CHAPTER 21 



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Chromatophores and Color Change 



INTRODUCTION 



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I HE ABILITY TO CHANGE color thiough movements of pigments within 

 I certain integumentary cells or organs is widely distributed among 

 B animals. It has been observed for numerous fishes, amphibians, and 

 reptiles among the vertebrates; among the invertebrates it is exhibited by 

 manv higher crustaceans, cephalopods, and leeches, and a few insects, 

 echiitoderms, and polvchaetes. A comparable activity has been described 

 for a euglenoid protozoan. The spectacular color changes of the chameleon 

 between black and green and the rapid color changes of the octopus were 

 described as earlv as the fourth century B.C. by Aristotle, and those of fishes 

 were described somewhat later by Pliny, who obserx'ed the changes of the 

 dvina mullet. The first changes recorded in amphibians were in the frog, 

 and those in crustaceans were in the prawn, Hip poly te.^'^'^ The relatively 

 rapid color changes in the cephalopods were early demonstrated to be due 

 principally to the activitv of special organs in the skin, to which the name 

 cromofora was given. Later, the movements of pigments in special integu- 

 mentary organs were shown clearly to account for color changes in the 

 chameleon,''" the frog,^ fishes,'^"- '■'■'' and crustaceans. '^'^'^ These special organs 

 have come to be known as chromatoj^hores. 



Briicke-'-^ made studies on the physiology of color change in the chameleon; 

 Pouchet,'^^- '^'•' in crustaceans and fishes; and Gamble and Keeble,^*'' ^''' *""• 

 '•'•'• •*' in crustaceans. All these early investigators concluded that the chroma- 

 tophore systems were under the control of the ner\'Ous system or responded 

 directly to the action of environmental stimuli on the chromatophores. The 

 jiossibility of a role of hormones in color changes was" suggested first b) the 

 disco\crv that the injection of adrenalin blanched frogs.^"^ The early work 

 on chromatophores has been thoroughly re\iewed in the extensixe accounts 

 of van Rvnberk'-'-' and Fuchs.-"^ Later general summaries include those of 

 Hogben-'and of Parker.'-^"" More recently many other reviews have em- 

 phasized restricted aspects of the subject. 



CHROMATOPHORES: STRUCTURE AND METHODS OF ACTION 



Chromatophores arc special pigment cells located in the skin or often even 

 in certain deeper tissues of the bodv of an animal. Chromatophores possess 

 the abilitv to bring about redistributions of their pigment in such a manner 

 as to inHuence the general coloration of the animal. A pigment that is con- 

 centrated into a small ball (punctate) contributes little or nothing to the 

 gross coloration of the indixidual, whereas its dispersion to cover a larger 



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