Transgenerational and Molecular Responses to Lanthanum Exposure in a Spodoptera littoralis-Brassica rapa System

The widespread use of rare earth elements (REEs) in agriculture, particularly Lanthanum (La), raises concerns about their ecological impact on non-target organisms. We investigated the direct and indirect effects of La on the insect pest <i>Spodoptera littoralis</i> and its host plant, <i>Brassica rapa</i>. Direct exposure to La-supplemented diets reduced larval growth, survival, and egg production. Interestingly, a transgenerational effect was observed, where larvae from La-exposed parents exhibited increased resilience, showing no performance reduction on the same diets. Indirectly, La accumulation in plants mediated a hormetic response in herbivores, increasing larval weight at low concentrations but reducing it at high concentrations, while modulating their oxidative stress and detoxification gene expression. From the plant perspective, La exposure amplified herbivory-induced calcium signalling and altered the expression of key genes related to calcium and reactive oxygen species pathways. These findings reveal the complex ecological risks of La accumulation in agroecosystems, affecting both plants and insects directly and through novel transgenerational effects.