We just learned about the Mantle of an Octopus or squid.
When the octopus or squid wants to breathe, they breathe through Gills just like fish.
The gills are inside the mantle, so they will take water into their mantle, and use some muscles to close their mantle.
This makes the water push through their gills where they can get the oxygen they need.
(from: wikipedia - octopus)
Amazing breathing of an Octopus - isarounddaworld
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