DISCREPANCY BETWEEN ACUTE AND CHRONIC TOXICITY INDUCED BY IMIDACLOPRID AND ITS METABOLITES IN APIS MELLIFERA

Séverine Suchail (1) , David Guez (1) , Luc P Belzunces (1)

1 INRA - Institut National de la Recherche Agronomique

Imidacloprid is a systemic nitroguanidine insecticide that belongs to the neonicotinoid family. As an agonist of the acetylcholine receptor, it attacks the insect nervous system and is extremely effective against various sucking and mining pests. Oral acute and chronic toxicity of imidacloprid and its main metabolites (5-hydroxyimidacloprid, 4,5-dihydroxyimidacloprid, desnitroimidacloprid, 6-chloronicotinic acid, olefin, and urea derivative) were investigated in Apis mellifera. Acute intoxication by imidacloprid or its metabolites resulted in the rapid appearance of neurotoxicity symptoms, such as hyperresponsiveness, hyper-activity, and trembling and led to hyporesponsiveness and hypoactivity. For acute toxicity tests, bees were treated with doses of toxic compounds ranging from 1 to 1,000 ng/bee (10-10,000 g/kg). Acute toxicity (LD50) values of imidacloprid were about 60 ng/bee (600 g/kg) at 48 h and about 40 ng/bee (400 g/kg) at 72 and 96 h. Out of the six imidacloprid metabolites tested, only two (5-hydroxyimidacloprid and olefin) exhibited a toxicity close to that of imidacloprid. Olefin LD50 values were lower than those of imidacloprid. The 5-hydroxyimidacloprid showed a lower toxicity than imidacloprid with a LD50 four to six times higher than that of imidacloprid. Urea also appeared as a compound of nonnegligible toxicity by eliciting close to 40% mortality at 1,000 ng/bee (10,000 g/kg). However, no significant toxicity was observed with 4,5-dihydroxyimidacloprid, 6-chloronicotinic acid, and desnitroimidacloprid in the range of doses tested. To test chronic toxicity, worker bees were fed sucrose solutions containing 0.1, 1, and 10 g/L of imidacloprid and its metabolites for 10 d. Fifty percent mortality was reached at approximately 8 d. Hence, considering that sucrose syrup was consumed at the mean rate of 12 l/d and per bee, after an 8-d period the cumulated doses were approximately 0.01, 0.

Domaines: Sciences de l'environnement

Séverine Suchail, David Guez, Luc P Belzunces. DISCREPANCY BETWEEN ACUTE AND CHRONIC TOXICITY INDUCED BY IMIDACLOPRID AND ITS METABOLITES IN APIS MELLIFERA. Environmental Toxicology and Chemistry, 2001, 20, pp.2482 - 2486. ⟨hal-02047800⟩