Question

Amphibians and chameleon have good capacity of metachrosis because of
A. Unique pigments
B. Poikilothermic behaviour
C. Humidity
D. Action of neurohormones

Answer 1

Hint: Chromatophores are the cells that contain pigments and have the ability to reflect light. A large number of animals including amphibians, fish, reptiles, crustaceans and cephalopods possess this feature.

Complete answer:
Mammals and birds have a category of cells called melanocytes for coloration. Chromatophores are responsible for generating skin and eye colorized ectothermic animals and are generated within the neural crest during embryonic development. Mature chromatophores are grouped into: xanthophores, erythrophores, iridophores, leucophores, melanophores, and cyanophores.

Various species have the ability to change colour by the mechanisms which translocate pigment and reorient reflective plates within chromatophores. This process, often used as a form of camouflage, is called physiological colour change or metachrosis. Cephalopods have complex chromatophore organs controlled by muscles to achieve this, whereas vertebrates like chameleons generate the same effect by cell signalling. Such signals are neurotransmitters and can be initiated by changes in mood, temperature, stress or visible changes within the local environment.

These types of animals escape detection by fixing their colour like a chameleon. They change their color according to their surroundings in cases such as when in problem. Their general shade was brownish purple, but when placed on the land, or in shallow water, this dark tint became one among viridity.

Colour-producing molecules structure two distinct classes: biochromes and structural colours or schemochromes. The biochromes include true pigments, like carotenoids and pteridines. These pigments selectively absorb parts of the electromagnetic wave spectrum that produces up white light while permitting other wavelengths to reach the eye of the observer. Structural colours are produced by various combinations of diffraction, reflection or scattering of sunshine. Many such structures interfere with some wavelengths (colours) of sunshine and transmit others, simply because of their scale, so that they often produce iridescence, creating different colours when seen from different directions.

Therefore, the correct option is D, action of neurohormones.

Note: Chromatophores which contain large amounts of yellow pteridine pigments are xanthophores while those with mainly red/orange carotenoids are termed erythrophores.