Dec 5, 2022
What purpose do internal shells have? Providing structure? I always thought that shells were for protection on the outside and stuff on the inside was bone lol
It's definitely true that most of the animals who have shells use them to protect themselves. Long long ago in evolutionary time, the shells were internalized and/or reduced because shells are friggen heavy and the cephalopods wanted to move FAST.
Nowadays, what the internal shell does depends on the species. Some species don't have a shell at all (like the bobtails). In cuttlefish that internal shell is the cuttlebone and is used for regulating buoyancy. In market squid, that "pen" (aka gladius), supports the animals structure.
