Oxygen uptake in developing eggs and larvae of the cod, Gadus morhua L.

Unfertilised cod eggs showed a mean oxygen uptake rate at 5°C of 0.089 μl O₂, dry wt.⁻¹ h⁻¹; this gradually rose to 0.768 μl O₂ mg dry wt.⁻¹ h⁻¹ in eggs about to hatch. From hatching to complete yolk absorption larvae respired at 1.6 μl O₂, mg dry wt.⁻¹ h⁻¹. During starvation following yolk absorption, uptake fell significantly to 1.1 μl O₂, mg dry ⁻¹ h⁻¹. Much of this decrease in oxygen consumption was shown to be caused by reduction in activity. Loss of weight during the embryo and larval phases could not easily be reconciled with total oxygen consumption; it is suggested that cod embryos and larvae may not rely solely upon endogenous energy reserves during development.     

Effects of thermal stress on respiratory responses to hypoxia of a South American Prochilodontid fish, Prochilodus scrofa

Oxygen consumption (o₂) and respiratory variables were measured in the Prochilodontid fish, Prochilodus scrofa exposed to graded hypoxia after changes in temperature. The measurements were performed on fish acclimated to 25°C and in four further groups also acclimated to 25°C and then changed to 15, 20, 30 and 35°C. An increase in o₂ occurred with rising temperature, but at each temperature o₂ was kept constant over a wide range of O₂ tensions of inspired water ( Pi o₂). The critical oxygen tensions ( Pc o₂) were Pi o₂= 22 mmHg for 25°C acclimated specimens and after transfer from 25°C to 15, 20, 30 and 35°C the Pc o₂ changed to Pi o₂= 28, 22, 24 and 45 mmHg, respectively. Gill ventilation ( _G ) increased or decreased following the changes in o₂ as the temperature changed and was the result of an accentuated increase in breath frequency. During hypoxia the increases in _G were characterized by larger increases in breath volume. Oxygen extraction was kept almost constant at about 63% regardless of temperature and ambient oxygen tensions in normoxia and moderate hypoxia ( P o₂∼70 mmHg). P. scrofa showed high tolerance to hypoxia after abrupt changes in temperature although its survival upon transfer to 35°C could become limited by the capacity of ventilatory mechanisms to alleviate hypoxic stress.     

The effect of temperature and mass on routine metabolism in Sarotherodon (Tilapia)mossambicus (Peters)

A reappraisal of oxygen uptake by Sarotherodon mossambicus was undertaken using a continuous flow respirometer. Measurements were obtained over the temperature range 16°C–37°C for fish weighing between 10 g and 150 g. Oxygen uptake was converted to energy equivalents ( Q _ox) using the value 13.68 J mg O₂^–1and the routine metabolic energy expenditure can be described by the equation E =0.0086 t ^{2 0783} M ^{0 652} where E is the energy requirement for routine metabolism expressed in J h^-1, t the temperature in °C and M the mass in g.     

Field estimates of oxygen consumption for the brine shrimp Parartemia zietziana Sayce (Crustacea: Anostraca) in two salt lakes in Victoria, Australia

SUMMARY. Oxygen consumption of P. zietziana was measured monthly in two saline (>60‰ salinity) lakes from November 1973 to November 1975 with short (<2 h) in situ incubations in BOD bottles. Tests in which oxygen decline was monitored continuously showed that there was no handling effect and respiratory rate was constant down to 1.8–1.9 mg O₂ 1⁻¹, about 40% of the usual initial concentration. Incubations over 24 h demonstrated no diurnal fluctuations in oxygen consumption. Multiple regression analysis indicated that 90% of the variance in respiratory rate ( R in mg O₂x10⁻⁴h⁻¹ individual⁻¹) was accounted for by changes in salinity (3%; S in ‰), temperature (7%; T in °C) and dry weight (8%; W in mg × 10⁻³): log R =−1.123+0.0025+0.021 T+ 0.756 log W. From this equation and data on population density, population respiration was calculated: 91864.5 mg O₂ m⁻² year⁻¹ in Pink Lake and 12367.5 mg O₂ m⁻²year⁻¹ in Lake Cundare.     

Oxygen consumption in Caridina nilotica (Decapoda: Atyidae) in relation to temperature and size

SUMMARY. The oxygen consumption of shrimps ranging from 1 to 30 mg dry mass was determined at 18, 24 and 30°C using a continuous flow recording respirometer based upon a Clark-type oxygen electrode. Respiration (ascribed to routine metabolism) is described by the power curve: R = a M^b , ( R =μg O₂ h⁻¹, M = mg dry mass), which gives values of a = 1.632, 2.564 and 4.181, and b = 0.800, 0.898, and 0.793, at 18, 24 and 30°C respectively. The single expression, R = 0.008 T ^1.829 M ^0.830 provides a reasonable prediction of respiration as a combined function of shrimp size ( M ) and temperature (T, °C). Using an energy equivalent of 14.14 J mg O₂⁻¹ estimates of the energy requirements ( E , J h⁻¹ 10⁻³) of routine metabolism are given by the expression: E = 0.115 T ^1.829 M ^0.830.
Variability in oxygen consumption values between individuals is discussed and the observations on C. nilotica are compared with other crustacean studies.     

A method for long-term measurement of respiration in intertidal fishes during simulated intertidal conditions

Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow-through respirometer system. The system allowed long-term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The M o ₂ of L. pholis , measured at 15° C, was 2·1 μmol O₂ g^–1 h^–1 during aquatic and 1·99 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the M co₂ were 1.67 and 1.59 μmol O₂ g^–1 h^–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The M o₂ of P. barbarus , measured at 28°C, was 4·05 μmol O₂ g^–1 h^–1 during aquatic and 3·44 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the Mco₂ were 3·29 μmol CO₂ g^–1 h^–1 and 2·63 μmol CO₂ g^–1 h^–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re-immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected.     

Routine metabolism of juvenile spot, Leiostomus xanthums (Lacépède), as a function of temperature, salinity and weight

Routine oxygen consumption rates of juvenile spot, Leiostomus xanthums , were measured over a range of temperatures, salinities and fish weights. As predicted, Q O₂ increased with temperature and decreased with body weight. However, Q O₂ decreased with decreasing salinity and did not show the expected minimum at isosmotic concentrations. The data are best described by the relationship: log₁₀ Q O₂ (mg O₂ g⁻¹ h⁻¹) = 0.129 log_lo salinity (%0) + 1.604 log₁₀ temperature (°C)-0.1401og₁₀(g)-2.767.     

Haemoglobin synthesis in Daphnia magna Straus (Crustacea: Cladocera): ecological differentiation between neighbouring populations

SUMMARY. 1. Variations in the haemoglobin index of two neighbouring populations of Daphnia magna were recorded over a range of dissolved oxygen concentrations (0.5–4.0ml O₂ 1⁻¹, 20°C). Reciprocal transfer experiments between habitats compared haemoglobin synthesis in situ.
2. An inverse relationship was found between the oxygen content of pond water and the haemoglobin indices of laboratory and natural populations.
3. Significant genetic differences in the synthesis of haemoglobin were found between the two populations. Animals from the poorly oxygenated habitat (0.8±0.18ml O₂ 1⁻¹) had consistently higher haemoglobin contents (maximum HI, 87.7±4.5) at all experimental and in situ oxygen levels. D. magna from the well oxygenated pond (4.3±0.59 ml O₂1⁻¹) had a lowered physiological ability to synthesize haemoglobin (maximum HI, 48.3±4.2). The process of ecological differentiation in Daphnia populations is discussed.     

Seasonal differences in routine oxygen consumption rates of the bonnethead shark

Routine oxygen consumption rates of bonnethead sharks, Sphyrna tiburo , increased from 141·3±29·7 mg O₂ kg⁻¹ h⁻¹ during autumn to 218·6±64·2 mg O₂ kg⁻¹ h⁻¹ during spring, and 329·7±38·3 mg O₂ kg⁻¹ h⁻¹ during summer. The rate of routine oxygen consumption increased over the entire seasonal temperature range (20–30° C) at a Q ₁₀=2·34.     

Respiration of the carp, Cyprinus carpio L., at 10 and 20° C and the effects of hypoxia

Oxygen consumption of carp acclimated at 10 and 20° C has been measured under routine conditions. Some complications and precautions necessary in continuous flow respirometry are discussed. Routine V o₂ at different levels of hypoxia have been determined. Individual variation leads to scatter in the data and different methods of plotting the relationship between V o₂ and P o₂ are proposed; attention is drawn to differences between inlet (or ambient) P o₂ and inspired P o₂. Using certain criteria a 'critical' oxygen tension of about 95 mm Hg was found at 20° C; Q ₁₀ values are about 2 at normoxia and some suggestions of an increase near to the critical oxygen tension were found. Blood samples from the dorsal aorta showed rising Pa,o₂ of 16 mm Hg which increased to 70–80 mm Hg when P _insp was 90 and they then fall as the inspired oxygen is lowered. During periods of deep hypoxia (25 mm Hg) blood lactate concentration increases steadily and indicates an increasing dependence on anaerobic mechanisms.     

The affect of temperature on the metabolism and behaviour of an endemic amphipod, Hyalella montezuma, from Montezuma Well, Arizona, U.S.A.

1. Hyalella montezuma is endemic to Montezuma Well, Arizona, and is exposed to minimal diel and seasonal temperature fluctuations in the pelagic zone (21 ± 4 °C). Juvenile H . montezuma feed in the pelagic zone during the day and migrate into the littoral vegetation at night, while adults remain primarily in the littoral vegetation.
2. Oxygen consumption ( V O₂) of adult and juvenile H . montezuma was measured at 20, 25 and 30 °C. The V O₂ of both adult and juvenile H . montezuma increased with temperature. However, the V O₂ of juveniles was significantly greater than that of adults at all temperatures, with greatest divergence at 30 °C where mean juvenile V O₂ (6.31 μl mg^–1 dry weight (DW) h^–1) was almost twice that of adults (3.60 μl mg^–1 DW h^–1).
3. Survivorship of juveniles was significantly lower (54%) at 30 °C than at 27.5 °C (95%) after 4 h, whereas adults showed at least a 93% survivorship at both temperatures.
4. Our data suggest that temperature may have been the proximate cue that elicited the diel horizontal migration of juvenile H . montezuma in Montezuma Well, with the behaviour maintained and enhanced by intensive invertebrate predation in the pelagic and littoral zones.     

The affect of temperature on the metabolism and behaviour of an endemic amphipod, Hyalella montezuma, from Montezuma Well, Arizona, U.S.A.

1. Hyalella montezuma is endemic to Montezuma Well, Arizona, and is exposed to minimal diel and seasonal temperature fluctuations in the pelagic zone (21 ± 4 °C). Juvenile H . montezuma feed in the pelagic zone during the day and migrate into the littoral vegetation at night, while adults remain primarily in the littoral vegetation.
2. Oxygen consumption ( V O₂) of adult and juvenile H . montezuma was measured at 20, 25 and 30 °C. The V O₂ of both adult and juvenile H . montezuma increased with temperature. However, the V O₂ of juveniles was significantly greater than that of adults at all temperatures, with greatest divergence at 30 °C where mean juvenile V O₂ (6.31 μl mg^–1 dry weight (DW) h^–1) was almost twice that of adults (3.60 μl mg^–1 DW h^–1).
3. Survivorship of juveniles was significantly lower (54%) at 30 °C than at 27.5 °C (95%) after 4 h, whereas adults showed at least a 93% survivorship at both temperatures.
4. Our data suggest that temperature may have been the proximate cue that elicited the diel horizontal migration of juvenile H . montezuma in Montezuma Well, with the behaviour maintained and enhanced by intensive invertebrate predation in the pelagic and littoral zones.     

Cardiorespiratory status of triploid brown trout during swimming at two acclimation temperatures

At 14° C, standard metabolic rate (75·1 mg O₂ h⁻¹ kg⁻¹), routine metabolic rate (108.8 mg O₂ h⁻¹ kg⁻¹), active metabolic rate ( c . 380 mg O₂ h⁻¹ kg⁻¹), critical swimming speed (U_crit 1·7 BL s⁻¹), heart rate 47 min⁻¹), dorsal aortic pressure (3·2 kPa) and ventilation frequency (63 min⁻¹) for triploid brown trout Salmo trutta were within the ranges reported for diploid brown trout and other salmonids at the same temperature. During prolonged swimming ( c . 80% U _crit), cardiac output increased by 2·3-fold due to increases in heart rate (1·8-fold) and stroke volume (1·2-fold). At 18° C, although standard and routine metabolic rates, as well as resting heart rate and ventilation frequency increased significantly, active metabolic rate and certain cardiorespiratory variables during exercise did not differ from those values for fish acclimated to 14° C. As a result, factorial metabolic scope was reduced (2·93-fold at 18° C v . 5·13-fold at 14° C). Therefore, it is concluded that cardiorespiratory performance in triploid brown trout was not unusual at 18° C, but that reduced factorial metabolic scope may be a contributing factor to the mortality observed in triploid brown trout at temperatures near 18° C.     

Effects of development, temperature and salinity on metabolism in eggs and yolk-sac larvae of milkfish, Chanos chanos (Forsskål)

Oxygen uptake rates and yolk-inclusive dry weiGhts were measured during the egg and yolk-sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk-sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk-sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk-sac stage at 23.28 and 33°C.
Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O₂ egg ⁻¹ h ⁻¹;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O₂ larva ⁻¹ h⁻¹ at 23, 28 and 33°C, respectively; Q₁₀= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q ₁₀= 1.69–3.58) and yolk-sac larvae (Q ₁₀=2.55). Salinity did not affect metabolic rates.
Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q ₁₀= 2.25).     

Respiratory metabolism of Utah chub, Gila atraria (Girard) and speckled dace, Rhinichthys osculus (Girard)

Measurements of active, standard and routine oxygen consumption were made for 207 Utah chub at 6°, 9°, 12°, 18° and 22° C; and 123 speckled dace at 4°, 8°, 12° and 18° C. These were expressed as mathematical functions of water temperature and size of the fish. The mean slopes of log_e oxygen consumption (mg O₂/h) and log_e wet weight (g) were 0.771, 0.526, and 0.619 for active, standard, and routine rates respectively for Utah chub, and 0.943, 0.486, and 0.683 respectively for speckled dace.     

On the diel rhythms in metabolism and activity of post-hatching lesser spotted dogfish, Scyliorhinus canicula

The diel rhythms in metabolic rate ( M_R ) and activity level ( A_L ) were measured for single post-hatching dogfish (weight range, 2.76–10.61 g) at 15° C by the indirect calorimetric method of rate of oxygen consumption ( V O₂) and by video-observation respectively, over a period of 72 b. The mean VO ₂ increased from 62.0 (s.e. 2.9) mg O₂ kg⁻¹ h⁻¹ in the daylight hours to 85.5 (s.e. 3.1) mg O₂ kg⁻¹ h⁻¹ during the dark (light regíme, 12 h L: 12 h D). The simultaneous measurement of A _L also showed mean night elevation from 0.6 (s.e. 0.2) min h⁻¹ in the light phase to 14.5 (s.e. 1.6) min h⁻¹ during the darkness. Bimodal nocturnal activity (BNA) was exhibited by the post-hatching dogfish within the 12 h dark period, with V O₂ increasing from 71.4 (s.e. 2.8) mg O₂ kg⁻¹ h⁻¹ before 01.00 hours to 99.5 (s.e. 4.2) mg O₂ kg⁻¹ h⁻¹ after 01.00 hours. Similarly, A _L also increased from 8.9 (s.e. I.7)min h⁻¹ before 01.00 hours to 21.1 (s.e. 2.8) min h⁻¹ after 01.00 hours. The importance of the results presented to the natural behavioural ecology of the hatching dogfish are discussed.     

Relationships between heart rate and metabolic rate of pike: integration of existing data

The percentage contribution of heart rate ( f _H) to change in oxygen consumption ( V o₂) was examined in relation to body weight and across the metabolic scope of pike. Also the consequences of variability around the regression relating V o₂ and f _H for estimating V o₂ were considered. The percentage contribution of f _H was calculated using two equations, one that ignored and one that included an estimate for oxygen consumed by the gills and absorbed across the skin ( V o_2s). Using both equations the percentage contribution of f _H calculated using maximum and resting values for f _H and V o₂ decreased with weight of pike. The omission of V o_2s, resulted in erroneously high estimates of the percentage contribution of f _H for pike of any given weight. The omission of V o_2s resulted in erroneously high estimates of the percentage contribution of f _H over the region of the metabolic scope where f _H is related linearly to V o₂, whereas the equation that included V o_2s resulted in the expected value of 100%. Assuming zero experimental error and under normoxic conditions, the 95% confidence limits for single estimates of V o₂ from 30–60-min readings of heart rate are ±39% at a heart rate of 30 beats min ⁻¹. Averaged over longer periods the error decreases, and used over several days to estimate meal size the error is of the order of 1%.     

Oxygen consumption of East Siberian cod: no support for the metabolic cold adaptation theory

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.     

Hypometabolism in torpid goldsinny wrasse subjected to rapid reductions in seawater temperature

Goldsinny Ctenolabrus rupestris were subjected to rapid, environmentally realistic, reductions in temperature at 2° C increments from 10 to 4° C over a 3-day period in full-strength sea water. In separate experiments, oxygen uptake measurements and ultrasound recordings of heart rate and opercular motion were carried out at regular intervals over the same temperature regime. Mean oxygen uptake rates fell from 0.042 to 0.028 ml O₂ g⁻¹ h⁻¹ between 10 and 6° C respectively (Q₁₀=2.71). Between 6 and 4° C mean rates decreased from 0.028 to 0.008 ml O₂ g⁻¹ h⁻¹ (Q₁₀=542). Mean opercular motion and heart beat rates decreased from 49.5 and 60.3 beats min⁻¹ respectively at 10° C to 18.7 and 18.0 beats min⁻¹ respectively at 4° C. Most goldsinny subjected to 4° C were observed in a torpid state and would not react to external stimulation. Opercular motion was erratic at 4° C and would at times cease altogether for periods up to 1.3 min duration. Heart movement was diffcult to detect at 4° C and may also have ceased for prolonged periods. Q₁₀ values for opercular motion and heart beat rates recorded between 6 and 4° C were 6.39 and 24.52 respectively compared with values of 2.42 and 2.93 respectively recorded between 10 and 8° C. Such large depressions in metabolism appear not to have been reported previously for a marine fish species. No goldsinny mortalities were recorded at any temperature. The possibility that hypometabolic torpor is an adaptive strategy for goldsinny survival at low environmental temperatures is discussed.     

Oxygen requirements of larvae of the smallmouth bass, Micropterus dolomieui Lacépède

Smallmouth bass larvae became highly sensitive to oxygen deficiency on the second day after hatching and continued so to the 10th day. During this period they could not survive exposure to 1 mg O₂ l^–1 for 3 h at 20° C, and many were killed within 1 h. At 2 mg O₂ l^–1 half the larvae survived 3 h at 20° C; at 2.5 mg l^–1 most survived, and at 3.5 mg l^–1 all survived. Resistance to oxygen deficiency was regained by the 11th day, the majority of the larvae withstanding a 3-h exposure at 1 mg O₂ l^–1. At 25° C the effects of low oxygen concentration were intensified. At 3 and 4 mg O₂ l^–1 and 20° C the normally quiescent larvae became very active, even swimming to the surface 5 or 6 cm above the substrate. Increasing the temperature increased this response. Smallmouth larvae were more sensitive than large-mouth bass larvae to oxygen deficiency.