Effects of deltamethrin pyrethroid on the respiratory metabolism of the neotropical millipedes Gymnostreptus olivaceus and Plusioporus setiger
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The effects of Deltamethrin on the respiratory metabolism of Gymnostreptus olivaceus and Plusioporus setiger were investigated. Acetone solutions corresponding to half the LD50 values, i.e., 20 mg.g-1 for G olivaceus and 4.40 mg.g-1 for P. setiger. Metabolism was determined with a Warburg respirometer at 25°C. Respirometric measurements were performed 1, 3 and 6 hours after administration of the pyrethroid to the same millipede group. After 24 hours, daily respirometric measurements lasting 1 hour each were detected only between millipede groups for a period of 10 days. Significant differences were detected only between the groups treated with pyrethroid and the two control groups. In G. olivaceus, respiratory rates increased by about 1.7-fold compared to normal immediately after administration of the pyrethroid, followed by a gradual decrease up to 72 hours and a return to normal levels thereafter. In P. setiger, the increase was about 1.2-fold compared to normal, with a decrease up to 95 hours and a return to normal thereafter. Although increased oxygen consumption was observed, a detoxication process occurred in bothe species, so that the possible metabolism of the pyrethroid may justify the low toxicity of Delthamethrin for G olivaceus and P. setiger.