This delicate being is a sea anemone of the species nematostella vectensis. With her thickened “foot” on the left in the picture, she stuck to sea grass, sand and rock, with her tentacles she catches small prey such as crustaceans and fish larvae. So there is a clear one at Nematostella, but where is left and right?
Since most lake anemones are built completely like a donut or cake, they are also referred to as radial symmetrical. In contrast, most other animals are bilateral symmetrical-that is, they have a head and tail axis, a back belly axis and a clear left and right side of the body. But although anemones are superficially radiantly symmetrical, their interior is already bilateral symmetrical and their embryonic development also follows this pattern.
This raises an important question: Has the bilateral-symmetrical body plan emerged when the bilateral and radial-symmetrical animals were used together or independently of one another in several groups of animals? Researchers at the University of Vienna have now found information on the former. Accordingly, radiermed symmetrical sea anemones use an ancient molecular mechanism to form a back-belly axis, which was previously only known from bilateral symmetrical animals such as frogs or flies.
Probably this mechanism existed over 600 million years ago in the last joint ancestor of bilateral and radiian symmetrical animals, which makes the “back” or at least the blueprint much older than before.
