Feeding Artemia to larvae of Atlantic halibut ( Hippoglossus hippoglossus L.) results in lower larval vitamin A content compared with feeding copepods

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Halibut ( Hippoglossus hippoglossus) larvae were fed excess DHA Selco enriched Artemia or natural copepods (mainly Temora longicornis). Fourteen days after onset of first feeding, a time that is critical for normal pigmentation of Atlantic halibut, the content of retinol and retinal were from 50 to 80% lower in halibut larvae fed Artemia compared with larvae fed zooplankton. At day 28 post first feeding, the differences between larvae fed Artemia and zooplankton were few although the content of retinol in larvae fed only Artemia was still only about 50% of the other groups. There were major differences in the vitamin A and carotenoid composition of Artemia and Temora. Temora did not contain any form of vitamin A: all- trans retinal and all- trans retinol. In Artemia, however, large amounts of an unknown retinoid component were present. This component was not seen in Temora. Lutein and astaxanthin, the quantitatively most important carotenoids in Temora, were not detected in Artemia. Likewise, cryptoxanthin/cantaxanthin, the major carotenoid in Artemia, was not observed in Temora. This suggests that halibut larvae are not able to efficiently convert the available carotenoids or the unknown retinoid component into retinal and retinol during the first period after onset of exogenous feeding.