Extracts of the dorid nudibranch Tritoniella belli and stoloniferan coral Clavularia frankliniana were chromatographed and analyzed by1H NMR 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 reverse-phase HPLC purification in the tissues of C. frankliniana. The common omnivorous predatory Antarctic sea star Odontaster validus, a likely predator of benthic invertebrates, showed feeding deterrence to small 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-paper disks soaked in an aqueous shrimp solution and then dried were found to elicit a broad range of feeding behaviors in O. validus, including movement of the shrimp disk to the mouth, extrusion of the cardiac stomach, and the assumption of a humped feeding posture. Chimyl alcohol-treated shrimp disks caused significant feeding deterrence in sea stars when compared with control disks (solvent plus shrimp treated disks alone). T. belli and C. frankliniana appear to employ a defensive compound that has been found in a variety of temperate and tropical mollusks, where it has been demonstrated to deter fish predators. We provide evidence for further deterrent capabilities of chimyl alcohol and of its trophic relationship in the polar ecosystem of McMurdo Sound, Antarctica. © 1994 Plenum Publishing Corporation.