Sepia officinalis
common or european cuttlefish

Sepia officinalis, often referred to as either the common or European cuttlefish, is a marine organism which lives in the Mediterranean Sea and adjacent Atlantic Ocean along the West coast of Africa to the southern-most point of Africa. These animals are usually found on shallow reefs or channels down to 80 feet. Some populations migrate from deep to shallow waters in the summer.

The cuttlefish is a marine animal which usually dwells on shallow reefs or channels up to 80 feet deep. Some populations migrate from deep to shallow waters in the summer. Cuttlefish are often found on the bottom of the water buried in a thin layer of sand.

Cuttlefish are dorso-ventrally compressed and oval in shape. The cuttlefish has eight regularly visible tentacles with suction rings along the inner surface and two additional elongated tentacles with suction tips only at the ends. These arms are usually tucked away, used only during hunting, mating, egg laying, and for defense. In the center of its arms is a parrot-like beak.

The body of the common cuttlefish can grow in excess of 45 centimeters long, but most are smaller, around 20-30 centimeters. The tentacles add an additional 30 centimeters of length. Their mouth is located in the middle of the "foot" or overall body cavity. There is a fin surrounding the mantle used for movement, especially hovering. The eyes are quite large and are very similar to those of vertebrate organisms. In fact, many studies of human vision are conducted using cuttlefish eyes.

This species has a zebra-like brown to violet crosspattern on the upper surface and a spotted bluish green belly. Specialized pigment cells, called chromataphores, cover the cuttlefish's skin and can rapidly change colors. This is useful both to avoid predation and as a means of communication between individuals as well. The characteristic molluscan shell has been reduced to the small, internal plate-like "cuttlebones". When threatened, cuttlefish, like other cephalopods, are able to secrete a cloud of dark, foul-tasting ink to confuse its predator. This ink has historically been used in art where its color, sepia, takes its name from the ancient Latin name for this species.

The cephalopods in general are the "smartest" invertebrates and the cuttlefish is no exception. Its large brain is complex and highly differentiated, coordinating lots of sensory information and locomotor information. Giant nerve fibers are specialized for very rapid impulse conduction which is important in synchronizing contraction to coordinate speedy escape locomotion. Cuttlefish have demonstrated memory and learning and can discriminate and be trained to respond to horizontal vs. vertical rectangles, color intensity, shape, and texture, but not weight. Their ability to change colors is used behaviorally in communication of warnings as well as mating.

Recent research has found that cephalopods (including cuttlefish) have sensory structures called "lateral line analogs" -- rows of sensors in the skin running the length of the animal, that are apparently used to detect minute motions of the water, similar to the way the lateral line system of fish works. These may allow them to detect the motions of predators and prey in the water around them, and possibly pressure waves of sound as well.

Common cuttlefish frequently rest on the bottom of the ocean, where their camouflage helps them avoid predators. They move to catch prey, flee from predators, or interact with other cuttlefish.

The common cuttlefish is entirely carnivorous, feeding on small mollusks, shrimp, crabs, other crustaceans, and other cuttlefish which it catches with its tentacles. Some will also eat fish. Once captured, its prey is paralyzed by poisonous saliva or crushed by the strong beak. When hunting, cuttlefish often blow water over the sandy areas to expose small crabs or shrimp.

Cuttlefish are eaten by sharks, fish, other cuttlefish, rays, ocean pike, eel, dolphin, seals, marine birds, and humans.

The common cuttlefish has remarkable powers of camouflage, it can change the color, pattern, and texture of its skin to match its surroundings.

There are no negative effects of cuttlefish on humans.

The cuttlefish is economically important for several reasons. Its meat is eaten, some medicines are derived from it, and the cuttlebone is used as a treat and nutritional supplement for caged birds. Cuttlefish are imported for food whole or as fillets.

This cuttlefish is also useful for research in several fields. Their highly developed brains make them interesting subjects for psychological and behavioral studies and their well-developed eyes are often substituted for vertebrate eyes in experiments. Since they share no vertebrate ancestors, this eye development illustrates a classical example of convergent evolution.

Sepia officinalis has no special conservation status nor do any other members of its genus. However, there is some pressure to add the giant cuttlefish of Australia to the endangered species list. With the consumption and export of cuttlefish on the rise, increased fishing pressures may adversely affect populations to the point that they may become endangered, but, as of yet, this has not happened.

Cephalopods are an ancient group that appeared some time in the late Cambrian several million years before the first primitive fish began swimming in the ocean. The coleoid cephalopods (cuttlefish, squid, and octopi) arose from their shelled ancestors during the late Devonian period. Diversification occurred during the Mesozoic, with substantial radiation during the Tertiary period.

Historically, cuttlefish ink has been used for both writing and in art.