The active transport of oxygen and carbon dioxide into the swim-bladder of fish

The active transport of oxygen and carbon dioxide into the swim-bladder of fish isdiscussed. The rete mirabile is a capillary network which is involved in the gas secretioninto the bladder. The rete is regarded as a counter-current multiplier. Lactic acid whichis produced in the gas gland generates in the rete single concentrating effects for oxygenand carbon dioxide; i.e., for equal partial pressures the concentrations of the gases inthe afferent rete capillaries are higher than those in the efferent ones. The singleconcentrating effects were calculated from measurements of sea robin blood (Root, 1931).The multiplication of these effects within the rete for different rete lengths anddifferent transport rates was numerically evaluated. The calculated O₂ andCO₂ pressures in the bladder are in good agreement with the experimentalresults of Scholander and van Dam (1953). The descent velocities at equilibrium betweenbladder pressure and hydrostatic pressure are discussed for fishes with different retelengths.