Total lipids, phospholipids, triacylglycerols and phospholipids subclasses fatty acid content of some aphid (İnsecta: Hemiptera: Aphidoidea) species

In this study, fatty acid composition of the total lipid, phospholipid (PL), triacylglycerol (TAG) and phospholipid subclasses such as phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserin (PS) and phosphatidylethanolamine (PE) fractions of the different aphid species collected for four years in the period when intense reproduction of the aphids were investigated. Aphids were collected from leaf and body parts of culture and weeds in Diyarbakir-Mardin-Gaziantep-Kahramanmaraş provinces in 2013-2016 between April-May and June in nonperiodic field studies. The fatty acid composition in total lipid, phospholipid, triacylglycerol and phospholipid subclasses (PC, PI, PS and PE) fractions of the insects were determined using fatty acid standards by gas chromatography. In all of the aphid species, in percent, mostly myristic acid (14:0) and palmitic acid (16:0) in the saturated fatty acids (SFA); oleic acid (18:1n-9) and palmitoleic acid (16:1n-7) from monounsaturated fatty acids (MUFA); linoleic acid (18:2n-6) and linolenic acid (18:3n-3) among polyunsaturated fatty acids (PUFA) were determined. In the fatty acid analysis of total lipids of insects, total saturated fatty acids (ΣSFA) were found to be much higher than total monounsaturated fatty acids (ΣMUFA) and total polyunsaturated fatty acids (ΣPUFA). The percentage of hexanoic acid (6:0) and sorbic acid (6:2n-2) changed between aphids. Fatty acid analysis of total lipids and triacylglycerol fraction of the aphids seemed three different groups: The first group included species with a high percentage of 14:0 and a low proportion of 16:0 (Aphis avicularis, Aphis punicae, Aphis rumicis, Hyperomyzus lactucae,Macrosiphum euphorbiae, Macrosiphum rosae, Myzus cerasi, Schizaphis graminum, Uroleucon sonchi, Chaitophorus leucomelas, Pterochloroides persicae). The second group included species that had 14:0 and 16:0 similar percentages (Aphis craccivora, Aphis fabae, Aphis gossypii, Aphis pomi, Hyalapterus amygdali, Brachycaudus persicae, Panaphis juglandis, Forda formicaria). The third group included species with a high proportion of 16:0, with a low proportion of 14:0 (Aphis verbasci, Aphis nerii, Anoecia corni, Brachycaudus helichrysi, Hyalapterus pruni, Dysaphis plantaginae, Myzus persicae, Rhopalisiphum maidi, Chromaphis juglandicola). In the fatty acid distribution of the triacylglycerol fraction of the 28 aphid species we analyzed, it was found that 14:0 and 16:0 from saturated fatty acids were dominant fatty acids. It was determined that the myristic acid varied between 7.99-88.25 %. In our study, the existence of hexanoic and sorbic fatty acids, which are not detected in insects other than aphids, were also determined in the triacylglycerol fraction analysis as in total lipid analysis. Hexanoic acid was found to be less than 1 % in some species, whereas in some species it was determined to reach 12.07 %. Sorbic acid was not detected in some species, while in some of them it was very low, and in some others it was up to 5.06 %. In the distribution of fatty acids of the triacylglycerol fraction, as in total lipids, the ΣSFA ratio was much higher than ΣMUFA and ΣPUFA. The percentages of phospholipid subclasses fatty acids in aphids were not stable, but they showed variability according to species. Although it varies according to species; 16:0 and 18:0 from SFA, 18:1n-9 from MUFA, and 18:2n-6 from PUFA were determined as dominant components in PL subclasses. In addition, components not found in other insects, such as 6:0 and 6:2n-2, found in total lipids and TAG fraction of insects, were not found in the PL fraction, nor in PL subclasses such as PE, PI, PS and PC. Each PL subclasses have a distinct fatty acid distribution and some fatty acids accumulate more in different PL subclasses for different physiological purposes. Some common results were obtained in the four aphid species of phospholipid subclasses fatty acid analysis. In the four insects, 18:1n-9 was found to have more PI fraction; 18:2n-6 and ΣPUFA were found to be higher in PC and PE and 18:0 were higher in the PE and PS fraction compared to the other subclasses. When PC and PE from the dominant subclasses PL subclasses compared, PE was found to have long chain saturated fatty acids such as 18:0 and 20:0, while PC was found to contain 18:2n-6 higher than the predominant PUFAs with relatively short-chain fatty acids such as 16:0 and 14:0. The same results were also determined in the fatty acid analysis of PL subclasses of 25 aphid species in another series of the study. Negatively charged acidic PL subclasses such as PI and PS contain saturated fatty acids compared to PC and PE, which are neutral and dominant subclasses, whereas PC and PE contain more polyunsaturated fatty acids. The fatty acid composition was different in the subclasses PL of the A. nerii and B.helichrysi species. Compared with wingless (apterae) forms, 16:0, 18:0 and ΣSFA were determined more and 18:2n-6, and the ΣPUFA were found less in the PE and PC subclasses of winged (alate) forms. The total lipid, TAG and PL fraction of the alate aphids and the saturated fatty acid percentages in the PL subclasses were higher than the apterae forms and the polyunsaturated fatty acids were found to be less. It has been observed that the fatty acid composition of total lipids of some aphids are species-specific and others changed depending on the nutrient. Compared to the phospholipid fraction and the PL subclasses, the saturated fatty acids in the TAG fraction 6:0, 14:0, 16:0 and depending on these fatty acids the ΣSFA were found more in percentage; 18:0, 20:0, 18:1n-9, 18:2n-6, ΣMUFA and ΣPUFA were detected in a lesser percentage. In our study, nongeneral fatty acids, 6:0 and 6:2n-2 were found only in the TAG fraction, while 20 carbon PUFAs were found only in the PL fraction and PL subclasses.