Potential dietary effects on the fatty acid composition of the common jellyfish Aurelia aurita

Fatty acid composition of the natural and aquarium-reared common jellyfish Aurelia aurita was investigated. Fatty acid composition of the aquarium-rea red A. aurita clearly reflected that of the diet, brine shrimp (Artemia). I n the same way, fatty acid composition of the natural A. aurita was assumed to reflect those of natural diets. Samples of natural A. aurita were colle cted from April 1995 to September 1995 in the Seto Inland Sea, Japan, and t heir fatty acids were analyzed by gas chromatography and mass spectrometry. Variation of fatty acid compositions was seasonal rather than dependent on body size. Two major seasonal groups were divided by the cluster analysis of the A. aurita fatty acid composition: the April-June and the August-Sept ember clusters. The April-June cluster was characterized by high contents o f the (n - 3)-fatty acids of diatom origin, accumulated via the grazing foo d chain. By contrast, the August-September cluster was characterized by an increase in (n - 6)-fatty acids of macroalgal origin, probably transferred via the detritus food chain. These results suggest that the diet of natural A. aurita may shift between the diatom-based food chain and the detritus-b ased food chain.