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
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Today's selected anniversaries:
Hussite Wars: Jan Å½iÅ¾ka and others threw several town councillors
out the window at the First Defenestrations of Prague.
The first representative assembly in the Americas, Virginia's House of
Burgesses, convened for the first time.
Bartolomeo Rastrelli presented the Catherine Palace, a Baroque palace
in Tsarskoye Selo, to Empress Elizabeth of Russia.
Malden Island (pictured), now one of Kiribati's Line Islands, was
discovered in the Pacific Ocean.
Uruguay won the first Football World Cup in front of their home crowd
at Estadio Centenario in Montevideo, beating Argentina 4 to 2.
Wikiquote of the day:
What am I singing? A song of seeds The food of love. Eat the music. --