Nicosulfuron, a sulfonylurea herbicide, alters embryonic development and oxidative status of hatchlings at environmental concentrations in an amphibian species
Résumé
The widespread use of agrochemicals for controlling pests and diseases of crops is recognized as a main threat to
biodiversity. Sulfonylurea herbicides are being increasingly used and display low levels of degradation in water
which suggest that they might affect non-target organisms. In a common garden experiment, eggs of a widespread
amphibian (Bufo spinosus) were exposed to sublethal environmentally relevant concentrations of a widely
used sulfonylurea herbicide, nicosulfuron, during the whole embryonic development. We assessed developmentrelated
traits (i.e., development duration, hatching success, hatchling size and occurrence of malformation) as
well as antioxidant markers in response to contamination (i.e., SOD, GPx, catalase, thiols and relevant ratios
thereof). We found that sublethal concentrations of nicosulfuron increased embryonic development duration,
increased hatchling size and tended to increase malformations. Embryos exposed to nicosulfuron displayed
decreased thiols and increased catalase activity suggesting alteration of oxidative status. We did not find any
effect of nicosulfuron on SOD and GPx levels. Interestingly, higher catalase activity was linked to higher proportion
of malformed individuals, suggesting that exposure to nicosulfuron induced teratogenic effects. Our
results suggest that alteration of antioxidant levels might be one physiological mechanism through which nicosulfuron
might cause detrimental effects on amphibian embryos. Sublethal effects of pesticides at environmentally
relevant concentrations have been overlooked and require further investigations, especially in nontarget
taxa occurring in agricultural landscapes.