Ecology of Rhizostomeae.

Max Egon Thiel's chapter on the ecology of rhizostomes in his review up to 1970 covered a bewildering variety of topics, many of which are the focus of other chapters in this volume: their interactions with humans; their associations with other organisms; their venoms. Although he also discussed their habitats and habits, the effects of environmental conditions on distribution, and patterns in seasonality, he paid scant attention to blooms, he did not write about their role in the wider ecosystem, and he ignored alien introductions. It is clearly impossible to comprehensively update Thiel's review in a similar vein - we don't have the space - and so we have decided to focus our efforts here on either those topics that particularly fascinated him (seasonality), or those that he did not write about (alien introductions, their role in the ecosystem). Our narrative is based on case studies of well known taxa, from which we attempt to draw patterns of commonality, where appropriate. We conclude our account with a discussion of rhizostomes as Discomedusae, and whether we should be considering them separately from semaeostomes in terms of ecology.