Carotenoid discrimination by the avian embryo: a lesson from wild birds

The concentrations (mug/g wet yolk) of total carotenoids in eggs of the com mon moorhen (Gallinula chloropus), American coot (Fulica americana) and les ser black-backed gull (Larus fuscus), collected in the wild, were 47.5, 131 .0 and 71.6, respectively. In contrast to data for eggs of the domestic chi cken, beta -carotene was a significant component in the yolks of these thre e wild species, forming 25-29% by wt, of the total carotenoids present. The concentration of total carotenoids in the livers of the newly-hatched chic ks was 5-10 times higher than in the other tissues and beta -carotene was a gain a major component, forming 37-58% of the hepatic carotenoids. In the n ewly-hatched gull, the proportions of both lutein and zeaxanthin were very low in the liver but high in the heart and muscle when compared with the yo lk. By contrast canthaxanthin, echinenone and beta -carotene were very mino r constituents of heart and muscle when compared with their proportions in the yolk of the gull. The proportions of lutein and zeaxanthin in the liver of the newly-hatched coot and moorhen were also far lower than in the yolk whereas the liver was relatively enriched with beta -cryptoxanthin, beta - carotene and (in the moorhen) echinenone. The results indicate that avian e mbryos discriminate between different carotenoids during their distribution from the yolk to the various tissues. (C) 2001 Elsevier Science Inc. All r ights reserved.