How Does an Octopus Get Oxygen?

Anatomy

All octopuses have eight muscular, flexible arms with rows of suckers on them. They have no bones. The main part of an octopus's body is called the mantle. The eyes are located on the outside of the mantle. The siphon, a tube for expelling water, is also located there. In the center of all the arms is the octopus's beak, which looks very like a parrot's beak. The beak is used for killing and eating prey.

Inside the cavity of the mantle are the octopus's organs, including the gills and three hearts that are vital to its respiratory system. Two of these hearts are near the gills, and are called gill hearts.

Octopuses have what is called a closed circulatory system. That means the blood travels through tubes. The only tubes in an octopus's system are blood vessels.

Breathing

An octopus breathes by drawing water into the cavity formed by the mantle. The water provides oxygen for the gills. Later, the water is pushed out of the body by the siphon.

The gill hearts pump blood to the gills where the blood dumps waste and loads up on oxygen. Then the oxygen-rich blood is pumped to the third heart. This heart, called the systemic heart, pumps blood through the rest of the octopus's body.

Blood

Octopuses have about the same blood volume as humans--about 5 percent of their body volume is blood. Their blood is about as loaded with hemocyanin as human blood is with hemoglobin. Both hemocyanin and hemoglobin are proteins that help blood absorb oxygen. (An octopus's blood is light blue because hemocyanin is blue. Hemoglobin gives human blood its red color.) But hemocyanin is about a quarter as effective as hemoglobin is in carrying oxygen, so the human system is more efficient. This is why an octopus can make a sudden jetting motion, but can't sustain fast movement.

References

• The Octopus News Magazine Online
• Borglum's Biology page
• Everything Octopus

Resources

• More on Circulatory Systems