Event Title

A Comparison Between Direct and Indirect Estimates of Gas Flux Across Avian Eggshells

Graduation Year

2013

Location

Atrium, Center for Natural Sciences, Illinois Wesleyan University

Start Date

20-4-2013 9:00 AM

End Date

20-4-2013 10:00 AM

Description

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.

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Apr 20th, 9:00 AM Apr 20th, 10:00 AM

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.