Understanding why some species are more sensitive that others is perhaps the most fundamental challenge in ecotoxicology. This talk will highlight how genome and transcriptome data can be mined to identify the toxicokinetic and toxicodynamic traits that govern species sensitivities to pesticide exposure. Using examples from comparative studies with earthworms and between earthworms and other taxa, we will show how pesticide sensitivity can be attributed to the genome complement and physiology of species in case studies for 1) the organophosphate chlorpyrifos among earthworms compared to arthropods, 2) among different earthworm species for the neonicotinoid imidacloprid and 3) of the differential effects for mixtures of azole fungicides and pyrethroid insecticides in earthworms and other species. For each case study, we used a combination of bioassays and genomic analyses to show that….

1. Chlorpyrifos. Earthworms (Lumbricus rubellus) show an approximate order of magnitude lower sensitivity to chlorpyrifos than a soil arthropod (Folsomia candida); this difference being linked to tissue specific cholinesterase orthologue expression.
2. Imidacloprid. A large-magnitude (>30-fold) difference in sensitivity for imidacloprid between earthworms; this difference can be explained by difference the expression of different isoforms of sub-unit of the nicotinic acetylcholine receptor that contain amino acid residue associated with strong or weak imidacloprid binding.
3. Mixtures. Difference in the degree of synergy found between different mixtures in earthworms compared to other invertebrate taxa; this difference has been linked to the potential for one chemical to affect the toxicokinetic of another by inhibiting phase one and two metabolism to different extents.