PIGMENTS AND COLOURS 



471 



Carotenoids. Carotenoids are very widespread and occur in the majority 

 of animals. They are divisible into two broad groups: carotenes, which 

 are hydrocarbons; and oxygen-containing carotene derivatives, namely 

 xanthophylls, carotenoid acids and esters. Empirical formulae are 

 C 40 H 56 for carotene, and C 40 H 56 O 2 for xanthophyll. Carotenoids are 

 soluble in lipoids and in typical lipoid solvents but insoluble in water. They 



Tentacles — *r 

 Ccipitulum\ 

 Pa.ra.pet 



Siphonog/yph 



Stomodaeum 





Simple Brown Simple Grey 



Mm 



Red with brown Red with grey Brown with grey 



Siphonoglyph 

 Stomodaeum 



Red with brown and #rey 

 Fig. 11.1. Diagrams of Different Colour Varieties in the 

 Plumose Anemone Metridium senile 



Oblique stripes, red; vertical stripes, brown; stipple, grey; unmarked, white. (From 

 Fox and Pantin (22).) 



range in colour from yellow and orange to rich red. Carotiproteins are 

 water-soluble compounds of considerable importance in animal coloration, 

 and showing a wide range of colours (grey, brown, red, green, blue and 

 dark violet) (16, 17, 35, 36, 42, 49, 58, 80). 



The ubiquitous occurrence of carotenoids in animals is noteworthy. 

 Ultimately derived from plants, they are often accumulated and stored by 

 animals. Carotenoids occur in adipose tissue, in the eyes or other photo- 



