Growth Aspects of Calcium Carbonate Crystals of the Endolymphatic Sac in the Tree Frog (Hyla arborea japonica): A Pulse-Chase Study

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Abstract
The growth process of CaCO3 crystals of the endolymphatic sac in the tree frog was studied. Tree frogs were maintained in a SrCl2 solution, and endolymphatic CaCO3 crystals were marked by incorporation of Sr salt. This “Sr mark” was then studied by line X-ray microanalysis (Sr, Lα line XMA) and scanning electron microscopy (SEM) with or without CaCl2 afterloading. When Sr-loaded frogs were chased with CaCl2, the peak of Sr specific X-ray pulse (Sr, Lα) which indicates the main location of this metal moved from the pointed ends toward the equator of the crystals, thereby changing the inverted V-shaped curve to an inverted V-shaped curve at the equator or a broad peak. However, these phenomena did not occur unless there was a CaCl2 afterload. These facts seem to indicate that endolymphatic CaCO3 crystals grow by adding Ca salt to their surfaces where they had previously incorporated Sr.