Figure 1. Osmotic performance of Pseudosesarma moeschi acclimated 14 d in 5%, 10%, 25%, 50%, 75% or 100% sea water (100% sea water = 1000 mOsm). Each symbol represents the mean value of measurements from 6-9 crabs; standard errors of the means are smaller than the symbols used. The solid line represents equal osmotic pressures in the hemolymph and in the external medium ("isoosmotic line").
Figure 2. Regulation of chloride ion concentration in the hemolymph of Pseudosesarma moeschi acclimated 14d in 5%, 10%, 25%, 50%, 75% or 100% sea water. Each symbol represents the mean value from 8-13 crabs; error bars indicate +/- 1 SEM. The solid line represents equal ion concentrations in the hemolymph and in the external medium ("isoionic line").
Figure 3. Na, K-ATPase enzyme specific activity (ESA) in homogenates of Pseudosesarma moeschi gills. Crabs were acclimated two weeks submerged in 5%, 10%, 25%, 50%, 75% or 100% sea water. Each symbol represents the mean value of homogenates from 6-9 crabs; error bars indicate +/- 1 SEM. ANOVA indicates that: a) Na, K-ATPase ESA is significantly affected by external salinity in all gills (F-5,729 = 42.29, P < 0.01); b) ESA varies significantly by gill (F-5,226 = 13.09, P < 0.01); and c) that gill number and external salinity interact significantly (F-23,36 = 2.10, P = 0.024). Duncan's multiple range test showed that: a) in 5%, 25% and 100% SW, ESA's of gills 5 and 6 are significantly larger than those of gills 1-4 and that gill 7 ESA's are not; c) in 50% SW the ESA's of all gills except number 5 are not significantly different from each other and that gill 5 ESA is significantly larger than those of the other gills; and d) in 75% SW none of the gills have ESA's significantly different from each other.
Figure 4. Time course of changes in Na, K-ATPase enzyme specific activity of gill 6 and hemolymph osmotic pressure in Pseudosesarma moeschi after transfer of crabs from 5% sea water to 50% sea water. Each symbol represents the mean value of homogenates or hemolymph samples from 5-6 crabs; error bars indicate +/- 1 SEM. Asterisks indicate significant differences (Student's unpaired t test) between mean ESA's at time zero and at the time indicated. Hemolymph osmolality did not change significantly during the experiment.
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