16.5 Thursday, Jan. 3 The effects of varying oxygen levels on size, growth, and development rate in the tobacco hornworm CEASE, Arianne*; ALBERT, Todd; VANDENBROOKS, John; DAVIDOWITZ, Goggy; HARRISON, Jon; Arizona State University; Arizona State University; Arizona State University; University of Arizona; Arizona State University email@example.com
Previous studies on fruitflies have shown that their body size increased when reared in hyperoxia and decreased in hypoxia, suggesting a beneficial effect of hyperoxia and a deleterious effect of hypoxia. Severe hyperoxia, however, can be toxic due to oxidative damage. To gain a better understanding of when varying oxygen conditions might be advantageous and when those effects turn deleterious, we generated a response curve of the well-studied tobacco hornworm (Manduca sexta) to a range of oxygen levels. Because larger insects may be more sensitive to changes in atmospheric oxygen, in addition to an unselected control group, we compared two experimental lines selected for large (“Big”) and small (“Small”) size. Approximately 25 animals from each line were reared at atmospheric pO2’s of 10, 21, 25, 33, and 40 kPa. In response to hypoxia, all lines showed a reduction in adult mass, larval growth rate, and total development time. In response to hyperoxia, the “Big” line exhibited a negative correlation between body mass and pO2 under hyperoxic conditions. This smaller size was due to a decrease in growth rates at pO2 levels above 25 kPa. In contrast, body masses were unaffected by hyperoxia in the control and “Small” lines. However, both of these latter lines exhibited increases in growth rates and reduced developmental times at pO2’s ranging from 33 to 40 kPa. These results suggest that selection for large size and fast growth in Manduca sexta has created a population that is more sensitive to hyperoxia, perhaps due to higher oxidative damage correlated with increased tissue pO2’s, or reduced investment in mechanisms for prevention or repair of oxidative damage. This research was partially supported by NSF IBN 0419704 to JFH.