Meeting Abstract

36.7  Thursday, Jan. 5  Plasticity of lung development in frogs ROSE, C.S.*; JAMES, B.; James Madison University

In contrast to previous attempts to raise frogs in normoxic water without access to air, we found that under such conditions Xenopus laevis tadpoles can routinely complete climax metamorphosis, albeit more slowly and with a higher percentage of laggards. More importantly, animals that complete metamorphosis appear fully viable with lungs that are highly stunted and uninflated or possibly absent altogether. This is the first demonstration that lung development in a tetrapod can be effectively inhibited by environmental factors and that a postlarval tetrapod that is normally reliant upon a significant amount of lung respiration under unstressed and inactive conditions can be raised to forego this requirement without suffering ill effects. We used histology to examine air-deprived tadpoles and frogs to determine whether inhibition of lung development results from failure of lung buds to develop and grow or from failure of differentiated lungs to inflate. To further test the plasticity of lung development, we scored the ability of air-restored animals to recover lungs of normal size as a function of developmental stage and time after air access is restored. Lung recovery was also correlated with swimming and breathing behaviors to assess their relationship with this process. Levels of cell division in the lung tissue of air-deprived, air-restored and untreated animals were compared to assess its role in the development and inflation of normal and recovered lungs. Experiments were also carried out to determine the effect of inhibiting lung development on growth and developmental rates under varying conditions of water flow.