Copepod Power

It’s human nature to think of the big bad animals that eat other animals as powerful and the animals that get eaten as wimpy. Of course, humans are often wrong (see “clusterf**kery”).

Copepods get eaten by lots of animals—even by critters like jellyfish and right whales, which are known for their lack of speed—but they’re not exactly wimpy. In fact, a recent study claims that the teeny tiny copepod, the munchable of the sea, is the most powerful animal in the world. When a copepod wants to get away from something (which happens fairly frequently for a critter on everyone’s menu), it can cover some serious ground (for a little critter between 0.3 mm and 3.0 mm long). And it can do it quickly. Copepods can jump at a speed of 500 bogy-lengths per second. The copepod’s jump, the scientists conclude, is over 10 times more powerful* than that of any other animal—relative to size, of course.

The key to the copepod’s ability to out-jump renowned jumpers like kangaroos, frogs and fleas is that it has two propulsion systems. Most animals (like kangaroos, frogs and fleas) only have one—they use their legs to walk, to swim and jump. Copepods, on the other hand, have feeding appendages and four to five pairs of “swimming” legs. They vibrate their feeding appendages almost constantly to feed and to swim. They can swim forever, though not very quickly. To jump, copepods kick their swimming legs back sequentially, much like a sprinting cheetah. These legs are designed for short bursts of power and because copepods use their swimming legs relatively rarely—they only jump to escape danger or to pounce on their own prey**—their swimming legs are always fresh.

One more thing: Apparently there are two ways to jump. There’s the cheater’s way and the real way (also known as “hopping”). Animals like fleas and grasshoppers cheat by pausing before jumping to store energy and then releasing it like a spring. Copepods and kangaroos use direct muscle action to jump father, higher and more powerfully than other animals.

*No one claimed that the copepod could jump farther than any other animal. A brief google search reveals that red kangaroos probably hold the record for longest jump (a female once jumped 42 feet). The same source also reports that red kangaroos can jump higher than other animals, easily clearing 10 feet.

**Copepods attack their prey so quickly that viscous friction doesn’t have time to create a layer of water around the copepod. That layer of water would push the prey away as the copepod approached.

Kiørboe T, Andersen A, Langlois VJ, & Jakobsen HH (2010). Unsteady motion: escape jumps in planktonic copepods, their kinematics and energetics. Journal of the Royal Society, Interface / the Royal Society PMID: 20462876