Size dependent respiration and growth of jellyfish, Aurella aurita

The relationship between growth, food uptake and respiration of jellyfish, Aurelia aurita, was examined by means of respiration rate measurements, supplemented with laboratory growth experiments with fed and unfed medusae. A. aurita fed rotifers (Blachionus) showed daily specific growth rates of maximum 24 % d(-1), with a net growth efficiency of about 80 %, while unfed medusae were decreasing with a mean specific degrowth rate of -4 % d(-1). Indirectly estimated respiration based on the degrowth rate, and the directly measured respiration were in satisfactory agreement. The respiration rate (R, mu l O-2 d(-1)) of different sized unfed medusae was correlated with the body dry weight (W, mg) according to the equation R = 10.89W(0.86). NO convincing difference in respiration rate was observed between fed and unfed jellyfish. An energy budget showed that the lowest prey concentration resulting in maximum growth of A. aurita was 68 mu g C l(-1) while the prey biomass necessary for maintaining the respiratory demand was 13 mu g C l(-1).