S1-5.2 Jan. 6 The effects of morphology on gill ventilation STROTHER, J.A.; Univ. of California, Irvine email@example.com
The gills of teleost fish have often been described as a counter-current exchanger, where water flows through the gills in the opposite direction to that of blood flow within the gills. Such counter-current exchange depends strongly on the spatio-temporal pattern of flow through the branchial cavity. Surprisingly, the flow patterns that develop around and irrigate the gills are not well understood. Is the flow of water through the gills uniform along their length, or do different regions of the gills experience different levels of irrigation? How does gill morphology affect the uniformity of the pressure gradient or the shunting of water around the gills? I addressed these questions by developing a computational fluid dynamics model of the water flow around the gills of a teleost fish. The gills were modeled as orthotropic porous structures whose porosity was calculated using an analytical model of the flow through the secondary lamellae. The model geometry was based on measurements of morphological parameters in the killifish Fundulus heteroclitis. The computational model predicts that the pressure gradient across the gills, and thus the flow of water through the gills, decreases to near-zero at the distal tips of the primary lamellae. Additionally, model calculations show that morphological differences generate functionally significant heterogeneity in the pressure gradient and shunting of water around the gills.