Loss of division potential in culture: aging or differentiation?

drostatic pressure (5), whereas the volume of gas deposited by the swim bladder decreases hyperbolically relative to increasing hydrostatic pressure (16). The maximum hydrostatic pressure for maintenance of swim bladder volume may be derived by integration of linear and hyperbolic models (Fig. 2). The hydrostatic pressure at which a 545-mm yellow eel can just maintain its swim bladder volume is 6.8 atm (58 m). A 545-mm silver eel can maintain its swim bladder volume to a pressure of 15.9 atm (149 m). Thus the elevated rate of gas deposition and the reduced rate of diffusive gas loss in silver eels may extend the depth at which the volume of their swim bladders is maintained by at least 91 m. The silver eels examined in this study would not be able to maintain an inflated swim bladder to a depth of 2000 m. However, silver eels collected during downstream migration close to the coast in Rhode Island are not fully mature (17). There probably is further modification in swim bladder morphology and physiology during the oceanic phase of the spawning migration. ROBERT C. KLECKNER Migratory Fish Research Institute and Department ofZoology, University of Maine, Orono 04469