DEFICIT OF DIDOCOSAHEXAENOYL PHOSPHOLIPID IN THE EYES OF LARVAL SEA BASS FED AN ESSENTIAL FATTY-ACID DEFICIENT DIET

Larval sea bass Dicentrarchus labrax of 27 days old were reared on Art emia enriched with Super Selco(C), Tuna Orbital Oil or Yeast. The firs t diet is commonly used in mariculture for larval rearing, the second diet was designed to deliver an optimal docosahexaenoic acid (22: 6n-3 ) to eicosapentaenoic acid (20 : 5n-3) ratio, and the third diet was d eficient in docosahexaenoic acid (22 : 6n-3). The eyes of these larvae were analysed after 28 days and the molecular species of the three ma in phospholipid classes, phosphatidylcholine (PC), phosphatidylethanor amine (PE) and phosphatidylserine (PS) determined. Eyes from larvae fe d Artemia enriched with yeast showed large decreases in molecular spec ies containing 22:6n-3 compared to those supplemented with tuna orbita l oil, most notably in 16:0/22:6n-3 PC which fell from 10.6 to 0.4%, i n 22 : 6n-3/22 : 6n-3 and Is : 1/22 : 6n-3 PE which fell from 29.6 to 0.3% and from 10.8 to 1.1% respectively, and in 22:6n-3/22:6n-3 PS whi ch fell from 34.3 to 1.7%. Molecular species containing all other fatt y acids, and especially 20:5n-3, were elevated in eyes from the yeast- supplemented fish. In larvae fed Artemia enriched with Super Selco, am ounts of eye 22:6n-3/22: 6n-3 phospholipid were slightly lower in all three phospholipid classes compared to eyes from the tuna orbital oil- supplemented larvae. There was also a trend of decreased saturated fat ty acid/22 : 6n-3 and monounsaturated fatty acid/22: 6n-3 molecular sp ecies in all classes From the Super Selco-supplemented fish, the defic its being made up with molecular species containing 20:5n-3 and 22:5n- 3. These results are discussed in relation to larval viability with pa rticular respect to visual function. (C) 1996 The Fisheries Society of the British Isles