Jemec A, Kos M, Drobne D, Koponen IK, Vukić J, Ferreira NGC, Loureiro S, McShane HVA
[ pdf ] [ site ] Science of the Total Environment, 2016

We investigated the effects of a commercial pigment grade rutile TiO₂ on the terrestrial isopod Porcellio scaber in three locations that differed in terms of abiotic and biotic conditions: the laboratory, open air, and the closed barn. Mortality and isopod energy reserves (digestive gland total proteins, lipids and carbohydrates) were not affected following 14 d exposure to up to 1000 mg TiO₂ per kg dry leaves (mg/kg) under any experimental scenario. However, in the field tests, isopods consumption of TiO₂-coated leaves was reduced compared to that of uncoated leaves and the decrease was not dose-dependent. The highest reduction was in the closed barn (45–56 %) rather than in the open-air (38–40 %). In laboratory-based food choice tests, isopods neither preferred nor avoided leaves coated with TiO₂, suggesting that rather than sensing the TiO₂ on the leaves directly, the isopods under open-air and barn exposure responded to altered attractiveness and/or palatability of the TiO₂ amended leaves. We propose that this could be due to altered microbial population on the leaves, a hypothesis that requires further investigation. Although short-term exposure to atmospheric deposition of up to 1000 mg/kg commercial TiO₂ is unlikely to pose an immediate threat to isopod mortality and energy balance, reduced leaf feeding may have implications for the decomposition of plant material.