The stealthy predator Mnemiopsis leidyi uses tiny hairs to render itself hydrodynamically invisible as it closes in on its next meal.
When you think of stealthy marine predators, a creature commonly called the sea walnut probably doesn't come to mind. However, new research shows the gelatinous blob hunts as effectively as a small, but much more sophisticated fish.
Stealth is the secret.
Mnemiopsis leidyi, as it's formally called, is a ctenophore, a group of simple animals often described as jellyfish that propel themselves using tiny hairs, called cilia. The animal also uses a different set of cilia to create a feeding current, gently sucking its prey – often tiny crustaceans called copepods measuring about 0.04 inches (1 millimeter) long – onto sticky cells in its mouth.Mnemiopsis can measure anywhere from 0.04 to 5 inches (1 millimeter to 12.7 centimeters) long. [Editor's note: The original version gave incorrect sizes in inches.]
However, if the copepods' antennae detect a slight change in the current, they'll jump away beforeMnemiopsis can close the lobes of its mouth region around them.
"The trick to getting them there is to sneak up on the copepods so they don't realize they are already completely surrounded by these lobes," study researcher Sean Colin, a marine biologist at Roger Williams University in Rhode Island, told LiveScience. "That's what we showed: The disturbance or deformation in the water doesn't reach levels detected by the copepods until they are in that region."