Affiliation:
1. School of Biological Sciences, University of Queensland, Queensland 4072, Australia
2. School of Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia
Abstract
The discontinuous gas exchange cycle (DGC) is a breathing pattern displayed by many insects, characterized by periodic breath-holding and intermittently low tracheal O
2
levels. It has been hypothesized that the adaptive value of DGCs is to reduce oxidative damage, with low tracheal O
2
partial pressures (
P
O
2
∼2–5 kPa) occurring to reduce the production of oxygen free radicals. If this is so, insects displaying DGCs should continue to actively defend a low tracheal
P
O
2
even when breathing higher than atmospheric levels of oxygen (hyperoxia). This behaviour has been observed in moth pupae exposed to ambient
P
O
2
up to 50 kPa. To test this observation in adult insects, we implanted fibre-optic oxygen optodes within the tracheal systems of adult migratory locusts
Locusta migratoria
exposed to normoxia, hypoxia and hyperoxia. In normoxic and hypoxic atmospheres, the minimum tracheal
P
O
2
that occurred during DGCs varied between 3.4 and 1.2 kPa. In hyperoxia up to 40.5 kPa, the minimum tracheal
P
O
2
achieved during a DGC exceeded 30 kPa, increasing with ambient levels. These results are consistent with a respiratory control mechanism that functions to satisfy O
2
requirements by maintaining
P
O
2
above a critical level, not defend against high levels of O
2
.
Subject
General Agricultural and Biological Sciences,Agricultural and Biological Sciences (miscellaneous)
Cited by
25 articles.
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