STORAGE OF CAROTENOIDS AND OF VITAMINS A 485 



vitamin was absent from the eyes; the bodies of these two groups contained 

 comparable amounts of vitamin A/^" Morton and Creed/" in 1939, also 

 noted the conversion of (3-carotene into vitamin A in two freshwater species, 

 the dace (Leuciscus, spp.) and the European freshwater perch (Perca 

 fluviatilis). 



a". Possible Sources of Vitamin A for the Whale. The source of the 

 vitamin A in the livers of species which have a large store of this com- 

 ponent has been widely discussed. Since the main sources of food for 

 fishes of this type are the zooplankton, it is only natural to assume that 

 they are the sources of vitamin A. Copepods are the "permanent" mem- 

 bers of the zooplankton, while the eggs and larvae of fishes and of inverte- 

 brates comprise the so-called ''transitory" sources.^^^ Phj'toplankton are 

 utilized to a smaller extent. 



The vitamin A content of copepods is relatively low. They live on di- 

 atoms which have a small content of |8-carotene and of fucoxanthin, which 

 is not a provitamin A. The copepod apparently converts these carote- 

 noids mainly to astaxanthin, and stores only a minute amount as carotene. 

 Goodwin ^^- indicates that a similar carotenoid distribution obtains in the 

 case of eggs and of larvae of invertebrates in the zooplankton. The /3- 

 carotene content of the phytoplankton is apparently similar to that of the 

 zooplankton. 



The amount of jS-carotene present in zooplankton is believed to be inade- 

 quate to account for the large accumulation of vitamin A in plankton- 

 eating fishes. It is claimed *^^ that the astaxanthin isolated from the fringed 

 decapod shrimp (Aristeomorpha {Penaeus) foliacea) is active as a source 

 of vitamin A. However, Goodwin^^^ considers it highly improbable, as do 

 most other investigators. If one discounts astaxanthin as a possible pro- 

 vitamin A, then, according to Goodwin, ^^^ the possible sources of the vita- 

 min A for the marine forms which consume the plankton are: (a) pre- 

 formed vitamin A in the zooplankton, (b) synthesis of vitamin A de novo, 

 or (c) sjnithesis of vitamin A from provitamins A. The first of these pos- 

 sibilities is considered to be the most probable. 



Some confusion has arisen since the report of Wagner''^" that the plank- 

 ton organisms, which were identified as Euphausia superba Dana, obtained 



«^ R. A. Morton and R. H. Creed, Biochem. J., S3, 318-324 (1939). 



^* J. Johnstone, A. Scott, and H. C. Chadwick, The Marine Plankton, Univ. Liver- 

 pool Press, 1934. 



«3 R. Grangaud and R. Massonet, Compt. rend., 230, 1319-1321 (1950). 



**° K. H. Wagner, Vitamin A und ^-Carotin des Finn-, Blau-, und Spermwals, J. A. 

 Barth, Leipzig, 1939, pp. 1-70; cited by L. R. Fisher, S. K. Kon, and S. Y. Thompson, 

 /. Marine Biol. Assoc. United Kingdom, 31, 229-258 (1952), p. 229. 



