Agricultural herbicide usage leads to the contaminating of aquatic ecosystems exposing aquatic organisms to toxic compounds. Herbicides may affect fish at different stages of development, such as gamete, embryonic early development, and mature adult. Sperm, embryos, and adult of Astyanax altiparanae were used to evaluate the detrimental effects of three herbicide formulations: glyphosate, imazapyr, and diquat. The LC50 values for adults using glyphosate and imazapyr were 2.99 mg/L and 4.17 mg/L, respectively, while diquat was impossible to assess. For the initial stages of development of embryos, the LC50 values for glyphosate, imazapyr, and diquat were 15.73 µg/L, 8.48 µg/L, and 0.96 µg/L, respectively. Inhibition of sperm motility was observed at concentrations of 240 µg/L for glyphosate, 125 µg/L for imazapyr, and 10 mg/L for diquat. Sperm viability measurements were taken at 96 µg/L for glyphosate, 30 µg/L for imazapyr, and 1.3 mg/L for diquat, observed 63.6%, 65.1%, and 62.9% of sperm viability, respectively, in comparison with 87.5% detected in control without herbicides. Astyanax altiparanae in different phases of development exhibited different sensitivities to the herbicide formulations investigated. Roundup Transorb® was a more toxic herbicide for adult individuals, while Reglone® was the most toxic for early embryonic development and Arsenal® NA for sperm motility. The initial stages of embryo development of Astyanax altiparanae were the phase more sensitive for the toxicological effects of herbicides, being the stage more appropriate to the toxicological studies of herbicides. A. altiparanae may be considered an emerging fish model for toxicological studies in the Neotropical region due to its wide distribution and biological characteristics.
