Another major animal body plan is radial symmetry, meaning these creatures organize their bodies around a central axis. Picture a jellyfish, and then try to figure out which side is the ‘front’, and you’ll likely understand.<\/p>\n
Most animals belonging to the cnidaria<\/a> phylum, which includes invertebrates like jellyfish, sea anemones, and corals, have this body plan.<\/p>\n But the categories aren’t as neat as biologists might like them to be. Although it’s a cnidarian, the sea anemone shows bilateral symmetry, which raises the question of when the feature evolved, and how many times.<\/p>\n To find out, researchers at the University of Vienna in Austria conducted experiments on starlet sea anemones (Nematostella vectensis<\/a>) to see how they develop as embryos.<\/p>\n Bone morphogenetic protein (BMP) is crucial to how bilaterians build their bodies. Essentially, a gradient of BMP tells developing cells what tissues they should become, based on where in the body they are.<\/p>\n In some bilaterians, like frogs and flies, this gradient is created thanks to another protein called chordin shuttling BMP around the body.<\/p>\n The team found that sea anemones also use this BMP shuttling mechanism. That suggests that the mechanism evolved before bilaterians<\/a> and cnidarians diverged, more than 600 million years ago.<\/p>\n “The fact that not only bilaterians but also sea anemones use shuttling to shape their body axes tells us that this mechanism is incredibly ancient,” says<\/a> developmental biologist David M\u00f6rsdorf, first author of the study.<\/p>\n “It opens up exciting possibilities for rethinking how body plans evolved in early animals.”<\/p>\n![\"A](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/06\/MoonJelly.png\")
The moon<\/a> jelly (Aurelia)<\/a> is radially symmetrical. (Oleg Kovtun Hydrobio\/Canva)<\/p>\n![\"The](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/06\/74ebadb2fe-642x367.jpg\")
Without the protein chordin, the BMP gradient couldn’t be created. (David M\u00f6rsdorf\/Grigory Genikhovich)<\/p>\n