Horseshoe crabs’ bodies are divided into three segments. The head, or prosoma, houses most vital organs, including the heart and the brain. The middle segment, the opisthosoma, contains the back ...

The horseshoe crab has been on Earth for 350 million years. An ancient and complex anatomy hides within its domed shell. From its 10 eyes to its tube-like heart, the horseshoe crab's unique ...