In 5.8 g turbot, fed AsA free diets, body AsA stores were depleted in 90 days, while growth was not affected before day 131. From day 94, hypertyrosinemia followed by tyrosine crystals deposition in tissues at mortality was observed in deficient fish. These symptoms were reinforced when the AsA deficient diet was also low in several vitamins: hypertyrosinemia appeared 40 days sooner and the frequency of deficiency symptoms was doubled. This interaction was in agreement with the vicariancy concept (sparing effect). No external sign of scurvy was found, though proline hydroxylation was depressed by AsA deficiency, both in skin and in vertebrae independently of the poly-hypovitaminosis.