Lipid absorption in the midgut of larval Aeshna cyanea

Lipid absorption through the larval midgut of Aeshna cyanea was studied with cytological and biochemical methods. The oral ingestion of triolein leads to the formation of lipid-absorption droplets in the epithelial cells. After fat feeding there is first an increase and finally a decrease in the number and size of droplets per cell. Feeding also causes an initial rise and subsequent reduction of lipolytic activity in the midgut lumen. Orally administered acid is rapidly taken up by the epithelial cells and esterified into di- and triglycerides. Lipid discharge into the haemolymph occurs in the form of free fatty acids and diglycerides. The results clearly demonstrate that alimentary fat is hydrolyzed in the midgut lumen, the hydrolysates then being absorbed by the epithelial cells and utilized for the resynthesis of triglycerides. Lipid release from the midgut epithelium into the haemolymph occurs in the form of free fatty acid and diglyceride.