BIOLOGY OF THE SEA-HOW THEY LIVE 



41 



TOP -LIGHTING 



& 



MO COUMTERSHADING 



COUNTERSHADING 



& 



UNIFORM ILLUniMATION 



TOP- LIGHTING 



& 



COUNTERSHADING 



Fig. 1 1 . An example of ohliterative coloration— the mako shark. The top figure 

 shows the shark as it would appear if it were uniformly colored and lifted from 

 above— a shadow is thrown on the lower side and the animal is conspicuous. The 

 center figure shows the shark uniformly illuminated, hut colored darker on its hack 

 (as the mako shark actually is')— still conspicuous. The bottom figure shows the shark 

 as it actually appears in the water with a combination of top-lighting and counter- 

 shading— flat and inconspicuous. (^Adapted from Cott, 1940.) 



The eye of many animals, being an especially noticeable part of the 

 body, is frequently concealed by a stripe or disguised as those of butterfly 

 fishes Ccolor photograph) and the porkfish QColor Plate 5). The eye also 

 may be included in the pattern of the rest of the body, as seen in anglers, 

 some groupers, and the scorpion fish, by extending body pattern and color 

 onto the eyeball. 



Shadow Elimination. Animals are very often not betrayed by their own 

 bodies but by the shadows that they cast. Shadows frame animals 

 conspicuously, and the elimination of shadows is a valuable aid in avoiding 

 detection. This method of concealment is common in bottom fishes. 

 Depressed species such as rays, flatfishes, and batfishes cast little or no 

 shadow. 



Rarely is only one of these four methods of concealment used by an animal. 

 The mackerel shows ohliterative coloration, but its blue to blue-green ground 



