Gene expression in Lepidostoma basale in response to chlorantraniliprole exposure

Pesticides are important agricultural stressors for freshwaters, but the physiological mechanisms induced by pesticide exposure are largely unknown for most aquatic non-target organisms. The insecticide chlorantraniliprole, an agonist of the ryanodine receptor, has been reported to be highly selective for target pest species, which comprises representatives of the order Lepidoptera (butterflies). Using RNA sequencing data, we quantified the insecticide effect on the gene expression profiles of the caddisfly Lepidostoma basale and other freshwater invertebrates. Organisms were exposed for 48 hours to three different concentrations of chlorantraniliprole. Further, the effect of biotic interaction between the two shredder species L. basale and G. pulex on the insecticide induced gene expression profiles was tested. RNA extracts were pooled from 8-10 larvae to one library, irrespective of their sexe and developmental stage. Per concentration, 6 libraries (replicates) were sequenced on an Illumina Novaseq 6000, resulting in 24 RNA-seq libraries (6 x control, 6 x low concentration treatment, 6 x medium concentration treatment, 6 x high concentration treatment). Each of the insecticide treatment levels comprised 3 replicates where only L. basale was present as shredder species, and 3 replicates where L. basale and the competing shredder G. pulex was present. We detected a strong cellular stress responses in L. basale and another insect species, implying that conserved cellular mechanisms are affected. However, the induced response pathways were not expected based on the insecticides' described mode of action. We found evidence for alterations of the developmental program, but the induced regulatory pathways were species-specific. If transcriptional changes in the developmental program induce alterations of emergence phenology, pronounced effects on food web dynamics in a cross-ecosystem context are expected.