Toxicity of a Common Glyphosate Metabolite to the Freshwater Planarian ( Girardia tigrina )

To establish meaningful policy directives for sustainable agrochemical use, we require baseline knowledge of the impacts of agrochemicals on non-target organisms. The widespread use of the herbicide glyphosate has resulted in the global presence of its metabolite, aminomethylphosphonic acid (AMPA). AMPA is commonly found in water bodies, including freshwater systems. We investigated the effects of AMPA exposure on the survivorship, regenerative abilities, and locomotion of the brown planarian ( Girardia tigrina ), a water-dwelling flatworm commonly found in freshwater ecosystems. In a series of experiments, we bisected and then exposed planarians to realistic field doses of AMPA for seven days and then fourteen days. For the 14-day experiment, we exposed planarians to two concentrations consistent with the high and low ranges of concentrations observed in water systems. Compared to the control group, we found that planarians exposed to AMPA for fourteen days (un-bisected for the first seven days and recovering from bisection for the subsequent seven) exhibited slower regeneration from the tail segment. Our findings highlight the potential ecological impacts of AMPA contamination on planarian populations. Quantifying the effects of AMPA exposure on planarians contributes to our understanding of the ecological consequences of our current and common agricultural practices on our freshwater ecosystems.