Stomatopod antennule design: The asymmetry, sampling efficiency and ontogeny of olfactory flicking

Many crustaceans detect odors from distant sources using chemosensory sensi lla (aesthetascs) on their antennules, The greater the flow of water throug h arrays of aesthetascs, the faster the access of odorant to receptors insi de the aesthetascs. Stomatopods facilitate odorant access by flicking their antennules, thus increasing the relative velocity of the water reaching th eir aesthetascs. We used dynamically scaled physical models to investigate how aesthetasc size and spacing and antennule flicking velocity affect flow penetration into the simple aesthetasc arrays of the stomatopod Gonodactyl aceus mutatus, Particle image velocimetry of flow fields near models of juv enile and adult antennules revealed that velocity gradients around the aest hetascs are steeper during the outward part of the flick than during the re turn stroke and that the velocity gradients are steeper at the aesthetasc t ips than at their bases. More fluid per unit time hows between aesthetasc r ows during the outward stroke than during the return stroke, ensuring that odor sampling is pulsatile, During flicking, velocity gradients are steeper near adult aesthetascs than near juvenile aesthetascs, and adults process more fluid per unit time than juveniles. The resulting differences in odora nt access can be related to size- and age-dependent changes in stomatopod e cology.