A Comparison Between Direct and Indirect Estimates of Gas Flux Across Avian Eggshells
Submission Type
Event
Expected Graduation Date
2013
Location
Atrium, Center for Natural Sciences, Illinois Wesleyan University
Start Date
4-20-2013 9:00 AM
End Date
4-20-2013 10:00 AM
Disciplines
Biology
Abstract
Gas exchange through pores in bird eggshells is necessary for normal embryonic development. Porosity of eggshells varies among species and among eggshell regions within species. Portugal et al. (2010) modified a method developed by Booth and Seymour (1987) to measure rates of gas exchange through eggshell fragments. We evaluated and subsequently modified this method to more accurately measure gas flux through eggshell pores using the eggs of the Brown-headed Cowbird (Molothrus ater). Correcting for gas movement around the eggshell showed that unchecked replicates overestimated the apparent gas flux by, on average, 50% (range: 0-620%). The presence of the internal shell membrane had no detectable effect on measured rates of gas flux (t(0.05, 54) = 0.261, p = 0.795). We compared measured rates of gas flux to predicted rates of gas flux (calculated from measurements of total pore area per fragment) and found no correlation (r(0.05, 54) = 0.189, p = 0.174). We hypothesize that this discrepancy is explained by the presence of organic matter within the pores which makes them undetectable using light microscopy. These results imply that indirect estimates of gas flux made using measurements of porosity may misrepresent the actual gas flux through avian eggshells.
A Comparison Between Direct and Indirect Estimates of Gas Flux Across Avian Eggshells
Atrium, Center for Natural Sciences, Illinois Wesleyan University
Gas exchange through pores in bird eggshells is necessary for normal embryonic development. Porosity of eggshells varies among species and among eggshell regions within species. Portugal et al. (2010) modified a method developed by Booth and Seymour (1987) to measure rates of gas exchange through eggshell fragments. We evaluated and subsequently modified this method to more accurately measure gas flux through eggshell pores using the eggs of the Brown-headed Cowbird (Molothrus ater). Correcting for gas movement around the eggshell showed that unchecked replicates overestimated the apparent gas flux by, on average, 50% (range: 0-620%). The presence of the internal shell membrane had no detectable effect on measured rates of gas flux (t(0.05, 54) = 0.261, p = 0.795). We compared measured rates of gas flux to predicted rates of gas flux (calculated from measurements of total pore area per fragment) and found no correlation (r(0.05, 54) = 0.189, p = 0.174). We hypothesize that this discrepancy is explained by the presence of organic matter within the pores which makes them undetectable using light microscopy. These results imply that indirect estimates of gas flux made using measurements of porosity may misrepresent the actual gas flux through avian eggshells.