Shrimp hearts live in their heads

A shrimp’s heart sits inside its head. Specifically, the organ is located in the cephalothorax, right next to the stomach and the brain.

This high-stakes placement means that if a shrimp gets a headache, it is literally a cardiac event. The heart is protected by the same thick shell that shields the brain, making the skull the most armored part of the entire body. It is a single-chambered pump that pushes clear blood through an open circulatory system, meaning their blood doesn't stay inside veins but sloshes freely around their organs.

Because the heart and stomach are neighbors, what the shrimp eats can affect its rhythm. If the stomach expands too much after a large meal, it physically presses against the heart.

Even weirder, the shrimp’s ovaries are also located in its head. This means the majority of its critical life functions—thinking, eating, pumping blood, and reproducing—all happen within a few millimeters of its antennae.