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First published online April 18, 2006
Journal of Experimental Biology 209, 1639-1650 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02180
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Metabolic, respiratory and cardiovascular responses to acute and chronic hypoxic exposure in tadpole shrimp Triops longicaudatus

S. L. Harper1,* and C. L. Reiber2

1 Department of Environmental and Molecular Toxicology, Oregon State University, Environmental Health Sciences Center, 1011 ALS, Corvallis, OR 97331, USA
2 Department of Biology, University of Nevada, Las Vegas NV 89154, USA


Figure 1
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  		Fig. 1. Mass-specific O2 consumption for tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderate (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions exposed to progressive hypoxia. Values are means ± s.e.m. (N≥7). In some cases, the error bars were smaller than the symbols.

 

Figure 2
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  		Fig. 2. (A) Ventilatory rate measured as the beats per minute of respiratory appendages and (B) ventilatory amplitude measured as the mean maximal distance between the 4th and 5th appendages during five consecutive ventilatory strokes. Tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderately hypoxic (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions were exposed to four environmental PO2s (20, 13.3, 10 and 1 kPa O2). Values are means ± s.e.m. (N≥13). *Significant difference from control animals at same PO2 (P<0.05).

 

Figure 3
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  		Fig. 3. (A) Heart rate, (B) stroke volume and (C) cardiac output of tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderately hypoxic (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions exposed to normoxic (20 kPa O2) and hypoxic (10, 5 and 2 kPa O2) conditions. Values are means ± s.e.m. (N≥13). Significance is assumed at the level of P<0.05: asignificant difference from control animals at same PO2; bsignificant difference from the same animal at preceding PO2; csignificant difference from the same animals at 20 kPa O2.

 

Figure 4
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  		Fig. 4. Hemoglobin concentrations of tadpole shrimp reared under normoxic (19–21 kPa O2), moderate (10–13 kPa O2) or severe hypoxic (1–3 kPa O2) conditions. Values are means ± s.e.m. (N≥10). *Significant difference from control (normoxic) animals (P<0.05).

 

Figure 5
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  		Fig. 5. Hemoglobin concentrations of tadpole shrimp reared under normoxic (19–21 kPa O2) (open bars) conditions and then switched as adults to severe hypoxic (1–3 kPa O2) conditions for 5, 7 or 10 days. Black bars indicate animals reared under severe hypoxic conditions and switched as adults to normoxic conditions for 5, 7 or 10 days. Day 0 is prior to switch. Values are means ± s.e.m. (N≥7). Significance is assumed at the level of P<0.05: asignificant difference from normoxic animals at the same day; bsignificant difference within rearing groups from the values at day 0.

 

Figure 6
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  		Fig. 6. Oxygen binding of hemoglobin from tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderately hypoxic (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions at 25°C. The partial pressures of O2 required to half-saturate hemoglobin (P50) are given in Table 1. Values are means ± s.e.m. (N≥7).

 

Figure 7
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  		Fig. 7. Hill plot of hemoglobin for tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderately hypoxic (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions. Maximal slope for each rearing group represented by regression line. Cooperativities (nH) for each group are given in Table 1. Values are means ± s.e.m. (N≥7). In some cases, the error bars were smaller than the symbols.

 

Figure 8
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  		Fig. 8. Changes in O2 consumption/transport ratio with PO2 for tadpole shrimp reared under normoxic (19–21 kPa O2; open circles), moderately hypoxic (10–13 kPa O2; gray circles) or severe hypoxic (1–3 kPa O2; black circles) conditions. Values are means ± s.e.m. (N≥7). Significance is assumed at the level of P<0.05: asignificant difference from control animals at same PO2; bsignificant difference from the same animal at preceding PO2; csignificant difference from the same animals at 20 kPa O2.

 




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