PIGMENTS AND COLOURS 



489 



persion of chromatophore pigment also bring about an increase in the 

 amount of pigment and in the number of chromatophores over long 

 periods. This is another manifestation of the effect of use and disuse seen 

 elsewhere ; for example, in the hypertrophy of muscle with exercise, and 



Fig. 1 1 .6 (a). Changes in the Numbers of Melanophores in the Skin of the 

 Flounder or Gulf Fluke Paralichthys albiguttus on Different Backgrounds 



Melanophore counts were made on a unit area of skin. I : reduction in number of 

 melanophores in a specimen kept on a white background. II: restoration of melano- 

 phores in a specimen which had been kept on a white background for four weeks, and 

 then placed upon a black background. (Redrawn from Kuntz, 1917.) 



Fig. 11.6(6). Decrease in Concentration of Carotenoid Pigments in 

 Shrimps Palaemonetes vulgaris when Kept on a White Background 



Concentration of carotenoids is expressed in terms of an artificial standard. (From 

 Brown, 1934.) 



wasting after nerve section. From an adaptive viewpoint morphological 

 colour changes are valuable in bringing about closer resemblance to the 

 animal's habitual environment, or protection against actinic rays. 



Colour Patterns 



Many marine animals are rather evenly coloured and show few or no 

 markings. This is seen in many deep-sea fish and Crustacea which are 

 uniformly drab brown, black or red in colour. Uniform colours are also of 

 common occurrence in numerous sedentary invertebrates from littoral and 

 deeper waters. Sponges, particularly, are characterized by absence of mark- 

 ings, but many examples can readily be found in other phyla. 



Colour patterns among marine animals are infinite in variety. Bold 

 patterns in black and white, or in different colour schemes, are common 

 in the non-segmented coelenterates and turbellarians. In coelenterates the 

 colours are sometimes differentiated into radial patterns in correlation with 



M.A. — 16* 



