オタマジャクシを使った呼吸行動の観察

―鰓呼吸から肺呼吸への変化―

抄録

For an elementary school children, observation of animal behavior would be important to understand life history of animals. In the present study, we developed teaching materials for the understanding of respiration, especially differences between branchial and pulmonary respirations. Tadpoles of the American bull frog (Rana catesbeiana) generally take dissolved oxygen from water by branchial respiration and through skin. However, if dissolved oxygen in water is low, they sometimes perform air breathing with pulmonary respiration. To understand the change from branchial respiration to pulmonary respiration in tadpoles, we manipulated conditions (abiotic conditions [water pressure, oxygen concentration, and carbon dioxide concentration], biotic conditions [quantity of motion, population density, and developmental stage]) of tank where tadpoles were introduced, and counted the number of air breathing. We also compared the number of air breathing among different developmental stages of tadpoles, because it is supposed that tadpoles during metamorphosis would increase the dependency on pulmonary respiration. The number of air breathing behavior of tadpoles clearly increased when the dissolved carbon dioxide was increased. This indicates that when dissolved oxygen in water is low, brachial respiration is not useful and tadpoles use pulmonary respiration to take the oxygen from air. As the developmental stage prodeeded, the number of air breathing behavior increased. This would reflect physiological transitions during the metamorphosis in which lungs are developing and gills are disappearing. Air breathing behavior of tadpoles is easily observed. By making this experiment with tadpoles, elementary school children would understand the respiration of animals. We emphasized that observation and experiment of animal behavior would be important as teaching materials at elementary school.