The Mobilization of the Calcium Carbonate Deposits in the Endolymphatic Sacs of Metamorphosing Frogs

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Abstract
1. Tadpoles of Rana temporaria have been reared in solutions of high and low pH with and without calcium. 2. Methods have been devised for analysing calcium, carbonate and phosphate in individual tadpoles. From these analyses it is possible to determine the distribution of calcium salts between the endolymphatic sacs and the skeleton throughout metamorphosis. 3. A system has been devised for correlating biochemical data with the morphological changes occurring during metamorphosis by means of a scale of ‘developmental days’. 4. The resorption of the endolymphatic deposits is not influenced by the acidity of the environmental solution. 5. Tadpoles reared in solutions containing added calcium had at any one stage in metamorphosis a larger reserve of endolymphatic calcium and a better ossified skeleton than the other tadpoles. 6. During metamorphic climax, when the tadpoles do not feed, the calcareous material in the endolymphatic sac is resorbed to provide calcium for the ossification of the skeleton and to make good any renal loss of calcium. 7. The resorption of endolymphatic calcium carbonate occurs in all tadpoles during metamorphic climax irrespective of the level of calcium in the environmental water. 8. The otoliths do not appear to be resorbed and the spinal portion of the deposits in the endolymphatic sacs may be more labile than those in the cranial regions.