Sea Spiders Use Their Guts, Not Hearts, To Pump Oxygen

Sea spiders, which have inhabited Earth for over 500 million years, are fascinating creatures. The marine arthropods, which range in size from a millimeter long to as big as a dinner plate, have eight jointed legs that convene around a tiny body. Since their torsos are so small, sea spiders use their legs to conduct normal body functions such as digestion and reproduction. Now, it seems the creatures also have a unique breathing mechanism.