What doesa siphon do on a octopus?

The siphon of an octopus is a versatile anatomical structure that serves multiple functions. Primarily, it is used for locomotion; the octopus can expel water through the siphon to propel itself quickly in the water. Additionally, the siphon aids in respiration by drawing water over the gills for oxygen extraction. It can also be involved in the release of ink as a defensive mechanism.