The Mediterranean dorid nudibranch Peltodoris atromaculata that had been collected while feeding on Haliclona fulva was shown to sequester long-chain fulvinol-like polyacetylene metabolites (compounds 2-5) from the prey. They were isolated along with previously reported bromorenierins from the diethyl ether extracts of both the mollusk and the sponge. Their structures were elucidated by NMR spectroscopy and tandem FABMS analysis. Compound 5 exhibited in vitro growth inhibitory effects against the SKMEL-28 melanoma cell line.