Exogenous octopamine increases antipredator aggression in scorpions (Centruroides vittatus)

Abstract

Abstract. In many invertebrates, the monoamine octopamine (OA) acts as a hormone and neurotransmitter, regulating “fight-or-flight” behavior and aggression. Though well-studied in some taxa (e.g., insects and crustaceans), the role of OA in arachnids is little understood, and information on any hormones within scorpions is lacking. Given its effects in most arthropods, we expected elevated levels of octopamine to increase aggressive antipredator behaviors in scorpions. We experimentally raised octopamine levels in striped bark scorpions (Centruroides vittatus (Say, 1821)) and measured changes in their behavioral responses to simulated predator attack. Elevated octopamine levels increased aggressive behaviors in C. vittatus scorpions, whereas an octopamine antagonist (phentolamine) had no effect on behavior. Overall, this study begins to extend our understanding of behavioral endocrinology to scorpions, finding general similarities with spiders. Future work promises to better elucidate the role of monoamines and other hormones in regulating scorpion behavior and their interactions with predators.