Effects of Dietary Intake of Volcanic ash from Puyehue Cordon Caulle on Tenebrio molitor (Coleoptera: Tenebrionidae) Larvae Under Laboratory Conditions

2018 
Abstract The Puyehue Cordon Caulle volcanic outbreak from 2011 affected the Patagonian Region of Argentina. The insecticidal effect of volcanic ash, as well as other inert dusts, has been proven to occur by contact exposure, disturbing the water balance in insects. However, little has been studied on sublethal effects of volcanic ash or inert dusts on coleopterans through chronic dietary intake. The aim of this study was to gain further understanding on the impact of volcanism on tenebrionid larvae by studying the chronic dietary exposure of volcanic ash in laboratory bioassays. For this purpose, Tenebrio molitor L. (Coleoptera: Tenebrionidae), an insect pest of stored grain, was used as an experimental model organism. Larvae were fed with flour discs prepared with volcanic ash at 500, 1,000, 5,000, 30,000, and 50,000 ppm. Chronic dietary intake of volcanic ash was dose-dependent, with effects visible after long-term exposure (15 and 27 d). Mortality was observed at the two highest concentrations tested (30,000 and 50,000 ppm). At the lower concentrations (500, 1,000, and 5,000 ppm), sub-lethal effects were observed, including larval size decrease, weight loss, and reduction in the number of molts. Thus, chronic dietary intake of volcanic ash causes adverse effects on T. molitor larvae that leads to mortality at high concentrations and decrease of larval size at sub-lethal concentrations. Resumen El complejo volcanico Puyehue-Cordon Caulle entro en erupcion en 2011 y afecto la region Patagonica Argentina. El efecto insecticida de la ceniza volcanica, asi como el de otros polvos inertes, se ha demostrado que ocurre por exposicion por contacto, perturbando el balance hidrico en los insectos. Sin embargo, poco se ha estudiado sobre los efectos subletales de cenizas volcanicas o polvos inertes sobre coleopteros mediante la exposicion alimentaria cronica. El objetivo principal del estudio fue obtener una mayor comprension del impacto del vulcanismo sobre las larvas de tenebrionidos mediante el estudio de la exposicion alimentaria cronica a ceniza volcanica en bioensayos de laboratorio. Para este proposito, se utilizo a Tenebrio molitor L. (Coleoptera: Tenebrionidae) como organismo modelo experimental dado que es una plaga de granos almacenados. Las larvas fueron alimentadas con discos de harina preparados con ceniza volcanica a 500, 1,000, 5,000, 30,000, y 50,000 ppm. Se descubrio que la exposicion alimentaria cronica de ceniza volcanica en larvas de Tenebrio molitor fue dosis-dependiente con efectos visibles despues de una exposicion a largo plazo (15 y 27 dias). La mortalidad fue observada en dos de las concentraciones altas testeadas (30,000 y 50,000 ppm). A bajas concentraciones (500, 1,000, y 5,000 ppm), efectos sub-letales como la disminucion del tamano larval, perdida de peso y reduccion en el numero de mudas fueron registrados. Por lo tanto, puede concluirse que la exposicion alimentaria cronica a ceniza volcanica causa efectos adversos sobre las larvas de T. molitor , que conducen a mortalidad a altas concentraciones y a una disminucion en el tamano de las larvas a concentraciones sub-letales. View this article in BioOne
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