Chromatophore and User:Lexein/AbleNET: Difference between pages

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[[Image:Zfishchroma.jpg|thumb|200px|[[Zebra Danio|zebrafish]] chromatophores mediate [[Camouflage#Natural_camouflage|background adaptation]] on exposure to dark (top) and light environments (bottom).]]

'''AbleNET''' is an [[Internet Relay Chat|IRC]] network. It was founded, May 2001, by [[AfterNET]] Co-Founder and long-time Admin Anthony Sanchez and several others from that network. The network was set up primarily as a chat network for friends, and as a response to growing disillusionment with the policies of some of the [[AfterNET]] administrators. Several users from AbleNET were involved in the creation of [[AfterNET]]; some even tracing their usage back to [[TheNET]] and [[InnerNET]].

'''Chromatophore''' is the collective term for [[pigment]] containing and light reflecting [[cell (biology)|cell]]s found in [[amphibian]]s, [[fish]], [[reptile]]s, [[crustacean]]s and [[cephalopod]]s. Derived from the [[neural crest]], chromatophores are largely responsible for generating skin and eye colour in [[poikilotherm]]ic animals. These cells are subclassed as xanthophores, erythrophores, iridophores, leucophores, melanophores and cyanophores according to their [[hue]] under white light. The translocation of pigment and reorientation of reflective plates within the cells are the mechanisms through which some species, notably [[chameleons]] and [[octopus]], can rapidly change colour. [[Mammal]]s and [[bird]]s have just one class of chromatophore-like cell type, the [[melanocyte]].

AbleNET is a small network with an average of 150-300 users online at any given time. The [[Undernet]]-compatible [[IRCu]] [[Daemon (computer software)|daemon]] software is used on the servers. [[IRC_Services|Channel services]] are provided using [[srvx]]; the user authentication service is named AuthServ and the channel service is named X.

== Classification ==

''Chromforo'' was first used to describe [[invertebrate]] pigment bearing cells in 1819 and the term ''chromatophore'' (Greek: ''khrōma'' = "colour", ''phoros'' = "bearing") later adopted as a name for the neural crest derived pigment bearing cells of [[cold blooded]] vertebrates and cephalopods (in contrast to the [[melanocyte|chromato-cyte]]s found in mammals and birds). By the 1960s, sufficient understanding of the structure and colour of chromatophores was available to sub-classify them according to appearance and, despite subsequent studies revealing the [[biochemical]] nature of the pigments within chromatophore types, this classification system persists.<ref name=Cytology> Bagnara JT. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=5337298&query_hl=1&itool=pubmed_docsum Cytology and cytophysiology of non-melanophore pigment cells.] ''Int Rev Cytol''. 1966; 20:173-205.</ref> While all chromatophores contain pigments or structural elements capable of reflecting light (except in [[mutant]] animals like [[albino]]s), not all pigment containing cells are chromatophores. [[Haem]], for example, is a biopigment responsible for the red appearance of blood. It is primarily found in [[erythrocyte]]s, which are generated in bone marrow and therefore not considered chromatophores.

AbleNET is noted for its distinct lack of [[IRCOp]]s, instead using various services to control the flow of network stability and activity. Additionally, the Network is noted for its high standards of access, regarding the limit of multiple connections and unverifiable "bots".

=== Xanthophores and erythrophores ===

Originally termed ''lipophores'' due to their fat-soluble content, chromatophores that contain large amounts of [[yellow]] [[pteridine]] pigments were renamed xanthophores and those with an excess of [[red]]/[[Orange (colour)|orange]] [[carotinoid]]s termed erythrophores. <ref name=Cytology>Bagnara JT. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=5337298&query_hl=1&itool=pubmed_docsum Cytology and cytophysiology of non-melanophore pigment cells.] ''Int Rev Cytol''. 1966; 20:173-205. </ref> Soon after, it was discovered that pterinosome and carotinoid [[Vesicle (biology)|vesicles]] are found within the same cell, and that the manifest colour depends on the ratio of red and yellow pigments. <ref name=Xiphophorus> Matsumoto J. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=5885426&query_hl=4&itool=pubmed_docsum Studies on fine structure and cytochemical properties of erythrophores in swordtail, ''Xiphophorus helleri''.] ''J Cell Biol''. 1965; 27:493-504. </ref> Thus the distinction between these chromatophore types is essentially arbitrary. The capacity to biosynthesise pteridines from [[guanosine triphosphate]] ''de novo'' is a feature common to most chromatophores, but xanthophores appear to have supplemental biochemical pathways that result in an excess accumulation of yellow pigment. In contrast, carotinoids are metabolised from the diet and transported to erythrophores. Thus normally green frogs reared on a diet of [[carotene]]-restricted [[Cricket (insect)|crickets]] display an erythrophore specific defect, resulting in a blue appearance.

The network can be reached using irc.ablenet.org.

[[Image:C Calyptratus female.jpg|thumb|left|260px|A [[veiled chameleon]], ''Chamaeleo calyptratus''. Structural green and blue colours are generated by overlaying chromatophore types to reflect filtered light. A process known as [[Rayleigh scattering]].]]

== Historical Timeline ==

=== Iridophores and leucophores ===

* May 2001, AbleNET is born and has served as a meeting place for chatters ever since.

Biochromes, such as pteridines and carotinoids, selectively absorb a part of the [[Optical spectrum|visual spectrum]] that makes up [[white]] incident light, while they let the other wavelengths pass and reach the eye of the observer. Not all colours are generated in this manner, however. Some, most notably blues and greens, are generated by the scattering, [[interference]] and diffusion of light by colourless crystalline structures called schemochromes.

* May 2003, with the looming threat of the [http://securityresponse.symantec.com/avcenter/venc/data/[e-mail] Fizzer Worm] AbleNET joins with a vast collection of [[IRC]] networks and news communities to form [http://www.irc-unity.org/ IRC-Unity]<ref>http://www.irc-unity.org/</ref>.

* December 2005, AbleNET becomes the first IRC Network to offer "blogging" to their community.

Iridophores are lower vertebrate pigment cells that reflect light using plates of crystalline [[guanine]] schemochromes.<ref name=intermedin> Taylor JD. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=5769930&query_hl=8&itool=pubmed_docsum The effects of intermedin on the ultrastructure of amphibian iridophores.] ''Gen Comp Endocrinol''. 1969; 12:405-16. </ref> When illuminated they generate [[Iridescence|iridescent]] colours due to the diffraction of light within the stacked plates. Orientation of the schemochrome determines the nature of the structural colour observed.<ref name=lizard> Morrison RL. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7792252&query_hl=12&itool=pubmed_docsum A transmission electron microscopic (TEM) method for determining structural colors reflected by lizard iridophores.] ''Pigment Cell Res''. 1995; 8:28-36.</ref> By using biochromes as filters, iridophores mediate an optical effect known as [[Tyndall effect|Tyndall]] or [[Rayleigh scattering]], producing bright [[blue]] or [[green]] colours that are not modified by the angle of vision.<ref name=fish> Fujii R. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11041206&query_hl=15&itool=pubmed_docsum The regulation of motile activity in fish chromatophores.] ''Pigment Cell Res''. 2000; 13:300-19.</ref> A related type of chromatophore, the leucophore, is found in some fish species. Like iridophores, they utilize crystalline [[purine]]s to reflect light, providing the bright [[white]] colour seen in some fish. As with xanthophores and erythrophores, the distinction between iridophores and leucophores in fish is not always obvious, but generally iridophores are considered to generate iridescent or [[metallic]] colours while leucophores produce structural white hues.<ref name=fish> Fujii R. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11041206&query_hl=15&itool=pubmed_docsum The regulation of motile activity in fish chromatophores.] ''Pigment Cell Res''. 2000; 13:300-19.</ref>

== NotesFounder ==

Anthony Sanchez has been using and administering IRC Networks since 1995, starting as an IRCop with InnerNET subsequently [[NewNET]] during it's founding year. Later he went on to Admin servers for [[TheNET]], [[AfterNET]] and finally AbleNET.

=== Melanophores ===

The most widely studied chromatophore, due both to its extensive taxonomic distribution and apparent colour, is the melanophore. [[Eumelanin]], the biochrome found in melanophores, is generated from [[tyrosine]] in a series of catalysed chemical reactions. The end product is a complex

Anthony was, coincidentally, the first to publish the story of the raid on and subsequent shutdown of the popular [[Lineage II]] private server, L2Extreme, on the AbleNET website.<ref>http://anthony.blogs.ablenet.org/l2extreme_fbi_shutdown</ref>

biopolymer containing units of dihydroxyindole and dihydroxyindole-2-carboxylic acid

with some [[pyrrole]] rings.<ref name=eumelanin> Ito S & Wakamatsu K. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12950732&query_hl=29&itool=pubmed_docsum Quantitative analysis of eumelanin and pheomelanin in humans, mice, and other animals: a comparative review.] ''Pigment Cell Res''. 2003; 16:523-31.</ref> This type of [[melanin]], when packaged in vesicles called melanosomes and distributed throughout the cell, appears [[black]] or dark [[brown]] due to its light absorbing qualities. The key enzyme in melanogenesis is [[tyrosinase]]. When this protein is defective, no melanin can be generated resulting in albinism.

In some amphibian species there are other pigments packaged alongside eumelanin. For example, a novel deep red coloured pigment called was identified in the melanophores of phyllomedusine [[frog]]s.<ref name=leaf> Bagnara JT ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=4748673&query_hl=31&itool=pubmed_docsum Color changes, unusual melanosomes, and a new pigment from leaf frogs.] ''Science''. 1973; 182:1034-5.</ref> This was subsequently identified as pterorhodin, a pterodine dimer that accumulates around eumelanin. While it is likely that other species have complex melanophore pigments, it is nevertheless true that the majority of melanophores studied to date contain eumelanin exclusively.

[[Image:Dendrobates pumilio.jpg|thumb|right|200px|''Dendrobates pumilio'', a [[poison dart frog]]. Some brightly coloured species have unusual chromatophores of unknown pigment composition.]]

=== Cyanophores ===

In 1995 it was demonstrated that the vibrant [[blue]] colours of [[mandarin fish]] are not structural in nature. Instead, a [[cyan]] biochrome of unknown chemical nature is responsible.<ref name=fish> Fujii R. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11041206&query_hl=15&itool=pubmed_docsum The regulation of motile activity in fish chromatophores.] ''Pigment Cell Res''. 2000; 13:300-19.</ref> This pigment, found within fibrous vesicles in at least two species callionymid fish, is highly unusual in the [[animal]] kingdom, as all other blue colourings thus far investigated are schemochromatic. Therefore a novel chromatophore type, the cyanophore, was proposed. Although cyanophores are unusual in their [[taxon]]omic restriction, there may be other unusual chromatophore types in lesser-studied fish and amphibians. Indeed, bright coloured chromatophores with undefined pigments have been observed in both [[poison dart frog]]s and [[glass frog]]s.<ref name=glass> Schwalm PA ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=860137&query_hl=27&itool=pubmed_docsum Infrared reflectance in leaf-sitting neotropical frogs.] ''Science''. 1977; 196:1225-7.</ref>

== Pigment translocation ==

Many species have the ability to translocate the pigment inside chromatophores, resulting in an apparent change in colour. This process, known as [[physiological]] colour change, is most widely studied in melanophores, as melanin is the darkest and most visible pigment. In most species with a relatively thin [[dermis]], the dermal melanophores tend to be flat and cover a large surface area. However, in animals with thick dermal layers, such as adult reptiles, dermal melanophores often form three-dimensional units with other chromatophores. These dermal chromatophore units (DCU) consist of an uppermost xanthophore or erythrophore layer, then an iridophore layer, and finally a basket-like melanophore layer with processes covering the iridophores.<ref name=DCU> Bagnara JT ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=5691979&query_hl=1&itool=pubmed_docsum The dermal chromatophore unit.] ''J Cell Biol''. 1968; 38:67-79.</ref>

Both types of dermal melanophores are extremely important in physiological colour change. Flat dermal melanophores will often overlay other chromatophores so when the pigment is dispersed throughout the cell the skin appears dark. When the pigment is aggregated towards the centre of the cell, the pigments in other chromatophores are exposed to light and thus the skin takes on their hue. Similarly, after melanin aggregation in DCUs, the skin appears green through xanthophore (yellow) filtering of scattered (blue) light from the iridophore layer. On the dispersion of melanin, the light is no longer scattered and the skin appears dark. As the other biochromatic chomatophores are also capable of pigment translocation, by making good use of the divisional effect animals with multiple chromatophore types can generate a spectacular array of skin colours.<ref name=goldfish> Palazzo RE ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2543509&query_hl=7&itool=pubmed_docsum Rearrangements of pterinosomes and cytoskeleton accompanying pigment dispersion in goldfish xanthophores.] ''Cell Motil Cytoskeleton''. 1989; 13:9-20.</ref>^,<ref name=crayfish> Porras MG ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14706537&query_hl=15&itool=pubmed_docsum Corazonin promotes tegumentary pigment migration in the crayfish ''Procambarus clarkii''.] ''Peptides''. 2003; 24:1581-9.</ref>

[[Image:melanophore.jpg|thumb|left|250px|A single [[Zebra Danio|zebrafish]] melanophore imaged by time lapse during pigment aggregation after treatment with [[melanin concentrating hormone]].]]

The control and mechanics of rapid pigment translocation has been well studied in a multitude of species, particularly amphibians and [[teleost]] fish. <ref name=Dynactin> Deacon SW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12566424&query_hl=25&itool=pubmed_docsum Dynactin is required for bidirectional organelle transport.] ''J Cell Biol''. 2003; 160:297-301.</ref>^,<ref name=fish> Fujii R. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11041206&query_hl=15&itool=pubmed_docsum The regulation of motile activity in fish chromatophores.] ''Pigment Cell Res''. 2000; 13:300-19.</ref> It has been demonstrated that the process can be under [[Hormone|hormonal]], [[neurotransmitter|neuronal]] control or both. Neurochemicals that are known to translocate pigment include [[noradrenaline]], via its α₂-[[adrenoceptor]] on the surface on melanophores.<ref name=noradrenaline> Aspengren S ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12519126&query_hl=30&itool=pubmed_docsum Noradrenaline- and melatonin-mediated regulation of pigment aggregation in fish melanophores.] ''Pigment Cell Res''. 2003; 16:59-64.</ref> The primary hormones involved in regulating translocation appear to be the [[melanocortin]]s, [[melatonin]] and [[melanin concentrating hormone]] (MCH), that are produced mainly in the [[pituitary]], [[pineal gland]] and [[hypothalamus]] respectively, though may also be generated in a [[paracrine]] fashion by peripheral tissues. At the surface of the melanophore these peptides have been shown to activate specific [[G protein coupled receptor]]s that, in turn, transduce the signal into the cell. Melanocortins result in the dispersion of pigment, while melatonin and MCH results in aggregation.<ref name=zebrafish> Logan DW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16704454&query_hl=4&itool=pubmed_docsum Regulation of pigmentation in zebrafish melanophores.] ''Pigment Cell Res''. 2006; 19:206-13.</ref>

Numerous melanocortin, MCH and melatonin receptors have been identified in fish <ref name=MCR1> Logan DW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12851332&query_hl=4&itool=pubmed_docsum Sequence characterization of teleost fish melanocortin receptors.] ''Ann N Y Acad Sci''. 2003; 994:319-30.</ref> and frogs,<ref name=Melatonin> Sugden D ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15357831&query_hl=8&itool=pubmed_docsum Melatonin, melatonin receptors and melanophores: a moving story.] ''Pigment Cell Res''. 2004; 17:454-60.</ref> including the [[orthologue]] of ''[[MC1R]]'',<ref name=MCR2> Logan DW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12620396&query_hl=4&itool=pubmed_docsum The structure and evolution of the melanocortin and MCH receptors in fish and mammals.] ''Genomics''. 2003; 81:184-91.</ref> a melanocortin receptor known to regulate [[skin colour|skin]] and [[hair colour]] in humans.<ref name=redhair> Valverde P ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7581459&query_hl=10&itool=pubmed_docsum Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans.] ''Nat Genet''. 1995; 11:328-30.</ref> Inside the cell, [[cyclic adenosine monophosphate]] (cAMP) has been shown to be an important [[second messenger]] of pigment translocation. Through a mechanism not yet fully understood, cAMP influences other proteins to drive [[Moving proteins|molecular motors]] carrying melanosomes along both [[microtubule]]s and [[microfilament]]s.<ref name=actin> Snider J ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15331778&query_hl=26&itool=pubmed_docsum Intracellular actin-based transport: how far you go depends on how often you switch.] ''Proc Natl Acad Sci USA''. 2004; 101:13204-9.</ref>^,<ref name=microtubule2> Rodionov VI ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9443917&query_hl=26&itool=pubmed_docsum Functional coordination of microtubule-based and actin-based motility in melanophores.] ''Curr Biol''. 1998; 8:165-8.</ref>^,<ref name=microtubule> Rodionov VI ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14588239&query_hl=26&itool=pubmed_docsum Switching between microtubule- and actin-based transport systems in melanophores is controlled by cAMP levels.] ''Curr Biol''. 2003; 13:1837-47.</ref>

== Background adaptation ==

Most fish, reptiles and amphibians animals undergo physiological colour change in response to a change in environment. Known as background adaptation, this most commonly manifests as a slight darkening or lightening of skin tone to approximately [[mimic]] the hue of the immediate environment, a type of [[camouflage]]. It has been demonstrated that the process is vision dependent (the animal needs to be able to see the environment to adapt to it),<ref name=vision> Neuhauss SC. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12486702&query_hl=36&itool=pubmed_docsum Behavioral genetic approaches to visual system development and function in zebrafish.] ''J Neurobiol''. 2003; 54:148-60.</ref> and that melanin translocation in melanophores is the primary mechanism for colour change.<ref name=zebrafish> Logan DW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16704454&query_hl=4&itool=pubmed_docsum Regulation of pigmentation in zebrafish melanophores.] ''Pigment Cell Res''. 2006; 19:206-13.</ref> Some animals, such as chameleons and [[anole]]s, have a highly evolved background adaptation response capable of generating different colours very rapidly. They have adapted this capability to change colour in response to temperature, mood, stress levels and social cues, rather than to simply mimic their environment.

[[Image:Neuralcrestroute.jpg|thumb|right|300px|[[Transverse]] [[Cross section (geometry)|section]] of a developing vertebrate [[torso|trunk]] showing the dosolateral (red) and ventromedial (blue) routes of chromatoblast migration.]]

== Development ==

During vertebrate [[embryonic development]], chromatophores are one of a number of cell types generated in the [[neural crest]], a paired strip of cells arising at the margins of the [[neural tube]]. These cells have the ability to migrate long distances, allowing chromatophores to populate many organs of the body, including the skin, eye, ear and brain. Leaving the neural crest in waves, chromatophores take either a dorsolateral route through the dermis, entering the [[ectoderm]] through small holes in the [[basal lamina]], or a ventromedial route between the [[somites]] and the neural tube. The exception to this are the melanophores of the retinal pigmented epithelium of the eye, these are not derived from the neural crest, instead an outpouching of the neural tube generates the [[optic cup]] which, in turn, forms the [[retina]].

When and how [[multipotent]] chromatophore precursor cells (called chromato''blasts'') develop into their daughter subtypes is an area of ongoing research. It is known in zebrafish embryos, for example, that by 3 days after [[fertilization]] each of the cell classes found in the adult fish - melanophores, xanthophores and iridophores - are already present. Studies using mutant fish have demonstrated that [[transcription factor]]s such as, ''kit'', ''[[SOX genes|sox10]]'' and ''[[Microphthalmia|mitf]]'' are important in controlling chromatophore differentiation.<ref name=development> Kelsh RN ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10985850&query_hl=17&itool=pubmed_docsum Genetic analysis of melanophore development in zebrafish embryos.] ''Dev Biol''. 2000; 225:277-93.</ref>

== Practical applications ==

In addition to [[basic research]] into better understanding of chromatophores themselves, the cells are used for applied research purposes. For example, zebrafish larvae are used to study how chromatophores undergo controlled proliferation and migration during embryogenesis to accurately generate the regular horizontal striped pattern in seen in adult fish.<ref name=development2> Kelsh RN. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15250934&query_hl=19&itool=pubmed_docsum Genetics and evolution of pigment patterns in fish.] ''Pigment Cell Res''. 2004; 17:326-36.</ref> This is seen as a useful [[Animal model|model]] system for understanding patterning in the [[evolutionary developmental biology]] field. Chromatophore biology has also been used to model human condition or disease, mainly [[melanoma]]. Recently the gene responsible for the melanophore-specific ''golden'' [[phenotype]] in zebrafish, ''[[SLC24A5|Slc24a5]]'', was shown to have a human equivalent that strongly corrolates with skin colour.<ref name=SLC24A5> Lamason RL ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed SLC24A5, a putative cation exchanger, affects pigmentation in zebrafish and humans.] ''Science''. 2005; 310:1782-6.</ref>

Chromatophores are also used as a [[Biomarker (medicine)|biomarker]] of blindness in poikilotherms, as animals with certain visual defects fail to background adapt to light environments. <ref name=vision> Neuhauss SC. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12486702&query_hl=36&itool=pubmed_docsum Behavioral genetic approaches to visual system development and function in zebrafish.] ''J Neurobiol''. 2003; 54:148-60.</ref>

Human [[homologue]]s of receptors that mediate pigment translocation in melanophores are thought to involved in processes such as [[appetite]] suppression and [[Sun tanning|tanning]], making them attractive targets for [[pharmaceutical|drugs]].<ref name=MCR2> Logan DW ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12620396&query_hl=4&itool=pubmed_docsum The structure and evolution of the melanocortin and MCH receptors in fish and mammals.] ''Genomics''. 2003; 81:184-91.</ref> Therefore pharmaceutical companies have developed a [[biological assay]] for rapidly identifying potential active compounds using melanophores from the [[African clawed frog]].<ref name=assay> Jayawickreme CK ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11033434&query_hl=15&itool=pubmed_docsum Use of a cell-based, lawn format assay to rapidly screen a 442,368 bead-based peptide library.] ''J Pharmacol Toxicol Methods''. 1999; 42:189-97.</ref> Other scientists have developed techniques for using melanophores as [[biosensor]]s,<ref name=sensor> Andersson TP ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15967358&query_hl=20&itool=pubmed_docsum Frog melanophores cultured on fluorescent microbeads: biomimic-based biosensing.] '' Biosens Bioelectron''. 2005; 21:111-20.</ref> and for rapid disease detection (based on the discovery that [[pertussis toxin]] blocks pigment aggregation in fish melanophores).<ref name=pertussis> Karlsson JO ''et al''. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1936946&query_hl=18&itool=pubmed_docsum The melanophore aggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough.] '' FEMS Microbiol Lett''. 1991; 66:169-75</ref> Potential [[military]] applications of chromatophore mediated colour changes have been proposed, mainly as a type of adaptive camouflage.<ref name=military> Lee I. [http://www.biron.usc.edu/~ianlee/index_files/thesis_ch5.pdf Nanotubes for noisy signal processing: Adaptive Camouflage] ''PhD Thesis''. 2005; University of Southern California</ref> However, currently this does not appear to have been realised.

[[Image:Euprymna scolopes1.jpg|thumb|left|260px|An adult ''Euprymna scolopes'', a species of [[sepiolid]] squid, displaying large melanophores, erthrophores and xanthophores.]]

== Cephalopod chromatophores ==

Most notable in brightly coloured [[squid]], [[cuttlefish]] and octopuses, cephalopods have complex multicellular 'organs' which they use to change colour rapidly. Each chromotophore unit is composed of a single chromatophore cell and numerous muscle, nerve, [[glial cell|glial]] and sheath cells.<ref name=cephalopod1> Cloney RA. & Florey E. [http://tolweb.org/tree/eukaryotes/animals/mollusca/cephalopoda/glossary/glossaryLichen/chromatophoreLichen/Chromatophore.html Ultrastructure of cephalopod chromatophore organs.] ''Zeits. für Zellforsch''. 1968; 89:250-280.</ref> Inside the chromatophore cell, pigment granules are inclosed in an elastic sac, called the cytoelastic sacculus. To change colour the animal distorts the sacculus form or size by muscular contraction, thus changing its translucency, reflectivity or opacity. This differs from the mechanism used in fish, amphibians and reptiles, in that the shape of the sacculus is being changed rather than a translocation of pigment vesicles within the cell. Octopuses operate chromatophores in complex, multi-cellular chromatic displays, resulting in a spectacular variety of colour schemes. Often repetitive waves of colour changes are observed as over 1 million neurons controlling the muscular contractions are patterned in the basal and peduncle lobes of the brain.<ref name=octopus> Demski LS. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1422807&query_hl=28&itool=pubmed_docsum Chromatophore systems in teleosts and cephalopods: a levels oriented analysis of convergent systems.] '' Brain Behav Evol''. 1992; 40:141-56.</ref> Like chameleons, cephalopods use physiological colour change for social interaction. They are also among the most skilled at background adaptation, having the ability to match both the colour and the texture of their local environment with remarkable accuracy.

== Notes ==

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== See also ==

*[[Camouflage]]

*[[Melanocyte]]

*[[Pigment]]

== External links ==

* [http://www.bioscience-explainedablenet.org/EN1.2/pdf/paletteEN.pdf Nature'sAbleNET PaletteIRC Website] (pdf)

* [http://wiki.ablenet.org/wiki/SRVX SRVX Help Files & Command List]

*[http://www.funny-games.biz/videos/78-octopus.html Video footage of octopus background adaptation]

* [http://directory.google.com/Top/Computers/Internet/Chat/IRC/Networks/A/ Google Directory]

*[http://www.gfai.de/~heinz/historic/biomodel/squids/squids.htm Video footage of squid chromatophore patterning]

* [http://searchirc.com/network/AbleNET Search Irc]

*[http://tolweb.org/tree/eukaryotes/animals/mollusca/cephalopoda/glossary/glossaryLichen/chromatophoreLichen/Chromatophore.html Tree of Life Web Project: Cephalopod Chromatophore]

* [http://irc.netsplit.de/networks/details.php?net=AbleNET NetSplit.de]

*[http://pbs.org/wnet/nature/octopus/chameleons.html The Octopus Show]

* [http://www.srvx.net/ SRVX IRC Services]

* [http://irc-unity.org/]

== References ==

[[Category:Cephalopod zootomy]]

{{Reflist}}

[[Category:cell biology]]

[[Category:CephalopodIRC zootomynetworks]]

[[de:Chromatophor]]

{{IRC networks}}

[[pl:Chromatofor]]