Mercury contamination impairs the hypothalamic-pituitary-adrenal axis of a neotropical caiman.

Wild smooth-fronted caimans with elevated blood mercury show reduced peak corticosterone during standardized stress tests, indicating a dampened maximal stress response.

• Why it matters: Mercury pollution may disrupt endocrine regulation needed for physiological flexibility, limiting how Hg-contaminated crocodylians cope with novel environmental stressors.
• What they did: The study measured blood Hg concentrations and corticosterone responses in wild smooth-fronted caimans using standardized stress tests, finding a negative correlation between Hg and corticosterone responsiveness.
• The result: Hg blood levels are linked to impaired hypothalamic-pituitary-adrenal axis function, and a methylmercury-sensitive cysteine in the glucocorticoid receptor is highly conserved across vertebrates, suggesting a shared molecular mechanism.