Polyunsaturated fatty acids in total lipid and phospholipids of chilean scallop Argopecten purpuratus (L.) larvae:: effects of diet and temperature

The composition of lipids and fatty acids of larval scallop Argopecten purpuratus were determined when cultured at one of two temperatures and using one of the three algal diets. Larvae grown at 12 degreesC had the lowest values of phosphatidylcholine (PC) and highest values of cholesterol and steryl esters (SE). The ratio of triacylglycerol (TAG)/cholesterol was affected by temperature but not by diet and the lowest values were observed in larvae grown at 12 degreesC. By using the ratio of TAG/cholesterol as an index of larval condition, the best condition was observed at the begining of the experiment, before feeding, with values of 3.9 and 2.9 in eggs and D-larvae, respectively. The best culture conditions for larval scallop from this point of view was a temperature of 19 degreesC and a diet of Isochrysis galbana grown at 25 degreesC while the poorest condition was observed in larvae cultured at 12 degreesC and 19 degreesC and fed the mixture of Isochrysis aff galbana (clone T-Iso) high-protein and Chaetoceros neogracile high-protein (IH/GH diet). However, no significant differences in the growth rate and survival of larvae fed different diets were detected. I. galbana grown at 25 degreesC had no detectable percentage of arachidonic acid (ARA; 20:4n - 6), but larvae grew well and ARA was detected in PC and phosphatidylethanolamine (PE) in similar quantities to other diets. This suggests ARA may not be essential during early life stages of larval Chilean scallops. Total lipids and PC of larvae were affected by the diet in their ratio of docosahexaenoic acid (DHA; 22:6n - 3)/eicosapentaenoic acid (EPA; 20:5n - 3), but PE composition was highly conserved and was unaffected by diet. DHA/EPA ratio in total lipid and in PC showed highest values when larvae were fed I. galbana grown at 25 degreesC. Temperature affected the total highly unsaturated fatty acids (HUFA) in total lipids, PC and PE of larvae. In all cases values were lowest when larvae were cultured at 12 degreesC. In addition, increased temperature increased the ratio of EPA/ARA in PC and decreased the ratio of monounsaturated fatty acids (MUFA)/saturated fatty acids in PE. The ratio of n - 6/n - 3 PUFA was constant in total lipid, PE and PC of larval scallops regardless of temperature or diet. (C) 2003 Elsevier Science B.V. All rights reserved.