Squids are called decapods because they have 10 arms, 8 short and two long with tentacles used for hunting. Squids are related to octopus and shells but have lost its shell over time. They are strong swimmers and certain species can “fly” for short distances out of the water. A squid is able to swim by sucking water into the mantle cavity, which is then removed through the siphon. This process continues all day long, even when they are sleeping. Every squid has three hearts. When threatened, they release dark colour ink as they try to escape the predator. Some species of squid are able to glow in the dark. Research shows this is due to them having bioluminescent organs. The small bone found in some of the squids is called gladius because it resembles a short roman sword. They are a favourite food for sperm whales.