The tube worm is quite a remarkable species because of its adaptions. Since it lives near underwater hydrothermal vents, it has developed a hard outer shell made of chitin, the same protein that makes up the exoskeletons of anthropods. Still though, the tube worm's cardiovascular system remains largely the same as its land ancestors. It still contains dorsal and ventral blood vessels that are connected by five pairs of aortic arches. The blood in a tube worm gets its nutrients and oxygen from the red plume that is an organ specialized just to this species. The plume is rich in hemoglobin, giving it its red hue, and is responsible for gas exchange. Thus, oxygen exchanged here enters the bloodstream, where it is distributed throughout the organism by the cardiovascular system.