THE MOLTING CYCLE OF THE SPINY LOBSTER, PANULIRUS ARGUS LATREILLE. III. PHYSIOLOGICAL CHANGES WHICH OCCUR IN THE BLOOD AND URINE DURING THE NORMAL MOLTING CYCLE

Abstract

1. Total resorption of organic and mineral material in the area of softening is 19.7%. Of the total organic material, 23.0% is resorbed and of the total mineral material 12.8% is resorbed. The most abundant mineral element making up the exoskeleton of Panulirus is calcium, followed by magnesium and phosphorus (Table I). Of the total of each mineral element determined as the oxide, 8.4% CaO, 20.0% MgO, and 14.3% of P2O5 are resorbed.2. The approximate amounts of organic and mineral material calculated, which would be resorbed from a carapace, devoid of endoskeleton and appendages, indicate that large quantities of these constituents would pass through the blood.3. The Bermuda sea water is rich in calcium and represents the most important source of this element for Panulirus argus. The concentration of phosphorus, on the other hand, is very low. The food is probably the major source of this element.4. Blood calcium rises markedly preceding molt, approaches the normal level rather. rapidly following molt and remains approximately normal for most of the fourteen-day postmolt observation period (Stage A, B and early C). The large amounts of calcium resorbed from the old skeleton preceding molt account for most of the excess calcium which appears in the blood. Some probably appears as a result of increased uptake from sea water at and shortly following molt. In spite of the amount needed to calcify the new skeleton, blood levels remain relatively normal following molt. This is facilitated by concentration of calcium from the sea water absorbed at and following molt, by reduced excretion of this ion, and by the use of reserve calcium stored in the hepatopancreas as calcospherite.5. Because of the amounts of calcium entering the blood from the old skeleton, large quantities are excreted during the premolt period. By the third day following molt (Stage B), urine calcium falls below normal intermolt levels (late Stage C), a time at which over-all hardening of the skeleton has begun. The green glands, therefore, are able to aid in conserving calcium for the hardening process following molt by excreting less. No inorganic phosphate was ever detected in the urine during any stage of the molting cycle. The green glands of Panulirus are indeed important in the regulation of these two ions. The ratio of urine calcium to blood calcium in normal intermolt animals is 1.4. Departure downward from this ratio occurs four and three days preceding molt (late Stage D) and three through seven days following molt (Stage B), otherwise it remains relatively constant.6. Blood protein of Panulirus increases preceding molt, declines following molt and reaches a subnormal value by the third day. The rise in blood protein preceding molt would appear to be brought about by the tremendous amount of organic material, some of which is amino acids, resorbed during this period. Synthesis of protein, by the reconversion of amino acids into new protein, could occur during this period even though the animals do not feed. The decline in blood protein below the normal intermolt level following molt is largely due to the dilution of blood proteins by the amount of water absorbed at and following molt.7. The elevation which occurs in total phosphorus at three days preceding molt is most likely accounted for by resorption from the old skeleton (see Discussion). As hardening of the new skeleton occurs, total phosphorus values decline and remain below normal during most of the fourteen-day observation period. This would appear to be caused by dilution of the blood, at and following molt, with phosphate-deficient sea water, coupled with depletion of phosphorus stores in the hepatopancreas and possibly in other soft tissues.8. No marked change occurs in blood inorganic phosphate preceding molt. This is probably due to the binding of the inorganic phosphate resorbed preceding molt, as acid-soluble or lipid phosphorus, thus causing increases in the total phosphorus content but not the inorganic fraction. Blood inorganic phosphate concentrations fall significantly below normal at seven days following molt (end of Stage B) and remain low throughout the fourteen-day period of observation. This is due to the fact that the animals have gone through a period of inanition (two weeks preceding molt and one week following molt) coupled with depletion of phosphorus stores in the hepatopancreas (end of Stage B) as hardening of the skeleton proceeds. Blood levels fall concomitantly with depletion of phosphorus stores and probably do not approach normal until phosphorus is replenished from food and until hardening of the skeleton is approximately complete.