Studies of medusan motion reveal secrets of the Earth's first muscle-powered swimmers
From the Jetsons to James Bond, flying via jet pack has become an icon of the futuristic way to travel. But jet propulsion is actually older than the Flintstones. It's a standard means of locomotion for jellyfish, the earliest animals to swim the seas using muscles. Jellies have been jet-propelling for at least 550 million years, yet only recently have scientists begun to understand how the challenges of moving in fluid have shaped jellyfish evolution.