Fun cephalopod fact of the day: the nautilus is the only cephalopod with an external shell. Adult shells can have up to 30 chambers, the living space in its shell that is connected to older chambers as it grows.
the humble octopus has three hearts. squid have donut shaped brains, through which their digestive tract runs. a large meal can give a squid brain damage. cuttlefish have W shaped pupils to balance out light conditions.