Appearing on Earth well before vertebrates during the Cambrian, the octopus – or octopus – is a cephalopod which has evolved over hundreds of millions of years. If its eight tentacles allow it to move in the water and capture its favorite foods, our Octopus does not only have 9 brains to ensure its survival, it also has three hearts.
The circulatory system of the octopus
The circulatory system of the octopus, although similar to that of mammals, is distinguished by an arterial heart and two branchial hearts. For our cephalopod we are talking about systemic hearts whose vascular architecture is specific to this animal which dredges the depths of subtropical, tropical or temperate seas and oceans. Their gills bring oxygen extracted from seawater into the bloodstream. The arterial heart consisting of a single ventricle and two atria carries blood from the gills to the main arteries. This single ventricle alone would not be able to ensure the high blood pressure necessary to survive in the depths. Two small gill hearts reinforce the action of the single ventricle to pump blood into the gills of the invertebrate.
Three hearts to ensure the survival of the species
The systemic heart extracts oxygenated blood and propels it throughout the octopus’ body, with the branchial hearts providing support to the main cardiac system. Their role is to increase the blood pressure of the cephalopod to deposit oxygen molecules on the hemocyanin. In fact, the octopus does not transport oxygen thanks to hemoglobin, but thanks to this metalloprotein which contains copper and gives it this blue color. Squid and cuttlefish have this same characteristic, the gill hearts transporting oxygen from the gills to the systemic heart. We owe this crucial discovery in understanding the octopus cardiac system to researcher Léon Fredericq. He will share his discoveries in a dissertation at the University of Ghent: “On hemocyanin, a new substance in octopus blood. Reports of the Paris Academy of Sciences, LXXXVII, p. 996, 1878”.
The environment in which octopuses live is not very generous in terms of oxygen. They also have nine brains which require an efficient oxygenation system to recover oxygen from seabeds where this element is poor. To hunt, escape, and fuel their brains, evolution has equipped them with a more than efficient circulatory system.
Did you know ?
Fascinating, endowed with great intelligence, the octopus has, like the cat and the dog, a world day just for it: every October 8, it is world octopus day.
Why does the octopus have three hearts?
The blue blood of the octopus seems responsible for this very particular cardiac anatomy. Hemocyanin is less efficient as a transporter of oxygen molecules than hemoglobin, even if the copper it contains has more affinity than iron. In the cold, poorly oxygenated depths of the deep seas and oceans, hemocyanin molecules prove more functional in oxygenating each tissue of our famous cephalopod. This feature, however, has a major drawback: it would make the blood more viscous. So that the blood circulates freely and efficiently, the two additional hearts ensure optimal exchange of molecules in this high pressure environment.
Nine brains, three hearts, exceptional cognitive abilities, the octopus stands out in the animal world through an adaptation of several million years to its environment. In addition to its physical characteristics, the cephalopod has many unusual abilities to survive in its natural environment.
With his many abilities, king of escape capable of carrying out complex operations is today recognized by scientists as the most intelligent octopod in the kingdom of invertebrates. If you want to know more about this fascinating animal, enjoy the book by Ludovic Dickel, professor-researcher in biology in his work “The Private Life of the Octopus”.