510 



THE BIOLOGY OF MARINE ANIMALS 



muscle fibres, and blanching is due to inhibition of peripheral tonus by 

 inhibitory nerve fibres which originate in the stellate ganglion. Such a 

 scheme involves double innervation of the muscle fibres, motor and 

 inhibitory. Superimposed upon peripheral tonus, however, are twitch con- 

 tractions and tetanic contractions which can be produced by electrical 

 stimulation of mantle nerves, and which normally are under central con- 







>m::U, 



>;'•••*• 



(a) 



(d) 



Fig. 12.2. Chromatophores of Different Fishes 



(a) Erythrophores from the red mullet Mullus barbatus and M. surmuletus, expanded 

 and contracted; (b) melanophores of the rough hound Mustelus cam's, expanded and 

 contracted ; (c) combination of a red (stippled) and a black (solid colour) chromatophore 

 from Gobius minutus; (d) melanophores of the weever-fish Trachinus vipera — {left) 

 expanded, {right) contracted and associated with an iridosome; {e) combination of an 

 iridophore (circles), melanophore (solid black), and xanthophores (cross-hatched) in the 

 common goby, Gobius minutus. (After Ballowitz, 1913, and Parker, 1937.) 



trol. It is these quick contractions that are responsible for rapid colour 

 changes and for the waves of colour which sweep over the animal (54). 



Although vision to a large extent controls chromatic changes in cephalo- 

 pods, enucleated animals still show colour responses, which are no longer 

 adaptive, however. The agencies then involved are the suckers, general 

 tactile receptors and postural influences. When all the suckers are removed, 

 there is considerable loss of tone in the chromatophores and the skin 

 blanches. The chromatophores in the lower surface of the animal are 



