Horseshoe crabs (Limulus polyphemus)
The heart of the Horseshoe crab extends almost over the entire length of the crab. The heart of the crab beats at about 32 beats per minute. It has an open circulatory system, which serves many purposes. Horseshoe crabs have a long, tubular heart that runs the length of their body. Blood enters the heart from the pericardial chamber through the double-valved, slit-like openings called ostia. From there blood is pumped through the heart until it reaches the three pairs of aorta, the pair of cerebral arteries, and the frontal artery. Blood is pumped from the arterial trunks that stem from the aortae throughout the crab's body. Meanwhile, another pair of large, veinous trunks collect blood from throughout the crab's body and direct it towards the gills, where it is reoxygenated and then brought back to pericardial membrane where it can enter the heart. |