Diffusion in the interlamellar water of fish gills.

The role of diffusion limitation in interlamellar water of fish gills can be studied on simplified gill models consisting of slits bounded by trapezoidal plates and perfused by water. The main factors determining the degree of O2 equilibration of gill water are shown to be interlamellar distance, length of the secondary lamellas, water velocity, and diffusion coefficient of O2 in water. Estimations indicate that a considerable part of the resistance to O2 transfer in fish gills is attributable to diffusion limitation in water, particularly with increased ventilation provoked by hypoxia or swimming.