THE GAS CONTENT OF THE SWIMBLADDER OF THE ROCK BASS, AMBLOPLITES RUPESTRIS, IN RELATION TO HYDROSTATIC PRESSURE

¹ From the Department of Zoology and Entomology, Ohio State University

1. Rockbass were subjected to various hydrostatic pressures ranging from 540 to 2223 mm. Hg and were observed to reach a state of equilibrium at each experimental pressure.

2. Oxygen deposition accounted for half of the adjustment at the higher hydrostatic pressures.

3. After hydrostatic equilibrium had been reached carbon dioxide diffused out of the swimbladder, and the carbon dioxide percentage decreased toward the level of this gas usually found in fish at the surface of the lake. This loss in volume by the outward diffusion of carbon dioxide was compensated for by the continued deposition of oxygen.

4. Nitrogen was not deposited, and appeared to be only passively important in the adjustment to the changes in hydrostatic pressure.

5. The final adjustment to hydrostatic pressure resulted in a high partial pressure of oxygen, a carbon dioxide partial pressure near the level usually found for this gas in fish at the surface, and a nitrogen partial pressure approximately equal to the partial pressure of this gas in the atmosphere.