Sea spiders are found across the globe in the Mediterranean and Caribbean Seas, but none grow to the huge size of the ones found in Antarctica. These marine arachnids discovered around the Ross Sea, a deep bay in southern Antarctica, can grow to the size of a dinner plate.
They're often orange-colored and look like something from John Carpenter's The Thing or the Alien movies, but scientists have yet to discover why these eight-legged creatures grow as big as 9.8 inches long.
It's part of a phenomenon known as polar gigantism where marine invertebrates in very cold water have much bigger bodies than other types which live in warmer places.
Polar gigantism isn't just seen in sea spiders but extends to marine sponges, worms, and single-celled organisms too. And it remains a mystery for the scientists who are currently studying this effect.
What exactly causes it is unknown, but theories include a lack of predators, high availability of oxygen in polar oceans coupled with low temperatures that slow metabolism, which could produce the conditions for the sea spiders to get so huge—and nightmare-inducing.
Hakai magazine reported that, "Multiple hypotheses have been put forth to explain this phenomenon, although none has been proven—yet. One group of researchers thinks that Antarctic sea spiders hold the key to this ginormous riddle. But first they had to catch some sea spiders to put their theories to the test."
However rising seas temperatures mean that oxygen levels will fall and this could have implications for the future of these creatures. Not just sea spiders either, but all types of gargantuan marine life.