Two novel bioassays useful for the quick assessment of chemical effects on the behavior of mosquito larvae (Culicidae) and adult earthworms (Lumbricidae).

The behavior, i.e., observable response of an organism can serve as a useful indicator of environmental quality. In the absence of death and other sublethal effects, behavioral changes can represent early warning signs of toxic effects. In the present contribution, we present two novel bioassays useful for the quick assessment of chemical effects on the behavior of mosquito larvae (Culicidae) and adult earthworms (Lumbricidae). These bioassays could have applications in ecological risk assessment and laboratory based ecotoxicological testing. The novel assays are:•A bioassay for the assessment of chemical toxicity on the swimming, breathing and resting behavior of Culicidae larvae.•A bioassay for the assessment of chemical toxicity on the escape behavior of Lumbricidae in water.•These bioassays were carried out using the systemic insecticide imidacloprid and documented the relatively rapid onset of the neurotoxic effects of imidacloprid to experimental organisms.

Behavioural changes and flight response of a mosquito (Culicidae) and an earthworm (Lumbricidae), respectively, after exposure to imidacloprid.

A major point of concern in ecotoxicology is the effects of pesticides on nontarget organisms. This can impact the ecological role played by certain beneficial species in nature. Regarding neonicotinoid insecticides such as imidacloprid (IMI), several measures, including limited trade, restrictive use, and ban have been implemented in Europe and the USA but not globally. The goal of our study was to evaluate the potential risk of this still widely used agrochemical on the behaviour of mosquito larvae (Culicidae) and the escape behaviour of earthworms (Lumbricidae). Changes in breathing, swimming and resting were recorded in mosquitoes postexposure to 0, 1 and 2 mg IMI/L for 10 min. Earthworms were topically exposed in water for 2 minutes to 0, 5, 10 and 20 mg IMI/L. The escape behaviour (initial escape distance and speed) of the earthworms were recorded. In culicids, resting particularly was significantly increased by the exposure to imidacloprid (p < 0.05). In earthworms, the initial escape distance was statistically longer (p < 0.05) when fleeing from the 5 mg IMI/L solution than the solutions with the two highest concentrations. The worms exposed to the 5 mg IMI/L reacted faster than those exposed to the higher concentrations, which explained the long distance covered in the same amount of time. These results point to the relatively quick onset of the neurotoxic effects of imidacloprid, crippling earthworms and altering the buoyancy of mosquito larvae. The ecological consequences of these findings on the completion of life cycles and the survival of these species in nature are yet to be established.