Cephalopod ink - wikipedia Cephalopod ink Ventral view of the viscera of Chtenopteryx sicula, showing the location of the ink sac Cephalopod ink is a dark pigment released into water by most species of cephalopod, usually as an escape mechanism. All cephalopods, with the exception of the Nautilidae and the Cirrina ( deep - sea octopuses ), are able to release ink. The ink is released from the ink sacs ( located between the gills ) and is dispersed more widely when its release is accompanied by a jet of water from the siphon. Its dark colour is caused by its main constituent, melanin. Each species of cephalopod produces slightly differently coloured inks ; generally, octopuses produce black ink, squid ink is blue - black, and cuttlefish ink is a shade of brown. A number of other aquatic molluscs have similar responses to attack, including the gastropod clade known as sea hares. Contents 1 Inking behaviours 2 Physical properties 3 Chemical composition 4 Protective mechanisms 5 Use by humans 6 References 7 External links Inking behaviours I was much interested, on several occasions, by watching the habits of an Octopus or cuttle - fish... they darted tail first, with the rapidity of an arrow, from one side of the pool to the other, at the same instant discolouring the water with a dark chestnut - brown ink. Charles Darwin, The Voyage of the Beagle Two distinct behaviours have been observed in inking cephalopods. The first is the release of large amounts of ink into the water by the cephalopod in order to create a dark, diffuse cloud ( much like a smoke screen ) that can obscure the predator 's view, allowing the cephalopod to make a rapid retreat by jetting away. The second response to a predator is to release pseudomorphs ( `` false bodies '' ), smaller clouds of ink with a greater mucus content, which allows them to hold their shape for longer. These are expelled slightly away from the cephalopod in question, which will often release several pseudomorphs and change colour ( blanch ) in conjunction with these releases. The pseudomorphs are roughly the same volume as and look similar to the cephalopod that released them, and many predators have been observed attacking them mistakenly, allowing the cephalopod to escape ( this behaviour is often referred to as the `` blanch - ink - jet manoeuvre '' ). Furthermore, green turtle ( Chelonia mydas ) hatchlings that have been observed mistakenly attacking pseudomorphs released by Octopus bocki have subsequently ignored conspecific octopuses. However, many cephalopod predators ( for instance moray eels ) have advanced chemosensory systems, and some anecdotal evidence suggests that compounds ( such as tyrosinase ) found in cephalopod ink can irritate, numb or even deactivate such apparatus. Unfortunately, few controlled experiments have been conducted to substantiate this. Cephalopod ink is nonetheless generally thought to be more sophisticated than a simple `` smoke screen '' ; the ink of a number of squid and cuttlefish has been shown to function as a conspecific chemical alarm. Octopuses have also been observed squirting ink at snails or crabs approaching their eggs. Numerous cuttlefish species add a coat of ink to their eggs, presumably to camouflage them from potential predators. Physical properties This section needs expansion with : examples of other inks besides that of the common cuttlefish, and comparisons between them. You can help by adding to it. ( July 2018 ) Sepia officinalis ink forms a polidisperse suspension composed by spheric particles with a size between 80 and 150 nm ( measured by TRPS and SEM ). The particles have a density of 1.27 g cm, which may be due to the amount of metals that has in its composition ( 4.7 % in weight ). Chemical composition Cephalopod ink contains a number of chemicals in a variety of different concentrations, depending on the species. However, its main constituents are melanin and mucus. It can also contain, among other things, tyrosinase, dopamine and L - DOPA, as well as small amounts of free amino acids, including taurine, aspartic acid, glutamic acid, alanine and lysine. Protective mechanisms Cephalopod inking in the sea hare Aplysia californica provides protection from spiny lobsters, a major predator of sea hares, by means of three mechanisms : chemical deterrence, sensory disruption, and phagomimicry. The typical defence response of the sea hare to a predator is the release of chemicals such as free amino acids, ink from the ink gland and opaline from the opaline gland. Chemical deterrence involves the release of toxic chemicals that are noxious to predators and rapidly dissuades them from feeding. Ink creates a dark, diffuse cloud in the water that disrupts the sensory perception of the predator by acting as a smoke screen and as a decoy. The opaline, which affects the senses dealing with feeding, causes the predator to instinctively attack the cloud of chemicals as if it were indeed food. Use by humans Arròs negre owes its dark colour to squid ink Cephalopod ink has, as its name suggests, been used in the past as ink ; indeed, the Greek name for cuttlefish, and the taxonomic name of a cuttlefish genus, Sepia, is associated with the brown colour of cuttlefish ink ( for more information, see sepia ). Modern use of cephalopod ink is generally limited to cooking, where it is used as a food colouring and flavouring, for example in pasta and sauces. For this purpose it is generally obtainable from fishmongers or gourmet food suppliers. The ink is extracted from the ink sacs during preparation of the dead cephalopod, usually squid, and therefore contains no mucus. Recent studies have shown that cephalopod ink is toxic to some cells, including tumor cells. References Jump up ^ Roger T. Hanlon, John B. Messenger : Cephalopod Behaviour, page 2. Cambridge University Press, 1999, ISBN 0 - 521 - 64583 - 2 Jump up ^ Roy L. Caldwell ( 2005 ), `` An Observation of Inking Behavior Protecting Adult Octopus bocki from Predation by Green Turtle ( Chelonia mydas ) Hatchlings '' http://muse.jhu.edu/journals/pacific_science/v059/59.1caldwell.pdf Jump up ^ G.E. MacGinitie, N. MacGinitie ( 1968 ) Natural History of Marine Animals, Pages 395 - 397, 2nd ed. McGraw - Hill, New York. ^ Jump up to : Charles D. Derby ( 2007 ), `` Escape by Inking and Secreting : Marine Molluscs Avoid Predators Through a Rich Array of Chemicals and Mechanisms '' http://www.biolbull.org/cgi/reprint/213/3/274.pdf Jump up ^ Roper, Clyde F.E. ; Jereb, P ( 2005 ). Cephalopods of the World : Chambered nautiluses and sepioids ( Nautilidae, Sepiidae, Sepiolidae, Sepiadariidae, Idiosepiidae, and Spirulidae ). Rome : Food and Agriculture Organization. p. 8. Jump up ^ Soto - Gómez, Diego ; Pérez - Rodríguez, Paula ; López - Periago, J. Eugenio ; Paradelo, Marcos. `` Sepia ink as a surrogate for colloid transport tests in porous media ''. Journal of Contaminant Hydrology. 191 : 88 -- 98. doi : 10.1016 / j. jconhyd. 2016.05. 005. Jump up ^ http://nationalzoo.si.edu/Animals/Invertebrates/Facts/cephalopods/inking.cfm ^ Jump up to : Derby, Charles D. ; Kicklighter, Cynthia E. ; Johnson, P.M. & Xu Zhang ( 29 March 2007 ). `` Chemical Composition of Inks of Diverse Marine Molluscs Suggests Convergent Chemical Defenses '' ( PDF ). Journal of Chemical Ecology. 2007 ( 33 ) : 1105 -- 1113. doi : 10.1007 / s10886 - 007 - 9279 - 0. Archived from the original ( PDF ) on 15 November 2009. Retrieved 9 May 2015. Jump up ^ Inman, Mason ( 29 March 2005 ). `` Sea Hares Lose Their Lunch ''. Sciencemag.org. Retrieved 10 May 2015. External links Book : Cephalopoda An article on harvesting squid ink hide Cephalopod anatomy Shell Shell types External shells : Ammonoid shell Argonautid eggcase Nautiloid shell Orthocone Internal shells : Belemnoid guard Cirrate shell Cuttlebone Gladius ( pen ) Spirula shell Stylet External features Aperture Apex Callus Lirae Periostracum Sculpture Spire Sutures Umbilicus Internal features Body chamber Camerae Nacre Phragmocone Septa Siphuncle Whorls Mantle and funnel External anatomy Dermal structures Fins ( wings ) Flotation devices ( `` secondary fins '' ) Funnel -- mantle locking apparatus Tail Internal anatomy Branchial hearts Ctenidia ( gills ) Hepatopancreas ( digestive gland ) Ink sac and ink Needham 's sac Nephridia ( `` kidneys '' ) Nidamental glands Osphradium Pericardial glands Head and limbs Brachial crown Arms Hectocotylus Tentacles Carpus Dactylus Manus Suckers and hooks Buccal region Aptychus Beak Odontophore Radula Spadix and antispadix Occipital region Nuchal crest ( occipital crest ) Nuchal folds ( occipital folds ) Occipital membrane Olfactory organ Nuchal organ Other parts Eyes Statocysts General Chromatophores Photophores Nervous system Squid giant axon Squid giant synapse Developmental stages : Spawn → Paralarva ( Doratopsis stage ) → Juvenile → Subadult → Adult Egg fossils Protoconch ( embryonic shell ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Cephalopod_ink&oldid=849297188 '' Categories : Antipredator adaptations Teuthology Mollusc products Hidden categories : All articles with unsourced statements Articles with unsourced statements from May 2015 Articles to be expanded from July 2018 All articles to be expanded Talk Contents About Wikipedia Español Français Galego 한국어 Italiano Magyar 日本 語 Polski Edit links This page was last edited on 8 July 2018, at 00 : 45 ( UTC ). 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Question: where is the ink located in a squid
Answer: ink sacs