Comparative biochemical studies of carotenoids in catfishes.

The carotenoids of 12 species of Siluriformes fishes (eight families) were investigated from a comparative biochemical point of view. The patterns of carotenoids in catfishes belonging to the family Siluridae were quite different from those of the other seven families of catfishes (Bagridae, Amblycipitidae, Clariidae, Plotosidae, Ictaluridae, Callichthyidae and Malapteruridae). 7, 8-Dihydro-β-carotene; 7, 8, 7′, 8′- and 7, 8, 9, 10-tetrahydro-β-carotene; (3R)-7′, 8′-dihydro-β-cryptoxanthin; 7, 8-dihydrolutein A; 7, 8-dihydrolutein B; parasiloxanthin; 7′, 8′-dihydroparasiloxanthin; and 4 or 4′-hydroxyparasiloxanthin were characteristic carotenoids found in only one family, Siluridae, and these carotenoids accounted for 24–60% of total carotenoids. In catfishes belonging to the other seven families except Siluridae, the carotenoid patterns were very similar and the most predominant carotenoid was zeaxanthins (23–56%).