The ancestral shell has been lost, with only an internal gladius, or pen, remaining. The pen is a feather-shaped internal structure that supports the squid's mantle and serves as a site for muscle attachment. It is made of a chitin-like material.
Keeping this in consideration, what is the function of the siphon in a squid?
A squid's siphon is multi-functional. It helps with locomotion in any direction by "spitting" out a stream of water. It helps the squid breathe by getting rid of the "wastewater" from the seawater pumped over the gills in the mantle (head). It also gets rid of other internal waste.
What is the function of the ink in a squid?
With the exception of nocturnal and very deep water cephalopods, all coeloids (squid, octopus and cuttlefish) which dwell in light conditions have an ink sac, which can be used to expel a cloud of dark ink in order to confuse predators.
What is the function of the Nidamental gland of a squid?
The accessory nidamental gland (ANG) is a female reproductive organ found among cephalopod mollusks that contains a consortium of bacteria, the exact function of which is unknown.