Effects of dietary polyunsaturated fatty acid deficiencies on mortality, growth and gill structure in the turbot, Scophthalmus maximus

Abstract

The preparation of fish oil concentrates containing only (n‐3) polyunsaturated fatty acids (PUFA) with different ratios of 20:5 (n‐3)/22:6 (n‐3) is described. Three groups of turbot were maintained on different diets containing: 1, 10% of the dry weight of the diet as natural fish oil, equivalent to 2.5% (n‐3) PUFA and 0–23% (n‐6) PUFA; 2, 10% of the dry weight of the diet as palmitic acid, i.e. no PUFA; 3, 8–7% palmitic acid and 1–3% of the dry weight as (n‐3 PUFA and negligible (n‐6) PUFA. Only the fish on the diet containing natural fish oil showed significant growth over a 15‐week period. In addition there were high mortalities on the two experimental diets (2 and 3). Changing the ratio of 20:5 (n‐3)/22:6 (n‐3) from 13–8 to 2–2 in the diet containing 1 3% (n‐3) PUFA and negligible (n‐6) PUFA markedly decreased the mortalities. Fish fed the two experimental diets (2 and 3) developed gross changes in gill structure involving the disappearance of chloride cells, a ‘sloughing off’ of the epithelium along the primary and secondary filaments and an accumulation of cellular material in the inter‐lamellar spaces. The tissue ultimately disintegrated to leave a skeleton of connective tissue and a mass of cellular material in the inter‐lamellar spaces. It is concluded that 22:6 (n‐3) is an essential fatty acid for turbot and that the gill epithelium is a sensitive indicator of this deficiency in this species.

The essential fatty acid requirement of milkfish (Chanos chanos Forsskal)

“…The common carp (Takeuchi and Watanabe 1977) and Japanese eel (Takeuchi et al 1980) require a mixture of (n-3) and (n-6) fatty acids, whereas tilapia (Kanazawa et al 1980;Takeuchi et al 1983) require only (n-6) fatty acids. Feeding experiments have also shown that the effects of 20:5(n-3) and 22:6(n-3) on weight gain were superior to those of 18:3(n-3) and 18:6(n-2) in red seabream ), turbot (Cowey et al 1976Bell et al 1985) and catfish (Satoh et al 1989). The differences in the effect of dietary 18:3(n-3) on the growth of fishes are ascribed to the differences in the capacity for bioconversion of 18:3(n-3) to (n-3) series HUFAs (Kanazawa 1979).…”

Respiration and nitrogen metabolism of Atlantic halibut eggs (Hippoglossus hippoglossus)

“…In order to develop a satisfactory first-feed for marine fish larvae, it has been found desirable to quantify the chemical composition and metabolic substrates of the developing eggs and larvae. There exists a vast accumulation of literature on the subject of essential fatty acids in marine fish larvae (Owen et al 1975, Gatesoupe et al 1977, L6ger et al 1979, Scott and Middleton 1979, Watanabe 1982, Bell et al 1985, Fraser et al 1988). More recently, free amino acids (FAA) have been proposed as a main energy substrate in larvae of halibut (Fyhn 1989(Fyhn , 1990 as well as in eggs and larvae of Atlantic cod (Gadus morhua) (Fyhn and Serigstad 1987).…”

Zebrafish cDNA Encoding Multifunctional Fatty Acid Elongase Involved in Production of Eicosapentaenoic (20:5n-3) and Docosahexaenoic (22:6n-3) Acids

“…Recently, enzymes catalyzing the elongation of C 18 PUFA have been cloned from the fungus Mortierella alpina (Parker-Barnes et al, 2000), the nematode Caenorhabditis elegans (Beaudoin et al, 2000), and humans (Leonard et al, 2000b). Variation in HUFA biosynthesis may also operate at the elongation steps as supported by the low C 18-20 elongase activity in the fish species turbot (Scophthalmus maximus) (Ghioni et al, 1999), a carnivorous marine teleost that requires a dietary supply of HUFA for normal growth (Bell et al, 1985).…”