Scientific name: order: sepiidaCuttlefish are not fish, but are a type of mollusc related to squid and octopi. Cuttlefish have three hearts, blue-green blood and a single bone inside them. You often see cuttle bones being given to budgerigars. They can change colour to camouflage with the environment around them. Cuttlefish are caught as food and prepared in a similar way to squid.