Squids have three hearts and move through the water tail-end first. These are short-lived animals where most species have a lifespan of about a year. In the Pacific Northwest stubby squids live for about 1 ½ years, and opalescent squids live for 6 to 9 months. Their fins are paired wing-like appendages attached to the posterior end of the mantle that flap rhythmically allowing the squid to “swim” with ease. The skin of these animals is covered entirely in chromatophores, or pigment containing cells. These chromatophores allow squids to change their colour very rapidly, which is ideal for camouflage, as well as mating rituals within their species.