10 Weird Creatures From the Mariana Trench

The tiny benthocodone is unique among jellyfish in its opaque red color. © 2015 HowStuffWorks, a division of Infospace LLC

Jellyfish are fairly common sea creatures, washing up on shores and clogging fishermen's nets. The benthocodon, though, is an unusual type of jellyfish that prefers an environment far out at sea at depths of more than 2,500 feet (762 meters), often right on the seafloor.

These are compact jellyfish with a rounded top, called the bell. The bell is typically smaller than three-quarters of an inch to 1.2 inches (2 to 3 centimeters) in diameter, and it's laced with an estimated 1,500 wispy red tentacles, which it uses to whisk itself through the water. The benthocodon dines on small crustaceans and foraminiferans, tiny unicellular organisms.

Although many types of jellyfish are transparent, the benthocodon has an opaque reddish coloring on its bell. Scientists believe that this hue may help mask the bioluminescent glow of the tiny animals that the jellyfish eats, hiding the benthocodon from danger.

Like so many animals in the trench, this species remains a mystery to scientists.