Strange creatures with eight spindly legs that crawl along the ocean floor, sea spiders may look like arachnids, but they're actually not.

There are about 1,000 sea spider species worldwide, ranging from an inch long to as big as a dinner plate. They're mostly all legs, with a tiny body and pointy proboscis that sucks juice out of unwitting prey.

“They do all their business in their legs,” explains Amy Moran, a marine ecologist at the University of Hawaii at Manoa. “Their gonads are in the legs, and the females store eggs in their legs.”

Sea spiders obtain oxygen by diffusing water over their thin, porous external skeleton. “They don’t have any specialized structures for gas exchange,” says Moran, co-author of a