Solifuges, or camel spiders (order Solifugae), keep their pedipalps extended when moving through the environment, utilizing them much the way insects use their antennae. The male also uses his pedipalps during copulation, staying in contact with the female throughout the process. The pedipalps are covered with setae that are assumed to function as chemo-, mechano-, thermo-, hygro-, and olfactory receptors. We surveyed setal forms and other possible sensory structures on the pedipalps of solifuges to determine 1 ) if certain setae and structures are common to all families, 2) if some may be unique to certain families, and 3) the possible function of the various setae and other structures. We found that all families had bifurcated and tapered setae, and that all families had dorsal tarsal pores. Other setal forms were evident only in one or a few families. Three of the setal types had distal pores suggesting that they function as chemoreceptors. These data suggest that the pattern and types of setae on the pedipalps of solifuges may be phylogenetically informative and confirm that the pedipalps do function as sensory appendages.
Some male camel spiders (Arachnida: Solifugae) in the families Eremobatidae, Karschiidae, and Solpugidae have clusters of specialized conical or acuminate setae called papillae, on the ventral surface of the metatarsus of the pedipalps. We compared the overall structure of the papillae found on representatives of the three families using scanning electron microscopy (SEM). We examined the ultrastructure of these setae using transmission electron microscopy (TEM). We also used extracellular electrophysiological recording techniques to examine the electrical properties of these sensory structures and test the hypotheses that they function as mechanoreceptors, olfactory receptors, and chemoreceptors.Wefound similarities in the structure of papillae among genera within a family or distinct family-level differences in structure. Thus, the papillae are phylogenetically informative; similar within family but differing between families. TEM results demonstrated the cuticular wall of a papilla is divided into three sublayers: endo-, meso-, and exocuticle. Mechanoreceptive dendrites are evident at the base of the setal shaft. Other dendrites innervate the shaft of the papilla and penetrate through the cuticular layers near the setal apex. Two SEM images show what appear to be pores on the branches of the papillae, and we found what appears to be a pore tubule extending from the distal portion of the dendrites through the exocuticular layer. Electrophysiological data support the hypothesis that the papillae function as mechanoreceptors and provide no support for chemosensory, thermoregulatory, or hygroreceptive functions. Our data suggest that the papillae function as mechanoreceptors and may also function as chemoreceptors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.