Effect of the insecticide cypermethrin on behaviour and oxidative stress in the spider Loxosceles laeta.

Loxoscelism, caused by bites from Loxosceles spiders, is a global health concern. Control of these spiders with insecticides remains poorly understood and requires assessment at both biochemical and behavioural levels. We evaluated the ability of Loxosceles laeta to detect cypermethrin-treated surfaces and examined the effects of exposure on enzymatic activity, oxidative stress, biomolecule oxidation and locomotor behaviour. Spiders preferred untreated surfaces and increased movement speed on treated ones, indicating a repellent effect. Acetylcholinesterase activity remained unchanged, whereas antioxidant enzymes showed varied responses: catalase and glutathione reductase increased significantly, while superoxide dismutase, glutathione S-transferase and glutathione peroxidase were unaffected. Reactive oxygen species levels and lipid peroxidation did not increase, although DNA damage was detected. Exposure also reduced the distance travelled over 24 h. This study provides the first combined behavioural and biochemical analysis of L. laeta exposed to cypermethrin, offering key insights for management and toxicity assessment in medically relevant urban spiders.