On the lipids of the egg of the grasshopper, Aulocara elliotti

Abstract

A qualitative and quantitative study was made of the lipids of the egg of the grasshopper species Aulocara elliotti (Thomas) during embryogenesis. Eggs from four wild populations and a fifth population reared in the greenhouse at three population densities were analysed and the results compared with respect to content of triglycerides, diglycerides, free sterols, and steryl esters. Column, thin-layer, and gas chromatography and infrared spectrophotometry were used for separation and identification of component lipids. Each 100 egg sample (0·7–1·0 g fresh weight) contained 28 to 37 mg of triglycerides and about 1 mg of each of the other three classes studied. Only trace amounts of free fatty acids, was esters, and monoglycerides were found. No fatty alcohols could be detected. About 15 mg or more of phospholipid material were present per 100 egg sample. Fatty acid methyl esters of triglycerides, diglycerides, and steryl ester fatty acids were found by gas chromatography to be composed of 12:0, 14:0, 16:0, 16:1, 18:0, 18:1, 18:2, and 18:3 fatty acids. Relative quantitative differences were found between the fatty acid patterns of different wild populations, whereas the eggs from greenhouse-reared grasshoppers, from all densities, differed widely from the wild populations. No direct effect of population density, on the lipids studied, could be demonstrated. The predominant fatty acid in the triglycerides and diglycerides was found to be 18:3, whereas the major fatty acid in the steryl esters of wild populations was 18:2. No change in lipid content throughout diapause could be discerned, but a considerable decrease, particularly in the triglyceride fraction, occurred during the course of post-diapause development. The free sterols consisted of about 95 per cent cholesterol, with campesterol and β-sitosterol making up the remainder. The steryl ester sterols were made up of essentially the same components as the free sterols. No noticeable change occurred in the sterols during either diapause or post-diapause development.