The Role of Protozoa in the Nutrition of Tadpoles

Abstract

The intestinal contents of natural populations of Bufo regularis tadpoles were examined and compared with samples of the ooze covering the substrates with which the tadpoles were associated. Random ingestion of faunal and floral organisms occurred. B. garmani tadpoles first fed on lettuce and mud containing microorganisms and then placed on a lettuce diet demonstrated a retarded development when compared to tadpoles maintained on a diet of lettuce and mud. Other tadpoles fed on mud alone never metamorphosed. In a second experiment it was found that B. regularis tadpoles could be reared to metamorphosis in the complete absence of protozoa, both in the presence and in the absence of mud which had been baked for some hours at high temperatures. It was concluded that protozoa are not necessary for the normal growth and metamorphosis of tadpoles. However, there are indications that mud is important for normal development, and it is suggested that this may be due to a variety of factors. Under certain experimental conditions it is proposed that protozoans compete with the tadpoles for the available food.