Glyphosate (Roundup) Impairs Embryonic Development and Thermal Adaptation in Lizard (Eremias argus) under Warming

Glyphosate-based herbicides (GBHs) are widely used in agriculture and increasingly detected in soils, yet their interactive effects with climate warming on the early developmental stages of oviparous reptiles remain poorly understood. This study examined the combined impacts of GBH (Roundup) exposure and elevated incubation temperature on embryonic development and physiological responses in the lizard Eremias argus. Eggs were incubated under control (26 °C) and warming (28 °C) scenarios, with exposure to 0, 1.0, or 10.0 mg/kg GBH in vermiculite. Higher temperature enhanced embryonic heart rate and shortened incubation periods without reducing hatch success, and induced adaptive responses including increased antioxidant enzyme activities, elevated ATP levels, and downregulation of DNA methyltransferases. In contrast, GBH caused oxidative damage, suppressed heart rate and cardiac gene expression, inhibited citrate synthase activity, and reduced hatchling size. Critically, GBH disrupted thermal adaptation: it diminished warming-induced benefits in antioxidant and metabolic function, altered heat shock protein expression, and impaired thermal preference plasticity in hatchlings. These results reveal a mechanism by which GBH exposure can undermine reptile resilience to climate warming in agroecosystems. However, because effects were observed at 10 mg/kg, the tested GBH formulation likely poses low risk to Eremias argus embryos with respect to the end points measured under typical field conditions.