. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESPIRATION IN A MARINE PULMONATE 341 PO. in d CM O ( mm Kg) 80 160. 50 °/o Air Saturation 100 FIGURE 3. The rates of oxygen consumption (VO2/W045, ml O2h ') by Amphibola crenata in declining oxygen tensions (PO2: mm Hg) at different salinities after two and 12 h exposure to anoxia. Solid circles: 125, 100, and 75% sea water and 2 h anoxia; open circles: 50% sea water and 2 h anoxia; triangles: 25 and 0% sea water and 2 h anoxia; solid squares: all salinities and 12 h anoxia. Pc = zone of critical pressure. N
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RESPIRATION IN A MARINE PULMONATE 341 PO. in d CM O ( mm Kg) 80 160. 50 °/o Air Saturation 100 FIGURE 3. The rates of oxygen consumption (VO2/W045, ml O2h ') by Amphibola crenata in declining oxygen tensions (PO2: mm Hg) at different salinities after two and 12 h exposure to anoxia. Solid circles: 125, 100, and 75% sea water and 2 h anoxia; open circles: 50% sea water and 2 h anoxia; triangles: 25 and 0% sea water and 2 h anoxia; solid squares: all salinities and 12 h anoxia. Pc = zone of critical pressure. N = 10 for each salinity tested. all three studies indicate that respiratory rates in air and water vary according to whether the animals are exposed or submerged. Accordingly, it might be expected that Amphibola would show a higher rate of oxygen consumption in air than in water. This is not the case (Table I). The one major difference between the snails previously studied and A. crenata is that Amphibola is a pulmonate, and the others are prosobranchs. Amphibola employs the mantle cavity as a lung and has been described as being at a "lung-fish" stage of gastropod evolution (Morton and Miller, 1973). As this snail occupies a tran- sitional habitat between marine and terrestrial conditions it is not surprising that it can use aerial and aquatic oxygen equally well. Possibly evolutionary position, not position on the shore, influences the snail's respiratory capabilities. Kinne (1971) has divided the effects of salinity on the rate of oxygen con- sumption in marine and brackish-water invertebrates into four categories: (1) in- crease in subnormal salinities and/or decrease in supranormal salinities, (2) increase in sub- and supranormal salinities (3) decrease in sub- and supranormal salinities, (4) both remain essentially Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration
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