Food supply effects on the asexual reproduction and respiratory metabolism of Aurelia aurita polyps

Abstract

Because Aurelia spp. blooms have important regional effects, it is urgent to determine factors that may affect their proliferation and their effects on food webs. The life cycle of most scyphozoans includes an attached stage (polyp or scyphistoma) that reproduces asexually. To test the effects of food availability (unfed, fed 1-, 2-, or 3-times weekly), we measured production rates, mass, and metabolism of Aurelia aurita polyps. Metabolic measurements were physiological respiratory O2 consumption (R), potential O2 consumption (Φ), and potential CO2 production (ψNADP). Φ and ψNADP were calculated from enzymatic activities of the respiratory electron transport system (ETS) and from the CO2-producing enzyme, NADP+-dependent isocitrate dehydrogenase (NADP-IDH), respectively. The production of polyps dramatically increased from ~ 0.1 polyp day−1 (unfed) to ~ 0.65 polyp day−1 (fed 3-times week−1) over 33 days. Mass and metabolism (R, Φ, ψNADP) per polyp were significantly lower in unfed polyps, but indistinguishable among fed polyps. Our results suggested that the polyps maintained low-metabolic rates, putting available energy into asexual reproduction. The polyps were adapted to survive and reproduce when unfed, confirming their contribution to population persistence and potential jellyfish blooms.