Changes in the density of circulating erythrocytes of the bullfrog tadpole, Rana catesbeiana, in relation to the transition of hemoglobin during metamorphosis.

Abstract 1. 1. The circulating crythrocytes of Rana catesbeiana tadpoles at varying metamorphic stages were studied by the phthalate-microcapillary technique of Danon & Marikovsky (1964 J. Lab. Clin. Med. 64 , 668–674) and by the method of Murphy (1973 J. Lab. Clin. Med. 82 , 334–341), which are used for the separation of erythrocytes according to the density. 2. 2. The erythrocytes of tadpoles were different in the mean density from those of adult frogs. 3. 3. At the metamorphic climax, aged erythrocytes having the tadpole hemoglobin coexisted with young erythrocytes having the frog hemoglobin in the circulating blood. 4. 4. The frog hemoglobin was preferentially synthesized during metamorphosis. 5. 5. All the results suggested that the transition of hemoglobin during metamorphosis was associated with the replacement of erythrocyte population.