Calcium homeostatic mechanisms and uptake of radioisotopes in the lobster

¹ Department of Physiological Chemistry, Medical School, University of Minnesota, Minneapolis, Minnesota

Hemolymph calcium levels were decreased by one-half by placing lobsters in artificial sea water containing less than 1 mEq/liter calcium ion. In these animals sodium and phosphate content of dry shell was increased but the shell calcium content was not detecsably altered. Calcium appearing in the bathing medium was apparently derived from two sources. While control animals exhibited a significant ability to select calcium in preference to strontium only in gill and mandible tissue, almost all tissues of hypocalcemic animals showed significant uptake of Ca⁴⁵ over Sr⁸⁵. Claw shell acquired more isotope per gram of dry weight than did other calcified tissue. Cesium (Cs¹³⁴) was not taken up to any great extent by internal soft tissues. Gills contained two to three times as much Cs¹³⁴ relative to bathing solution as did gills from animals exposed to solutions containing Ca⁴⁵ and Sr⁸⁵.