Mysterious jellyfish diet gets a fresh look

Jellyfish have been drifting around the planet for more than 500 million years, yet relatively little is known about their lifestyles. Now, scientists at the University of British Columbia’s Institute for the Oceans and Fisheries are using biochemical tools to unravel a key part of the jellyfish mystery: their diet (J. Exp. Mar. Biol. Ecol. 2021, DOI: 10.1016/j.jembe.2021.151631). Scientists frequently use the unique stable isotope and fatty acid signatures present in living things to investigate what predators eat. To calibrate these values for jellyfish, the team, led by Jessica Schaub, performed controlled feeding experiments at the Vancouver Aquarium. Docile moon jellies were fed frozen krill, which they unexpectedly rejected, and live brine shrimp. Voracious Japanese sea nettle jellies were fed live brine shrimp and the moon jellies. After analyzing the isotope and fatty acid signatures, the researchers were surprised to find that jellyfish appear to biosynthesize their own essential omega-3 and omega-6 fatty acids, a feat which was previously unreported. These findings suggest that jellyfish are more than just floating bags of water, as conventionally thought, Schaub says. They may actually be nutritious, key players in the marine food web.