One of the fundamental assumptions about what it takes to be an animal could well be wrong.
Possessing Hox genes has long been considered a defining characteristic of all animals: they control the development of body shape, instructing cells in an embryo to become an arm, eye or rib, for instance, based on where they are along the central body axis.
But now it seems that Cnidaria, such as the sea anemone Nematostella and a hydromedusa Eleutheria, have no Hox genes at all, says David Miller of James Cook University in Queensland, Australia. They still manage to shape themselves,…
