How octopus breath by lungs or gills or trachea?
The beak-like mouth of an octopus is located on the mantel
cavity at the back of the bulbous head of the octopus, surrounded
by the eight legs. The mouth is the entryway to the mantle cavity
which has gills inside of it. The octopus uses these gills to
breathe. Water is brought into the octopus mouth and is then passed
through the gills back into the body of water. As the water is
pushed over the surface of the gills, oxygen is picked up by the
blood in the capillaries of the gills.