Evidence cluster — Pet amphibian (anuran) toxicology (peer-reviewed, Europe PMC)

Evidence: Pet amphibian (anuran) toxicology

Source: Europe PMC (Europe PubMed Central) REST search — first-hand peer-reviewed abstract records, pulled 2026-08-01. Queries covered toxicology, poisoning, intoxication, heavy metals, mycotoxins and (for relevant taxa) envenomation for anuran. The cluster returns 12 representative studies with abstracts below. Abstract text is verbatim from source; each study is traceable by PMID.

Studies

PMID 41483836 (2026, Toxicology letters) — *[Paraphrased derived summary — non-Open-Access source.]* Noting global amphibian declines and the African clawed frog (Xenopus laevis) role as an OECD test species, this work built open-source quantitative structure–activity relationship (QSAR) models to predict acute developmental toxicity (12-hour LC50) for data-poor chemicals. It curated 1,978 historical entries (349 structures) from the US EPA ECOTOX and Ortiz-Santaliestra databases down to 359 entries covering 175 compounds, expressed as negative-log molar LC50, then split into training, test, and prediction sets; the excerpt is cut off before the model validation results.

Source: https://pubmed.ncbi.nlm.nih.gov/41483836/

PMID 41670719 (2026, Archives of environmental contamination and toxicology) — *[Paraphrased derived summary — non-Open-Access source.]* Experiments on Northwestern Salamander (Ambystoma gracile) larvae showed copper toxicity depends strongly on water hardness: acute LC50 was 33.16 µg/L in soft water versus 1383 µg/L in moderately hard water, and the 35-day subchronic LC50 was 28.97 µg/L, with delayed development, lower survival, and reduced growth. Acute exposure raised metallothionein-1 (mt1) expression—a metal-detoxification response—but left thyroid-hormone receptor (thra, thrb), estrogen receptor (esr1α), and deiodinase (dio1) genes unchanged. The authors highlight species-specific copper sensitivity and note caudate amphibians are often missing from ecological risk assessments.

Source: https://pubmed.ncbi.nlm.nih.gov/41670719/

PMID 41793491 (2026, Bulletin of environmental contamination and toxicology) — Subchronic Exposure to Nonylphenol Ethoxylate at Environmentally Relevant Level Promotes Mutagenic, Neurotoxic, and Pro-oxidant Effects in Bullfrog Tadpoles.. Abstract (opening): Nonylphenol compounds released into aquatic environments have been shown to exert deleterious effects on aquatic organisms. Amphibians, particularly during larval stages, are highly vulnerable to chemical stressors and are chronically exposed to pollutants such as nonylphenol ethoxylate (NPE). This study evaluated the sublethal effects of environmentally relevant concentrations of NPE (30 µg L−1) under sub-chronic exposure in Aquarana catesbeiana tadpoles (Gosner stage 25), with emphasis on mutagenic, neurotoxic, and oxidative responses. The analyses included blood cell composition, frequency of micronuclei (MN) and erythrocytic nuclear abnormalities (ENAs), acetylcholinesterase (AChE) activity in brain and muscle tissues, and oxidative stress biomarkers (lipid peroxidation and protein carbonylation) in blood. Results demonstrated that NPE exposure induced clastogenic and aneugenic effects in erythrocytes, impaired central and muscular cholinergic function, and triggered oxidative stress in blood. These findings highlight the NPE potential to disrupt critical physiological systems in amphibians. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/41793491/

PMID 42146017 (2026, Frontiers in physiology) — Physiological responses and adaptive mechanisms of amphibians and reptiles to multiple interacting environmental stressors: an integrative review.. Abstract (opening): This integrative review synthesizes current knowledge on the physiological responses and adaptive mechanisms of amphibians and reptiles to multiple interacting environmental stressors, with particular emphasis on synergistic effects among temperature, hydric stress, disease, and pollution. Given the stronger empirical basis for amphibians in the existing literature, amphibian responses are covered in greater depth, while reptile-specific physiology, immunology, and emerging infectious diseases are explicitly addressed in dedicated sections throughout the review. Critical thermal tolerance analyses reveal that approximately 7.5% of amphibian species will exceed their physiological limits under a 4 °C warming scenario, with tropical lowland species already operating near their CTmax thresholds. Thermal plasticity is limited, with acclimation responses averaging only 0.13 °C increase in CTmax per 1 °C environmental warming-insufficient to track rapid climate change. Water balance regulation shows dramatic interspecific variation, with cutaneous resistance ranging from 0.05 s/cm in aquatic amphibians to >1000 s/cm in desert-adapted reptiles. Synergistic interactions between thermal and hydric stress significantly amplify vulnerability, particularly in dehydration scenarios that reduce critical thermal limits. Chemical pollutants, including heavy metals and pesticides, cause developmental abnormalities (535% increase in malformation frequency), immunosuppression, and endocrine disruption across multiple life stages. Emerging infectious diseases, particularly chytridiomycosis (Batrachochytrium dendrobatidis and B. salamandrivorans) and ranaviruses, drive mass mortality events globally, with co-infections exacerbating population declines. Climate change intensifies disease susceptibility through stress-mediated immunosuppression and altered pathogen dynamics. Adaptive capacity varies markedly among species. While amphibians exhibit strong phenological responses (2-4× greater than other taxa), genetic adaptation potential remains limited by narrow dispersal abilities and habitat fragmentation. Microhabitat buffering can reduce thermal extremes by several degrees but depends critically on habitat structural integrity. This review demonstrates that the pace of anthropogenic change challenges the adaptive capacity of most species, necessitating integrated conservation strategies including microhabitat preservation, climate corridor establishment, pollution mitigation, disease surveillance, and ex-situ conservation programs. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/42146017/

PMID 40298996 (2025, Bulletin of environmental contamination and toxicology) — *[Paraphrased derived summary — non-Open-Access source.]* A laboratory bioassay tested the pyrethroid insecticide lambda-cyhalothrin on tadpoles of the Neotropical frog Boana pulchella (Argentine Pampas) at 1.5 and 10 µg/L versus a control, measuring swimming speed via video tracking after 2 and 96 hours. No deaths occurred, but tail-flexion appeared in all exposed tadpoles (absent in controls) and swimming velocity was significantly reduced, more so at the higher concentration. The authors conclude that field-realistic lambda-cyhalothrin levels alter tadpole morphology and swimming, with likely consequences for competitive fitness and non-target amphibian communities.

Source: https://pubmed.ncbi.nlm.nih.gov/40298996/

PMID 41008613 (2025, Biomolecules) — Gene Duplication, Translocation, and Molecular Evolution of Dmrt1 and Related Sex-Determining Genes in Anurans.. Abstract (opening): Sex determination, the developmental process that directs embryos toward male or female fates, is controlled by master sex-determining genes whose origins and evolutionary dynamics remain poorly understood outside of a few model systems. In contrast to the highly differentiated sex chromosomes of mammals, birds, and Drosophila, most anurans (frogs and toads) maintain homomorphic sex chromosomes that exhibit a rapid turnover, even among closely related species. Master sex-determining genes evolve via gene duplication or via allelic diversification, and sex chromosome turnover is driven by gene translocation or novel mutations in the existing genes involved in the sexual developmental pathway. To uncover the mechanisms underlying the emergence of master sex-determining genes and sex chromosome turnover, we analyzed 53 published anuran genomes and one caecilian genome (>200 Mya divergence) and available transcriptomes. We asked how often master sex-determining genes arise by gene duplication, whether and how often gene translocation associates with sex chromosome turnover, and if master sex-determining genes evolve under positive selection. We find that chromosome-level synteny is remarkably conserved, with only a few fusions or fissions and no evidence for translocation of four candidate master sex-determining genes (Dmrt1, Foxl2, Bod1l, and Sox3). Only Dmrt1 duplicated in 3 out of 50 species (excluding tetraploid Xenopus), and it showed strong testis-biased expression in all 8 species with available gonadal expression data. While Dmrt1 has evolved under purifying selection, Dmrt1 duplicates exhibit elevated nonsynonymous substitution rates and tendency towards positive selection. Lineage-specific amino acid changes were observed in the conserved DM domain of Dmrt1. These results demonstrate that, in anurans, master sex-determining genes rarely arise via gene duplication, and more likely evolve via allelic diversification. Sex chromosome turnover is not associated with gene translocation and is more likely driven by mutations on genes involved in sexual developmental pathways. All candidate sex-determining genes were under strong purifying selection, with the exception of duplications which are linked to positive selection. Our results suggest future research on anuran sex determination and sex chromosome evolution should focus on identifying allelic diversification and novel mutations on genes involved in sexual developmental pathways. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/41008613/

PMID 40181708 (2025, Journal of morphology) — Perichordal Vertebral Column Formation in Rana kobai.. Abstract (opening): The vertebral column of anurans exhibits morphological diversity that is often used in phylogenetic studies. The family Ranidae is one of the ecologically most successful groups of anurans, with the genus Rana being distributed broadly in Eurasia. However, there are relatively sparse detailed studies on the development of the vertebral column in Rana species, and images of the entire axial skeleton have seldom been illustrated till date. Here, we provide an illustrated description on the development of the entire vertebral column in Rana kobai, a Japanese small frog from the Amami Islands. Our observation of double-stained skeletal specimens revealed that in R. kobai, the original atlas and the first dorsal are fused into one vertebra, and the ninth neural arch is fused with the tenth arch in half of the examined larvae. Anuran vertebral column development is classified into two modes, perichordal and epichordal. Rana species undergo the typical perichordal mode of centrum formation. Kemp and Hoyt (1969) described that centrum formation in R. pipiens starts from a saddle-shaped bone on the dorsal half of the notochord. Nevertheless, our detailed observations revealed that centrum ossification initially emerges at the base of the paired neural arches and then forms the saddle-shaped bone. In Xenopus, a species with epichordal centra, centrum formation starts from a pair of ovoid bone elements at the base of the neural arches. Overall, our results imply that centrum ossification starts from the base of neural arches in anurans, irrespective of whether it is perichordal or epichordal. Our observations also revealed the presence of the crescent-shaped cartilage domain in the intervertebral region in R. kobai. The location of the crescent-shaped domain in R. kobai is consistent with that of the intercentrum in Ichthyostega and several temnospondyls. Based on our observations, we propose a hypothesis on the difference between perichordal and epichordal modes in light of evolution. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/40181708/

PMID 41561475 (2025, Frontiers in toxicology) — Comparative assessment of solvents toxicity using early life stages of amphibians and cell lines: a case study with dimethyl sulfoxide.. Abstract (opening): The reduction in the number of animals being used in experimental assays has been a concern of the scientific community. In this sense, non-animal alternative methods have been increasingly tested. This study intended to explore how cell-based responses compare to organismal outcomes and if the former models could contribute to minimizing the number of live animals needed in subsequent stages of hazard/risk assessment of chemicals on amphibians. For this, the toxicity of the commonly used solvent dimethyl sulfoxide (DMSO) was assessed in early life stages (embryos and tadpoles) of two anuran species (Xenopus laevis and Pelophylax perezi) and in 2 cell lines of X. laevis (A6 and XTC-2). In the in vivo assays, mortality, teratogenic effects, and biometric parameters were evaluated, while for in vitro assays, the assessed endpoint was viability. Overall, the obtained data suggest similar sensitivity of both species and life stages to DMSO. The 96 h-LC50 estimated for embryos and tadpoles were, respectively, 2.19% and 2.56% for X. laevis and 3.19 and 3.41 for P. perezi. The solvent DMSO induced several malformations in early life stages, which may have implications for the fitness of organisms at later stages. A slightly higher sensitivity to DMSO was observed in the in vivo approaches comparatively to in vitro approach (72 h-LC50 of 3.10% and 2.62% for A6 and XTC-2, respectively), though it can not be considered significantly different. As such, it is suggested that the latter approach may be considered to serve for first screenings of the ecotoxicity of organic solvents. Such a strategy of using in vitro assays as screening tools, has the potential to reduce the number of animals to be used in subsequent in vivo testing phases by providing information for the refinement of concentrations to be tested in in vivo assays, thereby supporting both reduction and replacement objectives. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/41561475/

PMID 39855321 (2025, Environmental toxicology and pharmacology) — *[Paraphrased derived summary — non-Open-Access source.]* Tadpoles of Boana faber were exposed for 168 hours to a glyphosate-based herbicide at 65, 260, and 520 µg/L. Body-condition biomarkers dropped significantly at the two higher concentrations; at the highest level superoxide dismutase activity rose while lipid-peroxidation levels were maintained, and carbonyl-protein reductions (with raised catalase) appeared at the lower concentrations. Glycogen fell across all exposed groups, indicating its use for energy production. The authors propose these body-condition markers as a non-invasive way to assess amphibian health.

Source: https://pubmed.ncbi.nlm.nih.gov/39855321/

PMID 41295741 (2025, Veterinary sciences) — Hematology Reference Values for the Iberian Ribbed Newt (Pleurodeles waltl) Under Human Care.. Abstract (opening): The Iberian ribbed newt (Pleurodeles waltl) is a salamander in the Salamandridae family. Endemic to the Iberian Peninsula and North Africa, it is not commonly found in zoological institutions or wildlife rescue centers. As in other species, routine blood analysis of amphibians under human care is highly recommended, forming an essential component of preventive medicine and effective clinical management. However, despite the great utility of hematological parameters for the diagnosis and prevention of diseases in amphibians, the lack of reliable reference values for many species severely limits their clinical use. The aim of this study is to establish preliminary reference values (RV) for the main hematological parameters in the Iberian ribbed newt. Blood samples were taken from healthy adult individuals (n = 30), females (n = 9) and males (n = 21) maintained under controlled conditions in two zoological institutions. A complete hematological analysis was conducted, which included measurements of hematocrit, total erythrocyte and leukocyte counts, as well as a leukocyte differential. The reference intervals were established according to the guidelines provided by the American Society for Veterinary Clinical Pathology (ASVCP) for sample sizes between 20 and 40 individuals. No significant sex-related differences were detected in the hematological parameters analyzed. Despite the broad reference ranges obtained, these preliminary data provide an essential foundation for the clinical assessment and preventive medical management of P. waltl under human care. Expanding the dataset through collaboration with additional institutions will further refine and improve the accuracy and clinical utility of these reference values. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/41295741/

PMID 41234787 (2025, Royal Society open science) — Arid habitats intensify sexual conflict in invasive cane toads (Rhinella marina).. Abstract (opening): Amplexus by male cane toads (Rhinella marina) impairs a female's mobility and may impose a risk of drowning. Near the arid-zone edge of the toads' Australian invasion, artificial ponds provide the only permanent open water. Cane toads must access water to hydrate every few nights, creating a potential for sexual conflict. Our field-based experiments show that a female toad that approaches one of these steep-sided dams encounters numerous reproductively active males, most of which are facing the shore. When amplexed by these males, she may find herself in deep water even close to the shore and is vulnerable to drowning. In trials with tethered females, toads amplexed in deep water could not hold their heads above the water's surface. Demographic effects of this sexual conflict are evident from population surveys: toad populations around dams are strongly male-biased whereas females are concentrated at mesic refuges around buildings that provide less dangerous conditions. Even around the same dam, female toads are often found on land whereas most males are found in the water. If sexual conflict around scarce waterbodies is lethal for female toads, we might reduce recruitment by allowing dense populations of male toads to persist. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/41234787/

PMID 40274765 (2025, Nature communications) — Structural basis for saxitoxin congener binding and neutralization by anuran saxiphilins.. Abstract (opening): Dinoflagellates and cyanobacteria produce saxitoxin (STX) and ~50 congeners that disrupt bioelectrical signals by blocking voltage-gated sodium channels (NaVs). Consuming seafood carrying these toxins causes paralytic shellfish poisoning (PSP). Although NaVs and anuran STX binding proteins (saxiphilins, Sxphs) use convergent STX binding modes, the structural basis for STX congener recognition is unknown. Here, we show that American bullfrog (Rana catesbeiana) RcSxph and High Himalaya frog (Nanorana parkeri) NpSxph sequester STX congeners using a 'lock and key' mode shared with STX. Importantly, functional studies demonstrate that Sxph 'toxin sponges' reverse NaV block by multiple STX congeners and detect these toxins in a radioligand binding assay (RBA) used for environmental testing. Together, our study establishes how Sxphs sequester select neurotoxins and uncover STX congener-specific interactions distinct from NaVs. These findings expand understanding of toxin sponge action and provide a foundation for strategies to monitor and mitigate the harmful effects of STX congeners. *[CC BY — Open Access, verbatim with attribution.]*

Source: https://pubmed.ncbi.nlm.nih.gov/40274765/

Source text: pdf-raw/evidence/europepmc_amphibian_toxicology_2026-08-01.txt (Europe PMC first-hand abstracts, pulled 2026-08-01).

License & attribution

Mixed licensing per COPYRIGHT_POLICY §3: Open Access (CC BY / CC BY-NC / CC BY-NC-ND) studies are reproduced verbatim with attribution under their specific CC license; non-Open-Access studies are paraphrased as derived fact summaries (numbers and proper nouns preserved, sentences rewritten). Original records:

https://pubmed.ncbi.nlm.nih.gov/39855321/
https://pubmed.ncbi.nlm.nih.gov/40181708/
https://pubmed.ncbi.nlm.nih.gov/40274765/
https://pubmed.ncbi.nlm.nih.gov/40298996/
https://pubmed.ncbi.nlm.nih.gov/41008613/
https://pubmed.ncbi.nlm.nih.gov/41234787/
https://pubmed.ncbi.nlm.nih.gov/41295741/
https://pubmed.ncbi.nlm.nih.gov/41483836/
https://pubmed.ncbi.nlm.nih.gov/41561475/
https://pubmed.ncbi.nlm.nih.gov/41670719/
https://pubmed.ncbi.nlm.nih.gov/41793491/
https://pubmed.ncbi.nlm.nih.gov/42146017/

Evidence cluster — Pet amphibian (anuran) toxicology (peer-reviewed, Europe PMC)

Evidence: Pet amphibian (anuran) toxicology

Studies

License & attribution

Sources

Machine access