Storage and Fatty Acid Composition of Triglycerides during Adult Diapause of the Boll Weevil1

Abstract

Total body fat of the boll weevil, Anthonomus grandis Boheman, and relative distribution in major lipid classes, as shown by silicic acid column chromatography, is dependent on adult age, larval and adult diet, and diapause. Neutral glyceride and free fatty acid fractions account for as much as 90% of extractable lipids of diapausing adults. Newly emerged weevils have 2%–6% body fat (about 2% triglyceride). After 2–3 weeks of feeding, nondiapausing adults have 6%–10% body fat (40%–60% triglyceride), whereas diapausing adults have 18%–25% body fat (75%–85% triglyceride). The triglyceride level drops during winter when the insects are not feeding. By the following June fat content drops to 3% (28%– 30% triglyceride). Boll-fed adults accumulate more triglycerides than square-fed; adults feeding on both squares and bolls accumulate an intermediate amount. Adult diet is the major factor controlling the type of fatty acid incorporated into the triglycerides. Square-fed adults have about equal amounts of oleic and palmitic acids, the 2 major fatty acids. However, boll-fed adults have a much higher proportion of oleic. On a given diet the amount of palmitic acid appears to be constant for both physiological states, while oleic acid is slightly higher in diapausing as opposed to nondiapausing weevils. The mono-unsaturated fatty acids tend to decrease during reproductive activity whereas the d s poly-unsaturated fatty acids increase. Preliminary evidence with the thurberia weevil, Anthonomus grandis thurberiae Pierce, as with the boll weevil, indicates that incorporated triglyceride fatty acids are a reflection of those in the diet.