Meeting Abstract
Underlying the exquisite diversity of complex arthropod behaviors are intricate neuromodulatory systems that can finely adjust those behaviors to meet specific demands. Although such systems are well described in some arthropod groups, they are poorly known in others, including the subphylum Chelicerata. Since the Chelicerata are the most basal of extant arthropod groups, a better understanding of their neuromodulatory systems is key for determining how complex modulatory systems evolved within the Arthropoda as a whole. We have investigated the presence, distribution, and functions of several behaviorally important neuromodulators—the catecholamines (dopamine and norepinephrine) and octopamine— in a representative chelicerate, the scorpion Centruroides sculpturatus (Scorpiones: Buthidae). We have localized catecholaminergic and octopaminergic neurons in the CNS of the scorpion via immunocytochemistry, and quantified levels of catecholamines in the CNS via ultra-performance liquid chromatography-mass spectrometry. Using recently available genomic data for C. sculpturatus, we also identified putative genes and transcripts for enzymes in catecholamine and octopamine biosynthesis, as well as receptors for these modulators. In addition, extracellular electrophysiological recordings indicate that catecholamines and octopamine elicit different physiological responses in the scorpion, which may underlie distinct behavioral programs not yet fully understood. When compared to data from other organisms, our results suggest that chelicerates may retain several ancient features of neuromodulatory systems thought to have been present in the common ancestor of Bilaterian animals, but lost in other arthropods.
