CAROTENOIDS 



for Glover * ' found no carotenoids in the halibut (although traces may 

 be present in the ova) ' ^ in spite of its main food being a fish, Sebastes 

 marinuSy rich in astaxanthin. * 



Glover, Morton and Rosen ^^ have follovv^ed the metabolism of 

 astaxanthin in salmon (Salmo salar) eggs. For the six weeks betw^een 

 the fertilization of the eggs and hatching no change took place in the 

 amount of astaxanthin. Two months after the hatching the content 

 had decreased by 12 per cent. ; whether this drop is significant or not 

 it is difficult to say. At hatching 92 per cent, of the total astaxanthin 

 present was in the yolk sac. As the embryos develop there is a constant 

 transfer of pigment from the sac to the embryo, so that a two month 

 embryo contains 80 per cent, of the total pigment. Not only is there a 

 transfer but the astaxanthin is esterified as it is laid down in the em- 

 bryo. The same type of change occurs in entirely fresh water fish 

 (see p. 207). 



60 



^ 40 



20 



^ Astaxanchin in coca! 

 embryonic sysCem 



O Astaxanthin in yolk sac 



# Astaxanchin in embryo 



^ 



45 



35 25 15 



Pre-hatching period 



5 

 Days 



15 25 35 



Posc-hatching period 



45 



Fig. 



26. — Showing the Astaxanthin distribution in the developing salmon embryo. 

 (After Glover, M., Morton, R. A., and Rosen, G. D. (1949) Biochem, J., 50, 425). 



Function 



(a) In Photoresponses. The work of Sumner and Fox ^ 2- 1 * indicates 

 that carotenoids do play a part in photoresponses in some fish. Fundulus 

 parvipinnis and Gillichthys mirabilis maintain their carotenoid content 

 in different optical environments although the colours of the fish 



196 



