In consequence, they may prefer to hunt the prey they saw before hatching. The cuttlefish's eyes are thought to be fully developed before birth, and they start observing their surroundings while still in the egg. They are capable of using stereopsis, enabling them to discern depth/distance because their brain calculates the input from both eyes. Unlike the vertebrate eye, no blind spot exists, because the optic nerve is positioned behind the retina. The eye changes focus by shifting the position of the entire lens with respect to the retina, instead of reshaping the lens as in mammals. They have two spots of concentrated sensor cells on their retinas (known as foveae), one to look more forward, and one to look more backward. Although cuttlefish cannot see color, they can perceive the polarization of light, which enhances their perception of contrast. The cuttlefish pupil is a smoothly curving W-shape. Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The organogenesis and the final structure of the cephalopod eye fundamentally differ from those of vertebrates such as humans. Anatomy and physiology Visual system Ĭuttlefish, like other cephalopods, have sophisticated eyes. Ocean acidification, however, caused largely by higher levels of carbon dioxide emitted into the atmosphere, is cited as a potential threat. This means that while some over-exploitation of the marine animal has occurred in some regions due to large-scale commercial fishing, their wide geographic range prevents them from being too threatened. The cuttlefish is listed under the Red List category of "least concern" by the IUCN Red List of Threatened Species. They are found in sublittoral depths, between the low tide line and the edge of the continental shelf, to about 180 m (600 ft). The common cuttlefish ( Sepia officinalis), is found in the Mediterranean, North and Baltic seas, although populations may occur as far south as South Africa. By the time the family evolved, ostensibly in the Old World, the North Atlantic possibly had become too cold and deep for these warm-water species to cross. They have an unusual biogeographic pattern they are present along the coasts of East and South Asia, Western Europe, and the Mediterranean, as well as all coasts of Africa and Australia, but are totally absent from the Americas. They are mostly shallow-water animals, although they are known to go to depths of about 600 m (2,000 ft). The family Sepiidae, which contains all cuttlefish, inhabits tropical and temperate ocean waters. The word for it in both Greek and Latin, sepia, now refers to the reddish-brown color sepia in English. The Greco-Roman world valued the cuttlefish as a source of the unique brown pigment the creature releases from its siphon when it is alarmed. The "cuttle" in cuttlefish comes from the Old English name for the species, cudele, which may be cognate with the Old Norse koddi (cushion) and the Middle Low German Kudel (rag). Cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates. Studies are said to indicate cuttlefish to be among the most intelligent invertebrates. The typical life expectancy of a cuttlefish is about 1–2 years. Their predators include dolphins, sharks, fish, seals, seabirds, and other cuttlefish. Ĭuttlefish eat small molluscs, crabs, shrimp, fish, octopus, worms, and other cuttlefish. They generally range in size from 15 to 25 cm (6 to 10 in), with the largest species, the giant cuttlefish ( Sepia apama), reaching 50 cm (20 in) in mantle length and over 10.5 kg (23 lb) in mass. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of buoyancy.Ĭuttlefish have large, W-shaped pupils, eight arms, and two tentacles furnished with denticulated suckers, with which they secure their prey. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. ![]() ![]() The giant cuttlefish ( Sepia apama), above, is the largest speciesĬuttlefish or cuttles are marine molluscs of the order Sepiida.
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