CHEMICAL DEFENSE OF COMMON ANTARCTIC SHALLOW-WATER NUDIBRANCH TRITONIELLA-BELLI ELIOT (MOLLUSCA, TRITONIDAE) AND ITS PREY, CLAVULARIA-FRANKLINIANA ROUEL (CNIDARIA, OCTOCORALLIA)

Extracts of the dorid nudibranch Tritoniella belli and stoloniferan co ral Clavularia frankliniana were chromatographed and analyzed by H-1 N MR and thin-layer chromatography. Three glycerol ethers were detected in T. belli, primarily 1-O-hexadecyl glycerol (chimyl alcohol). Chimyl alcohol was also detected after gradient flash chromatography and rev erse-phase HPLC purification in the tissues of C. frankliniana. The co mmon omnivorous predatory Antarctic sea star Odontaster validus, a lik ely predator of benthic invertebrates, showed feeding deterrence to sm alt cubes of T. belli mantle tissue placed on the tube feet along the ambulacral feeding groove, while always extruding the cardiac stomach when presented with cubes of shrimp tissue of similar size. Filter-pap er disks soaked in an aqueous shrimp solution and then dried were foun d to elicit a broad range of feeding behaviors in O. validus, includin g movement of the shrimp disk to the mouth, extrusion of the cardiac s tomach, and the assumption of a humped feeding posture. Chimyl alcohol -treated shrimp disks caused significant feeding deterrence in sea sta rs when compared with control disks (solvent plus shrimp treated disks alone). T. belli and C. frankliniana appear to employ a defensive com pound that has been found in a variety of temperate and tropical mollu sks, where it has been demonstrated to deter fish predators. We provid e evidence for further deterrent capabilities of chimyl alcohol and of its trophic relationship in the polar ecosystem of McMurdo Sound, Ant arctica.