CONICET | Buscador de Institutos y Recursos Humanos

The Puyehue Cordon Caulle (PCC) volcanic outbreak from 2011 affected most of the surface of the Monte Austral region in the Argentine Patagonia. This area is rich in endemic species and Tenebrionidae is well represented, playing a key role by interlocking in the ecosystem food web. The insecticidal effect of volcanic ash (VA) has been proven to occur by contact exposure, disturbing the water balance in insects. Tenebrionid larvae are somewhat protected from massive exposure to VA fall due to their cryptic habits. However, particles from VA deposits move progressively into the underlying soil and tenebrionid larvae may become exposed to VA contaminated food. The aim of the study was gain further understanding of the impact of volcanism on food chain processes and nutrient cycling in the Monte Austral. For this purpose, we studied the intake toxicity of VA on tenebrionid larvae in laboratory bioassays, fed on flour discs prepared with VA at 500, 1,000; 5,000; 30,000 and 50,000 ppm. Tenebrio molitor was used as an experimental model organism, given that it develops in conditions analogous to those of many other tenebrionid euryphagous species from xerophilic habitats, mostly associated with the soil. It was found that intake toxicity of VA in T. molitor larvae was dose-dependent with effects visible after long term exposure. Mortality was observed at the two highest concentrations tested and at the lower concentrations, sub-lethal effects as larval size lessening, weight loss and reduction in the number of molts were registered. It can therefore be concluded that intake toxicity is a major adverse effect of VA on tenebrionid larvae that would lead to massive mortality at high concentrations and dwarfing effects at sub-lethal concentrations. Thus, the intake of VA by larvae may have harmful effects on tenebrionid natural populations and consequently on the Monte Austral ecosystem.