Fig. 1

Cnidarian model systems represented at Cnidofest. a A hermaphroditic green Hydra polyp bearing a testes and an egg (courtesy of Stefan Siebert). b Gastrozooids and gonozooids of a Hydractinia symbiolongicarpus colony (courtesy of Steven Sanders). c Nematostella vectensis adult polyp (courtesy of Shuonan He). d The banded tube-dwelling anemone, Isarachnanthus nocturnes (courtesy of Sérgio Stampar). e A Cordylophora colony growing on eelgrass (courtesy of Nadine Folino Rorem and E. Sally Chang). f Medusa of Cassiopea spp. (courtesy of Casandra Newkirk)