Effects of Glyphosate or Glyphosate-Based Herbicide during the Zebrafish Life Cycle: A Review Addressing the Mechanisms of Toxicity

Herbicides with glyphosate (GLY) as an active ingredient (a.i.) are increasingly used, and GLY is currently the most used herbicide in the world. Consequently, its residues have often been found in aquatic ecosystems. Investigating how this substance affects aquatic species is a priority in ecotoxicology research, especially in fish, as they can absorb and concentrate toxins. In this sense, a critical review was performed, synthesizing data from the peer-reviewed bibliography, reporting on the toxicity of exposure to pure GLY and glyphosate-based herbicides (GBHs), using zebrafish as an animal model. The concentrations of this herbicide that induced toxic effects are highly variable, with some exceeding the limits determined by regulatory agencies. Globally, relevant toxic effects have been reported in zebrafish, namely, teratogenic effects incompatible with life, which translates directly into an increase in reported zebrafish mortality. Neurotoxicity, genotoxicity, changes in energy metabolism and oxidative stress, and immune and hormonal system dysfunction with an impact on fish reproduction were also described. In conclusion, both GLY and GBHs may induce damage to zebrafish, compromising their survival, reproduction, and maintenance. These results may be valid and applied to other fish species and aquatic ecosystems.