Distribution of calcium in the suctorian Discophrya collini: an x-ray microanalytical study.

Discophrya collini is a free-living suctorian with tentacles which can be induced to contract by means of a range of experimental stimuli, including the application of CaCl2 and MgCl2 but not BaCl2. X-ray microanalysis of glutaraldehyde-only fixed cells shows Ca to be present in the cytoplasmic ground substance and elongate dense bodies (EDB). In 10(-1) M CaCl2-treated cells, calcium levels remain unchanged except for a three-fold increase in the EDB. Treatment of cells with 10(-1) M MgCl2 and 10(-1) M BaCl2 does not result in their detection in the cell. It is suggested that EDB may act as reservoirs controlling levels of calcium.