Acute toxic effects of deltamethrin on red swamp crayfish, Procambarus clarkii (Decapoda, Cambaridae)

In order to know the acute toxic effects of the synthetic pyrethroid deltamethrin on red swamp crayfish, Procambarus clarkii, an acute toxicity test was carried out. The results showed that the 24, 48 and 96 h LC50 values were 0.156, 0.099 and 0.056 mu g/l, respectively. The abnormal behavioural responses and toxic signs can be described as typical neurotoxic symptoms, characterized by ataxia, hyperexcitation, convulsion, and paralysis. The residue of deltamethrin in haemolymph, gill, muscle, and liver of the crayfish was under the limit of quantification of the GC-MS method after a 96-h exposure to 0.05 mu g/l deltamethrin and a 24-h exposure to 0.1 mu g/l deltamethrin. Besides that, the sublethal effects caused by deltamethrin were assessed by using cytochrome c oxidase (CCO) activity, lactase dehydrogenase (LDH) activity, and lactic acid levels as sensitive biomarkers. Results showed that 24 h exposure to 0.1 mu g/l deltamethrin significantly inhibited the CCO activity (P < 0.05), but increased LDH activity (P < 0.05) and the lactic acid level (P < 0.05) in gills, which further indicated that the aerobic metabolism was inhibited by deltamethrin in the gill while the anaerobic metabolism was stimulated.