Haemolymph lipids of healthy and diseased Japanese beetle larvae

Abstract

Extractable lipids from the haemolymph of healthy and diseased larvae of the Japanese beetle, Popilliae japonica, have been characterized and compared. Total lipid content of normal larvae was 5·7 to 7·2 mg/ml haemolymph. This value was reduced to 3·1 to 3·9 mg/ml in haemolymph from larvae infected with the milky disease organism, Bacillus popilliae. Neutral lipids accounted for 70 per cent of total lipids in both normal and diseased larvae haemolymph. Phospholipids accounted for 30 per cent of the total lipids. The neutral lipid fraction is composed of sterols, monoglycerides, free fatty acids, 1,2- and 1,3-diglycerides, triglycerides, sterol esters, and hydrocarbons. Haemolymph phospholipids are composed primarily of phosphatidic acid, phosphatidyl choline, and phosphatidyl ethanolamine. The fatty acid composition of both neutral lipid and phospholipid fractions is predominately C 16 and C 18 fatty acids. Significant quantities of hydrocarbons have been detected in the neutral lipids of haemolymph from both healthy and diseased larvae. Infection with B. popilliae resulted in a non-selective decrease of 45 per cent in neutral lipids and phospholipids in haemolymph from third instar larvae.