Exposure to sublethal concentrations of the glyphosate-based herbicide Faena® increases sensitivity in the progeny of the American cladoceran Daphnia exilis (Herrick, 1895)

The use of herbicides has increased over the last decades. Glyphosate is the most widely used herbicide commercialized in more than 750 formulations. While information about glyphosate's toxicity on different non-target aquatic organisms has been vastly documented, we know little about the transgenerational effects in aquatic biota. This study determined the cross-generation effects produced by the glyphosate-based herbicide Faena® on the American cladoceran Daphnia exilis. Measured endpoints were survival, reproductive responses, metabolic biomarkers, and the size of neonates. D. exilis was exposed to glyphosate concentrations of 2.09, 2.49, and 3.15 (mg L^-1) (as content in Faena®) during 21 days starting from neonates, at 25°C, 16:8 photoperiod, fed with 8 × 10⁵ cells mL^-1 of Pseudokirchneriella subcapitata. The LC₅₀ was 4.22 mg L^-1. Survival, accumulated progeny, and the number of clutches in the parental generation (P₁) were significantly higher than those observed in the first generation (F₁). Exposure to the herbicide completely inhibited reproduction in the F₁. The size of the neonates varied among treatments and broods in P₁; nevertheless, neonate size (body and total lengths, as well as body width) was significantly affected in F₁. Toxic effects on the survival and reproduction of D. exilis were significantly increased in the F₁ exposed to Faena®. Results warn about the augmented effect on progeny where parents were exposed to this herbicide. Multigenerational adverse effects could be expected in freshwater zooplankton exposed to Faena®. The frequently claimed low toxicity of glyphosate must be revised to control the indiscriminate use of this herbicide.