A Shrimp’s Heart Is in Its Head

Shrimp may be small, but they have one of the strangest body plans in the animal kingdom. Their heart, for example, sits so close to the brain that it’s effectively inside the head. A shrimp’s heart is located inside the cephalothorax — the fused body section that combines its head and thorax beneath a hard protective shell. Since a shrimp doesn’t have a distinct neck separating its head from the rest of its body, the heart ends up sitting just behind the brain, making it appear as though it’s tucked inside its head.

Unlike humans, shrimp have an open circulatory system. Instead of pumping blood through a network of arteries and veins, their heart pushes a copper-rich fluid called hemolymph into open spaces surrounding their organs. This fluid delivers oxygen and nutrients before eventually making its way back to the heart to begin the cycle again. It’s an efficient design for the small crustacean.