. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SALT AND WATER BALANCE IX CRABS 21 z O z LU U Z O O Pugett Blood Ca++ Normal Occluded N j—i—i—i—i—i—i—i—i i i i i i i i i i i i i i. 1 105 75 10 15 20 HOURS IN 80% SW T) m O 100 !I! o 95 ^ O 3 90 | QC O 85 o Z o m 80 5 O FIGURE 4. Changes in the blood concentration of calcium in normal and nephropore- occluded specimens of Pugettia producta transferred from 100 to 80% sea water. See Figure 2 for other details. there is a difference among chloride, sodium and calcium (P < ). Comparison of the relative initial rates of
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SALT AND WATER BALANCE IX CRABS 21 z O z LU U Z O O Pugett Blood Ca++ Normal Occluded N j—i—i—i—i—i—i—i—i i i i i i i i i i i i i i. 1 105 75 10 15 20 HOURS IN 80% SW T) m O 100 !I! o 95 ^ O 3 90 | QC O 85 o Z o m 80 5 O FIGURE 4. Changes in the blood concentration of calcium in normal and nephropore- occluded specimens of Pugettia producta transferred from 100 to 80% sea water. See Figure 2 for other details. there is a difference among chloride, sodium and calcium (P < ). Comparison of the relative initial rates of concentration change (Table I), for normal and nephropore-occluded crabs, suggests that the urine is the major route for mag- nesium loss, but that extra-renal routes are of major importance for the other ions. Some estimates of sodium and magnesium loss via the urine are shown in Table II. DISCUSSION Changes in volume and urine production, and diffusion of salts across the body wall are important factors in the short-term adaptation of Libinia einarginata and Pugettia producta to dilute salinity. Weight gain in these crabs is small when compared to that in some soft bodied animals, , Phascolosoma gains 22% bw when placed in 80% SW (Adolph, 1936) ; however, it serves temporarily to store a large portion of the influx of water (Fig. 1), thus lowering the demand on the antennal gland and reducing the potential hydrostatic pressure. At the time of transfer from 100 to 80% SW, if no weight gain occurred, urine would have to be produced at 25 and 15 times the normal rate in Pugettia and Libinia, respectively. Between the first and second hours after transfer, urine production accounts for most of the water influx, since urine production increases by a factor of about 5 and the concentration gradient is much reduced. In both Libinia and Pngettia the sum of the cumulative volume of urine and the weight gain is less than the weight gain in nephropore-occluded animal
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
