA (region ITS1- ITS2) and 18S rRNA (ribosomal RNA) genes. One potential interpretation for this finding is that the flagellates may have migrated from the intestine to the bile duct, ultimately reaching the liver. This is the first successful characterization of T. batrachorum in the liver of a lizard, and provides a solid foundation for further research to elucidate the potential pathogenicity of this flagellate and the role of A. ameiva in the epidemiology of parabasalids in other animal species. Full article

Understanding the factors influencing amphibian populations is essential for effective freshwater conservation, particularly for species with biphasic life histories. This study examined how pond- and landscape-level characteristics shape larval amphibian occupancy, abundance, and detection in a remnant Tupelo-Cypress wetland in southeastern Illinois. Given the small number of available ponds (n = 4), we standardized survey effort across sites and incorporated robust hierarchical Bayesian models to evaluate environmental effects at both community and species levels. Occupancy probabilities were generally high across species, with canopy cover significantly increasing both community and species occupancy, particularly for salamanders (up to 6.4-fold). Predatory backswimmers and fish substantially reduced occupancy (by 21.7-fold and 6.0-fold, respectively). Anurans, especially Pseudacris spp., were more abundant than salamanders, with abundance positively associated with canopy cover, leaf litter, and pond perimeter. Detection probabilities were generally low and varied by species, with predatory invertebrates reducing detection up to 83.3-fold. These findings underscore the importance of maintaining canopy cover while mitigating predation risks to support amphibian populations. The application of multi-species hierarchical models provides a nuanced understanding of species-specific responses, offering valuable insights for conservation strategies in regions affected by habitat loss and climate change. However, given the limited spatial replication, these findings should be interpreted cautiously and validated through additional studies across broader temporal and spatial scales. Full article

The genus Polystoma includes parasites with direct life cycles that involve a short-lived free-living, aquatic oncomiracidia, post-larvae infecting the gill chambers of tadpoles, and adults parasitizing the urinary bladder of adult anurans. Despite the high diversity of anurans in the South American sub-continent, less than 20 species of Polystoma have been reported to date, and, particularly, in Argentina, only five species have been described from adult frogs. The aim of this work was to describe and characterize taxonomically the specimens found parasitizing tadpoles and frogs living in a well in Chicoana, Salta province, Argentina. Parasites were observed under optical and scanning electron microscopy and characterized genotypically by sequencing ITS1 and COI fragments. Frogs and tadpoles were characterized by morphology and sequencing a partial fragment of the cytochrome B region, confirming that the hosts corresponded to Pleurodema borellii. Given their morphology and the strict specificity of Polystoma species for their hosts, the identity of the parasites was established as P. borellii. The morphology of oncomiracidia and post-larvae was described, expanding adults’ description with insights provided by COI and ITS1 molecular analysis. The present work summarizes a complete description of the life cycle, with the genetic characterization of Polystoma borellii in Salta, Argentina. Full article

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a significant threat to global amphibian populations, leading to widespread declines and extinctions. In the spring of 2023, Bd presence was detected in different amphibian species within two protected areas near Turin, Piedmont, Italy, following an unusual mortality event among the common toad (Bufo bufo). Histological and molecular analyses confirmed Bd infection in a deceased Pelophylax sp. specimen, prompting further investigation. Sampling of 166 individuals across seven amphibian taxa revealed an overall Bd occurrence of 38.6%, with Pelophylax sp. showing the highest detection rate (50.5% of 93 individuals). A marked difference in the positivity rate was observed between the two locations, with La Mandria (67.2% of 58) exhibiting significantly higher rates than Vauda (22.9% of 35). While Bd was identified in the sampled amphibians, the exact cause of the observed mortality remains unclear and may involve other pathogens or multifactorial causes, including but not limited to Bd. These findings represent the first documented case of Bd presence in Piedmont after an 18-year gap, highlighting the potential influence of local environmental factors on infection dynamics. The study emphasises the need for expanded, standardised field sampling and further investigation into the various factors affecting amphibian health to guide conservation efforts for vulnerable amphibian species. Full article

Brain size asymmetry differs considerably across species, including humans, vertebrates, and invertebrates. The subtle structural, functional, or size differences between the two brain sides are associated with processing specific cognitive tasks. To evaluate the differences between the sizes of the left and right sides of the whole brain and brain regions and the effect of predation risk (i.e., snake density) on brain size asymmetry among Chinese anurans, we compared the differences between the left and right hemisphere sizes of the whole brain and brain regions among anuran species and analyzed the correlations between the predation risk and size asymmetry index of the brain and brain regions. We found that when one side of the brain was consistently larger than the other, there was a significant difference between the sizes of the left and right sides of the brain and brain regions, displaying directional asymmetry of the whole brain and brain regions. We also found that total brain size was positively correlated with the size asymmetry index of the olfactory bulb and optic tecta when the left hemispheres of the whole brain and brain regions were larger than the right ones. Meanwhile, the index of telencephalon size asymmetry was positively correlated with predation risk when the right hemispheres of the brain and brain regions were larger than the left ones. However, there were non-significant differences between the sizes of the left and right sides of the brain and brain regions across 99 species of anurans. Our findings suggest that an increased predation risk linked to sociality is likely to drive an increase in right telencephalon size. Full article

The gonads of amphibians, like other vertebrates, consist of somatic tissues, which create a specific environment essential for the differentiation of germline cells. The earliest stages of gametogenesis still remain underexplored in anuran amphibians. We propose to introduce the term “pregametogenesis” for a specific period of gonocyte proliferation and differentiation that occurs exclusively during the early stages of gonadal development. This review shows the key steps of early gonad differentiation in anuran amphibians and further compares chromatin reorganization in gonocytes of mammals and hybridogenetic water frogs. In mammals, this phase involves resetting genomic imprinting, which is crucial for determining gene expression in offspring. In hybridogenetic Pelophylax water frogs, we highlight the unique phenomenon of genome elimination, where one parental subgenome is eliminated while the other is replicated. This process, occurring at the same developmental phase as imprinting in mammals, underscores the evolutionary importance of pregametogenesis. The study of amphibian gonocytes provides valuable insights into chromatin reorganization and genome plasticity, offering new perspectives on reproductive biology. Full article

Nestedness in community ecology predicts that species in a species-poor site should be a subset of species of a species-rich site. A variety of ecological mechanisms have been offered to explain community nestedness; however, few studies have systematically discussed the issue of scale dependence when interpreting community nestedness. This study conducted surveys of anuran species data in the vicinity of Chengdu, Sichuan, in the summers of 2019–2020, using the transect method. The study area was divided into 23 sampling sites and 8 regions to explore the relationship between environmental factors and the nested distribution pattern of anuran communities under different sampling extents (with sampling buffers set at 1 km, 2 km, and 5 km). The WNODF (weighted-nestedness metric based on overlap and decreasing fill) results indicated that anurans exhibited a strong nested pattern at both the sampling sites scale and the regional scale. The habitat matrix test results suggested that a small-scale study area requires a correspondingly small habitat-sampling extent to effectively test for habitat nestedness. As the study area expands, the habitat-sampling range can be appropriately increased. The nested pattern of anurans in the vicinity of Chengdu can only be explained by habitat nestedness, as a Spearman’s correlation analysis showed that other environmental factors (area size, connectivity index, concentration index, proximity index, and distance to the city center) were not significantly correlated with the nested sequences of sampling points and regions. Therefore, regarding the conservation strategies for anurans in the vicinity of Chengdu, we recommend prioritizing the protection of areas with higher habitat diversity. Full article

Machine learning approaches for pattern recognition are increasingly popular. However, the underlying algorithms are often not open source, may require substantial data for model training, and are not geared toward specific tasks. We used open-source software to build a green toad breeding call detection algorithm that will aid in field data analysis. We provide instructions on how to reproduce our approach for other animal sounds and research questions. Our approach using 34 green toad call sequences and 166 audio files without green toad sounds had an accuracy of 0.99 when split into training (70%) and testing (30%) datasets. The final algorithm was applied to amphibian sounds newly collected by citizen scientists. Our function used three categories: “Green toad(s) detected”, “No green toad(s) detected”, and “Double check”. Ninety percent of files containing green toad calls were classified as “Green toad(s) detected”, and the remaining 10% as “Double check”. Eighty-nine percent of files not containing green toad calls were classified as “No green toad(s) detected”, and the remaining 11% as “Double check”. Hence, none of the files were classified in the wrong category. We conclude that it is feasible for researchers to build their own efficient pattern recognition algorithm. Full article