cuttlefish
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Cuttlefish or cuttles are
marine Marine is an adjective meaning of or pertaining to the sea or ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is es ...

molluscs
of the
order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the habit of achieving a ...
Sepiida. They belong to the
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
Cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symme ...
a, which also includes
squid Squid are cephalopod A cephalopod is any member of the mollusca Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, ext ...

squid
,
octopus Octopus (pl. octopuses, see below for variants) relates to approximately 300 species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodi ...

octopus
es, and
nautilus The nautilus (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of th ...

nautilus
es. Cuttlefish have a unique internal
shell Shell may refer to: Architecture and design * Shell (structure)A shell is a type of structural element which is characterized by its geometry, being a three-dimensional solid whose thickness is very small when compared with other dimensions, and i ...

shell
, the
cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family In human society, family (from la, familia) is a group of people related either by consanguinity ...

cuttlebone
, which is used for control of
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
. Cuttlefish have large, W-shaped
pupil The pupil is a black hole located in the center of the Iris (anatomy), iris of the Human eye, eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing C ...

pupil
s, eight
arm In human anatomy, the arm is the part of the upper limb The upper Limb (anatomy), limbs or upper extremities are the forelimbs of an upright posture, upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and incl ...
s, and two
tentacle with 2 tentacles and 8 arms In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the anatomy, structure, emb ...

tentacle
s furnished with denticulated suckers, with which they secure their prey. They generally range in size from , with the largest species, ''
Sepia apama ''Sepia apama'', also known as the giant cuttlefish and Australian giant cuttlefish, is the world's largest cuttlefish Cuttlefish or cuttles are marine molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arth ...

Sepia apama
'', reaching in mantle length and over in mass. Cuttlefish eat small molluscs, crabs, shrimp, fish, octopus, worms, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds, and other cuttlefish. The typical life expectancy of a cuttlefish is about 1–2 years. Studies are said to indicate cuttlefish to be among the most intelligent
invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the subphylum vertebrate, Vertebrata. Familiar example ...
s.NOVA, 2007. Cuttlefish: Kings of Camouflage.
(television program) NOVA, PBS, April 3, 2007.
Cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates. The "cuttle" in cuttlefish comes from the
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventu ...
name for the species, ''cudele'', which may be cognate with the
Old Norse Old Norse, Old Nordic, or Old Scandinavian is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and th ...
''koddi'' (cushion) and the
Middle Low German ''Der Keyserliken Stadt Lübeck Christlike Ordeninge/ tho denste dem hilgen Evangelio/ Christliker leve/ tucht/ frede unde enicheyt/ vor de yöget yn eyner guden Schole tho lerende. Unde de Kercken denere und rechten armen Christlick tho vorsorge ...
''Kudel'' (rag). The
Greco-Roman world Roman Theatre of Mérida, Spain. The term "Greco-Roman world" (also "Greco-Roman culture" or ; spelled Graeco-Roman in the Commonwealth), as understood by modern scholars and writers, refers to geographical regions and countries that cultura ...
valued the cuttlefish as a source of the unique brown
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compound , CH4; is among the simplest organic compou ...
the creature releases from its
siphon A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an ...
when it is alarmed. The word for it in both
Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of 2018; Athens is ...
and
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...
, ''sepia'', now refers to the reddish-brown color in English.


Fossil record

The earliest fossils of cuttlefish are from the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions ...
period. represented by '' Ceratisepia'' from the Late
Maastrichtian The Maastrichtian () is, in the ICS geologic timescale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologist ...
-
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era ...
. Whether the earlier ''
Trachyteuthis ''Trachyteuthis'' is a genus of fossil cephalopod, comprising five species: ''T. hastiformis'', ''T. latipinnis'', ''T. nusplingensis'', ''T. teudopsiformis'', ''T. covacevichi'' and ''T. chilensis''. Taxonomy The Taxonomy (biology), taxonomic ...
'' is assigned to this order, or to the
Octopodiformes Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopus Octopus (pl. octopuses, see below for variants) relates to approximately 300 species In biology, a species is the basic unit of biological classificat ...
, remains unclear.


Range and habitat

The family Sepiidae, which contains all cuttlefish, inhabits tropical and temperate ocean waters. They are mostly shallow-water animals, although they are known to go to depths of about . 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. 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. The common cuttlefish (''Sepia officinalis''), is found in the Mediterranean, North and Baltic seas, although populations may occur as far south as South Africa. They are found in
sublittoral The littoral zone or nearshore is the part of a sea, lake A lake is an area filled with water, localized in a basin, surrounded by land, apart from any river A river is a natural flowing watercourse, usually freshwater, flowing ...
depths, between the low tide line and the edge of the continental shelf, to about . The cuttlefish is listed under the Red List category of "least concern" by the IUCN Red List of Threatened Species. 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.


Anatomy and physiology


Visual system

Cuttlefish, like other cephalopods, have sophisticated eyes. The
organogenesis Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In ma ...
and the final structure of the
cephalopod eye Cephalopods A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symmetry, bilatera ...
fundamentally differ from those of
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...

vertebrate
s such as humans. Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of
convergent evolution Convergent evolution is the independent evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expre ...
. The cuttlefish pupil is a smoothly curving W-shape. Although cuttlefish cannot see color, they can perceive the polarization of light, which enhances their perception of contrast. They have two spots of concentrated sensor cells on their
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a Focus (optics), focused two-dimensional image of the visual world on ...

retina
s (known as foveae), one to look more forward, and one to look more backward. 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. Unlike the vertebrate eye, no blind spot exists, because the
optic nerve The optic nerve, also known as cranial nerve II, or simply as CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the sev ...

optic nerve
is positioned behind the retina. They are capable of using stereopsis, enabling them to discern depth/distance because their brain calculates the input from both eyes. The cuttlefish's eyes are thought to be fully developed before birth, and they start observing their surroundings while still in the egg. In consequence, they may prefer to hunt the prey they saw before hatching.


Circulatory system

The blood of a cuttlefish is an unusual shade of green-blue, because it uses the copper-containing protein haemocyanin to carry oxygen instead of the red, iron-containing protein
haemoglobin Hemoglobin or haemoglobin (spelling differences) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cel ...

haemoglobin
found in vertebrates' blood. The blood is pumped by three separate hearts: two
branchial heart 250px, Ventral view of the viscera of '' Chtenopteryx sicula'', showing the presence of the branchial hearts. Branchial hearts are accessory pumps that supplement the action of the systemic heart in a cephalopod's body. They are myogenic in nature. ...
s pump blood to the cuttlefish's pair of gills (one heart for each), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than that of most other animals because haemocyanin carries substantially less oxygen than haemoglobin. Unlike most other mollusks, cephalopods like cuttlefish have a closed circulatory system.


Cuttlebone

Cuttlefish possess an internal structure called the
cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family In human society, family (from la, familia) is a group of people related either by consanguinity ...

cuttlebone
, which is porous and is made of
aragonite Aragonite is a carbonate mineral Carbonate minerals are those minerals containing the carbonate ion, CO32−. Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspeite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otav ...

aragonite
. The pores provide it with
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
, which the cuttlefish regulates by changing the gas-to-liquid ratio in the chambered cuttlebone via the
ventral Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. Terms used generally derive from Latin or Greek language, Greek roots and used to describe something in its standard anatomical position. This ...

ventral
siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the l ...

siphuncle
. Each
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
' cuttlebone has a distinct shape, size, and pattern of ridges or texture. The cuttlebone is unique to cuttlefish, and is one of the features that distinguish them from their squid relatives.


Ink

Like other marine mollusks, cuttlefish have ink stores that are used for chemical deterrence, phagomimicry, sensory distraction, and evasion when attacked. Its composition results in a dark colored ink, rich in
ammonium The ammonium cation An ion () is an atom or molecule with a net electric charge, electrical charge. The charge of an electron is considered negative by convention and this charge is equal and opposite to charge of a proton, which is conside ...
salts and
amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, c ...
s that may have a role in phagomimicry defenses. The ink can be ejected to create a "
smoke screen A smoke screen is smoke released to mask the movement or location of military units such as infantry, tanks, aircraft, or ships. Smoke screens are commonly deployed either by a wikt:canister, canister (such as a Smoke grenade, grenade) or gener ...

smoke screen
" to hide the cuttlefish's escape, or it can be released as a
pseudomorph In mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifac ...
of similar size to the cuttlefish, acting as a decoy while the cuttlefish swims away. Human use of this substance is wide-ranged. A common use is in cooking with squid ink to darken and flavor rice and pasta. It adds a black tint and a sweet flavor to the food. In addition to food, cuttlefish ink can be used with plastics and staining of materials. The diverse composition of cuttlefish ink, and its deep complexity of colors, allows for dilution and modification of its color. Cuttlefish ink can be used to make noniridescent reds, blues, and greens, subsequently used for
biomimetic Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality ...
colors and materials.


Arms and mantle cavity

Cuttlefish have eight arms and two additional elongated tentacles that are used to grasp prey. The elongated tentacles and mantle cavity serve as defense mechanisms; when approached by a predator, the cuttlefish can suck water into its mantle cavity and spread its arms in order to appear larger than normal. 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.


Suckers and venom

The suckers of cuttlefish extend most of the length of their arms and along the distal portion of their tentacles. Like other cephalopods, cuttlefish have "taste-by-touch" sensitivity in their suckers, allowing them to discriminate among objects and water currents that they contact. Some cuttlefish are venomous. The genes for venom production are thought to be descended from a common ancestor. The muscles of the flamboyant cuttlefish ('' Metasepia pfefferi'') contain a highly toxic, unidentified compound as lethal as that of a fellow cephalopod, the
blue-ringed octopus Blue-ringed octopuses, comprising the genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...
.


Sleep-like behavior

Sleep Sleep is a Nature, naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement sle ...

Sleep
is a state of immobility characterized by being rapidly reversible, homeostatically controlled, and increasing an organism's arousal threshold. To date one cephalopod species, ''Octopus vulgaris'', has been shown to satisfy these criteria. Another species, ''Sepia officinalis'', satisfies two of the three criteria but has not yet been tested on the third (arousal threshold). Recent research shows that the sleep-like state in a common species of cuttlefish, ''Sepia officinalis'', shows predictable periods of rapid eye movement, arm twitching and rapid chromatophore changes.


Lifecycle

The lifespan of cuttlefish is typically around one to two years, depending on the species. They hatch from eggs fully developed, around long, reaching around the first two months. Before death, cuttlefish go through
senescence Ann Pouder (8 April 1807 – 10 July 1917) photographed on her 110th birthday. A heavily lined face is common in human senescence. Senescence () or biological aging is the gradual deterioration of Function (biology), functional characteristics. ...

senescence
when the cephalopod essentially deteriorates, or rots in place. Their eyesight begins to fail, which affects their ability to see, move, and hunt efficiently. Once this process begins, cuttlefish tend to not live long due to predation by other organisms. Captive breeders may euthanize dying cuttlefish by freezing them or using life-ending chemicals that are made by aquarium companies.


Reproduction

Cuttlefish start to actively mate at around five months of age. Male cuttlefish challenge one another for dominance and the best den during mating season. During this challenge, no direct contact is usually made. The animals threaten each other until one of them backs down and swims away. Eventually, the larger male cuttlefish mate with the females by grabbing them with their tentacles, turning the female so that the two animals are face-to-face, then using a specialized tentacle to insert sperm sacs into an opening near the female's mouth. As males can also use their funnels to flush others' sperm out of the female's pouch, the male then guards the female until she lays the eggs a few hours later. After laying her cluster of eggs, the female cuttlefish secretes ink on them making them look very similar to grapes. The egg case is produced through a complex capsule of the female accessory genital glands and the ink bag. On occasion, a large competitor arrives to threaten the male cuttlefish. In these instances, the male first attempts to intimidate the other male. If the competitor does not flee, the male eventually attacks it to force it away. The cuttlefish that can paralyze the other first, by forcing it near its mouth, wins the fight and the female. Since typically four or five (and sometimes as many as 10) males are available for every female, this behavior is inevitable.Mating Trick: Science Videos
Science News – ScienCentral
Cuttlefish are indeterminate growers, so smaller cuttlefish always have a chance of finding a mate the next year when they are bigger. Additionally, cuttlefish unable to win in a direct confrontation with a guard male have been observed employing several other tactics to acquire a mate. The most successful of these methods is camouflage; smaller cuttlefish use their camouflage abilities to disguise themselves as a female cuttlefish. Changing their body color, and even pretending to be holding an egg sack, disguised males are able to swim past the larger guard male and mate with the female.


Communication

Cephalopods are able to communicate visually using a diverse range of signals. To produce these signals, cephalopods can vary four types of communication element: chromatic (skin coloration), skin texture (e.g. rough or smooth), posture, and locomotion. Changes in body appearance such as these are sometimes called
polyphenism A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyph ...
. The common cuttlefish can display 34 chromatic, six textural, eight postural and six locomotor elements, whereas flamboyant cuttlefish use between 42 and 75 chromatic, 14 postural, and seven textural and locomotor elements. The
Caribbean reef squid The Caribbean reef squid (''Sepioteuthis sepioidea''), commonly called the reef squid, is a species of small, torpedo-shaped squid with undulating fins that extend nearly the entire length of the body, approximately in length. In 2001, marine bio ...
(''Sepioteuthis sepioidea'') is thought to have up to 35 distinct signalling states.


Chromatic

As with real chameleons, cuttlefish are sometimes referred to as the "
chameleons Chameleons or chamaeleons (family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to mai ...
of the sea" because of their ability to rapidly alter their skin color – this can occur within one second. Cuttlefish change color and pattern (including the
polarization Polarization or polarisation may refer to: In the physical sciences *Polarization (waves), the ability of waves to oscillate in more than one direction, in particular polarization of light, responsible for example for the glare-reducing effect of ...
of the reflected light waves), and the shape of the skin to communicate to other cuttlefish, to
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the battl ...

camouflage
themselves, and as a
deimatic display Deimatic behaviour or startle display means any pattern of bluffing behaviour in an animal that lacks strong defences, such as suddenly displaying conspicuous eyespots, to scare off or momentarily distract a predator, thus giving the prey animal ...
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. 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, as well as being able to influence the color of light as it reflects off their skin. 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. The cuttlefish's wide pupil attenuates chromatic aberration, allowing it to perceive color by focusing specific wavelengths onto the retina. The three broad categories of color patterns are uniform, mottle, and disruptive. Cuttlefish can display as many as 12 to 14 patterns, 13 of which have been categorized as seven "acute" (relatively brief) and six "chronic" (long-lasting) patterns. although other researchers suggest the patterns occur on a continuum. The color-changing ability of cuttlefish is due to multiple types of cells. These are arranged (from the skin's surface going deeper) as
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compound , CH4; is among the simplest organic compou ...
ed
chromatophore Chromatophores are cells that produce color, of which many types are pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Genera ...
s above a layer of reflective iridophores and below them, leucophores.


Chromatophores

The
chromatophores Chromatophores are cells that produce color, of which many types are Biological pigment, pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and ...
are sacs containing hundreds of thousands of pigment granules and a large membrane that is folded when retracted. Hundreds of muscles radiate from the chromatophore. These are under neural control and when they expand, they reveal the hue of the pigment contained in the sac. Cuttlefish have three types of chromatophore: yellow/orange (the uppermost layer), red, and brown/black (the deepest layer). 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. Furthermore, the chromatophores contain luminescent protein nanostructures in which tethered pigment granules modify light through absorbance, reflection, and
fluorescence light. Fluorescence is the emission of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defi ...

fluorescence
between 650 and 720 nm. For cephalopods in general, the hues of the pigment granules are relatively constant within a species, but can vary slightly between species. For example, the common cuttlefish and the opalescent inshore squid ('' Doryteuthis opalescens'') have yellow, red, and brown, the European common squid (''Alloteuthis subulata'') has yellow and red, and the common octopus has yellow, orange, red, brown, and black. In cuttlefish, activation of a chromatophore can expand its surface area by 500%. Up to 200 chromatophores per mm2 of skin may occur. In ''Loligo plei'', an expanded chromatophore may be up to 1.5 mm in diameter, but when retracted, it can measure as little as 0.1 mm.


Iridophores

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. Iridophores are structures that produce Iridescence, iridescent colors with a metallic sheen. They reflect light using plates of crystalline chemochromes made from guanine. When illuminated, they reflect iridescent colors because of the diffraction of light within the stacked plates. Orientation of the chemochromes determines the nature of the color observed. By using Biochrome, biochromes as colored filters, iridophores create an optical effect known as Tyndall effect, Tyndall or Rayleigh scattering, producing bright blue or blue-green colors. Iridophores vary in size, but are generally smaller than 1 mm. Squid at least are able to change their iridescence. This takes several seconds or minutes, and the mechanism is not understood. However, iridescence can also be altered by expanding and retracting the chromatophores above the iridophores. Because chromatophores are under direct neural control from the brain, this effect can be immediate. Cephalopod iridophores polarize light. Cephalopods have a rhabdomeric visual system which means they are visually sensitive to polarized light. Cuttlefish use their polarization vision when hunting for silvery fish (their scales polarize light). Female cuttlefish exhibit a greater number of polarized light displays than males and also alter their behavior when responding to polarized patterns. The use of polarized reflective patterns has led some to suggest that cephalopods may communicate intraspecifically in a mode that is "hidden" or "private" because many of their predators are insensitive to polarized light.


Leucophores

Leucophores, usually located deeper in the skin than iridophores, are also structural reflectors using crystalline Purine, purines, often guanine, to reflect light. Unlike iridophores, however, leucophores have more organized crystals that reduce diffraction. Given a source of white light, they produce a white shine, in red they produce red, and in blue they produce blue. 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). The reflectance spectra of cuttlefish patterns and several natural substrates (Stippling, stipple, mottle, Disruptive coloration, disruptive) can be measured using an optic spectrometer.


Intraspecific communication

Cuttlefish sometimes use their color patterns to signal future intent to other cuttlefish. For example, during agonistic encounters, male cuttlefish adopt a pattern called the intense zebra pattern, considered to be an Signalling theory#Honest signals, honest signal. If a male is intending to attack, it adopts a "dark face" change, otherwise, it remains pale. In at least one species, female cuttlefish react to their own reflection in a mirror and to other females by displaying a body pattern called "splotch". However, they do not use this display in response to males, inanimate objects, or prey. This indicates they are able to discriminate same-sex Biological specificity, conspecifics, even when human observers are unable to discern the sex of a cuttlefish in the absence of sexual dimorphism. Female cuttlefish signal their receptivity to mating using a display called precopulatory grey. Male cuttlefish sometimes use deception toward guarding males to mate with females. Small males hide their sexual dimorphism, sexually dimorphic fourth arms, change their skin pattern to the mottled appearance of females, and change the shape of their arms to mimic those of nonreceptive, egg-laying females. Displays on one side of a cuttlefish can be independent of the other side of the body; males can display courtship signals to females on one side while simultaneously showing female-like displays with the other side to stop rival males interfering with their courtship.


Interspecific communication

The deimatic display (a rapid change to black and white with dark ‘eyespots’ and contour, and spreading of the body and fins) is used to startle small fish that are unlikely to prey on the cuttlefish, but use the flamboyant display towards larger, more dangerous fish, and give no display at all to chemosensory predators such as crabs and dogfish. One dynamic pattern shown by cuttlefish is dark mottled waves apparently repeatedly moving down the body of the animals. This has been called the passing cloud pattern. In the common cuttlefish, this is primarily observed during hunting, and is thought to communicate to potential prey – “stop and watch me” – which some have interpreted as a type of "hypnosis".


Camouflage

Cuttlefish are able to rapidly change the color of their skin to match their surroundings and create chromatically complex patterns, despite their inability to perceive color, through some mechanism which is not completely understood. They have been seen to have the ability to assess their surroundings and match the color, contrast and texture of the substrate even in nearly total darkness. The color variations in the mimicked substrate and animal skin are similar. Depending on the species, the skin of cuttlefish responds to substrate changes in distinctive ways. By changing naturalistic backgrounds, the camouflage responses of different species can be measured. ''Sepia officinalis'' changes color to match the substrate by disruptive patterning (contrast to break up the outline), whereas ''Sepia pharaonis, S. pharaonis'' matches the substrate by blending in. Although camouflage is achieved in different ways, and in an absence of color vision, both species change their skin colors to match the substrate. Cuttlefish adapt their own camouflage pattern in ways that are specific for a particular habitat. An animal could settle in the sand and appear one way, with another animal a few feet away in a slightly different microhabitat, settled in algae for example, will be camouflaged quite differently. Cuttlefish are also able to change the texture of their skin. The skin contains bands of circular muscle which as they contract, push fluid up. These can be seen as little spikes, bumps, or flat blades. This can help with camouflage when the cuttlefish becomes texturally as well as chromatically similar to objects in its environment such as kelp or rocks.


Diet

While the preferred diet of cuttlefish is crabs and fish, they feed on small shrimp shortly after hatching. Cuttlefish use their camouflage to hunt and sneak up on their prey. They swim at the bottom, where shrimp and crabs are found, and shoot out a jet of water to uncover the prey buried in the sand. Then when the prey tries to escape, the cuttlefish open their eight arms and shoot out two long feeding tentacles to grab them. Each arm has a pad covered in suckers, which grabs and pulls prey toward its beak, paralyzing it with venom before eating it.Cuttlefish Basics
Tonmo.com (2003-02-12). Retrieved on 2011-09-18.
To achieve a hypnotic effect and stun prey before catching it, cuttlefish are also known to change color rapidly.


Taxonomy

Over 120
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
of cuttlefish are currently recognised, grouped into six Family (biology), families divided between two suborders. One suborder and three families are extinct. *Order Sepiida: cuttlefish **Suborder †Vasseuriina ***Family †Vasseuriidae ***Family †Belosepiellidae **Suborder Sepiina ***Family †Belosaepiidae ***Family Sepiadariidae ***Family Sepiidae ***Family Sepiolidae File:Sepia officinalis (aquarium).jpg, The common cuttlefish (''Sepia officinalis'') is the best-known cuttlefish species File:Hooded Cuttlefish.jpg, Hooded cuttlefish (''Sepia prashadi'') File:Seba molluscas.jpg, Engravings by the Dutch zoologist Albertus Seba, 1665–1736


Human uses


As food

Cuttlefish are caught for food in the Mediterranean, East Asia, the English Channel, and elsewhere. In East Asia, dried shredded squid, dried, shredded cuttlefish is a popular snack food. 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. Cuttlefish are quite popular in Europe. For example, in northeast Italy, they are used in ''risotto al nero di seppia'' (risotto with cuttlefish ink), also found in Croatia and Montenegro as ''crni rižot'' (black risotto). Catalan cuisine, especially that of the coastal regions, uses cuttlefish and squid ink in a variety of ''tapas'' and dishes such as ''arròs negre''. Breaded and deep-fried cuttlefish is a popular dish in Andalusia. In Portugal, cuttlefish is present in many popular dishes. ''Chocos com tinta'' (cuttlefish in black ink), for example, is grilled cuttlefish in a sauce of its own ink. Cuttlefish is also popular in the region of Setúbal, where it is served as deep-fried strips or in a variant of ''feijoada'', with white beans. Black pasta is often made using cuttlefish ink.


Sepia

Cuttlefish ink was formerly an important dye, called . To extract the sepia pigment from a cuttlefish (or squid), the ink sac is removed and dried then dissolved in a dilute alkali. The resulting solution is filtered to isolate the pigment, which is then precipitated with dilute hydrochloric acid. The isolated precipitate is the sepia pigment. It is relatively chemically inert, which contributes to its longevity. Today, artificial dyes have mostly replaced natural sepia.


Metal casting

Cuttlebone has been used since antiquity to make casts for metal. A model is pushed into the cuttlebone and removed, leaving an impression. Molten gold, silver or pewter can then be poured into the cast.


Smart clothing

Research into replicating biological color-changing has led to engineering artificial chromatophores out of small devices known as Dielectric elastomers, dielectric elastomer actuators. Engineers at the University of Bristol have engineered soft materials that mimic the color-changing skin of animals like cuttlefish, paving the way for "smart clothing" and camouflage applications.


Pets

Though cuttlefish are rarely kept as pets, due in part to their fairly short lifetimes, the most common to be kept are ''Sepia officinalis'' and ''Sepia bandensis''.Ceph Care , TONMO.com: The Octopus News Magazine Online
. TONMO.com. Retrieved on 2015-09-25.
Cuttlefish may fight or even eat each other if there is inadequate tank space for multiple individuals. Cuttlebone is given to parakeets and other cagebirds as a source of dietary calcium.


See also

*Cephalopod size


References


External links


YouTube video with examples of cuttlefish color and texture modulations
*
The new CEPHBASE within the Encyclopedia of Life (EOL)
{{Taxonbar, from=Q184479 Cuttlefish, Commercial molluscs Articles containing video clips Cenozoic cephalopods