Edilberto R. Rubiolo

Flight Metabolism in Panstrongylus megistus (Hemiptera: Reduviidae): the Role of Carbohydrates and Lipids

The metabolism of lipids and carbohydrates related to flight activity in Panstrongylus megistus was investigated. Insects were subjected to different times of flight under laboratory conditions and changes in total lipids, lipophorin density and carbohydrates were followed in the hemolymph. Lipids and glycogen were also assayed in fat body and flight muscle. In resting insects, hemolymph lipids averaged 3.4 mg/ml and significantly increased after 45 min of flight (8.8 mg/ml, P < 0.001). High-density lipophorin was the sole lipoprotein observed in resting animals. A second fraction with lower density corresponding to low-density lipophorin appeared in insects subjected to flight. Particles from both fractions showed significant differences in diacylglycerol content and size. In resting insects, carbohydrate levels averaged 0.52 mg/ml. They sharply declined more than twofold after 15 min of flight, being undetectable in hemolymph of insects flown for 45 min. Lipid and glycogen from fat body and flight muscle decreased significantly after 45 min of flight. Taken together, the results indicate that P. megistus uses carbohydrates during the initiation of the flight after which, switching fuel for flight from carbohydrates to lipids.

Interconversions of lipophorin particles by adipokinetic hormone in hemolymph of Panstrongylus megistus, Dipetalogaster maximus and Triatoma infestans (Hemiptera: Reduviidae)

Abstract Hemolymph of Panstrongylus megistus , Dipetalogaster maximus and Triatoma infestans (Hemiptera: Reduviidae), in the presence of adipokinetic hormone and fat bodies, has the molecular components for generating low density lipophorin (1.060–1.070 m ml −1 ) from high density lipophorin (1.130–1.140 g ml −1 ), similar to that observed in long-distance flight insects. Low density lipophorin showed a significant increase of acylglycerols and a higher amount of apolipophorin-III (mol.wt ∼ 18 kDa) with respect to the original fraction of the incubation media. This process was dependent upon the nutritional status of the insects, whose fat bodies with > 20 days of starvation had the highest levels of acylglycerols. Antiserum against high density lipophorin produced a single precipitation line when it reacted by using Ouchterlonys test with high and low density lipophorins from the three species, and no reaction was observed with other lipophorins.

Metabolic Post-feeding Changes in Fat Body and Hemolymph of Dipetalogaster maximus (Hemiptera:Reduviidae)

Lipids and glycogen in fat body as well as the modifications in the wet weight of this organ were evaluated in an unfed insect, Dipetalogaster maximus, on day 5 after adult ecdysis (time 0) and during a 30-day period after ingestion of blood meal, total lipids, high density lipophorin (HDLp), carbohydrates, total proteins and uric acid were determined in the hemolymph during the same period. Fat body wet weight was maximum on day 10 post-feeding and represented on day only 42% of the maximum weight. Lipids stored in the fat body increased up to day 15 reach 24% of the total weight of tissue. Glycogen was maximum on day 20, representing approximately 3% of the fat body weight. HDLp represented at all times between 17-24% of the total proteins, whose levels ranged between 35 and 47 mg/ml uric acid showed at 20, 25 and 30 days similar levels and significantly higher than the one shown at days 10 and 15. Hemolymphatic lipids fluctuated during starvation between 3-4 mg/ml and carbohydrates showed a maximum on day 15 after a blood meal, decreasing up to 0.26 mg/ml on day 25. The above results suggest that during physiological events such as starvation, the availability of nutrients is affected, involving principally the fat body reserves.