ACTION OF 1,25-DIHYDROXYVITAMIN D(3) ON CALCIUM-METABOLISM IN THE CRUSTACEAN ORCHESTIA-CAVIMANA DURING THE MOLT CYCLE

1. The possible involvement of vitamin D3 in the calcium metabolism of the terrestrial crustacean Orchestia during the molt cycle was furthe r investigated by measuring the effects of administration of exogenous 1,25 (OH)2D3 on three parameters of the calcium balance in two differ ent compartments of the body. 2. At the hemolymph level, a strong hypo calcemic effect was observed in intermolt and early premolt. Within th e posterior caeca of the midgut, stimulation of calcium storage and ca lcium release were noticed during a short period surrounding the time of exuviation, with concomitant variations of the epithelial carbonic anhydrase activity. 3. These results, together with other data, are di scussed to determine the possible functions of vitamin D3, or related molecules, in the calcium turnover within the different compartments o f the body, according to the successive stages of the molt cycle.