Color Changes in Animals' 



By D. B. Carlisle 



Anti-Locust Research Centre, London 



[With 2 plates] 



"Ten more days of this smi and I shall have a tan that should last 

 the winter through." A. common enough remark to hear on the beach 

 any day during the summer. A few minutes later I disturbed a 

 cuttlefish on the sea bottom 25 feet down. With startling suddenness 

 a white rectangle appeared in the middle of its back, then a pair of 

 "eye-spots," before it finally puffed out a cloud of ink. Here we have 

 examples of the two chief methods of color change and illustrations 

 of the extremes of duration of the changes. Ten days of exposure to 

 the sun may be needed to produce the new pigmentation which we 

 call a suntan, and several months may elapse before all this pigment 

 is removed or destroyed again. The cuttlefish changes color by re- 

 deployment of pigments already within the skin and can achieve 

 changes of color and pattern within a fraction of a second. Color 

 changes wliich depend on the deposition of new pigment within the 

 skin or integument or on the removal or destruction of pigment are 

 known as morphogenetic color changes; changes which are brought 

 about by redistribution of existing pigments within the integument 

 with little or no metabolism of the pigments are often called kinetic 

 color changes. 



Both types of color change may be brought about in response to a 

 great many different factors. Heat and light, diet, the color of the 

 background, and the degi*ee of crowding of the animals may all play 

 a part in morphogenetic changes. A suntan is produced by the direct 

 action of certain ^vavelengths of ultraviolet light on the cells of the 

 skin, wliich stimulates pigment formation in each cell which is exposed 

 to the radiation. The pink plumage of the flamingo (pi. 1) is a 

 result of diet and the pigment is taken almost unchanged from the 

 small shrimplike creatures which form a large part of the food. This 

 red pigment is then deposited in the feathers where it slowly fades in 



1 Reprinted by permission from The Times Science Review (London), Winter 1962. 

 Copyright 1963 by The Times Publishing Company, Limited. All rights reserved. 



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