This video from the USA says about itself:
15 November 2016
William Gilpin, Stanford University
Vivek N. Prakash, Stanford University
Manu Prakash, Stanford University
We show the surprising flow patterns created by a starfish larva, which churns the water around its body as it searches for algae, its primary food source. These vortices are unique to many invertebrates, which often struggle to obtain sufficient nutrients during the early stages of their development.
Our video shows how millions of years of evolution have allowed the larva to master fluid physics in order to solve the unique dilemma of feeding at the microscale. But this innovation comes with a price: the vortices decrease the animal’s swimming speed, and thus its ability to change locations and escape predators. By studying how physical forces shape the adaptation of simple animals, we hope to uncover the subtle manner in which physics shapes evolution.
From Science News:
Baby starfish whip up whirlpools to snag a meal
by Emily Conover
12:00pm, December 23, 2016
A baby starfish scoops up snacks by spinning miniature whirlpools. These vortices catch tasty algae and draw them close 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 freely swim ocean waters as millimeter-sized larvae. To swim around on the hunt for food, the larvae paddle the water with hairlike appendages called cilia. But, the scientists found, starfish larvae also adjust the orientation of these cilia 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, by observing their activities 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.