Source and fate oflipids in polar gelatinous zooplankton

The presence or absence of accumulated lipids in arctic and Antarctic medusae and ctenophores was determined by visual examinationof living specimens with a dissecting microscope. Lipid accumulations were obvious because of their high refractive indices. Lipids were seenin many of the 200+ gelatinous zooplankton specimens collected. They always consisted of various-sized droplets and larger masses withinthe lumen of the gastrovascular system. No true depot lipids or adipose tissue were present. The accumulation of lipids was observed infeeding animals, suggesting that the prey-derived lipids were unmodified. Disappearance of lipids in starved animals suggested that lipidsare taken up and assimilated. In medusae, they occurred in the stomach, ring and/or radial canals. In most ctenophores, lipids were foundin the meridional canals below the comb rows. However, in one ctenophore species, Mertensia ovum, lipids are stored in special sacs associatedwith the tentacle bulbs. Lipids were more frequently observed in arctic than in Antarctic gelatinous zooplankton.