EFFECT OF DIETARY TREATMENTS ON THE LIPOPHORIN TITER IN THE LARVAL HEMOLYMPH OF THE SOUTHWESTERN CORN-BORER, DIATRAEA-GRANDIOSELLA

This study examined whether the availability of stored lipid controls the release of lipophorin from the larval fat body of the southwestern corn borer, Diatraea grandiosella. The larval fat body of this insect synthesizes and releases a high-density lipophorin. Larvae transferre d from a diet containing 1.22% lipid (wet wt) to a lipid-free diet at 9 days-of-age had a lipophorin titer in their hemolymph 8 days after t ransfer that was 2 mg/ml lower than that in larvae retained on the 1.2 2% Lipid diet. Neonate larvae fed a diet containing 0.25% sucrose and 0.1% Lipid had a lower Lipophorin titer in their hemolymph at 15 days- of-age than had larvae fed a diet containing 3.25% sucrose and 0.1% li pid. Neonate larvae fed a diet containing 0.03% of the hypolipidemic a gent, 5-tetradecyloxy-2-furanocarboxylic acid, and 0.24% lipid had a l ower lipophorin titer in their hemolymph at 15 days-of-age than had la rvae fed a diet containing no inhibitor and 0.24% lipid. In vitro incu bation of fat bodies showed that the release of lipophorin, but not to tal protein, was inhibited by transferring fourth instars onto a lipid -free diet. Therefore, the availability of lipids for loading onto lip ophorin in the fat body is one factor controlling the titer of lipopho rin in the larval hemolymph of this insect.