Sea urchins are slow-moving animals that defend themselves with a unique armament of spines and pincer-like structures called pedicellariae. Pedicellariae are the main defensive system against pests, parasites, and predators. Globiferous pedicellariae are a specialized type that are able to inject venom. Despite the fact that venomous pedicellariae are inferred to have been present in the crown group ancestor of sea urchins, toxin profiles of pedicellarial venoms are unknown for any sea urchin species. This project aims to produce the first comprehensive insights into the composition, bioactivities, and evolution of pedicellarial venoms. The focal species for studying this unique defensive system will be Strongylocentrotus purpuratus. The main advantages of S. purpuratus are that: 1) it is kept in the lab of Dr Paola Oliveri, which provides a fresh source of material, extensive experience working with this species, and the opportunity to do functional experiments, 2) it has a published genome, and 3) it has different types of venomous pedicellariae that may be used for different functions, and may thus contain different venoms. The main objectives of this project are 1) to generate the first comprehensive proteotranscriptomic profiles of pedicellarial venoms, 2) compare the venom profiles of different pedicellarial types, 3) determine the effects of the venoms on naturally occurring pests, parasites and predators, 4) determine whether the presence of natural predators or clues of predation events can affect the venom profiles (very little is known about venom plasticity in general), and 5) infer the evolutionary origins of pedicellarial venom components.