Crustaceans, in particular larger crustaceans such as crayfish and lobsters, are among the animal models used to study olfaction, the sense of smell. Although crustaceans as a group are largely aquatic animals, and have their olfactory receptor neurons packaged in sensilla (hairlike sensory structures), the crustacean olfactory organ is functionally similar to noses of other animals and has contributed to common understanding of the sense of smell. The olfactory organ or “nose” of crustaceans has been especially well studied.