The octopus could not survive because it is the heart that provides blood to the whole body, which also helps deliver important oxygen around the body. If you thought that three hearts is a lot, you'd be even more surprised to learn about the witchfish, which looks like a sticky, viscous eel. Regardless of this, the octopus doesn't need all three hearts to survive. You can live with less than your three hearts.
While reading the book The Soul of an Octopus by Sy Montgomery, I learned that octopuses have three hearts. According to a Wikipedia article, two of the three are used to pump blood through each of the two gills, while the third pumps blood through the body. That said, not all creatures that have blue blood need three hearts. The cephalopod nautilus, the fascinating marine animal with a spiral shell, has only one heart that pumps blood, unlike its three-hearted relatives.
You probably don't need the two extra hearts due to their relatively smaller size and the creature's very sedentary lifestyle. Similarly, octopus and other cephalopods have developed three hearts. These three hearts are located inside the animal's head, with the systematic heart serving as the primary circulatory pump and two gill hearts helping. This is not functionally that different from how the heart works in other creatures, although it does divide duties.
The two gill hearts take pure oxygen-rich blood and pump it through the gills of the octopus so that oxygen and nutrients can be distributed to the remote tissues of the body. Once this blood finishes its cycle, it will return to the systematic heart, where it will be pressurized and sent back through the cycle. Hemocyanin is a copper ion protein that transports oxygen around the bodies of invertebrate animals, such as octopus. This exhausts the octopus, which is probably why they prefer to crawl rather than swim, according to the Smithsonian article.
Common octopus, for example, can live only two years, while giant octopus can live up to three years, but up to five years as long as they don't mate. The three hearts help compensate for this by pumping blood at higher pressure around the body to provide the octopus's active lifestyle. Losing one more of the main heart means that the octopus can pump blood through a heart and oxygenate it, but then it will not be able to pump blood to the rest of the body. Keep in mind that hearts are not redundant, that is, one heart cannot perform the function of the other (if that other one stops).
Octopuses have proven to be very efficient at using all the oxygen that their hearts pump through their body, but that may be less a sign that they have efficient circulatory systems and more a result of the need. Both cuttlefish and squid have three hearts, an evolution that they also adapted to remedy the unique difficulties of the aquatic ecosystems they inhabit. Because their copper-based blood is not an efficient oxygen carrier, octopuses prefer cooler, oxygen-rich water. There are about 300 species of octopus, ranging in size from the giant Pacific octopus, which can weigh 50 kilograms, to the tiny Octopus wolfi, which weighs less than a gram.
Based on the known facts, it can be argued that cockroaches have 13 hearts, although some scientists argue that, instead, they have a single heart with 13 chambers. The number and nature of these arms may vary depending on the animal, but octopus species are particularly well developed. The loss of two of your three hearts means that you have lost both gill hearts or one gill heart and your main (systemic) heart. Many of the octopus species live in the depths of the oceans, where there is less oxygen available and the water is cold.
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