Fig. 1

Principles underlying medusa formation in cnidarians. a Phylogenetic relationship of the cnidarian taxa (blue box) [14, 55, 56]. Anthozoans only form polyps, whereas medusozoan taxa show life cycles with polyps and medusae. Staurozoans, cubozoans and scyphozoans form their medusae by different forms of apical metamorphosis of polyps (pink box) [55]. Hydrozoans form their medusae through lateral budding on polyps (green box). b Polydisc strobilation in Aurelia aurita. c Lateral budding of young medusae in Clytia hemisphaerica from a specialized polyp form within the polyp colony