Ecotoxicological Assessment of a Glyphosate-Based Commercial Formulation and a Novel Experimental Formulation by Standardized Amphibian Bioassays

Abstract

Herbicide effectiveness depends on the adjuvants in the formulation, with surfactants being crucial for systemic ones such as glyphosate, but surfactants are often more toxic than the pesticide itself to nontarget organisms, such as amphibians. Previously, a novel experimental formulation (EF) of glyphosate has been developed with natural products (alkylglucosides and saponin) with great efficiency in field tests. The objective of this study was to compare the toxicity of the EF with a commercial formulation of glyphosate (Roundup Full II, CF) by standardized bioassays (AMPHITOX). For this, embryos and larvae of Rhinella arenarum were exposed to EF and CF (1–500 mg a.i./L), and various endpoints were assessed, including lethality, morphological and ethological abnormalities, neurotoxicity through the response of the enzyme butyrylcholinesterase (BChE), and genotoxicity using the micronucleus assay (MNs). The results showed that CF was almost 45 times more toxic than EF in embryos (LC 50–504 h = 1.43 and 72.53 mg/L CF and EF, respectively) and larvae (LC 50–504 h = 6.25 and 288.54 mg/L CF and EF, respectively). Regarding abnormalities, exposed embryos to CF exhibited microcephaly, hydropsy, reduced weight, and absenceof movements. Likewise, the analysis of biomarkers revealed that CF inhibited BChE activity and significantly increased the frequency of MNs, whereas larvae exposed to EF showed no significant differences compared to the control group. The results demonstrate a marked decrease in the adverse effects of the EF, highlighting the importance of developing new formulations with natural and less toxic surfactants for the conservation of the biota.