Chromatophores and Color Change 



681 



The chromatophores of the vertebrates in general resemble those of crusta- 

 ceans. Unlike the latter, however, they usually comprise single cells and 

 are for the most part monochromatic. The predominant pigment is melanin, 

 and it is the activity of the melanophores which is principally responsible 

 for the conspicuous color changes in this group. In many vertebrates reflect- 

 ing white chromatophores, the guanophores or leucophores are also found. 

 Chromatophores known as lipophores, containing fat-soluble red pigment 

 (erythrophores) or yellow pigment (xanthophores), are often present. These 

 pigments are commonly xanthophyll or derivatives of it.'*^ In addition to 

 these more conventional types of pigment cells, there are sometimes glisten- 

 ing bluish-green bodies, the iridocytes, whose color and color changes are 

 structural ones dependent on the form, arrangement, and movements of fine, 

 platelike crystals. 



Fig. 257. Sections through scales of Anolis showing the condition of the chromatophores, 

 A, in the brown state and B, in the green state. From Kleinholz."* 



Supplementing the contribution of the chromatophores themselves to the 

 coloration of the vertebrate there is often, as in the cephalopods, an immobile 

 layer of whitish or yellowish pigment. This pigment is responsible entirely 

 for the tint of the animal when the active chromatophores contribute little 

 or nothing, or it cooperates with the chromatophores in producing the normal 

 coloration. In species such as the lizard, Anolis, the bodies of the melano- 

 phores lie beneath such a passive layer of pigment. As the animal darkens 

 in response to appropriate stimulation the melanin streams within melano- 



