Meeting Abstract
26.1 Monday, Jan. 4 Respiratory gas exchange patterns of a semi-aquatic insect: effects of environmental humidity vs. oxygen demand CONTRERAS, H.L.*; BRADLEY, T. J.; University of California, Irvine; University of California, Irvine hcontrer@uci.edu
The adaptive significance of insect gas exchange patterns, in particular the importance of the discontinuous gas exchange cycle (DGC), has been extensively debated by insect physiologist for decades. The debate continues to date and data supporting the importance of DGC for water conservation or to limit oxidative damage continues to flourish in the literature. In order to address the significance of the DGC as a response to environmental humidity or oxygen availability, we used a semi-aquatic insect (Aquarius remigis) to determine gas exchange patterns when these insects were found under humid conditions while their metabolic rates were altered using temperature (10, 20, 30°C). Insects were placed in a vial containing 1ml of degassed water while humid CO2-free air entered the experimental chamber and then passed into a CO2 analyzer. We found that at low temperatures, insects exhibited lengthy periods of spiracular closure reflecting a discontinuous pattern of respiration. In fact, on average A. remigis spent 80% of the total experimental time with the spiracles closed. As temperature and metabolic rate increased, the insects showed shortened closed periods, transitioning to the cyclical respiratory pattern (spiracles were closed only 35% of experimental time). Finally, at the highest temperatures, the insects exhibited a continuous respiratory pattern, were they spent only 9% of total experimental time with the spiracles closed. Our results suggest that environmental humidity does not play an important role in determining gas exchange patterns in these semi-aquatic insects as our data was collected while insects were found under very humid conditions. However, the insect’s metabolic rate (oxygen demand) had a strong effect on the gas exchange pattern displayed and therefore our data continues to support the oxidative damage hypothesis.
