Effects of deltamethrin pyrethroid on the respiratory metabolism of the neotropical millipedes Gymnostreptus olivaceus and Plusioporus setiger

Abstract

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.