Meeting Abstract
The increased metabolism during digestion, known as specific dynamic action (SDA), has been measured in hundreds of animal species, but only a few insects. Newly emerged adult tsetse flies are voracious feeders consuming a blood meal equal to half of their own body mass every other day. We measured the SDA at different ambient temperatures (25, 30, 35°C) and found that it decreased in duration from ~48h at 25°C to ~24h at 35°C – a response seen in other animals. However, unlike most animals the SDA response was also significantly smaller at the higher temperatures suggesting that warmer temperatures speed digestion and minimize costs. We also measured the δ13C in the breath of flies fed blood meals labeled with 13C-leucine and 13C-glucose to measure the rates at which they oxidized these dietary nutrients. The 13C in their breath of both groups peaked within the first couple of hours after feeding and then rapidly declined. As the flies became postabsorptive the oxidation of the leucine tracer approached zero and the flies at 35°C and 25°C succumbed to starvation by 36h and 96h, respectively. The increased starvation tolerance at 25°C was correlated with an increase in breath δ13C in the glucose tracer flies presumably as they oxidized newly synthesized lipids. We are now testing whether the flies actually prefer to digest meals at warm temperatures and then retreat to cool temperatures while fasting if given a range of temperatures to choose in a behavioral thermal gradient.
