Chemistry and utilization of plankton. IX Pigmentation of cultured sweet smelt fed diets supplemented with a blue-green alga Spirulina maxima.

Pigmentation of cultured sweet smelt Plecoglossus altivelis was attempted by using diets supplemented with a commercial preparation of Spirulina maxima, whose main carotenoid is zeaxanthin. Addition of 3 to 6% Spirulina to diets and feeding them for 10 weeks improved successfully the color of test fish. Supplementation of 4 to 8mg lutein A per 100g of diet was also tried for comparison and was found to be effective. Carotenoids in the diets were accumu-lated not only in the integuments but in the subcutaneous tissues. The contents of the integu-ments and subcutaneous tissues in the test groups were 4.2 to 5.7mg/100g and 19.5 to 44.0mg/100g, whereas those in the control group were 2.9mg/100g and 12.7mg/100g, respectively. In the integuments major carotenoids were zeaxanthin, β-cryptoxanthin, lutein B, and diatoxanthin together with minor ones such as 3'-hydroxyechinenone, cynthiaxanthin, and β-carotene triol. No lutein A was detected in the Spirulina-fed groups. In the subcutaneous tissues appreciable amounts of β-carotene and canthaxanthin were found in addition to the carotenoids mentioned above, but no lutein B was detected. Presumed metabolic pathways of carotenoids from diets to the integuments via the subcutaneous tissues were discussed.