Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development. Some species can rapidly change colour through mechanisms that translocate pigment and reorient reflective plates within chromatophores. This process, often used as a type of camouflage, is called physiological colour change. Cephalopods such as octopuses have complex chromatophore organs controlled by muscles to achieve this, while vertebrates such as chameleons generate a similar effect through cell signaling. Such signals can be hormones or neurotransmitters, and may be initiated by changes in mood, temperature or stress, or by visible changes in the local environment. Unlike cold-blooded animals, mammals and birds have only one class of chromatophore-like cells, the melanocyte. The cold-blooded equivalents, melanophores, are studied by scientists to understand human disease, and are used as a tool in drug discovery.
Read the rest of this article: http://en.wikipedia.org/wiki/Chromatophore
_______________________________ Today's selected anniversaries:
1419: Hussite Wars: Jan Žižka and others threw several town councillors out the window at the First Defenestrations of Prague. (http://en.wikipedia.org/wiki/Defenestrations_of_Prague)
1619: The first representative assembly in the Americas, Virginia's House of Burgesses, convened for the first time. (http://en.wikipedia.org/wiki/House_of_Burgesses)
1756: Bartolomeo Rastrelli presented the Catherine Palace, a Baroque palace in Tsarskoye Selo, to Empress Elizabeth of Russia. (http://en.wikipedia.org/wiki/Catherine_Palace)
1825: Malden Island (pictured), now one of Kiribati's Line Islands, was discovered in the Pacific Ocean. (http://en.wikipedia.org/wiki/Malden_Island)
1930: Uruguay won the first Football World Cup in front of their home crowd at Estadio Centenario in Montevideo, beating Argentina 4 to 2. (http://en.wikipedia.org/wiki/1930_FIFA_World_Cup)
_____________________ Wikiquote of the day:
What am I singing? A song of seeds The food of love. Eat the music. -- Kate Bush (http://en.wikiquote.org/wiki/Kate_Bush)