Circulatory System
A tarantula’s blood is unique; an oxygen-transporting protein is present (the copper-based hemocyanin) but not enclosed in blood cells such as the erythrocytes of mammals. A tarantula’s blood is not true blood but rather a liquid called haemolymph, or hemolymph. There are at least four types of hemocytes, or hemolymph cells. The tarantula’s heart is a long slender tube that is located along the top of the opisthosoma. The heart is neurogenic as opposed to myogenic, so nerve cells instead of muscle cells initiate and coordinate the heart. The heart pumps hemolymph to all parts of the body through open passages often referred to as sinuses, and not through a circular system of blood vessels. If the exoskeleton is breached, loss of hemolymph will kill the tarantula unless the wound is small enough that the hemolymph can dry and close the wound.
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