Table 2.
PCr or AP depletion rates and Na+-K+-ATPase cost and maximal activity. Absolute cost is the difference in rates between treatments ((CN+IA) – (CN+IA+OU)), and fractional cost is absolute cost divided by the rate with CN+IA.
| Species | PCr or AP depletion rate (mM min-1) (CN + IA) |
PCr or AP depletion rate (mM min-1) (CN + IA + OU) |
Na+-K+-ATPase cost (mM min-1) |
Na+-K+-ATPase fractional cost |
Na+-K+-ATPase activity (µmol min-1 g-1) |
|||||
|---|---|---|---|---|---|---|---|---|---|---|
| Small†‡ | Large†‡ | Small†‡ | Large†‡ | Small§ | Large§ | Small§ | Large§ | Small†§ | Large†§ | |
| F. aztecus | 0.14 ± 0.01 (5) | 0.11 ± 0.01 (5) | 0.04 ± 0.02 (5) | 0.07 ± 0.01 (8) | 0.096 | 0.046 | 0.68 | 0.41 | 18.96 ± 2.58 (11) | 8.83 ± 3.70 (9)* |
| P. pugio | 0.18 ± 0.03 (5) | 0.20 ± 0.02 (5) | 0.06 ± 0.02 (5) | 0.14 ± 0.04 (5) | 0.115 | 0.059 | 0.64 | 0.3 | 31.37 ± 4.16 (13) | 29.56 ± 3.86 (11) |
| P. argus | 0.15 ± 0.01 (5) | 0.09 ± 0.02 (6) | 0.06 ± 0.01 (5) | 0.06 ± 0.01 (5) | 0.086 | 0.038 | 0.57 | 0.41 | 15.05 ± 2.81 (10) | 11.51 ± 2.18 (11) |
| H. americanus# | 0.14 ± 0.01 (5) | 0.09 ± 0.18 (5) | 0.07 ± 0.01 (5) | 0.06 ± 0.01 (5) | 0.073 | 0.036 | 0.52 | 0.39 | 24.03 ± 0.10 (11) | 12.80 ± 0.22 (13)* |
| P. clarkii | 0.21 ± 0.02 (5) | 0.35 ± 0.02 (6) | 0.10 ± 0.02 (5) | 0.18 ± 0.02 (5) | 0.105 | 0.171 | 0.51 | 0.49 | 25.96 ± 2.89 (10) | 10.94 ± 1.22 (11)* |
| C. sapidus | 0.18 ± 0.26 (5) | 0.33 ± 0.04 (5) | 0.09 ± 0.02 (5) | 0.13 ± 0.01 (5) | 0.097 | 0.199 | 0.53 | 0.6 | 17.26 ± 3.17 (11) | 12.90 ± 3.01 (13) |
| M. mercenaria | 0.16 ± 0.02 (5) | 0.17 ± 0.02 (5) | 0.08 ± 0.02 (5) | 0.08 ± 0.01 (5) | 0.078 | 0.092 | 0.5 | 0.55 | 19.81 ± 5.45 (8) | 4.16 ± 0.79 (10)* |
| F. majalis | 0.12 ± 0.01 (5) | 0.10 ± 0.02 (4) | 0.06 ± 0.01 (5) | 0.09 ± 0.02 (5) | 0.058 | 0.018 | 0.49 | 0.17 | 7.91 ± 2.23 (10) | 5.55 ± 1.26 (9) |
| C. striata | 0.10 ± 0.01 (5) | 0.07 ± 0.01 (5) | 0.06 ± 0.01 (6) | 0.06 ± 0.01 (5) | 0.039 | 0.01 | 0.38 | 0.15 | 3.93 ± 0.43 (15) | 3.37 ± 0.61 (17) |
| O. chrysoptera | 0.12 ± 0.01 (5) | 0.11 ± 0.02 (4) | 0.07 ± 0.01 (5) | 0.08 ± 0.01 (6) | 0.054 | 0.035 | 0.44 | 0.3 | 5.92 ± 0.95 (9) | 3.97 ± 0.86 (6) |
| L. rhomboides | 0.10 ± 0.03 (5) | 0.11 ± 0.01 (6) | 0.05 ± 0.01 (8) | 0.10 ± 0.01 (6) | 0.047 | 0.008 | 0.48 | 0.07 | 3.09± 0.51 (15) | 2.77 ± 0.70 (9) |
| M. littoralis | 0.13 ± 0.02 (6) | 0.10 ± 0.01 (7) | 0.11 ± 0.01 (6) | 0.09 ± 0.01 (7) | 0.016 | 0.002 | 0.13 | 0.02 | 11.04 ± 2.82 (11) | 3.91 ± 0.71 (13) |
| T. carolinus | 0.13 ± 0.04 (5) | 0.09 ± 0.03 (5) | 0.09 ± 0.01 (5) | 0.08 ± 0.02 (6) | 0.04 | 0.017 | 0.32 | 0.18 | 11.00 ± 1.96 (13) | 8.16 ± 1.10 (11) |
| P. lethostigma | 0.11 ± 0.02 (5) | 0.10 ± 0.01 (5) | 0.08 ± 0.02 (7) | 0.09 ± 0.01 (7) | 0.033 | 0.012 | 0.29 | 0.13 | 20.68 ± 3.39 (17) | 5.10 ± 0.63 (14)* |
| L. microlophus | 0.07 ± 0.01 (5) | 0.08 ± 0.01 (4) | 0.05 ± 0.01 (5) | 0.06 ± 0.02 (4) | 0.016 | 0.013 | 0.24 | 0.17 | 3.80 ± 0.60 (9) | 2.35 ± 0.53 (10) |
| G. micrura | 0.11 ±0.02 (6) | 0.10 ± 0.015 (6) | 0.07 ± 0.01 (4) | 0.09 ± 0.01 (4) | 0.04 | 0.014 | 0.36 | 0.14 | 3.23 ± 0.79 (10) | 2.60 ± 0.44 (10) |
Kruskal-Wallis tests found effects of species (†) and
Wilcoxon tests found a difference between inhibitor treatments when all species were pooled (‡) in PCr/AP depletion rate for both size classes.
Absolute and fractional Na+-K+-ATPase cost was significantly lower in the large size class than the small when all species were pooled (§, Wilcoxon test).
Na+-K+-ATPase activity had effects of species (†) and
a difference between size classes when species were pooled (§) and
the * indicates significant differences between size classes within a species (Wilcoxon tests).
Values are means ± SEM and N values are in parentheses.
Data for H. americanus are from18.