Studies in the Calcium and Phosphorus Metabolism of the Crab, Podophthalmus vigil (Fabricius)

By employing modifications of the molt classification by Drach (1939) and Hiatt (1948), it was discovered in laboratory-maintained crabs (Podopbtbalmus vigil) that a partial desiccation occurred during proecdysis followed by a rehydration at the A stages. The inorganic and organic content of the carapace, mid-gut gland, gills, and muscles were followed during the molt cycle. The carapace had the greatest inorganic fluctuations. The mid-gut gland and muscle tended to increase in both organic and inorganic matter during premolt, suggesting that these organs may serve as reservoirs for these components. The calcium and total phosphorus constituents of these organs and of the blood were determined at the various molt stages. Fluctuations in the amounts of these two elements were observed in all sampled tissues. The storage of calcium in the mid-gut gland and muscles during premolt is discussed. Phosphorus was found to be stored in the digestive gland during postecdysis but not in proecdysis. The muscle also tended to store phosphorus during premolt. As P. vigil becomes older, i.e., larger, it is unable to resorb from the exoskeleton the same quantity of calcium, but it is able to recalcify the new exoskeleton to the same extent as does a smaller crab