Culture and growth of the jellyfish Pelagia noctiluca in the laboratory

International audience; Four cohorts of the scyphozoan jellyfish Pelagia noctiluca were grown in the laboratory. For the first time, P. noctiluca was grown from eggs through to reproductive adults. The maximum life span in the laboratory was 17 mo. Pelagia noctiluca were first observed to release gametes at an umbrella diameter of 2.4 cm. Laboratory growth under steady feeding conditions showed initial growth followed by stagnation until dietary conditions were altered. A mismatch between the availability of optimal food and the presence of developmental stages may significantly increase the mortality rates of the young stages. Non-motile prey improved survival of ephyrae stages compared with zooplankton, but good survival and ephyrae growth were only obtained with a high-energy sea urchin egg diet. Maximal growth rates were up to 30% d(-1) for young ephyrae and 1.5-4% d(-1) for adults. Maximal growth rates were comparable between laboratory and in situ growth observations in the Ligurian Sea during 1969 and 2013. Combining observations would suggest that 230 d of continuous growth are required to reach the largest mean size observed in the wild (June 2013, mean +/- SD = 15.6 +/- 2.8 cm, range = 12-21 cm). We suggest that 90-120 d of continuous growth from planula larvae would yield reproductive individuals under ideal growing conditions. We discuss the daily prey abundances required by each individual to sustain basal metabolism and the observed growth rates.