Impact of essential fatty acid deficiency and temperature on tissues' fatty acid composition of European sea bass (Dicentrarchus labrax)

The effects of essential fatty acid deficiency and temperature on the fatty acid profiles of polar lipids (PL) and neutral lipids (NL) from various tissues (muscle, liver, gills, eyes and brain) of European sea bass juveniles were compared in a two factorial design. Fish (60 g) were held for 84 days at 22 or 29 C (upper limit for growth) and fed either at a lower or a higher level than n-3 HUFA minimal requirement for growth (0.4% and 2.2% n-3 HUFA dry matter for diets LD and HD, respectively). Essential fatty acid deficiency had a major influence on fatty acids in NL fraction of all tissues, a more moderate influence on PL of muscle, liver and gills, while a low and very low diet influence was observed on eyes and brain PL fatty acid content, respectively. DHA and EPA content in brain PL as well as DHA in eyes PL were not affected by diet. DHA contents were similar in gill PL of 22-HD, 29-HD and 22-LD but was reduced in 29-LD fish. Most of brain PL fatty acids displayed a significant effect of temperature (at 29 C; 18:0, 18: 1n-9 contents were higher, and 20:5n-3, 22:6n-3, 20:4n-6 contents were lower than at 22 C). Temperature had more influence on PL than on NL fatty acid content, except in liver. A lipogenic activity seemed to occur, both 16: 0 and 18: 0 were high particularly in liver NL and dependent on temperature (higher at 29 than at 22 C). An enhanced 18: 3n-6 content in fish fed on the deficient HUFA diet indicated a desaturation activity, mainly in liver NL and gill PL, with higher arachidonic acid content in PL of gills than other tissues. Muscle fatty acid profiles in NL and PL were more similar to those of whole body than other tissues, however total lipid content then PL: NL ratio differed. This study shown that beside known characteristics of each tissue in term of PL fatty acid content, each tissue have also characteristics in term of response to temperature and dietary deficiency influence. Among then, neural tissue displayed the highest capacity to regulate DHA content in PL, preserving functionality despite HUFA deficiency. (c) 2005 Elsevier B.V. All rights reserved.