A neurobiological study of the stomatopod central complex

Abstract

Since the seminal work of Nils Holmgren in the early 1900s, comparativeneuroanatomy in arthropods has contributed greatly to the functional and phylogenetic understanding of neural circuits. The cerebral ganglion, better known as the brain, is structurally and functionally differentiated from the rest of the arthropod nervous system. It receives inputs both from anterior sensory organs as well as feedback through the ventral nerve cord. Outputs from the cerebral ganglion are comprised of motor and pre-motor commands, all of which coordinate to generate animal behaviors. One anatomical region of great recent interest to invertebrate neurobiologists in the cerebral ganglion has been the central complex (CX), a highly conserved group of midline neuropils. Characteristic features of CX anatomy include discrete modules along the lateral axis, distinct layering, and inter-hemispheric fiber organization. Most current understanding of the CX originates from such insect species as locusts, crickets, flies, and cockroaches. Recent studies of these insects have implicated the CX in sensory integration, motor coordination, spatial orientation, visual memory, and various forms of arousal. However, the CX is almost entirely unexplored in crustaceans � the paraphyletic group to insects � many of whom have complex behaviors in their own right. Stomatopod crustaceans, also known as mantis shrimps, make up the eponymousStomatopoda, an order of marine arthropods famed for their destructive strikes and highly developed sensory systems. In particular, their visual systems are unrivalled in complexity, being capable of color vision, polarization vision, circular polarization vision, and motion vision. Each of their trinocular eyes can move independently, a behavior that is unique among arthropods, generating compelling questions about optic flow and its relation to self-motion information and visually-guided behaviors. Additionally, their predatory strike is among the fastest movements in the animal kingdom, delivering forces often compared with 0.22-caliber rifle bullets. Given the complexity of stomatopod sensation and behavior, my dissertations work has thus focused on investigating, via neuroanatomical methods, the stomatopod central complex and drawing conclusions about the neural organization, development, and connections therein.