Behavioral and toxic effects of the neonicotinoid pesticide thiacloprid in the planarian Girardia dorotocephala

Neonicotinoids were developed in the 1990s and are among the most popular pesticides worldwide. However, a significant fraction of neonicotinoids end up in freshwater, affecting non-target organisms, including planarians, a type of free-living flatworm. In this work, we explored the effect of the neonicotinoid thiacloprid on planarian behavior. Thiacloprid decreased planarian motility reversibly and increased seizure-like movements (paroxysm-like movements different from the normal gliding behavior of the worms) in a concentration-dependent manner but did not influence planarian environmental light/dark preference at sub-µM concentrations. Exposure to up to 10 µM thiacloprid for 24 h did not cause lethality but markedly decreased motility and caused a concentration-dependent incidence of a “wrinkled” morphology at rest. The quantification of thiacloprid’s behavioral effects reported in the present work allows us to suggest strategies for screening possible alleviators of neonicotinoid effects in planarians and potentially other non-target species. To the best of our knowledge, this is the first report on the effect of thiacloprid on planarians.