Responses of Freshwater Planarian Girardia tigrina to Fipronil-Based Insecticide: Survival, Behavioral and Physiological Endpoints

Fipronil is a pyrazole insecticide used to control undesirable insect populations. Due to its large-scale application, there is the potential for surface waters' contamination, with toxic action for non-target organisms, and consequent impacts on aquatic ecosystems. Planarians are potential non-target aquatic invertebrates to these insecticides. They are widespread in tropical freshwaters and have been proposed as good candidates to assess the toxic effects of freshwater systems contaminated by insecticides. Thus, the present study aims to evaluate the sublethal concentrations of a fipronil-based insecticide that may affect the planarian physiology. After chronic exposure to Regent 800 WG (R), a significant decrease in locomotor velocity (LOEC-6.25 mg.L-1), regeneration of the auricles and photoreceptors (LOEC-3.13 mg.L-1), and reproduction (fecundity-LOEC 12.5 mg.L-1) were observed. The results of our study demonstrate that long-term exposure to a pyrazole insecticide can compromise non-target aquatic invertebrates while reinforcing the need for a better investigation of complementary parameters (such as behavior, regeneration, and reproduction) for a more accurate risk assessment of commercial pesticide toxicity in freshwater systems.

Automated summary

This study evaluated the sublethal concentrations of a Fipronil-based insecticide on planarians and found that chronic exposure to the insecticide resulted in significant decreases in locomotor velocity, regeneration of auricles and photoreceptors, and reproduction. These findings highlight the potential detrimental effects of pyrazole insecticides on non-target aquatic invertebrates and emphasize the need for further investigation on complementary parameters to accurately assess the toxicity of commercial pesticides in freshwater systems.