animal carotenoids 



Function 



Fox and Pantin'^' in their work on Metridium have ruled out any 

 suggestion that carotenoids play any part in adaptive coloration of the 

 animals and conclude that their function is " biochemical." Just v^hat 

 this biochemical function is, is not at the moment apparent. 



It is very possible that carotenoids play a role in reproduction for 

 the very small amounts of carotenoids present in the pale variants of 

 Metridium are concentrated in the gonads. Other observations sug- 

 gestive of such a function have been recorded: — M'lntosh^** and 

 Guberlet^i state that the ovaries and testes of Aurelia flavidula {A, 

 aurita) are yellow and red respectively. The stalk tissue of Corymorpha 

 tomoensis, which according to Okeda ^ ^ has special powers of regenera- 

 tion, is deep red, but there is yet no evidence that the pigment is a caro- 

 tenoid. Perhaps the most important pointer is that provided by 

 Schultze 1 3 who noted a transference of carotenoids in Hydra ctrcum- 

 cinta during regeneration and gametogenesis. Carotenoids move from 

 the tissues into the maturing egg leaving the parent deficient in caro- 

 tenoids. No explanation can be given why the process is not essential 

 to all Hydra, because, for example, the gonads of Hydra fusca (Pelmato- 

 hydra oligactis) are not red. 



The important relationship between structure and general pigmenta- 

 tion in the coelenterata is discussed by Fox and Pantin. ^ 



ECHINODERMATA 



ASTEROIDEA 



In 1881 Merejkowsky 1 2 reported that 20 species of echinoderms 

 contained " zooerythrine rouge " which is probably identical with 

 astaxanthin. It was however not until 1934 that Karrer and Benz^^ 

 identified astaxanthin (astacin) in Ophidiaster ophidianus. In the same 

 year von Euler and Hellstrom ^ * isolated from Asterias rubens a blue 

 chromoprotein which yielded a carotenoid which they named asteric 

 acid (C40H66O6). Later work leaves no doubt that asteric acid is 

 astaxanthin. 3 *A Echinaster sepositus contains astaxanthin^ as does 

 Crossaster (Solaster) papposus, Solaster endica, and Porania pulvillus. ^ ^ 

 It occurs in the latter as a violet-i:ed chromoprotein, exhibiting an 

 absorption spectrum in water with maxima at 492 and 458 n\\j.. The 

 dorsal skin of Crossaster papposus contains a water soluble carotenoid 

 protein which yields free astaxanthin on denaturation and extraction 

 with acetone. The red variety gives a protein complex which is pre- 

 cipitated at 50 per cent, saturation with ammonium sulphate, and the 

 blue variety a complex precipitated at 33 per cent, saturation. ^ * 



IGl 



