ANIMAL CAROTENOIDS 



of algal symbionts, but as the latter anenome is free from such sym- 

 bionts, it refutes the suggestion that sulcatoxanthin was obtained from 

 sjonbiotic colonies. 



M. senile contains an ester which on saponification yields a carotenoid 

 somewhat similar to astacin. Fox and Pantin ^ ' have concluded that 

 this pigment is not astacin and have named it metridin. By analogy 

 with the properties of astaxanthin and astacin, it is very probable that 

 the naturally occurring pigment is not metridin itself but a reduced 

 form. This species also contains an xanthophyllic ester (? taraxanthin) " * 

 and astaxanthin.*' The coloured variants of M. senile have been 

 studied by Fox and Pantin. 2' It will be seen from Table 25 that 

 xanthophylls play an important part in the coloration of these animals 

 and carotenes little or no part. The concentration of xanthophylls 

 varied from 14-96 mg. per 100 g, dry weight for the red variants to 

 1'76 mg. per 100 g. dry weight for the white variants. 



Table 25. — Colour Variants of Metridium senile* 



* After Fox, D. L., and Pantin, C. F. A., (1944), Biol. Rev., 19, 121. 

 t Pigments italicized predominate. 



Heilbron and his colleagues ^ ^ isolated two esters from Tealia felina ; 

 one was very similar to actinioerythrin and the other gave on hydrolysis 

 an acidic carotenoid very similar to astacin. Similar pigments were 

 encountered in the red variant of the Pacific Coast Epiactis prolifera 



159 



