Title: EFFECTS OF THIOUREA UPON THE DEVELOPMENT OF ANURAN LARVAE
Abstract: Tadpoles of Rhacophorus schlegelii, Rana japonica and Bufo vulgaris formosus were treated with thiourea of various concentrations, and effects of thiourea on the growth and metamorphosis were examined.1. A passing hyperthyroidism-like condition was observed directly following the initiation of thiourea treatment.2. When the treatment was initiated at earlier tadpole stage and much concentrated solution of thiourea was used, the growth of tadpoles was much more significantly inhibited. When tadpoles were treated for longer periods of time, however, reversed was the case.3. Metamorphic change of the animals was inhibited when treated with thiourea from the early tadpole stage. Among those animals, however, considerable individual variations were observed, and in less concentrated solutions, some of the treated animals continued to advance at metamorphosis.4. It appears likely that a small quantity of the thyroid hormone might be produced in spite of thiourea treatment.5. The treated animals metamorphosed shortly after the cessation of thiourea treatment. The rate of resumed development, however, was learned to be dependent on the magnitude of the preceding treatment.