The influence of thiacloprid on the feeding behaviour of the copepod, Diacyclops bicuspidatus, preying on nematodes

Nowadays, neonicotinoids are the most widespread insecticides. As neurotoxins with high toxicity to many arthropods, they provide effective pest control, but it also became apparent that they are impacting non-target organisms in freshwater habitats. This study investigated the influence of the neonicotinoid thiacloprid on the behaviour of the copepod, Diacyclops bicuspidatus, feeding on different nematode species (Caenorhabditis elegans, Plectus aquatilis, Panagrolaimus sp.) and on a natural nematode community. All experiments demonstrated that thiacloprid led to decreased feeding of D. bicuspidatus (EC50 values 116-158 mu g l(-1)). In addition, in the experiment where nematodes from a natural sediment were offered as prey, copepod feeding was significantly reduced. The copepod feeding response was a more sensitive endpoint than acute and chronic toxicity tests with daphnids that are routinely used for regulatory risk assessment. An impact on feeding is also a parameter with immediate relevance for the copepod population (reduced fitness) and the associated ecosystem.