Exposure of Folsomia candida (Willem 1902) to teflubenzuron over three generations – Increase of toxicity in the third generation

The potential implications of long-term exposure to contaminants are not covered by current standard toxicity guidelines, usually referring to one generation and a fraction of the life cycle of the test species. Hence, in the present study, we aimed to assess the effects of the multigenerational exposure (generation 1–3: F1-F3) of Folsomia candida to an insect growth regulator (IGR) compound: teflubenzuron (TFB). The selected endpoints included both the standard ones as in the OECD and ISO guidelines (survival, reproduction, and avoidance) as well as additional ones (organisms size and cellular oxidative stress markers: acetylcholinesterase, glutathione S-transferase, catalase, glutathione peroxidase, lipid peroxidation). Although no avoidance behaviour was recorded at field-relevant concentrations (PEC (Predicted Environmental Concentration) = 0.06 mg/kg soil dry weigh (dwt)), survival and reproduction were impacted (LC50 = 0.1 mg/kg soil dwt; EC50 = 0.05 mg/kg soil dwt). Multigenerational exposure to TFB caused increased toxicity in F. candida in F3 in terms of survival and reproduction. This could be related to the mode of action of TFB which does not seem to activate some of the general stress mechanisms of response like oxidative stress. In addition, TFB causes a reduction of the organisms’ size, with a reduction of the number of large-sized juveniles, which has potential adverse consequences in terms of organisms’ performance, e.g. change in age structure and hence population dynamics. Hence, both observations may increase the environmental concern and associated risk of this insecticide.