THE SUBCELLULAR-DISTRIBUTION OF CALCIUM IN THE VISUAL CELLS OF CRAYFISH, OBSERVED WITH THE COMBINED OXALATE-PYROANTIMONATE TECHNIQUE, DEPENDS ON EXTRACELLULAR CALCIUM

1. With the combined oxalate-pyroantimonate method we determined the s ubcellular distribution of calcium in the photoreceptor cells of the c rayfish Orconectes limosus. 2. The calcium antimonate deposits were id entified with the electron microscope. Energy-dispersion X-ray analysi s verified that the electron dense deposits contained calcium and anti mony. 3. Calcium antimonate deposits were found in the submicrovillar cisternae, mitochondria, multivesicular bodies, and pigment granules, as well as in the cytoplasm. 4. The calcium deposits in the cytoplasm of the retinula cell and in the pigment granules were reduced after in cubation of the retinae in a solution with a lowered calcium concentra tion and even more after we permeabilized the plasma membrane with the saponin beta-escin. 5. We suppose that the calcium-storing pigment gr anules participate in the regulation of the cytosolic calcium concentr ation of the crayfish photoreceptor cells.