Interesting Animal - The Octopus
Octopuses have three hearts. Two branchial hearts pump blood through each of the two gills, while the third is a systemic heart that pumps blood through the body.
(Octopus blood contains the copper-rich protein heamocyanin for transporting oxygen. Although less efficient under normal conditions than the iron-rich haemoglobin we have, in cold conditions with low oxygen pressure, heamocyanin oxygen transportation is more efficient than heamoglobin oxygen transportation. The heamocyanin is dissolved in the plasma instead of being carried within red blood cells, and gives the blood a bluish color, which of course we had to call "ink".
Yet another reason not to eat these remarkable marine animals: The main reason being they can juggle.)