BRADLEY, TJ; HETZ, S: Specific Dynamic Action in the Insect Rhodnius prolixus

Larval instars of the Reduviid bug Rhodnius prolixus take blood meals that are up to ten times their previous body volume. Digestion and absorption of the meal is necessary for growth of the insect prior to the subsequent molt. We measured carbon dioxide production of the insects using flow-through respirometry (Sable Systems) to measure indirectly the metabolic rate of these insects prior to feeding, and on days 4, 6, 10, 15, 20 and 25 after feeding. Insects were weighed following the measurement of metabolic rate. The insects were then dissected, the gut contents removed, and the carcass dried and reweighed to determine the dry weight of the insect’s tissues. Metabolic rates were calculated per animal, per gram wet weight and per gram dry weight of animal tissue. The results indicate that metabolic rate per animal goes up ten-fold, peaking about ten days after feeding. Metabolic rate per gram wet weight drops initially as the insect takes on the large, non-metabolizing meal, but then levels off, returning to prefeeding values. The metabolic rate per gram dry weight of insect tissue rises sharply for the first 6 days, indicating an increased metabolic intensity per gram. Prior to molting, the specific metabolic rate of the tissue returns to non-feeding levels. These data will be discussed in the context of the timing of hormone release, cellular activation, protein synthesis, and cuticle formation in this insect, as well as their effects on metabolic rate. Supported by NSF Grant IBN 0079501 and a grant from the Deutsche Akademische Austauschdienst.