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

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Abstract
Blood Ca rises markedly preceding molt, approaches the normal level rather rapidly following molt and remains approximately normal for most of the 14-day postmolt observation period (Stage A, B and early C). The large amounts of Ca resorbed from the old skeleton preceding molt account for most of the excess Ca which appears in the blood. Blood levels remain relatively normal following molt. This is facilitated by concentration of Ca from the sea water absorbed at and following molt, by reduced excretion of this ion, and by the use of reserve Ca stored in the hepatopancreas as calcospherite. Because of the amounts of Ca entering the blood from the old skeleton, large quantities are excreted during the premolt period. By the 3d day following molt (Stage B), urine Ca falls below normal inter-molt 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 Ca 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. Blood protein of Panulirus increases preceding molt, declines following molt and reaches a subnormal value by the 3d day. 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 P thus causing increases in the total P content but not the inorganic fraction. Blood inorganic phosphate concentrations fall significantly below normal at 7 days following molt (end of Stage B) and remain low throughout the 14-day period of observation. This is due to the fact that the animals have gone through a period of inanition (2 weeks preceding molt and 1 week following molt) coupled with depletion of P stores in the hepatopancreas (end of Stage B) as hardening of the skeleton proceeds. Blood levels fall concomitantly with depletion of P stores and probably do not approach normal until P is replenished from food and until hardening of the skeleton is approximately complete.

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