Selected neonicotinoids and associated risk for aquatic organisms.

Neonicotinoids are one of the newest groups of systemic pesticides, effective on a wide range of invertebrate pests. The success of neonicotinoids can be assessed according to the amount used, for example, in the Czech Republic, which now accounts for 1/3 of the insecticide market. The European Union (EU) has a relatively interesting attitude towards neonicotinoids. Three neonicotinoid substances (imidacloprid, clothianidin and thiamethoxam) were severely restricted in 2013. In 2019, imidacloprid and clothianidin were banned, while thiamethoxam and thiacloprid were banned in 2020. In 2022, another substance, sulfoxaflor, was banned. Therefore, only two neonicotinoid substances (acetamiprid and flupyradifurone) are approved for outdoor use in the EU. Neonicotinoids enter aquatic ecosystems in many ways. In European rivers, neonicotinoids usually occur in nanograms per litre. Due to the low toxicity of neonicotinoids to standard test species, they were not expected to significantly impact the aquatic ecosystem until later studies showed that aquatic invertebrates, especially insects, are much more sensitive to neonicotinoids. In addition to the lethal effects, many studies point to sublethal impacts - reduced reproductive capacity, initiation of downstream drift of organisms, reduced ability to eat, or a change in feeding strategies. Neonicotinoids can affect individuals, populations, and entire ecosystems.

Acute exposure of common yabby (Cherax destructor) to the neonicotinoid pesticide.

Calypso 480 SC (CAL) is an insecticide containing the active substance thiacloprid (480g/L) belonging to the family of neonicotinoids. Crayfish represent an important component of aquatic ecosystems and are considered sensitive indicators of water pollution. The aim of this study was to investigate the effects of acute exposure of CAL on common yabby crayfish (Cherax destructor) at concentrations of 0.1, 0.5, 1, 5, 10, 25, and 50mg/L. Crayfish behavior and mortality were monitored daily, and the lethal concentrations (LC0, LC50, LC100) of CAL were evaluated at 24h, 48h, 72h, and 96h. Three concentrations of CAL (0.1, 1, 10mg/L) were selected for assessment of oxidative stress (lipid peroxidation) and antioxidant parameters superoxide dismutase, catalase, glutathione S-transferase and reduced glutathione in crayfish hepatopancreas, muscle, and gill tissue at the conclusion of the acute test. Differences in behavior of exposed crayfish from controls were observed at concentration≥5mg/L of CAL. The 96h LC50 value for the common yabby was 7.7mg/L for Calypso 480 SC. The acute exposure showed reduction of the level lipid peroxidation in hepatopancreas in all experimental groups compared with control. The results of antioxidant activity showed a significant change on glutathione S-transferase in tissue of hepatopancreas while no differences were observed on the others antioxidant parameters in crayfish's tissues. The study provides valuable information on effects of neonicotinoid insecticides on a non-target organism, the crayfish, an indicator of pollution and an important element of stable aquatic ecosystems.