Effects of dietary intake of volcanic ash from Puyehue Cordon Caulle on Tenebrio molitor (Coleoptera: Tenebrionidae) larvae under laboratory conditions
Keywords:
Dietary toxicity, insecticidal activity, Puyehue-Caulle Range, volcanic dustsAbstract
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 volcánico Puyehue-Cordón Caulle entró en erupción en 2011 y afectó la región Patagónica Argentina. El efecto insecticida de la ceniza volcánica, así como el de otros polvos inertes, se ha demostrado que ocurre por exposición por contacto, perturbando el balance hídrico en los insectos. Sin embargo, poco se ha estudiado sobre los efectos subletales de cenizas volcánicas o polvos inertes sobre coleópteros mediante la exposición alimentaria crónica. El objetivo principal del estudio fue obtener una mayor comprensión del impacto del vulcanismo sobre las larvas de tenebriónidos mediante el estudio de la exposición alimentaria crónica a ceniza volcánica en bioensayos de laboratorio. Para este propósito, se utilizó 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 volcánica a 500, 1,000, 5,000, 30,000, y 50,000 ppm. Se descubrió que la exposición alimentaria crónica de ceniza volcánica en larvas de Tenebrio molitor fue dosis-dependiente con efectos visibles después de una exposición a largo plazo (15 y 27 días). 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 disminución del tamaño larval, pérdida de peso y reducción en el número de mudas fueron registrados. Por lo tanto, puede concluirse que la exposición alimentaria crónica a ceniza volcánica causa efectos adversos sobre las larvas de T. molitor, que conducen a mortalidad a altas concentraciones y a una disminución en el tamaño de las larvas a concentraciones sub-letales.
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