MEET THE ONLY ANIMAL KNOWN TO PUMP BLOOD WITH ITS GUTS

- story published by Science

High school biology classes teach us that the circulatory system pumps blood and the digestive system pumps food. But sea spiders apparently skipped that lesson: They pump blood using their guts. Researchers discovered the remarkable physiological strategy after injecting dye into sea spiders—common inhabitants of the world's oceans named for their resemblance to land-based spiders—and watching the flow of blood. They noticed that the animals’ hearts were beating weakly. But the digestive system—which is unusually extensive in sea spiders, running down each leg—was contracting in waves, moving food in the gut as well as blood in the surrounding hemocoel cavity, the spider equivalent of veins and arteries. 

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