KLOK, CJ*; KAISER, A; MCKINLEY, B; RASCON , B; HENRY, J; LEE, WK; SOCHA, J; HARRISON, JF; Arizona State University; Midwestern University/ASU; ASU; ASU; ASU; Argonne National Laboratory; Argonne National Laboratory; ASU: Plastic and evolutionary responses of body size and tracheal dimensions to atmospheric oxygen concentration in fruitflies

We measured the effect of rearing oxygen levels for single generations (10, 21, 40, 60% oxygen) or up to ten generations (10, 21, 40% O₂) on body size and tracheal dimensions of Drosophila melanogaster. These varying atmospheric oxygen concentrations produced consistent positive relationships between adult body size (live mass) and oxygen concentration. This occurred in both small and larger founding populations (5 or 30 founding females per replicate). In addition, we tested whether the sensitivity to oxygen levels occurred primarily at larval or pupal stages by rearing flies under varied oxygen conditions within one stage (larval vs. pupal) only. These experiments indicated that growth rates during both larval and pupal stages are oxygen-sensitive. A possible explanation for this positive relationship between size (mass) and atmospheric oxygen is that more energy and material reserves are directed toward optimizing the tracheal system at lower oxygen levels, thereby reducing growth of other tissues. To date, there have been no studies of the effect of rearing oxygen levels on the tracheal system of adult D. melanogaster. Images of flies� meso- and metathoracic leg tracheae were captured using x-ray synchrotron imaging at the Advanced Photon Source, Argonne National Laboratories. Dry mass, femur lengths and tracheal dimension measures were taken to investigate allometric relationships related to oxygen selection. Supported by NSF 0419704