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

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, were used. Metabolism was determined with a Warburg respirometer at 25ºC. Respirometric measurements were performed 1, 3 and 6 hours after administration of the pyrethroid to the same groups of millipedes. After 24 hours, daily respirometric measurements lasting 1 hour each were made on different millipede groups for a period of 10 days. Significant differences were detected only between the groups treated with the pyrethroid and the two control groups. In G. olivaceus, respiratory rates increased by about 1.65-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 1.1-fold compared to normal, with a decrease up to 96 hours and a return to normal thereafter. Although increased oxygen consumption was observed, a detoxification process occurred in both species, so that the possible metabolism of the pyrethroid may justify the low toxicity of deltamethrin for G. olivaceus and P. setiger

Toxidade do carbonato methiocarb para os diplópodos gymnostreptus olivaceus e plusioporus setiger / Toxicity of methiocarb carbamat on millipedes Gimnostreptus olivaceus e Plusioporus setiger

A toxidade por aplicação tópica, do carbamato Methiocarb foi avaliada para os diplódos Gymnostreptus olivaceus e Plusioporus setiger. Os valores das DL50 foram Altos para as duas espécies:515;216;137 e 93mg.g1 para G. olivaceus e 489;222;108 e 71 para P. setiger, respectivamente, 24,48,72 e 96 horas após aplicação do Methiocarb, indicando baixa toxidade. A baixa toxidade do Methiocarb, em diplópodos, pode estar relacionada à dificuldade de penetração do produto principalmente em animais na fase adulta que possuem um exoesqueleto calcificado e rígido. Os resultados sugerem a necessidade de um melhor conhecimento do modo de ação de defensivos químicos em diplópodos, a fim de adequar a sua aplicação e vitar riscos de contaminação ambiental pela utilização dos mesmos