Carotenoids from nudibranchs

Abstract

1. 1. The nudibranchs, Anisodoris nobilis, Dendrodoris fulva and Doriopsilla albopunctata, were found to contain unusually high percentages of carotenes in their integumental carotenoids. The first two fractions isolated in each case were identified as α-carotene and β-carotene, respectively. 2. 2. A third fraction, also isolated in good yield from each nudibranch, has been identified as isorenieratene, an aromatic carotenoid previously found only in sponges and bacteria. The carotenoids isolated from these nudibranchs seem to reflect the pigment composition of the sponges which comprise their diets. 3. 3. The main pigment of Triopha carpenteri (“triophaxanthin”) has been identified as an acetylenic apo-carotenoid (C 31H 42O 2). It was also found in the food carotenoids, as were all of the other fractions isolated from this nudibranch. 4. 4. Astaxanthin, the only carotenoid found in Flabellinopsis iodinea, was isolated in three different forms: free, esterified and conjugated to a protein. Astaxanthin was also found to be the only carotenoid in the food. 5. 5. It is proposed that nudibranchs most probably lack the biochemical ability to alter carotenoids from one structure to another.