Glyphosate and Roundup® Ready Effects in Hydra viridissima: New Data in an Old Issue

Abstract

Herbicides are used worldwide to protect agricultural crops, glyphosate being among the most frequently applied. In 2019 the European Commission approved the use of this herbicide for another 5 years and is now preparing its re-authorization for marketing. It is known that glyphosate (an active ingredient—AI) is usually less toxic than its commercial formulations, which may be related to adjuvants presents in such formulas. In this context, this work aimed to evaluate and compare the effects of glyphosate, as the commercial formulation Roundup® Ready (RR), and the AI in the Hydra viridissima life cycle, namely: mortality, morphology, feeding, reproduction, and regeneration. To attain this goal, H. viridissima was exposed to an environmentally relevant concentration of glyphosate (5.2 mg AI/L, both for RR and the AI) and to its culture medium (control). The mortality was lower than 0.03% for both RR and AI. Regarding morphological alterations, these were more severe on organisms exposed to RR, while a high recovery capacity in hydras exposed to AI was observed. No hydra was able to completely regenerate its body parts when exposed to RR, while 95% of the organisms exposed to AI were able to regenerate completely. The feeding rates of hydras exposed to RR decreased by from ~20% to ~50% compared to AI. As for reproduction, hydras exposed to RR released ~70% less buds than those exposed to AI. These timely results suggest that adjuvants present in the commercial formulation of glyphosate may cause higher toxicity to biota than the AI at environmentally relevant concentrations. Though the commercial formulation exerted higher toxicity in hydra, the effects AI induced in the morphology of the hydra cannot be disregarded, suggesting that a deeper understanding on the long-term toxicity of this AI is still needed to further support the decision on its marketing authorization and environmentally safe use.