. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESPIRATION IN THE EXCISED GILL 249 The oxygen consumption of excised C. guanhumi gill tissue (Fig. 1) is higher in dilute sea water than in full strength or concentrated sea water. The elevated Qo2 of excised C. gnanhiiini gill segments in dilute sea water is similar to the in- creased gill Qo2 in Callinectes (King, 1965) where the Q02 of isolated gills mea- sured in 50% sea water increased 10-30% over that in 100% sea water. In C. guanhumi maximum Q02 of gill tissue occurs in 75% sea water (Fig. 1), suggesting that this co
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESPIRATION IN THE EXCISED GILL 249 The oxygen consumption of excised C. guanhumi gill tissue (Fig. 1) is higher in dilute sea water than in full strength or concentrated sea water. The elevated Qo2 of excised C. gnanhiiini gill segments in dilute sea water is similar to the in- creased gill Qo2 in Callinectes (King, 1965) where the Q02 of isolated gills mea- sured in 50% sea water increased 10-30% over that in 100% sea water. In C. guanhumi maximum Q02 of gill tissue occurs in 75% sea water (Fig. 1), suggesting that this concentration of ions is optimal for isolated gill tissue respiration. It 5. O - 20 ' A - CHOLINE CHLORIDE. 0 CONCN. OF KCI OR CHOLINE CHLORIDE (mM) FIGURE 4. Effect of KCI and choline chloride on excised gill respiration. Procedure was similar to that in Figure 3, except that KCI was substituted for NaCl. Each point is the average of up to 6 different crabs. may be noted that Na+ and K+ concentrations in the blood of C. guanhumi are isosmotic with 75% sea water (Quinn and Lane, 1966; Lane, Quinn, and Gifford, unpublished results). We attribute the decrease in Q02 of gill tissues immersed in either more concentrated or more dilute media to diminished activity of ion pumps when the ionic composition of the extracellular fluids is abnormal. Alternatively the decrease in oxygen consumption may reflect a breakdown of the ion pumps as a consequence of osmotic disruption of the tissue. Indeed, the lowest gill oxygen consumption occurred in hyperosmotic media. The cardiac glycoside ouabain inhibits Na+ transport in frog skin (Kofoed- Johnson, 1958), in red blood cells (Glynn, 1957; Whittam, 1958), and in squid. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (
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