194 
PACIFIC SCIENCE, Vol. XXI, April 1967 
excess. If the availability of the resorbed con- 
stituent is sparse, the majority of this element 
is usually stored. Crayfish generally store some 
of the resorbed calcium and phosphorus as 
small buttons, called gastroliths, in the lin- 
ing of the stomach. Gastrolith formation and 
dissolution have been followed throughout 
the ecdysis cycle by Damboviceanu (1932), 
Numanoi (1937), Keyer (1942), Scudamore 
(1942, 1947), Travis (1955 b, I960, 1963), 
and McWhinnie (1962). Marine crustaceans 
generally store some of the resorbed calcium 
and phosphorus in the mid-gut gland. Paul and 
Sharpe (1916) have reported that this process 
occurs in Cancer pagurus. This also occurs in 
Carcinus maenas (von Schonborn, 1912 ; Robert- 
son, 1937), in Maia squinado (Drach, 1939), in 
Hemigrapsus nudis (Kincaid and Scheer, 1952) 
and in the lobster, Panulirus argus (Travis, 
1955^). Miyawaki and Sasaki (1961) found 
the same in the fresh water crayfish, Procam- 
barus. Calcium is present in relatively high con- 
centrations in sea water and therefore this ele- 
ment may not be a limiting factor in molting, 
and so not much of it may need to be stored 
during proecdysis of a marine crab. The con- 
centration of phosphate in Hawaiian waters, 
however, is small (Sather, 1966), and there- 
fore it would seem to be necessary for the ani- 
mal to conserve this element to a greater extent 
than calcium. After ecdysis is completed, the 
organism would use the resorbed and stored 
materials for calcification of the new exoskele- 
ton. The amount of inorganic material stored, 
however, is not sufficient to account for the 
total amount found in the intermolt crustacean. 
Therefore, the animal must actively concentrate 
the elements from the environment. 
The molt cycle of crustaceans has been the 
subject of a great number of investigations. 
Apart from descriptions of morphological 
changes, the mineral metabolism has been stud- 
ied to a certain extent, particularly changes in 
calcium and phosphorus content (Travis, 1954, 
1955^, 1963). But such changes have been in- 
vestigated only at random periods in the molt 
cycle, and only in certain tissues and organs 
(glands). Some emphasis has been placed on 
the effect of hormonal influences (eyestalk hor- 
mones, etc.) on the alterations (Carlisle, 1954; 
McWhinney, 1962). No data have been avail- 
able on calcium and phosphorus metabolism 
throughout the entire molt cycle of a crab, nor 
has anything been known of the concentrations 
and distribution of these elements in the animal 
at times of calcification and decalcification, pe- 
riods of major importance in the cycle. There- 
fore, these studies were undertaken on the 
physiological processes which occur in the molt 
cycle of the crab, Podophthalmus vigil. 
MATERIALS AND METHODS 
In the period from March 1961 to October 
1963, approximately 1,450 specimens of P. 
vigil were collected from Kaneohe Bay, Oahu, 
Hawaii and transported to the University of 
Hawaii Marine Laboratory. The animals were 
sexed, staged, tagged, and placed in aquaria 
with a continuous supply of fresh sea water. 
Modifications of the classification schemes of 
Drach (1939) and Hiatt (1948) were em- 
ployed to determine the molt stages of P. vigil. 
A descriptive analysis of the molt scheme was 
presented by Sather (1966). Crabs in the same 
stage were placed in a specific aquarium. The 
animals were usually fed pieces of frozen fish 
twice a week, but occasionally fresh crab muscle 
or frozen beef liver was substituted. 
When a crab reached a desired stage, it was 
removed from the aquarium and carefully dried 
with tissue paper. A 1 ml blood sample was 
taken from the heart by making a small hole 
with a dental drill in the carapace immediately 
posterior of the cardiac and mesobranchial su- 
ture and inserting a No. 21 -gauge hypodermic 
needle fitted to a syringe into the exposed peri- 
cardium. The crab was then killed and rinsed 
with distilled water. The gills, mid-gut gland, 
muscle, and carapace were dissected free, and 
these, together with the "remainder,” were 
placed into separate tared crucibles. After weigh- 
ing, the crucibles were placed in a drying oven 
for 12 hours at 114°C. After weighing, they 
were dry-ashed at 550°C for 24 hours. The 
fresh, dry, and ashed weights were recorded and 
the water, organic, and inorganic contents were 
calculated. Aliquots of the ashed tissues were 
taken for the determinations of calcium and 
phosphorus. The blood samples were stored for 
later chemical analysis. The exuviae were treated 
in the same manner except that the fresh 
