Blood oxygen content and affinity in developing embryos of snapping turtle Chelydra serpentina (879.8)

Abstract

In egg‐laying amniotic vertebrates gas exchange takes place over the chorioallantoic membrane (CAM). Oxygen diffuses from air in contact with the shell into blood perfusing the membrane where it combines reversibly with hemoglobin. The capacity of the blood to transport oxygen is determined by the functional characteristics of the hemoglobin. In this study we investigated changes in oxygen content and affinity during development in embryos of snapping turtle (Chelydra serpentina). Blood samples were taken from embryos at 50, 70 and 90% of incubation. Samples withdrawn from the CAM artery had statistically similar mean oxygen contents for all stages (combined mean ± SEM; 0.94 ± 0.13 mL O2/100 mL of blood). Mean CAM venous blood oxygen content was 2.74 ± 0.44 at 50%, 3.25 ± 0.26 at 70% and increased to 4.97 ± 0.47 mL O2/100 mL at 90% of development. Consequently, the arteriovenous difference increased by 72% late in incubation. Oxygen equilibrium curves were the same at 2% and 6% CO2 at 50% incubation but showed an increased affinity in 2% CO2 and a rightward shift in 6% CO2 at 70 and 90% of development. These results show that embryonic turtles increase oxygen content and affinity and show a Bohr shift late in development likely favoring hemoglobin loading at the CAM and unloading at the tissues, ensuring adequate O2 supply for the increased demand of later stages of development.Grant Funding Source: Supported by NSF CAREER IBN IOS‐0845741 (DAC) and FAPESP 2012/06938‐8 (EWT); 2013/05677‐9 (MRS)