Cuttlefish have large, W-shaped pupils, eight arms, and two tentacles furnished with denticulated suckers, with which they secure their prey.

[2] 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.

[5][6][7] The earliest fossils of cuttlefish are from the end of the Cretaceous period,[8][9] represented by Ceratisepia from the Late Maastrichtian Maastricht Formation of the Netherlands.

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.

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.

Ocean acidification, however, caused largely by higher levels of carbon dioxide emitted into the atmosphere, is cited as a potential threat.

[16] Some studies suggest that ocean acidification does not impair normal embryonic development, survival rates or body size.

[17] The pores provide it with buoyancy, which the cuttlefish regulates by changing the gas-to-liquid ratio in the chambered cuttlebone via the ventral siphuncle.

[27] Though the mantle cavity is used for jet propulsion, the main parts of the body that are used for basic mobility are the fins, which can maneuver the cuttlefish in all directions.

[30] Like other marine mollusks, cuttlefish have ink stores that are used for chemical deterrence, phagomimicry, sensory distraction, and evasion when attacked.

[31] Its composition results in a dark colored ink, rich in ammonium salts and amino acids that may have a role in phagomimicry defenses.

[citation needed] A common gene between cuttlefish and almost all other cephalopods allows them to produce venom, excreting it through their beak to help kill their prey.

[34] Additionally, the muscles of the flamboyant cuttlefish (Metasepia pfefferi) contain a highly toxic, unidentified compound[2] as lethal as the venom of fellow cephalopod, the blue-ringed octopus.

Sleep is a state of immobility characterized by being rapidly reversible, homeostatically controlled, and increasing an organism's arousal threshold.

[42] Additionally, cuttlefish unable to win in a direct confrontation with a guard male have been observed employing several other tactics to acquire a mate.

[49] The cuttlefish's wide pupil may accentuate chromatic aberration, allowing it to perceive color by focusing specific wavelengths onto the retina.

[54][55] The chromatophores are sacs containing hundreds of thousands of pigment granules and a large membrane that is folded when retracted.

The cuttlefish can control the contraction and relaxation of the muscles around individual chromatophores, thereby opening or closing the elastic sacs and allowing different levels of pigment to be exposed.

[46] Furthermore, the chromatophores contain luminescent protein nanostructures in which tethered pigment granules modify light through absorbance, reflection, and fluorescence between 650 and 720 nm.

[56][58][59] Retracting the chromatophores reveals the iridophores and leucophores beneath them, thereby allowing cuttlefish to use another modality of visual signalling brought about by structural coloration.

[60][61][59] Leucophores, usually located deeper in the skin than iridophores, are also structural reflectors using crystalline purines, often guanine, to reflect light.

Leucophores assist in camouflage by providing light areas during background matching (e.g. by resembling light-colored objects in the environment) and disruptive coloration (by making the body appear to be composed of high-contrasting patches).

[60] The reflectance spectra of cuttlefish patterns and several natural substrates (stipple, mottle, disruptive) can be measured using an optic spectrometer.

This indicates they are able to discriminate same-sex conspecifics, even when human observers are unable to discern the sex of a cuttlefish in the absence of sexual dimorphism.

[66] One dynamic pattern shown by cuttlefish is dark mottled waves apparently repeatedly moving down the body of the animals.

In the common cuttlefish, this is primarily observed during hunting, and is thought to communicate to potential prey – "stop and watch me"[46] – which some[who?]

In the Qing Dynasty manual of Chinese gastronomy, the Suiyuan shidan, the roe of the cuttlefish, is considered a difficult-to-prepare, but sought-after delicacy.

Catalan cuisine, especially that of the coastal regions, uses cuttlefish and squid ink in a variety of tapas and dishes such as arròs negre.

To extract the sepia pigment from a cuttlefish (or squid), the ink sac is removed and dried then dissolved in a dilute alkali.

[71][72][73] Research into replicating biological color-changing has led to engineering artificial chromatophores out of small devices known as dielectric elastomer actuators.