Preface.- Identification key for young ephyrae: a first step for early detection of jellyfish blooms.- Blooms of the invasive ctenophore, Mnemiopsis leidyi, span the Mediterranean Sea in 2009.- Effects of pH on asexual reproduction and statolith formation of the scyphozoan, Aurelia labiata.- Effects of low salinity on settlement and strobilation of scyphozoa (Cnidaria): Is the lion's mane Cyanea capillata (L.) able to reproduce in the brackish Baltic Sea?.- Effects of El Niño-driven environmental variability on black turtle migration to Peruvian foraging grounds.- Recurrence of bloom-forming scyphomedusae: wavelet analysis of a 200-year time series.- Behavior of Nemopsis bachei L. Agassiz, 1849 medusae in the presence of physical gradients and biological thin layers.- Avoidance of hydrodynamically mixed environments by Mnemiopsis leidyi (Ctenophora: Lobata) in open-sea populations from Patagonia, Argentina.- Response of Chrysaora quinquecirrha medusae to low temperature.- Use of respiration rates of scyphozoan jellyfish to estimate their effects on the food web.- Planktonic cnidarian distribution and feeding of Pelagia noctiluca in the NW Mediterranean Sea.- Bioenergetics and growth in the ctenophore Pleurobrachia pileus.- Degradation of the Adriatic medusa Aurelia sp. by ambient bacteria.- Identification of jellyfish from Continuous Plankton Recorder samples.- Separation and analysis of different types of nematocysts from Cyanea capillata (L.) medusae.- Characterisation of neurotoxic polypeptides from Cyanea capillata medusae (Scyphozoa).- Gill cell toxicity of northern boreal scyphomedusae Cyanea capillata and Aurelia aurita measured by an in vitro cell assay.