A baby starfish scoops up snacks by spinning miniature whirlpools. These vortices draw in tasty algae so the larva can slurp them up, scientists from Stanford University report December 19 in Nature Physics.
Before starfish take on their familiar shape, they swim the ocean as millimeter-sized larvae. They use hairlike appendages called cilia to paddle. The larvae also adjust the orientation of these cilia, the scientists found, to fine-tune their food-grabbing vortices.
Scientists studied larvae of the bat star (Patiria miniata), a starfish found on the U.S. Pacific coast, in seawater suffused with tiny beads that traced the flow of liquid. Too many swirls can slow a larva down, the scientists found, so the baby starfish adapts to the task at hand, creating fewer vortices while swimming and whipping up more of them when stopping to feed.