Morphological and Physiological Colour Changes in the Animal Kingdom


Colour change is the ability of an organism to modify its colouration in response to specific stimuli. Several biological functions have been proposed to explain colour changes, including ultraviolet (UV) protection, thermoregulation, crypsis, inter‐ and intraspecific communication. Changes in body colouration are mainly performed through two types of mechanisms referred to as morphological and physiological. Mechanistically, these two types of colour changes differ in their speed and the way coloured structures are altered. The proximal causes of these colour changes are identified in a handful number of species and demonstrate that common physiological, cellular and molecular actors are at play. However, the reasons why both colour‐change types are widespread in the animal kingdom and how they have evolved are still unknown. This is partly due to a lack of knowledge about the fitness implications of colour changes, particularly their energetic costs.

Key Concepts

  • Morphological and physiological colour changes are widespread in the animal kingdom.
  • It has been suggested that both types of colour changes have the same biological functions, which are UV protection, thermoregulation, crypsis, inter‐ and intraspecific communication.
  • Despite differences in speed and mechanisms, similar cellular and molecular actors are at play for both types of colour changes.
  • Colour changes are triggered by environmental stimuli, mainly light, and are regulated by the neuronal and hormonal systems.
  • The evolution of colour‐changing abilities is still poorly understood because the consequences of colour changes on individual fitness remain to be investigated.

Keywords: colour changing; morphological colour changes; physiological colour changes; animal evolution; pigment; chromatophore; camouflage; melanin; ommochrome

Figure 1. Model organisms and their contributions to the study of colour changes in the animal kingdom. For each model species, contributions in the fields of evolution, ecology, physiology, cellular and molecular mechanisms of colour changes have been highlighted. A red cross indicates that no study has yet investigated this field for this particular species. A yellow question mark indicates that few studies have started to investigate this field. A green tick indicates that numerous studies have dealt with this field, even though many important biological questions may remain unanswered. (a) The colour‐changing crab spiders Thomisus onustus and Misumena vatia (not shown). Size: few millimetres. Left: Courtesy of Fritz Geller‐Grimm; right: Courtesy of Paul‐Henri Cahier. (b) A desert locust (Schistocerca gregaria) in its solitarious (left) and gregarious (right) phases. Size: few centimetres. Courtesy of Compton Tucker, NASA GSFC. (c) Human‐melanoma derived melanocyte in culture producing melanin (from left to right) and highlighting the process of tanning at the cellular level. Black dots within the melanocyte are melanin‐containing organelles called melanosomes. Cell size: several micrometres. (d) Example of camouflage in a cephalopod, the cuttlefish. Size: several centimetres. Courtesy of Nick Hobgood. (e) Rapid darkening of a rock pool goby (Gobius paganellus) subjected to a dark background (left to right). The same process has been studied in the frog Xenopus laevis (not shown). Size: several centimetres. Reprinted from Stevens M, Lowen AE, Denton AM. 2014 Rockpool gobies change colour for camouflage. PLoS ONE 10, e110325 under the Creative Commons Attribution License. (f) Reddening of a Panther chameleon (Furcifer pardalis) in the presence of a male rival. Size: tens of centimetres. Left: Courtesy of Kris Norvig; right: Courtesy of Eric Mathieu.
Figure 2. Morphological colour changes in a crab spider. (a) At the tissue level, colour‐changing chromatophores of crab spiders are beneath a transparent cuticle and on top of light‐reflecting guanocytes. In white crab spiders, chromatophores possess unpigmented ommochromasomes that do not absorb the incoming light, which is then fully reflected by guanine crystals in guanocytes. During morphological colour change, ommochromasomes progressively mature and acquire yellow ommochromes, such as xanthommatin. Hence, in yellow crab spiders, the incoming light is first partly absorbed by mature ommochromasomes. This transmitted light deprived of blue and violet wavelengths is then reflected by guanine crystals and thus appears yellow to the eye. Courtesy of Fritz Geller‐Grimm. (b) In chromatophores of crab spiders, ommochromasomes can undergo a full cycle of pigmentation and depigmentation, which is the cellular basis of their morphological colour change. (1) During white‐to‐yellow transition, transparent preommochromasomes acquire ommochrome precursors that are slightly yellow. (2) Precursors then form yellow ommochromes leading to a mature ommochromasome. (3) For yellow‐to‐white transition, ommochromasomes enter an autocatalytic process leading to the degradation of their pigments. (4) Degrading ommochromasomes are ultimately recycled into unpigmented organelles, ready for another cycle of ommochrome metabolism. Courtesy of Paul‐Henri Cahier. (c) The production of xanthommatin within maturing ommochromasomes is the molecular basis of their yellow colouration. Thanks to its electronic delocalisation structure, xanthommatin absorbs wavelengths between 400 and 500 nm (i.e. violet and blue). Thus, visible light passing through xanthommatin is deprived of these wavelengths making it yellow (the complementary colour of blue and violet) to the eye. See text for references. Nuc., nucleus.
Figure 3. Environmental and intrinsic factors controlling morphological colour changes. (a) When chromatophores directly sense light stimuli and trigger colour change, it is called a primary response. Colour change can be proportional to the light stimulus, such as in the tanning process of humans. (b) When the visual system is the intermediary between the light stimuli and the chromatophores response, it is called a secondary response. Both neuronal and hormonal systems can be involved in the regulation of colour‐changing chromatophores. Hence, colour‐change pattern can match the light stimuli dynamics. For example, seasonal colour moulting is cyclic because it is linked to the change in photoperiod during the year. One hormonal factor involved in the regulation of skin melanocytes is α‐MSH. (c) From the same pool of premelanosomes, skin melanocytes can produce either black melanosomes containing eumelanins or reddish ones with phaeomelanins. The fate of premelanosomes depends on the balance of two factors, α‐MSH and ASIP; both bind to MC1R at the melanocytic membrane and activate antagonistic signalling cascades. See text for references. ASIP, agouti signalling protein; α‐MSH, α‐melanocyte‐stimulating hormone; MC1R, melanocortin 1 receptor; UV, ultraviolet radiation.
Figure 4. Physiological colour changes at the tissue level in cephalopods. In cephalopods, two layers of chromatophores are involved in colour change: pigmented chromatophores and iridophores. When leucophores are present, they only reflect the incoming light. Cephalopods can produce a wide array of coloured patches using a combination of expanded/retracted pigmented chromatophores together with activated/inactivated iridophores. (a) When pigmented chromatophores are expanded, the incoming light is partly absorbed by pigments and thus appears coloured to the eye (e.g. yellow when absorbed by xanthophores). (b) When iridophores are in an activated state and xanthophores are expanded, a yellow (xanthophores) and a blue iridescent (iridophores) layers are superimposed, leading to an overall green colouration. (c) Another combination is when all pigmented chromatophores are expanded and iridophores are inactivated, the incoming light is then deprived of most of its wavelengths and will thus appear as dark brown.
Figure 5. Factors regulating physiological colour changes at the cellular level. (a) Physiological colour change is mostly a secondary response to light stimuli, although other types of stimuli can be involved, such as temperature (not shown). Both neuronal and hormonal systems can regulate chromatophores responses and thus colour change. (b) Pigmented chromatophores of cephalopods are under the control of a radial neuromuscular system. When radial muscles are relaxed, chromatophores are in a retracted state that do not absorb light. Upon neuronal activity, radial muscles contraction forces chromatophores to expand. As pigmented organelles of chromatophores are tethered together and are located within a cytoelastic saccule, the chromatophores expansion increases light absorption surface. This expanded and coloured state is fully reversible and allows for rapid colour change. (c) Cephalopod iridophores contain iridosomes made of reflectin platelets separated by layers of cytoplasm. In their inactivated ‘off’ state, reflectin platelet structure and layers width do not create light interference and thus colouration. Upon activation of muscarinic receptors by the neurotransmitter acetylcholine, reflectin platelets are phosphorylated, change their conformation and layers of cytoplasm are reduced. The overall effect is the production of light interferences leading to red light. This activated ‘on’ state of iridophores is fully and quickly reversible. (d) In fishes and amphibians, melanophores are the main pigmented cells providing physiological colour change. In their inactivated and unpigmented state, their melanosomes aggregate around the nucleus. Upon binding of α‐MSH to MC1R, melanosomes are moved along microtubules towards their (+)‐end by molecular motors. The dispersion of melanosomes to the edge of the cell increases the surface of light absorption. This activated and pigmented state of melanophores is fully and quickly reversible. See text for references. Ach, acetylcholine; α‐MSH, α‐melanocyte‐stimulating hormone; MC1R, melanocortin 1 receptor; Nuc., nucleus.


Anstey ML, Rogers SM, Ott SR, Burrows M and Simpson SJ (2009) Serotonin mediates behavioral gregarization underlying swarm formation in desert locusts. Science 323: 627–630.

Archetti M, Döring TF, Hagen SB, et al. (2009) Unravelling the evolution of autumn colours: an interdisciplinary approach. Trends in Ecology & Evolution 24: 166–173.

Auerswald L, Freier U, Lopata A and Meyer B (2008) Physiological and morphological colour change in Antarctic krill, Euphausia superba: a field study in the Lazarev Sea. Journal of Experimental Biology 211: 3850–3858.

Brechbühl R, Casas J and Bacher S (2010) Ineffective crypsis in a crab spider: a prey community perspective. Proceedings of the Royal Society B: Biological Sciences 277: 739–746.

Cadena V, Rankin K, Smith KR, Endler JA and Stuart‐Fox D (2017) Temperature‐induced colour change varies seasonally in bearded dragon lizards. Biological Journal of the Linnean Society 123 (2): 422–430.

Caro T (2017) Wallace on coloration: contemporary perspective and unresolved insights. Trends in Ecology & Evolution 32: 23–30.

Defrize J, Thery M and Casas J (2010) Background colour matching by a crab spider in the field: a community sensory ecology perspective. Journal of Experimental Biology 213: 1425–1435.

DeMartini DG, Krogstad DV and Morse DE (2013) Membrane invaginations facilitate reversible water flux driving tunable iridescence in a dynamic biophotonic system. Proceedings of the National Academy of Sciences 110: 2552–2556.

DeMartini DG, Izumi M, Weaver AT, Pandolfi E and Morse DE (2015) Structures, organization, and function of reflectin proteins in dynamically tunable reflective cells. Journal of Biological Chemistry 290: 15238–15249.

Deravi LF, Magyar AP, Sheehy SP, et al. (2014) The structure‐function relationships of a natural nanoscale photonic device in cuttlefish chromatophores. Journal of the Royal Society Interface 11: 20130942.

Duarte RC, Flores AAV and Stevens M (2017) Camouflage through colour change: mechanisms, adaptive value and ecological significance. Philosophical Transactions of the Royal Society, B: Biological Sciences 372: 20160342.

Figon F and Casas J (2018) Ommochromes in Invertebrates: Biochemistry and Cell Biology. Manuscript submitted for publication.

Gawryszewski FM, Birch D, Kemp DJ and Herberstein ME (2015) Dissecting the variation of a visual trait: the proximate basis of UV‐Visible reflectance in crab spiders (Thomisidae). Functional Ecology 29: 44–54.

Ghoshal A, DeMartini DG, Eck E and Morse DE (2013) Optical parameters of the tunable Bragg reflectors in squid. Journal of the Royal Society Interface 10: 20130386.

Hanlon R, Chiao C‐C, Mäthger L, et al. (2009) Cephalopod dynamic camouflage: bridging the continuum between background matching and disruptive coloration. Philosophical Transactions of the Royal Society, B: Biological Sciences 364: 429–437.

Insausti TC and Casas J (2008) The functional morphology of color changing in a spider: development of ommochrome pigment granules. Journal of Experimental Biology 211: 780–789.

Insausti TC and Casas J (2009) Turnover of pigment granules: cyclic catabolism and anabolism of ommochromes within epidermal cells. Tissue and Cell 41: 421–429.

Ligon RA and McCartney KL (2016) Biochemical regulation of pigment motility in vertebrate chromatophores: a review of physiological color change mechanisms. Current Zoology 62: 237–252.

Linzen B (1974) The tryptophan → ommochrome pathway in insects. In: Berridge M.J. and Wigglesworth V.B. (ed) Advances in Insect Physiology, pp. 117–246. Elsevier, Academic Press.

Llandres AL, Figon F, Christidès J‐P, Mandon N and Casas J (2013) Environmental and hormonal factors controlling reversible colour change in crab spiders. Journal of Experimental Biology 216: 3886–3895.

López S and Alonso S (2014) Evolution of skin pigmentation differences in humans. In: Encyclopedia of Life Sciences. Chichester, UK: John Wiley & Sons, Ltd.

Masthay MB (1997) Color changes induced by pigment granule aggregation in chromatophores: a quantitative model based on Beer's Law. Photochemistry and Photobiology 66: 649–658.

Mäthger LM (2003) Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus. Journal of Experimental Biology 206: 3607–3613.

Mäthger LM and Hanlon RT (2007) Malleable skin coloration in cephalopods: selective reflectance, transmission and absorbance of light by chromatophores and iridophores. Cell and Tissue Research 329: 179–186.

Mäthger LM, Denton EJ, Marshall NJ and Hanlon RT (2009) Mechanisms and behavioural functions of structural coloration in cephalopods. Journal of the Royal Society Interface 6: S149–S163.

Messenger JB (2001) Cephalopod chromatophores: neurobiology and natural history. Biological Reviews 76: 473–528.

Morse DH (2007) Predator Upon a Flower: Life History and Fitness in a Crab Spider. Cambridge, MA: Harvard University Press.

Norman MD, Finn J and Tregenza T (2001) Dynamic mimicry in an Indo‐Malayan octopus. Proceedings of the Royal Society B: Biological Sciences 268: 1755–1758.

Poulton EB (1890) The colours of animals, their meaning and use, especially considered in the case of insects. New York: D. Appleton and Company.

Stevens M, Rong CP and Todd PA (2013) Colour change and camouflage in the horned ghost crab Ocypode ceratophthalmus. Biological Journal of the Linnean Society 109: 257–270.

Stuart‐Fox D and Moussalli A (2009) Camouflage, communication and thermoregulation: lessons from colour changing organisms. Philosophical Transactions of the Royal Society, B: Biological Sciences 364: 463–470.

Sun J, Wu W, Liu C and Tong J (2017) Investigating the nanomechanical properties and reversible color change properties of the beetle Dynastes tityus. Journal of Materials Science 52: 6150–6160.

Tanaka S, Harano K, Nishide Y and Sugahara R (2016) The mechanism controlling phenotypic plasticity of body color in the desert locust: some recent progress. Current Opinion in Insect Science 17: 10–15.

Teyssier J, Saenko SV, van der Marel D and Milinkovitch MC (2015) Photonic crystals cause active colour change in chameleons. Nature Communications 6: 6368.

Umbers KDL, Fabricant SA, Gawryszewski FM, Seago AE and Herberstein ME (2014) Reversible colour change in Arthropoda. Biological Reviews 89: 820–848.

Williams TL, DiBona CW, Dinneen SR, et al. (2016) Contributions of phenoxazone‐based pigments to the structure and function of nanostructured granules in squid chromatophores. Langmuir 32: 3754–3759.

Wunderlin J and Kropf C (2013a) Rapid colour change in spiders. In: Nentwig W (ed) Spider Ecophysiology, pp. 361–370. Berlin/Heidelberg: Springer.

Zimova M, Hackländer K, Good JM, et al. (2018) Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world? Biological Reviews. doi: 10.1111/brv.12405

Further Reading

Caro T, Sherratt TN and Stevens M (2016) The ecology of multiple colour defences. Evolutionary Ecology 30: 797–809.

Cuthill IC, Allen WL, Arbuckle K, et al. (2017) The biology of color. Science 357: eaan0221.

Diamond J and Bond AB (2013) Concealing Coloration in Animals. Cambridge, MA: The Belknap Press of Harvard University Press.

Endler JA and Mappes J (2017) The current and future state of animal coloration research. Philosophical Transactions of the Royal Society, B: Biological Sciences 372: 20160352.

Nilsson Sköld H, Aspengren S and Wallin M (2013) Rapid color change in fish and amphibians ‐ function, regulation, and emerging applications. Pigment Cell & Melanoma Research 26: 29–38.

Pener MP and Simpson SJ (2009) Locust phase polyphenism: an update. In: Simpson S.J. and Pener MP.P (ed) Advances in Insect Physiology, pp. 1–272. London, UK: Elsevier.

Protas ME and Patel NH (2008) Evolution of coloration patterns. Annual Review of Cell and Developmental Biology 24: 425–446.

Quicke DLJ (2017) Mimicry, Crypsis, Masquerade and Other Adaptive Resemblances. Hoboken, NJ: John Wiley & Sons, Inc.

Raabe M (1982) Morphological and physiological color change. In: Raabe M. (ed) Insect Neurohormones, pp. 141–162. Boston, MA: Springer US.

Wunderlin J and Kropf C (2013b) Rapid colour change in spiders. In: Nentwig W (ed) Spider Ecophysiology, pp. 361–370. Berlin/Heidelberg: Springer.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Figon, Florent, and Casas, Jérôme(Aug 2018) Morphological and Physiological Colour Changes in the Animal Kingdom. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0028065]