Octopuses have gills and therefore depend on water for the exchange of oxygen and carbon dioxide. The gills collapse on land due to lack of buoyancy. Octopuses have three hearts. Two of them are dedicated to transporting blood to the animal’s gills, emphasizing the animal’s dependence on its gills for oxygen supply.
Octopuses can therefore breathe on land, but this rarely lasts very long, about 5-6 minutes maximum! It remains dependent on water for its survival.
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How do octopuses move on land?
Octopuses depend on water to breathe, so in addition to being a cumbersome mode of transportation, land exploration is also a gamble. When their skin remains wet, a limited amount of gas exchange can occur by passive diffusion.
This allows the octopus to survive on land for short periods of time, as oxygen is absorbed through the skin, instead of the gills. In wet coastal areas, it is believed that they can crawl on land for at least several minutes. Most of the time they go from pool to pool, never staying out of the water for long periods. If they are confronted with a dry surface in the sun, they will not survive long.
How do octopuses breathe?
All living things need oxygen. Oxygen is found in the atmosphere and in the water. Aquatic creatures must filter oxygen out of the water and then release the water so that they do not drown. An octopus breathes the same way all fish breathe, through gills.
The octopus gills are located inside the mantle cavity and exit outside the body. The octopus’ oxygen requirements are greater than those required by other mollusks and fish. Octopuses have three hearts, two of which pump blood through the two gills, where oxygen exchange takes place.
The mouth of an octopus
The beak-shaped mouth of an octopus is located on the mantle cavity at the back of the octopus’ bulbous head, surrounded by the eight legs. The mouth is the entrance to the mantle cavity which has gills inside it. The octopus uses these gills to breathe.
Water is brought into the octopus’ mouth and then passed through the gills into the water body. As the water is pushed over the surface of the gills, oxygen is taken up by the blood in the capillaries of the gills.
The gills of an octopus
The gills are composed of several feathery filaments. These filaments allow a larger surface area through which oxygenated water passes. This large surface area allows the octopus to take in more oxygen through respiration.
The exchange of oxygen
Oxygen is captured in the capillaries by a counter-current exchange. Oxygen will be taken up into the capillaries as long as the oxygen level is lower in the blood than in the water. When countercurrent exchange is used, the oxygen level will always be lower in the blood than in the water, allowing a continuous exchange of oxygen between the water and the blood. This means that the blood moves in an opposite direction in the gills than the direction in which the water moves.
This allows for maximum oxygen exchange by respiration. Because of the octopus’s muscular system that contracts the mantle cavity, forcing oxygenated water through the gill filaments, the octopus is able to achieve the 11 percent oxygen saturation level in the blood that it needs. Most fish and mollusks achieve an average oxygen saturation of 3 percent.