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1.
When exposed to hypoxia, eels Anguilla anguilla were able to regulate and maintain Vo2 down to a water oxygen tension ( Pwo2 ) of about 25 mmHg, a value far below those reported in other studies. When exposed to hypercapnia, eels showed a depression in Vo2 as water carbon dioxide tension ( Pwco2 ) increased. Faced with combined hypoxia-hypercapnia, eels showed an increase in their sensitivity to hypoxia, and the critical oxygen tension increased to 40–45 mmHg. The possible mechanisms underlying these responses were discussed, and the implications of such findings for extensive culture of eels were highlighted.  相似文献   

2.
Standard metabolic rates were measured as the rate of oxygen consumption in 33 Scyliorhinus canicula , ranging in weight from 3–929 g. The amount of oxygen consumed per hour (Vo2) changed predictably with body size according to the relationship Vo2=0–104 W0.855, where W represents fish weight in g. On a weight specific basis, the level of standard metabolism in juvenile dogfish (5 g) was nearly double that measured in adults (500 g).  相似文献   

3.
Standard metabolic rate (SMR), active metabolic rate (AMR) and critical oxygen saturation ( Scrit ) were measured in Atlantic cod Gadus morhua at 5, 10 and 15° C. The SMR was 35.5, 57.0 and 78.2 mg O2 kg−1 h−1 and Scrit was 16.5, 23.2 and 30.3%, at 5, 10 and 15° C, respectively. Previously reported SMR for Atlantic cod from arctic waters at 4° C was twice that measured at 5° C in the present study. A possible intraspecific latitudinal difference in the SMR is discussed. The AMR was 146.6, 197.9 and 200.4 mg O2 kg−1 h−1 and the critical swimming speed ( Ucrit ) was 1 6, 1.7 and 1.9 at 5, 10 and 15° C, respectively. The maximum oxygen consumption was found to be associated with exercise, rather than recovery from exercise as previously reported in another Study of Cod metabolism.  相似文献   

4.
Standard metabolic rate ( R s) at 2°C of eight East Siberian cod Arctogadus borisovi , caught in West Greenland, body mass of 601.5 ± 147.6 g (mean ± s.D.), was 40.9 ± 5.9 mg O2 kg-1 h-1 and 59.0 ± 6.6mg O2 kg-1 h-1 when extrapolated to a standardized 100 g fish. R s was compared with three other Gadidae, to test the theory of metabolic cold adaptation (MCA). There was no evidence of MCA in the family.  相似文献   

5.
Abstract. This study investigated the effect of acquired resistance in guinea-pigs on the metabolic rate of adult females of the tick Rhipicephalus evertsi evertsi. Guinea-pigs were subjected to three successive infestations of ticks and the rate of CO2 production (Vco2) measured in first and third infestation engorged females. Ticks which fed on resistant hosts showed a 52% decrease in mass compared to ticks that fed on naive animals. Reduction in mass was accompanied by a decrease in Vco2 (mlh-1) per tick but an increase in mass specific Vco2 (mlg_1h_1). However, both groups shared a single allometric relationship between body mass and metabolic rate (Vco2). We suggest that the differences in size rather than any factor directly relating to the mechanism of acquired resistance account for the differences in metabolic rate between ticks fed on naive and resistant guinea-pigs.  相似文献   

6.
1. The metabolic or respiratory cost of growth ( R G) is the increase in metabolic rate of a growing animal, and it represents chemical potential energy expended in support of net biosynthesis but not deposited as new tissue.
2. Two statistical methods (multiple non-linear regression and analysis of regression residuals) were used to calculate R G from data ( n = 68) from a doubly labelled water study of free-ranging Garter Snakes ( Thamnophis sirtalis fitchi ) in northern California.
3. The sample-wise ('ecological') cost of growth was 2·07 kJ per gram of net growth (equivalent to 8·63 kJ g–1 dry tissue); reanalysis of a subset of efficient growers yielded a more conservative 'physiological' estimate of 1·67 kJ g–1.
4. Our empirical estimate of R G, among the first reported for squamate reptiles and free-living animals of any kind, compares closely with published, laboratory-derived values for ectotherms.
5. The metabolic costs of growth accounted for an average of 30% of total field metabolic rates for these snakes, which were growing at a mean rate of 3% of body mass per day. However, our method probably underestimated the total ecological cost of growth for large animals, because potential growth costs that covary with body size were not included.
6. Distinction between conceptual and empirical energy budgets clarifies relationships among body size, metabolic rates, and the physiological and ecological costs of growth.  相似文献   

7.
Apparent specific dynamic action (SDA) amplitude in young juvenile Atlantic cod Gadus morhua (1 to 8 g wet mass), fed a standardized meal and then exercised in a circular swimming respirometer at a constant swimming speed of 0·5 ± 0·3 body lengths s-1, occurred within l h after feeding in all juveniles. SDA amplitude were 1·4 to 1·8 times higher in fed fish compared to unfed fish, and rates of oxygen consumption decreased as body mass increased. SDA duration had a tendency to decrease with increasing body mass and was shortest, at 6 h, in the smallest fish (1–1·5 g), but increased to 10–11 h in the largest fish. Apparent SDA in fed fish ( R r) scaled with a mass exponent of 0·89, while maximum metabolic rate ( R max) determined by chasing fish to exhaustion and then measuring oxygen consumption for 12 h, and unfed routine metabolic rate (Rr) scaled with a mass exponent of 0·79 and 0·76 respectively. Relative aerobic scope ( R max– unfed R r) did not appear to vary over the 1 to 8 g increase in wet mass. These results show that as body mass increased in young juvenile Atlantic cod: (1) apparent SDA ( R f) increased more rapidly than R max, and (2) apparent SDA took up >98% of the relative aerobic scope and that young Atlantic cod allocated most of the energy to growth, and left little for other metabolic activities.  相似文献   

8.
Abstract.  Metabolic rate variation with temperature, body mass, gender and feeding status is documented for Glossina morsitans centralis . Metabolic rate [mean ± SE; VCO2= 19.78 ± 3.11 μL CO2 h−1 in males (mean mass = 22.72 ± 1.41 mg) and 27.34 ± 3.86 μL CO2 h−1 in females (mean mass = 29.28 ± 1.96 mg) at 24 °C in fasted individuals] is strongly influenced by temperature, body mass and feeding status, but not by gender once the effects of body mass have been accounted for. A significant interaction between gender and feeding status is seen, similar to patterns of metabolic rate variation documented in Glossina morsitans morsitans . Synthesis of metabolic rate-temperature relationships in G. m. centralis , G. m. morsitans and Glossina pallidipes indicate that biting frequency as well as mortality risks associated with foraging will probably increase with temperature as a consequence of increasing metabolic demands, although there is little evidence for variation among species at present. Furthermore, metabolic rate–body mass relationships appear to be similarly invariant among these species. These data provide important physiological information for bottom-up modelling of tsetse fly population dynamics.  相似文献   

9.
Abstract. We determined standard metabolic rate at 25°C in forty-eight species of millipede from southern Africa and compared these data with confident measures of standard metabolic rate previously published for other arthropod groups.Metabolic rate in millipedes was not significantly different from that in beetles, ants or spiders once body mass effects had been accounted for, but was significantly higher than that in ticks.The exponent for the mass scaling of metabolic rate did not vary significantly between the five arthropod orders.Our best estimate for the relationship between standard metabolic rate (μl O2 h-1) and body mass (mg) in non-tick arthropods was 0.86 mass0.73.  相似文献   

10.
To elucidate how excess light energy is dissipated during water deficit, net photosynthesis (PN), stomatal conductance (gs), intercellular CO2 concentration (ci) and Chl a fluorescence were investigated in control and drought-stressed tomato plants ( Lycopersicon esculentum ). Gross O2 evolution (Eo) and gross O2 uptake (Uo) were determined by a mass spectrometric 16O/18O2 isotope technique. Under drought stress PN, gs, ci and Uo decline. While photochemical fluorescence quenching decreases under water deficit, non-photochemical quenching rises. The maximal efficiency of PSII measured in the dark is not affected by drought; however, in the light, Eo decreases under water deficit. The ratio PN/Eo falls under stress while the ratio Uo/Eo increases. We conclude that tomato plants follow a double strategy to avoid photodamage under drought stress conditions: (1) a substantial portion of light energy is emitted as heat and PSII activity is downregulated. This results in a decrease in Eo as well as PN and Uo. Despite reduced charge separation at PSII, the decline of CO2 assimilation because of lowered stomatal conductance and metabolic changes results in the need of degrading excessive photosynthetic electrons. (2) Oxygen is used as an alternative electron acceptor in photorespiration or Mehler reaction and Uo rises relative to Eo.  相似文献   

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