Fig. 1

Cnidarians discussed at Hydroidfest. a Two colonies of Hydractinia that are rejecting each other (courtesy of Matthew Nicotra; scale bar 1 mm). b Cassiopea (courtesy of C. Newkirk; scale bar 3 mm), c Hydra male (left) and female (right) (courtesy of S. Siebert; scale bar 1 mm), d Aiptasia (courtesy of T. Tivey; scale bar 2 mm), e Physonect siphonophore Apolemia sp. with functionally specialized zooids arranged along the stem of the colony. Anterior part of a colony is shown