Tarantula
Circulatory system

A tarantula's blood is unique (not only in appearance); 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 hemolymph (or haemolymph). At least four types of hemocytes, or hemolymph cells, are known.

The tarantula's heart is a long, slender tube 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. It 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 spider unless the wound is small enough that the hemolymph can dry and close it.
detectable_content:postscript