Seasonal variation of total lipid and fatty acids in various tissues as muscle, liver and gonad of the pearl mullet (Alburnus tarichi) living in Lake Van

In this study, the sexual and seasonal variations in total lipid and fatty acid composition of total lipid, phospholipid (PL), triacylglycerol (TAG) and phospholipid subclasses such as phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserin (PS) and phosphatidylethanolamine (PE) fractions in muscle, liver and gonads of Alburnus tarichi, the only fish that can live in the biggest lake of Turkeywere investigated. Fish samples have been obtained from Lake Van in two-month periods between February 2012 and December 2012. The total lipid content varied seasonally from 3.21 % to 5.57 % in female muscles, 3.33 % to 5.57 % in male muscles, 4.93 % to 6.95 % in ovary, 3.54 % to 7.87 % in testis, 7.79 % to 27.27 % in female livers, 10.69 % to 29.73 % in male livers of wet weight for A. tarichi. It was determined that liver of A. tarichi contained higher percentages of total lipid than other tissues.The total lipid amount in tissues of A.tarichi was influenced by reproduction period and season. For example, the total lipid content in muscles of A.tarichi decreased to minimum in april beginning of the reproductive period, increased to maximum in august after spawning. Total lipid content of muscle was found lower than other tissues.Total lipid content of female all tissue (muscle, liver and ovary) was found higher in august than other period and season. According to the Gas Chromatography results, following saturated fatty acids: myristic acid (14:0), pentadecanoic acid (15:0) palmitic acid (16:0), heptadecanoic acid (17:0) and stearic acid (18:0) monounsaturated fatty acids, palmitoleic acid (16:1n-7), oleic acid (18:1n-9) and eicosenoic acid (20:1n-9); and polyunsaturated fatty acids: linoleic acid (18:2n-6), linolenic acid (18:3n-3),eikosadienoic asit (20:2n-6) eikosatrienoik asit (20:3n-6), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (DHA) were determined in three tissues such as muscle, gonad and liver of fishes. Fatty acid compositions of total lipid, PL, TAG and PL subclasses (PC, PI, PS and PE) fractions have been determined in muscle, gonad and liver tissues of fish by gas chromatography using a mixture of fatty acid standards. The present study revealed that ΣSFA(Saturated Fatty Acids), ΣMUFA(Mono unsaturated Fatty Acids) and ΣPUFA(Poly unsaturated Fatty Acids) levels varied among seasons and tissues of the same fish species. The ΣSFA and ΣMUFA percentages of the total lipid extracted from tissues of A. tarichi ranged from 18.90 % to 40.30 % and from 24.75 % to 52.87 %, respectively. The ΣPUFA percentages of the total lipid in tissues was found from 18.83 % to 45.13 %. Generally,ΣMUFA percentages of the total lipid in liver of A. tarichi were found higher than muscles and gonads. The distributions ofΣSFA, ΣMUFA and ΣPUFA proportions were found different among total lipid, PL and TAG fractions from lipids in tissues of pearl mulletin all seasons. Triacylglycerol contained a lower proportion of ΣPUFA and a higher proportion of ΣMUFA than PL while PL contained higher proportion of ΣPUFA and ΣSFA than proportion of ΣMUFA compared to TAG. The main constituents were 16:0 (11.58-21.56 %) among SFAs, 16:1n-7 (7.27-21.23 %) and 18:1n-9 (16.95-36.94 %) among MUFAs, DHA (5.66-20.07 %) and EPA (5.19-14.38 %) among PUFAs in the total lipid extracted from tissues of pearl mulletin all seasons.The proportions of major fatty acids in tissues of pearl mulletvaried depending on reproduction period, temperature and season.It was found that the percentage of 16:0 in the total lipid extracted from muscles of both sexes of A. tarichi was higher in February and August than to other months while percentage of DHA was found lower in October than the other months. The proportion of ΣSFA and 16:0 in PL fractions of muscle lipids of A. tarichi was found to be low in june prespawning period whereas the proportions of ΣSFA and 16:0 were found to be high august in postspawning. In this study, the n-3/n-6 ratio was determined to range from 3.50 to 4.41 for dorsal muscle, 3.03 to 5.54 for liver and 3.14 to 6.09 for gonads in total lipids in both sexes of pearl mullet. Triacylglycerol and PL fatty acid compositions in tissues of A. tarichi were found different. Triacylglycerols were characterized by a high content of ΣMUFA, 14:0,16:1n-7, 18:2n-6 and 18:3n-3; whereas phospholipids contained a large quantity of ΣPUFA, mainly, 20:3n-6, AA, EPA, 22:5n-3, DHA and 18:0 and among SFAs. In this study, seasonal variations of fatty acid compositions of phospholipid subclasses such as PC, PE, PI and PS in various tissues of pearl mullet were also determined.The predominant phospholipids in the tissues were PC, PE, PI and PS. It was found that quantitative fatty acid compositions varied among PL subclasses. For example, the predominant fatty acids of PC were 16:0 and DHA while PI had higher 18:0 and AA in pearl mullet. The main constituents of PE were 18:0 and DHA.Some changes in percentages of fatty acids of PL subclasses in tissues of Van fish occured during the year.The percentages of saturated fatty acids and 16:0 found in PL fractions increased in august while amount of DHA and PUFAs increased in december. The fatty acid contents of same PL subclasses in various tissues of pearl mullet varied. For example, the PI of ovary had higher percentage of AA than the PI of other tisssues in A. tarichi. Some changes in percentages of fatty acids of PE, PC, PI and PS occurred during the year. Furthermore, The fatty acid contents of TAG and PL subclasses in tissues of pearl mullet were different. Myristic acid, 16:1n-7, 18:1n-9, ΣMUFA, 18:2n-6 and 18:3n-3 levels were higher in the TAG than determined for the PL subclasses. Phospholipid subclasses in A. tarichi had higher 16:0, 18:0, AA, DHA and ΣPUFA percentages than TAG fraction.