The Horseshoe Crab has a large cardiovascular system that uses mainly one vessel to transfer blood. This blood vessel is called the ostia, and it has eight slits that connect to different arteries and veins that transfer blood to and away from the central heart. Valves from the ostia go into the heart, through different cardio chambers. The blood is pumped is out into different places using three aortae (middle left of the picture), along with the cerebral artery by the brain, and the frontal artery.