Phospholipids and their fatty acids in infective juveniles of entomopathogenic steinernematid nematodes

The composition of phospholipids and their fatty acids was investigated in the infective juveniles (IJs) of four species of entomopathogenic nematodes: Steinernema carpocapsae (strain All), S. riobravis (strain Biosys 355), S. feltiae (strain UK76) and S. glaseri (strain NC). In newly emerged IJs of the four species, phospholipids comprised 15-18% dry weight of the total lipids (or 5-6% dry weight of the nematode), and phosphatidylethanolamine and phosphatidylcholine constituted about 40 and 30%, respectively, of the total phospholipids, with phosphatidylserine (PS) and phosphatidylinositol (PI) collectively accounting for about 25%. Qualitatively, the four species had identical total phospholipid (combined non-acidic and acidic fractions) fatty acid profiles, although there were some differences in the relative proportions (mol%) of specific fatty acids. The fatty acid composition of the total phospholipids in newly emerged IJs was dominated by C16 fatty acids, specifically C16:0 (14-18%), C16:1n-7 (up to 20%) and C16:4 (up to 26%), whereas the major C18 fatty acid was C18:1n-9 (20-23%). Polyunsaturated C20 fatty acids collectively made up 8-13% of the total composition. When newly emerged IJs were stored in distilled water at 25 degrees C, the proportions of C16:0 and C16:4 decreased with storage time, whereas C16:3n-3 increased (by 30-fold in S. glaseri). These changes were mostly observed in the acidic phospholipid fraction (mainly PI and PS). No evidence was found for a correlation between the fatty acid composition of the phospholipids and the relative ability of the IJs of the four Steinernema species to survive desiccation stress.