Morphophysiological impacts of methomyl and warming on frog tadpoles ( Leptodactylus knudseni )

This is the authors' abstract. We don't add key points for this paper.

Amphibians are particularly vulnerable to environmental stressors due to their permeable skin, ectothermy and complex life cycles. Increase in the use of pesticides and climate change in the Amazon rainforest represent growing threats to native species. This study assessed the individual and combined effects of methomyl, and elevated temperature on tadpoles of Leptodactylus knudseni, a common Amazonian frog species. Tadpoles were chronically exposed to methomyl under current (26.5°C) and projected (30°C) temperature conditions. We evaluated survival, developmental rate, growth, morphology, neurophysiology and antioxidant responses. Methomyl exposure significantly increased mortality and accelerated metamorphosis while reducing body mass, a combination of effects that suggests endocrine disruption. Morphological analysis revealed systematic reductions in overall body dimensions and tail musculature across all experimental treatments, resulting in a significantly smaller and less robust phenotype, which may compromise post-metamorphic performance. Methomyl significantly inhibited acetylcholinesterase activity and upregulated superoxide dismutase, indicating neurotoxicity and oxidative stress. Although temperature and methomyl acted independently, with no synergistic interactions detected across any response variable, the growing threats posed by agricultural intensification and climate change in the Amazon emphasise the need for integrated ecotoxicological assessments. Such assessments are crucial for developing effective conservation strategies for tropical freshwater biodiversity.