Insects mostly use their venom to subdue prey, or for both subduing prey and defense, but some rare species like larval lepidopterans (caterpillars) use venom solely to deter predators(1).Of the 133 lepidopteran families, nine can cause serious pathophysiological conditions in humans and animals(2).Although they present a health hazard, caterpillars are under-represented in venom research.
Limacodidae is a family of more than 1,500 species, over half of which, known as stinging nettles, have venomous larvae(3).Envenomation by limacodids mainly causes pain, itch, and erythema, and occasionally numbness, nausea, and dizziness.Using a combination of imaging technologies, transcriptomics, proteomics and functional assays, we recently provided a holistic portrait of the venom system of one species, Doratifera vulnerans, which produces a complex peptide-rich venom,contrary to the common belief that defensive venoms are simple(4).Three most abundant families of venom peptides are 1)disulfide-rich knottins similar to inhibitor cystine knots that dominate spider venoms; 2)cecropin-like peptides,linear cationic peptides that disrupt cell membranes, causing pain in mammals, and also killing bacteria, insects and parasites;and 3)homologues of adipokinetic hormone/corazonin-related neuropeptide(4).
Using proteomics and transcriptomics, I am currently expanding research into additional species, including the saddleback caterpillar Acharia stimulea native to eastern North America, and an undescribed species collected in Townsville, Australia. Surprisingly, I found that the North American species possesses highly similar venom to the Australian D. vulnerans whereas venom of the undescribed Australian species was radically different.I am also expanding knowledge of the evolutionary trajectory of individual toxins, by synthesising and characterising peptides intermediate in structure between the ancestral cecropin of non-venomous Lepidoptera and D. vulnerans cecropin-like venom toxins.Finally, I am producing a library of limacodid venom peptides that I will test on mammalian ion channels including those involved in pain as well as current drug targets.This research will provide insights into multiple aspects of venoms produced by Limacodidae.