Ontogeny of the Digestive Enzymes of Tadpoles ofLithobates catesbeianus

The transition from aquatic to terrestrial phase in amphibians, called metamorphosis, is accompanied by ecological, morphological, physiological, and biochemical changes. These enable the digestive system of the animal to take up nutrients when the feeding habit changes from omnivorous/herbivorous in tadpoles to carnivorous in adults. To better understand this process, this study investigated the activity of four hydrolases in the digestive system of bullfrog (Lithobates catesbeianus) at all stages of larval development in which the animals feed from exogenous sources. Digestive enzyme activity increased from the beginning of the feeding phase until pre-metamorphosis, which is related to the maturation of the digestive system. The increase was more significant in the period of pro-metamorphosis, coinciding with the accumulation of energy reserves necessary for metamorphosis and the increased growth of the animal. During the climax of metamorphosis, the activities of digestive enzymes decreased, because th...