L-ASCORBIC ACID SYNTHESIS IN BIRDS - PHYLOGENETIC TREND

The ability of several species of birds to synthesize L-ascorbic acid is correlated with their phytogeny. In the more primitive species, synthesis of L-ascorbic acid occurs in the kidney. Among the highly evolved passeriform species, kidney and liver can synthesize L-ascorbic acid in some, whereas in others synthesis occurs in the liver. In still others, the capacity for the synthesis of L-ascorbic acid is apparently lost. The pattern of evolution of the ascorbic acid pathway among birds is thus similar to that among mammals.