Investigating sensory processing in the pectines of the striped bark scorpion, Centruroides vittatus.

Scorpion pectines detect chemical and physical stimuli via thousands of peg sensilla on ground-facing teeth. Each sensillum has multiple neurons that detect stimuli and transmit neural impulses to the subesophageal ganglion (SEG) in the central nervous system. Anatomically, the organization of the pectinal neuropil in the SEG reflects the arrangement of pectinal teeth, suggesting conservation of information about stimulus location in the SEG. In this study, neural impulses from the pectinal nerve of the striped bark scorpion (Centruroides vittatus) were recorded in the pecten, abdominal cavity, and SEG using electrophysiology. Recordings from the right pectinal nerve in the pecten showed that right tooth stimulations elicit sensory activity milliseconds before motor feedback, while left tooth stimulations only evoked motor spikes, suggesting no contralateral afferent communication between pectines. In the abdominal cavity recordings, two distinct waveforms (PN1 and PN2) were detected in baseline activity; PN1 seemed to enhance the likelihood that PN2 would fire, suggesting a possible excitatory interaction. Recordings from the SEG showed that mechanically stimulating different pectinal teeth evoked different compound neural activity patterns in the same SEG location. Stimulating the same tooth in succession showed mechanosensory adaptation. These recordings show promise for continued electrophysiological investigations of the scorpion SEG, and, in particular, how information from the pectines is processed and used for orientation.