The swimbladder volume and air volume within the breathing chambers of the anabantoid fish Colisa lalia have been measured. These data help in the understanding of some of the functions of these organs and are necessary for an analysis of their role in hearing and sound production. By means of a simple trick (based on new data) it was possible to analyse the time course of air volume changes in the breathing chambers at different temperatures. The results are well described by a simple diffusion model. The temperature-dependence of the time course suggests an interesting increase of the diffusion constant with temperature.