Decremental Conduction over "Giant" Afferent Processes in an Arthropod.

Four "giant" mechanoreceptive cells form part of a stretch receptor organ at the base of the uropod in the sand crab, Emerita (Crustacea, Anomura). Injection of the fluorescent dye Procion Yellow revealed that these sensory cells are monopolar with somata located in the central nervous system. No such cells have previously been described in arthropods. These neurons are also unusual in that they do not generate propagated action potentials; rather, they mediate stretch reflexes by transmission of graded, decremental potentials.