Digital image analysis of shark gills: modeling of oxygen transfer in the domain of time

Digital radiographic imaging of blood circulation through leopard shark gills establishes a secondary lamellar transit time of 6.5 s. This duration, combined with estimates of cardiac output and hemoglobin-oxygen affinity, permits novel modeling of gill oxygen transfer in the time domain. The temporal model allows assessment of factors contributing to previously noted discrepancies between physiological and morphometric branchial oxygen conductance estimates. Lamellar transit time for shark blood is 20 times greater than human alveolar transit time, and thus correlates with a slower rate of hemoglobin-oxygen binding and a greater diffusion distance.