Cuttlefish (Sepiida) are squid-like creatures found in tropical/temperate waters. They are usually found in shallow waters but can be found at a depth up to 600m. Cuttlefish have large, S-shaped pupils, eight arms, and two tentacles with denticulated suckers, with which they secure their prey. They generally range in size from 15 to 25 cm, with the largest species, Sepia apama, reaching 50 cm (20 in) in mantle length and over 10.5 kg (23 lb) in mass.
Cuttlefish eat small mollusks, crabs, shrimp, fish, octopus, worms, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds, and other cuttlefish. The average life expectancy of a cuttlefish is about one to two years. Cuttlefish have one of the largest brain-to-body size ratios of all invertebrates.
Cuttlefish are sometimes referred to as the “chameleons of the sea” because of their ability to alter their skin color – this can occur within a second. Cuttlefish change color and pattern, and the shape of the skin to communicate to other cuttlefish, to camouflage themselves, and as a deimatic display to warn off potential predators. Under some circumstances, cuttlefish can be trained to change color in response to stimuli, thereby indicating their color changing is not completely innate. As well as being able to influence the color of light as it reflects off their skin, cuttlefish can also affect the light’s polarization, which can be used to signal to other marine animals, many of which can also sense polarization.
It has been suggested that although cuttlefish (and most other cephalopods) lack color vision, high-resolution polarisation vision may provide an alternative mode of receiving contrast information that is just as defined. There are three broad categories of color patterns – Uniform, Mottle and Disruptive. Some researchers have suggested that cuttlefish can display 12 to 14 patterns, 13 of which have been categorized as 7 “acute” (relatively brief) and 6 “chronic” (long-lasting) patterns. although other researchers suggest the patterns occur on a continuum.