Cephalopod ink
Encyclopedia
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 species of octopus
belonging to the suborder
Cirrina, are able to release ink.
The ink is released from the ink sac
s (located between the gill
s) and is dispersed more widely by accompanying its release with a jet of water from the funnel. Its dark color 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 brown (see Use by humans).
A number of other aquatic molluscs have evolved similar responses to attack, including the gastropod clade known as sea hare
s. This is an example of convergent evolution
.
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 color (blanch) in conjunction with these releases. The pseudomorphs are roughly the same volume and look similar to the cephalopod that released them, and many predators have been observed attacking them mistakenly, allowing the cephalopod to escape (this behavior is often referred to as the ‘Blanch-Ink-Jet Maneuver’).
Furthermore, green turtle hatchlings (Chelonia mydas) that have been observed mistakenly attacking pseudomorphs released by Octopus bocki have subsequently ignored conspecific
octopuses.
However, many cephalopod predators (for instance moray eel
s) have advanced chemosensor
y 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 ‘smokescreen;’ 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 snail
s or crab
s approaching their eggs
.
and mucus
. It can also contain, among other things, tyrosinase
, dopamine
and L-DOPA, and small amounts of amino acid
s, including taurine, aspartic acid
, glutamic acid
, alanine
and lysine
.
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 fishmonger
s 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 cell
s, including tumor cells
.
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
, usually as an escape mechanism. All cephalopods, with the exception of the Nautilidae and the species of octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
belonging to the suborder
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Cirrina, are able to release ink.
The ink is released from the ink sac
Ink sac
With the exception of nocturnal and very deep water cephalopods, all coeloids which dwell in light conditions have an ink sac, which can be used to expel a cloud of dark ink to confuse predators. This sac is a muscular bag which originated as an extension of the hind gut...
s (located between the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s) and is dispersed more widely by accompanying its release with a jet of water from the funnel. Its dark color is caused by its main constituent, melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
. Each species of cephalopod produces slightly differently coloured inks; generally, octopuses produce black ink, squid ink is blue-black and cuttlefish ink is brown (see Use by humans).
A number of other aquatic molluscs have evolved similar responses to attack, including the gastropod clade known as sea hare
Sea hare
The clade Aplysiomorpha, commonly known as Sea hares or Sea Bags , are medium-sized to very large Opisthobranchia with a soft internal shell made of protein...
s. This is an example of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
.
Inking behaviours
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 smokescreen) which 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
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
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 color (blanch) in conjunction with these releases. The pseudomorphs are roughly the same volume and look similar to the cephalopod that released them, and many predators have been observed attacking them mistakenly, allowing the cephalopod to escape (this behavior is often referred to as the ‘Blanch-Ink-Jet Maneuver’).
Furthermore, green turtle hatchlings (Chelonia mydas) that have been observed mistakenly attacking pseudomorphs released by Octopus bocki have subsequently ignored conspecific
Conspecificity
Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....
octopuses.
However, many cephalopod predators (for instance moray eel
Moray eel
Moray eels are cosmopolitan eels of the family Muraenidae. The approximately 200 species in 15 genera are almost exclusively marine, but several species are regularly seen in brackish water and a few, for example the freshwater moray can sometimes be found in freshwater...
s) have advanced chemosensor
Chemosensor
A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment.- Classes :...
y systems, and some anecdotal evidence suggests that compounds such as tyrosinase
Tyrosinase
Tyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
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 ‘smokescreen;’ 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 snail
Gastropoda
The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to quite large...
s or crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s approaching their eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
.
Chemical composition
Cephalopod ink contains a number of chemicals in a variety of different concentrations, depending on the species. However, its main constituents are melaninMelanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
and mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
. It can also contain, among other things, tyrosinase
Tyrosinase
Tyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
, dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
and L-DOPA, and small amounts of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s, including taurine, aspartic acid
Aspartic acid
Aspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...
, glutamic acid
Glutamic acid
Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
, alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
and lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
.
Use by humans
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...
; indeed, the Greek
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
name for cuttlefish, and the taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
name of a cuttlefish genus, Sepia
Sepia (genus)
Sepia is a genus of cuttlefish in the family Sepiidae encompassing some of the best known and most common species. The cuttlebone is relatively ellipsoid in shape...
, is associated with the brown colour of cuttlefish ink (for more information, see sepia
Sepia (color)
Sepia is a dark brown-grey color, named after the rich brown pigment derived from the ink sac of the common cuttlefish Sepia.The word sepia is the Latinized form of the Greek σηπία, sēpía, cuttlefish.-Sepia in human culture:...
). Modern use of cephalopod ink is generally limited to cooking
Cooking
Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...
, where it is used as a food colouring and flavouring, for example in pasta
Pasta
Pasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...
and sauces. For this purpose it is generally obtainable from fishmonger
Fishmonger
A fishmonger is someone who sells fish and seafood...
s 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 cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s, including tumor cells
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
.
See also
- CephalopodCephalopodA cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
- OctopusOctopusThe octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
- SquidSquidSquid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
- CuttlefishCuttlefishCuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
- Inkfish