BEHAVIORAL-EFFECTS OF CAROTENOID SEQUESTRATION BY THE PARSNIP WEBWORM, DEPRESSARIA-PASTINACELLA

The parsnip webworm, Depressaria pastinacella, acquires a distinct yel low stripe when it consumes the yellow flowers of its principal host p lant, Pastinaca saliva, the wild parsnip. Caterpillars raised on artif icial diet lacking host-plant material lack this yellow coloration. By chemical characterization and comparison of caterpillars raised on pa rsnip flowers and on artificial diet, we were able to determine that l utein, along with smaller amounts of other xanthophylls from the host plant, is selectively sequestered in the fat body. In bioassays design ed to measure avoidance of ultraviolet light, caterpillars raised on p arsnip flowers or on artificial diet supplemented with lutein were les s likely to avoid exposure to ultraviolet light than caterpillars rais ed on unaugmented artificial diet and thus lacking sequestered caroten oids. The ability to sequester xanthophylls, which are highly effectiv e antioxidants, may confer a selective advantage on these caterpillars , whose apiaceous host plants produce large quantities of furanocoumar ins, natural products that are photoactivated by light wavelengths in the ultraviolet region; such sequestered pigments may reduce not only the oxidative stress associated with ultraviolet light and diurnal for aging but also the photooxidative stress associated with ingestion of photoactive furanocoumarins.