Earth's oceans are well-stocked with otherworldly inhabitants, but few of these critters are quite as strange as sea spiders, which look like something that would lurk in the crawlspace under Slender Man's house. With their impossibly spindly legs, sea spiders -- which aren't even actual spiders -- stride across the ocean floor with eerily slow, deliberate steps. They eat by piercing stationary animals such as sea anemones and sponges with their long proboscises, and sucking up chunks of tissue softened by digestive juices. Now, new research published in the journal Current Biology piles onto the weirdness, demonstrating that sea spiders move blood and oxygen around their bodies not by pumping their hearts, but by pumping their guts.