Carotenoids in the reproductive cycle of the brown trout.

In the first paper of this series (Steven, 1948) it was shown that the tissues of the trout (Salmo trutta Linn.) normally contain j8-carotene, lutein and astacene. Lutein and astacene occur as esters in the red and yellow chromatophores of the skin, and may also be present in the muscles as free hydroxy-carotenoids. Carotene is present in the liver, which also contains xanthophylls but no astacene. The ripening oocytes, however, contain all three types of carotenoid. Red and yellow chromatophores first appear during the larval period of development before the young fish has commenced to feed independently, and appear to obtain their pigment from the carotenoids laid down in the yolk. This paper records the chemical changes and distribution of these substances from the maturation of the oocytes to the stage of metamorphosis of the larva.