ANIMAL CAROTENOIDS 



Because of this, Gillam and his colleagues rightly refused to consider 

 that their investigation proved the presence of preformed vitamin A 

 in zooplankton and it was not until ten years later that, largely owing 

 to the considerable advances in chromatographic and spectrographic 

 techniques, the problem was solved. 



Nielands "*^ found considerable amounts of vitamin A in the eyes 

 and hepatopancreas of the common lobster {Homarus vulgaris) and Kon 

 and Thompson, ^ ^^'^ at almost the same time, showed that it was 

 present in a number of species of smaller Crustacea, being concentrated 

 in the eyes and the exoskeleton. 



It seems, then, that the major portions of vitamin A of plankton- 

 feeding fish comes to these animals preformed. It must not, however, 

 be assumed that fish cannot convert the small amount of ^-carotene in 

 their diet into vitamin A. There is some positive evidence concerning 

 this point ; Neilands^^^ in 1949 demonstrated this conversion in the 

 Atlantic cod {Gadus callarias), whilst as long ago as 1939 Morton and 

 Creed "^^ observed the conversion of ^-carotene into vitamin A, by 

 fresh water fish (dace and perch). 



MOLLUSCS 



Lamellibranchs 



Although Lonnberg* had found that a number of species gave 

 positive tests for carotenoids, the first intensive investigation was 

 carried out by Lederer « « who isolated a neutral xanthophyllic pigment, 

 glycymerin^ from the sex glands of the scallop, Pectunculus glycymerts. 

 The pigment which is not attached to proteins is distributed on the 

 inside and in the lower superficial layers of the gonads ; the upper 

 superficial layer being colourless. Lederer «' later examined the 

 gonads of Pecten maximus and found that the fat-soluble pigments were 

 principally a mixture of non-esterified xanthophylls although a little 

 P-carotene was detected. The main pigment was unique, and termed 

 pectenoxanthin. This pigment (C4oH6e+205) has also been identified 

 in the gonads of Pecten jacohaeus ;' and a very similar pigment exists 

 in the gonads of Volsella modiolus. * ' In this instance a portion of the 

 pigment is attached to the protein. Astaxanthin occurs in Pleurobranchus 

 species and in the feet of Lima excavata. * ^ Preliminary work by the 

 author has revealed the presence of highly oxygenated xanthophylls 

 in Modiolus modiolus. ' ^^ 



However, by far the most comprehensive study on Lamellibranchs 

 is that of Scheer ' ^ on Mytilus calif ornianus. This species contains 



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