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Biol Bull 157: 221-233. (October 1979)
© 1979 Marine Biological Laboratory
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SALT AND WATER BALANCE IN TWO MARINE SPIDER CRABS, LIBINIA EMARGINATA AND PUGETTIA PRODUCTA. I. URINE PRODUCTION AND MAGNESIUM REGULATION

JOHN C. CORNELL 1

1 Department of Zoology, University of California, Berkeley, California 94720, U.S.A., and the Bodega Marine Laboratory, Bodega Bay, California 94923, U.S.A.

1. A new technique for the continuous collection of crab urine is described. Estimates of urine production, based on this technique, indicate that specimens of Pugettia producta in sea water produce urine at 6.4% body weight (bw)/day. Premolt and postmolt crabs produce 30 and 3.0% bw/day, respectively. Intermolt specimens of Libinia emarginata produce 5% bw/day.

2. The urine production rate for specimens of Pugettia, estimated by weight gain following 24 hr of nephropore-occlusion, is 3.0% bw/day. This is significantly less than that determined by the continuous collection of urine, suggesting that back pressure can interfere with urine production.

3. Ion regulation was examined in specimens of Pugettia. When expressed as a percentage of their concentrations in sea water, the values in blood plasma of chloride, sodium, magnesium, calcium, and potassium are 98, 98, 88, 118, and 105%, respectively, for crabs in sea water. Likewise in the urine, the values for these same ions are 99, 96, 135, 124, and 114%, respectively. Ninhydrin positive substances, measured with glycine standards, are 3.7 and 0.39 mM in blood plasma, respectively. The electrical potential across the body wall of both species of crab is zero.

4. In Pugettia, blocking the nephropores causes an increase in the magnesium concentration in the blood, suggesting that the excretory system is mainly responsible for regulating this ion. However, blocking the nephropores causes no change in the magnesium concentration of urine stored in the bladder, which suggests that the antennal gland is mainly responsible for concentrating magnesium in the urine. Libinia and Pugettia excrete magnesium at a lower rate, and are more permeable to magnesium, than brachyurans which are strong magnesium regulators.




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P. S. Dickinson, E. A. Stemmler, and A. E. Christie
The pyloric neural circuit of the herbivorous crab Pugettia producta shows limited sensitivity to several neuromodulators that elicit robust effects in more opportunistically feeding decapods
J. Exp. Biol., May 1, 2008; 211(9): 1434 - 1447.
[Abstract] [Full Text] [PDF]


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