Chromatophores and Color Change 



699 



Crago as are eyestalks from other groups. This principle which is present 

 in Groups I and II, but absent in Group III, has been called Crflgo-"tair'- 

 lightening hormone (CTLH). The information at hand, although indicat- 

 ing the presence of three chromatophorotropins in crustacean sinus glands, 

 does not permit us to decide between two possibilities: (1) species in Groups 

 I and II possess three principles and those of Group III possess two prin- 

 ciples, and (2) all possess only two principles, with one of the two differ- 

 ing in physiological properties between Groups I and II, and Group III. 



The sinus glands of the eyestalks are not the sole sites of production of 

 chromatophorotropins in crustaceans. It is well known that undisturbed 

 eyestalkless specimens of Crago not uncommonly exhibit random color 

 changes. Since Roller's original work, it has been found by a number of in- 

 vestigators that eyestalkless crustaceans may be induced to undergo char- 

 acteristic color changes through the action of blood-borne factors by stimu- 

 lation with electrical or other means of the cut ends of their optic nerves. 

 Crustaceans of Group I are induced to blanch, but whereas blanching under 

 the influence of sinus gland principles includes white-pigment dispersion, 

 by this means the white concentrates. Members of Group III darken, but 

 here, too, the white concentrates as the black disperses, unlike under sinus 

 gland influence. The responses of Crago of Group II are more obviously 

 complex, and its reactions to electrical stimulation of its optic nerve stubs 



OROUPl 

 ce MLMuoHcres 



cnoup n 



e.G. Cll*60 

 ITIAL IteSPOMSe riHAL ST4Tt 



mo WMiTi 



tL'icir wMire 



mjccTto 



WITH eiTDACT i 

 or NIKVOUS 



GROUP rn 



ee. ucj) 



o 



SLACK »nrTt 



Fig. 265. Schematic representation of the coloration of eyestalkless crustaceans and 

 state of their dominant chromatophores for each of the three differently responding 

 groups, and of the responses of these to injection of extracts of the nervous system. Solid 

 arrows indicate extract of total water-soluble material, dashed arrows indicate an alcohol- 

 insoluble fraction, and dotted arrows indicate an alcohol-soluble fraction. From Brown, 

 1948. 



provided a clue to much of our knowledge of the chromatophorotropins in- 

 volved in these reactions. If stimulation is mild, the whole animal blackens; 

 if stimulation is intense, only the telson and uropods darken, the remainder 

 of the body blanching.^'^ It is thus evident that some of the chromatophoro- 

 tropins arising outside of the eystalks obviously antagonize the activity of 

 sinus gland factors and others, at least in part, supplement them. 



