Fatty acid composition of neutral lipid energy reserves in infective juveniles of entomopathogenic nematodes.

The fatty acid composition of neutral lipids from infective juveniles (IJs) of Steinernema carpocapsae strain All, S. riobravis strain Biosys 355, S. feltiae strain UK76, and S. glaseri strain NC stored in distilled water at 25 degrees C was determined. Newly emerged IJs of all four species had similar neutral lipid fatty acid profiles and of the 18 fatty acids identified, C18:1n-9 (43-49 mol %), C16:0 (18-23%), C18:2n-6 (8-14%) and C18:0 (4-8%) were the most abundant. Unsaturated fatty acids predominated, with about 50% being monoene and 14-22% polyene; the unsaturation index ranged from 91.6 in S. glaseri to 111.6 in S. carpocapsae. The fatty acid composition of the total lipid and the free fatty acid fraction mirrored that of the neutral lipids. During storage, the relative levels (%) of C16:0, C18:0, and C18:ln-9 in the neutral lipids declined significantly, suggesting they were preferentially utilised.