Are They the Same, or Are They Different?

Summary Thousands of peg sensilla adorn the ground-facing surfaces of the elaborate chemosensory organs of scorpions called pectines. From external appearances, these sensilla appear identical, however, it is not known if they are functionally the same. The answer to this question will influence our thinking on the organization and function of the pecten chemosensory system. Identical sensilla would suggest a parallel sampling scheme, lending support to an “information enhancement” hypothesis. Conversely, functionally distinct sensilla would support a “segmentation” hypothesis similar to the decomposition of sensory elements in the well-studied mammalian visual processing system. We are using a newly developed chemical delivery approach to test peg response patterns to consistent, repeatable stimulation. We report our findings based on electrophysiological recordings of stimulated peg sensilla of desert scorpions Paruroctonus utahensis (Vaejovidae). We also report on other relevant characteristics, including the nature and time course of a typical pecten “sniff” and the density of peg sensilla relative to substrate particle size from the animals’ natural sand habitat.