Regul Toxicol Pharmacol
January 2025
The amphibian metamorphosis assay (AMA) is an in vivo screen to assess potential interactions of chemicals with the amphibian thyroid system. Tadpoles are exposed for 21-days, then assessed for development and growth after 7 days and at test termination. This paper presents data from studies performed to satisfy test orders from the US EPA's Endocrine Disruptor Screening Program.
View Article and Find Full Text PDFAccording to the World Health Organisation and European Commission definitions, substances shall be considered as having endocrine disrupting properties if they show adverse effects, have endocrine activity and the adverse effects are a consequence of the endocrine activity (using a weight-of-evidence approach based on biological plausibility), unless the adverse effects are not relevant to humans or non-target organisms at the (sub)population level. To date, there is no decision logic on how to establish endocrine disruption via the thyroid modality in non-mammalian vertebrates. This paper describes an evidence-based decision logic compliant with the integrated approach to testing and assessment (IATA) concept, to identify thyroid-mediated effect patterns in aquatic vertebrates using amphibians as relevant models for thyroid disruption assessment.
View Article and Find Full Text PDFAmphibians are currently considered to be covered by pesticide Environmental Risk Assessment schemes by surrogacy assumptions of exposure and susceptibility based on typical laboratory test species such as fish, mammals, and birds. While multiple reviews have shown for this approach to be adequate in the case of aquatic stages, the same cannot be definitively stated for terrestrial stages. Concerns have risen that exposure of amphibians is likely to be highly influenced by dermal absorption, primarily due to the high permeability of their skin and the lack of a protective layer, such as fur or feathers.
View Article and Find Full Text PDFThe Amphibian Metamorphosis Assay (AMA) is used to determine if a tested chemical has potential to impact the hypothalamic-pituitary-thyroid (HPT) axis of Xenopus laevis tadpoles, while the Fish Short Term Reproduction Assay (FSTRA) assesses potential effects on the hypothalamic-pituitary-gonadal (HPG) axis of fish such as the fathead minnow (Pimephales promelas). Several global regulatory programs routinely require these internationally validated tests be performed to determine the potential endocrine activity of chemicals. As such, they are conducted in accordance with standardized protocols and test criteria, which were originally developed more than a decade ago.
View Article and Find Full Text PDFThe amphibian metamorphosis assay (AMA) is a key in vivo endocrine screen to investigate chemicals with potential thyroid activity. The test guidelines and associated guidance consider that treatment-related effects on thyroid gland histomorphology automatically result in the assay being considered positive for thyroid activity, independent of the direction of change or conflicting results in the other biological endpoints. An AMA study was conducted with five different feeding rations equivalent to 50%, 30%, 20%, 10%, and 5% of the recommended feeding rate.
View Article and Find Full Text PDFThe use of enzymatic biomarkers constitutes a widely used approach in ecotoxicology. However, standard sampling procedures are invasive, requiring tissue, organ or blood extraction. This leads to concerns regarding conservation practice, animal welfare and restrictions in study design.
View Article and Find Full Text PDFBacillus thuringiensis var. israelensis (Bti) is presumed to be an environmental friendly agent for the use in either health-related mosquito control or the reduction of nuisance associated with mosquitoes from seasonal wetlands. Amphibians inhabiting these valuable wetlands may be exposed to Bti products several times during their breeding season.
View Article and Find Full Text PDFEnvironmental pollution and habitat loss are described as underlying causes for population declines in reptiles and especially affect species in agricultural landscapes. Studies dealing with effects of pesticide exposure on reptiles are limited, mainly addressing the orders Testudines and Crocodylia, but largely neglecting the most diverse reptile order Squamata (lizards and snakes). As a consequence, information regarding effects on their organisms, as well as exposure probability and pesticide uptake in the Reptilia has to be considered rather uncharted.
View Article and Find Full Text PDFHabitat loss and environmental pollution are among the main causes responsible for worldwide biodiversity loss. The resulting species and population declines affect all vertebrates including reptiles. Especially in industrialized countries, pollution by agrochemicals is of remarkable importance.
View Article and Find Full Text PDFEnvironmental pollution has an especially high impact on wildlife. This is especially the case in industrialized countries. Although, many species within the European Union benefit from protection by the Habitats Directive, no special consideration is given to possible detrimental effects of pesticides.
View Article and Find Full Text PDF