Biomechanics of venom delivery in South America's first spitting scorpion

Abstract

Venom is a metabolically expensive secretion used sparingly in a variety of ecological contexts, most notably predation and defense. Accordingly, few animals use their toxins in ranged attacks, and venom-squirting behaviour is only known from select taxa. In scorpions, species belonging to two genera are known to spray venom when threatened, and previous work in Parabuthus transvaalicus shows that venom delivery depends on perceived levels of threat. Here, I describe Tityus (Tityus) XXX sp. nov., a new species of Buthid scorpion from Cundinamarca, Colombia. Remarkably, this species is capable of venom spraying, a first for both the genus and the South American continent. Using frame-by-frame video analysis and ballistic equations, I show that T. XXX sp. nov. employs not one, but two types of airborne attacks with dramatic differences in range and venom expenditure. Further, the new species uses an unusually large reserve of prevenom-like secretion for spraying, as opposed to the costly venom used by other spitting scorpions. In light of these key specializations, I propose that venom spraying convergently evolved in response to different selection pressures, laying the groundwork for future investigation.