DERBY, C.D.*; KICKLIGHTER, C.E.; SHABANI, S.; JOHNSON, P.M.; KO, K.-C.; KAMIO, M.; YANG, H.; SCHMIDT, M.; Georgia State University: Chemical defenses of sea hares: novel and adaptive strategies for escape and defense via inking

Defensive secretions are usually complex mixtures of chemicals that can be distasteful, harmful, or toxic. We have investigated inking by sea hares (Aplysia) to examine, within an ecological perspective, neural and molecular mechanisms of chemical defense, including identifying active compounds and how they interact with the predators� chemosensory systems. We have found an impressive array of defensive mechanisms, including novel ones, which vary according to the attacking species. These include the following. 1) �Phagomimetics� � a novel mechanism whereby chemicals in ink mimic food of spiny lobsters (Panulirus) and in so doing distract lobsters to attend to the secretion and thereby allow sea hares to escape. 2) �Sensory disruptors� � produced in high concentration and in a viscous matrix that massively stimulate the chemosensory pathway of the predator, disrupting the subsequent reception capabilities of that predator. 3) Aversive or toxic substances functioning against spiny lobsters and sea anemones (Anthopleura). This is the most prominent mechanism for sea anemone predators, but it also operates against spiny lobsters. 4) Alarm cues � produced by attacked conspecifics and which evoke escape. 5) Chemicals that protect sea hares against bacterial infections but which may also protect against unidentified predators; these include an enzyme � escapin, an L-amino acid oxidase � and its substrates lysine and arginine. Several principles are emerging from our work. First, several mechanisms can operate against a single species of predator. Second, one chemical can mediate different mechanisms. Third, a given mechanism acts through different compounds for different predators. Supported by NSF IBN-0324435, IBN-9876754, IBN-0322773