Abstract
Most terrestrial insect embryos support metabolism with oxygen from the environment by diffusion across the eggshell. Because metabolism is more temperature sensitive than diffusion, embryos should be relatively oxygen-limited at high temperatures. We tested whether survival, development time and metabolism of eggs of a moth, Manduca sexta, were sensitive to experimentally imposed variation in atmospheric oxygen availability (5-50 kPa; normoxia at sea level is 21 kPa) across a range of biologically realistic temperatures. Temperature-oxygen interactions were apparent in most experiments. Hypoxia affected survival more strongly at warmer temperatures. Metabolic rates, measured as rates of CO2 emission, were virtually insensitive to hypo- and hyperoxia at 22°C but were strongly influenced at 37°C. Radial profiles of PO2 inside eggs, measured using an oxygen microelectrode, demonstrated that 3-day-old eggs had broad central volumes with PO2 less than 2 kPa, and that higher temperature led to lower P O2. These data indicate that at realistically high temperatures (32-37°C) eggs of M. sexta were oxygen limited, even in normoxia. This result has important implications for insect population ecology and the evolution of eggshell structures, and it suggests a novel hypothesis about insect gigantism during Paleozoic hyperoxia.
Original language | English |
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Pages (from-to) | 2267-2276 |
Number of pages | 10 |
Journal | Journal of Experimental Biology |
Volume | 207 |
Issue number | 13 |
DOIs | |
State | Published - Jun 2004 |
Keywords
- Egg
- Eggshell
- Insect gigantism
- Manduca sexta
- Metabolism
- Moth
- Oxygen availability
- Paleozoic hyperoxia
- Temperature