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.     

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.     

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.     

Oxygen consumption in Oreochromis niloticus (L.) in relation to development, salinity, temperature and time of day

Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O₂ larva⁻¹ h⁻¹, of older yolk sac larvae 10.09 μl O₂ larva⁻¹ h⁻¹, and of one-month-old fry 32.99 μl O₂ larva⁻¹ h⁻¹. The QO₂ values showed a decrease with development and growth, ranging from 21.2–26.0 μl O₂ mg⁻¹ h⁻¹ in newly hatched larvae to 2.97 μl mg⁻¹ h⁻¹ in one-month-old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12-24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q₁₀ factor increased from 2.25 to 3.43 with increasing size. Day-old yolk-sac larvae, late yolk-sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.     

Simultaneous phototrophic and chemotrophic growth in the purple sulfur bacterium Thiocapsa roseopersicina M1

Abstract The anoxygenic phototrophic purple sulfur bacterium Thiocapsa roseopersicina was grown in illuminated continuous cultures with thiosulfate as growth limiting substrate. Aeration resulted in completely colorless cells growing chemotrophically, whereafter the conditions were changed to a 23 h oxic/1 h anoxic regime. After 11 volume changes at a dilution rate of 0.031 h⁻¹ (35% of μ_max) a time dependent equilibrium was established. During the 23 h oxic periods bacteriochlorophyll a synthesis (BChl a ) was not observed, whereas during the 1 h anoxic periods synthesis was maximal (i.e. 1.1 μg (mg protein)⁻¹ h⁻¹). As a result the BChl a concentration gradually increased from zero to an average value over 24 h of 1.9 μg (mg protein)⁻¹. Concomitantly, the protein concentration increased from 13.9 mg 1⁻¹ during continuous oxic conditions to 28.8 mg 1⁻¹. For comparison, the protein concentration during fully phototrophic growth at an identical thiosulfate concentration in the inflowing medium was 53.7 mg 1⁻¹. The specific respiration rate was 8 μmol O₂ (mg protein)⁻¹ h⁻¹ during full chemotrophic growth and gradually decreased to 3.5 μmol O₂ (mg protein)⁻¹ h⁻¹ after 11 volume changes at the regime employed. These data show that T. rosepersicina is able to simultaneously utilize light and aerobic respiration of thiosulfate as sources of energy. The ecological relevance of the data is discussed.     

Ammonium ion affecting tylosin production by Streptomyces fradiae NRRL 2702 in continuous culture

Nitrogen regulation in tylosin production by Streptomyces fradiae NRRL 2702 was studied in chemostat culture using a soluble synthetic medium. The maximum value of specific tylosin formation rate ( q _TYL) was 1·13 mg g⁻¹ h⁻¹ at the specific growth rate (μ) of 0·05 h⁻¹, and q _TYL decreased with increasing levels of the specific growth rate after reaching a rate of 0·1 h⁻¹. The optimum conditions for tylosin formation were that the specific ammonium ion uptake rate ( q _N) and μ were 0·13 mmol g⁻¹ h⁻¹ and 0·05 h⁻¹, respectively. The specific formation rates of threonine dehydratase (TDT) and tylosin were repressed by high levels of specific ammonium ion uptake rate. This study showed the adaptation to chemostat cultures of the nitrogen regulation of tylosin fermentations.     

Photosynthesis and photoassimilation of glucose during photomixotrophic growth of Marchantia polymorpha cells in suspension culture

Even in the presence of glucose the growth of Marchantia polymorpha L. (cell line HYH-2F) requires light, and growth is more sensitive to 10⁻⁶ M 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea than to 10⁻⁴ Antimycin A. The inability of the cells to grow in the dark is due to the low level of respiration. The respiration rate under light increased to four times the dark value. The values of the compensation ratio (the photosyntehtic rate/the respiration rate) for the oxygen exchange were below 1.0 daring the growth period, although oxygen evolution was found. At the early exponential phase, oxygen evolution was 0.373 μmol (mg cell dry weight)⁻¹ h⁻¹ [61.7 μmol (mg chlorophyll)⁻¹ h⁻¹]. M. polymorpha cells are unable to grow anaerobically in the light without a supply of carbon dioxide. When 1% carbon dioxide in nitrogen is supplied, photochemically produced oxygen and energy are sufficient for sustained growth although at significantly reduced yields in both cell dry weight and chlorophyll. Photosyntehtic CO₂ assimilation rate was 0.13 μmol (mg cell dry weight)⁻¹ h⁻¹[11.3 μmol (mg chlorophyll)⁻¹ h⁻¹]. At least one-third of the carbon atoms in cellular constituents seem to be derived from atmospheric carbon dioxide, which indicates that M. polymorpha cells grow photomixotrophicaily.     

Gas exchange in intact isolated chloroplasts from Chlamydomonas reinhardtii during starch degradation in the dark

During starch degradation in intact isolated chloroplasts from Chlamydomonas reinhardtii gas exchange was studied with a mass spectrometer. Oxygen uptake by intact chloroplasts in the dark never exceeded 1.5% of the starch degradation rate [maximum 15 nmol O₂ (mg Chl)⁻¹ h⁻¹ consumed. 1 000 nmol glucose (mg Chl)⁻¹h⁻¹ degraded]. Evolution of CO₂ under aerobic conditions [9.8–28 nmol (mg Chl)⁻¹ h⁻¹] was stimulated by addition of 0.1–0.5 m M oxaloacetate [393–425 nmol CO₂ (mg Chl)⁻¹ h⁻¹]. Pyridoxal phosphate (5 m M ) inhibited starch degradation by more than 80%, but had no effect on O₂ uptake. Starch degradation rates and CO₂ evolution did not differ under acrobic and anaerobic conditions. Increasing P_i in the reaction medium from 0.5 m M to 5.0 m M stimulated starch degradation by 230 and 260% under aerobic and anaerobic conditions, respectively. A rapid autooxidation of reduced ferredoxin was observed in a reconstituted system consisting of purified Chlamydomonas ferredoxin, purified Chlamydomonas NADP-ferredoxin oxidoreductase (EC 1.6.7.1) and NADPH. Addition of isolated thylakoids from C. reinhardtii did not affect the rate of O₂ uptake. Our results clearly indicate the absence of any oxygen requirement during starch degradation in isolated chloroplasts.     

EFFECT OF DISSOLVED OXYGEN PARTIAL PRESSURE ON THE ACCUMULATION OF ASTAXANTHIN IN CHEMOSTAT CULTURES OF HAEMATOCOCCUS LACUSTRIS (CHLOROPHYTA)

The effect of dissolved oxygen partial pressure on the accumulation of astaxanthin in the green alga Haematococcus lacustris ( Gir.) Rostaf (UTEX16) was studied in N-limited continuous chemostat cultures. The steady-state astaxanthin content measured against culture volume, cell number, and biomass dry weigh of Haematococcus cultures was proportional to the dissolved O₂ partial pressure in the culture medium, over the range of 0–50% O₂ The steady-state biomass dry weight concentrations remained at between 0.52 and 0.57 g. L^-1 over the range of dissolved O₂ partial pressure studied. Steady-state cell densities at dissolved O₂ partial pressures above the air saturation level (1.13–1.58 × 10⁵ cells.mL^-1) were about half of that measured at lower dissolved O₂ partial pressures (2.42–2.63 × 10⁵ cells.mL^-1). Both biflagellated zoospores and nonmotile aplanospores were found at steady state. The fraction of nonmotile cells was higher at dissolved O₂ partial pressures above the air saturation level (94.44–98.01%) than at dissolved O₂ partial pressure below the air level (79.64–86.12 and 91.75% ).     

Effects of rapid changes in oxygen concentration on the respiration of carrot roots

Rates of CO₂ production and O₂ consumption from aged disks of carrot ( Daucus carota L.) root tissues were measured for 4 h after they were transferred from 21% to 0, 1, 2, 4 or 8% O₂ in gas mixtures. A transient peak in the rate of CO₂ production started 5 to 7 min after transfer to 2% or lower O₂ mixtures and peaked at 50 min. After the peaks in CO₂ production from the 0, 1 and 2% O₂ treatments and after the stable production from the 4 and 8% O₂ treatments, the rate of CO₂ production from all low O₂ treatments started to decline at 50 min, reaching stable rates by 160 to 240 min. Concentrations of lactate and ethanol that were significantly higher than the 21% O₂ controls had started to accumulate in disks between 10 and 50 min after exposure to atmospheres containing 2% or less O₂. Production of CO₂ started to increase 5 to 7 min after transfer to 0, 1 and 2% O₂, while the initial decline and then rise in pH and the accumulation of ethanol did not occur until 30 min after the change in atmosphere. Ethanol accumulation paralleled the increase in pH; first at 0.4 μmol g⁻¹ h⁻¹ from 30 to 60 min as the pH shifted from 5.97 to 6.11, and then at 0.08 μmol g⁻¹ h⁻¹ from 60 to 100 min as the pH stablized around 6.12. The peak at 50 min in CO₂ production roughly coincided with the shift from the rapid to the slow change in pH and ethanol accumulation.     

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.     

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.     

Influence of soil O2 and CO2 on root respiration for Agave deserti

Respiration measured as CO₂ efflux was determined at various soil O₂ and CO₂ concentrations for individual, attached roots of a succulent perennial from the Sonoran Desert, Agave deserti Engelm. The respiration rate increased with increasing O₂ concentration up to about 16% O₂ for established roots and 5% O₂ for rain roots (fine branch roots on established roots induced by wetting of the soil) and then remained fairly constant up to 21% O₂. When O₂ was decreased from 21 to 0%, the respiration rates were similar to those obtained with increasing O₂ concentration. The CO₂ concentration in the root zone, which for the shallow-rooted A. deserti in the field was about 1 000 μl l^-1, did not affect root respiration at concentrations up to 2 000 μl l^-1, but higher concentrations reduced it, respiration being abolished at 20 000 μl l^-1 (2%) CO₂ for both established and rain roots. Upon lowering CO₂ to 1 000 μl l^-1 after exposure to concentrations up to 10000 μl l^-1 CO₂, inhibition of respiration was reversible. Uptake of the vital stain neutral red by root cortical cells was reduced to zero, indicating cell death, in about 4 h at 2% CO₂, substantiating the detrimental effects of high soil CO₂ concentrations on roots of A. deserti . This CO₂ response may explain why roots of desert succulents tend to occur in porous, well-aerated soils.     

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).     

Oxygen and nitrate respiration in a reed swamp sediment from a eutrophic lake

Seasonal measurements of the oxygen and nitrate uptake by a reed swamp sediment were carried out in a shallow, eutrophic Danish lake, Arreskov Sø. The oxidation of organic carbon in the sediment by aerobic and nitrate respiration was 290 and 188 g C m⁻² yr⁻¹ respectively. During winter, nitrate respiration amounted to 94% of the total carbon oxidation, whereas it was zero during summer. On an annual basis nitrate respiration constituted 39% of total respiration. Sediment nitrate uptake was correlated to nitrate concentration. In consequence of this the nitrate uptake rates varied during the year from zero in summer to 55 mg N m⁻² d⁻¹ in spring.
Oxygen uptake rates varied from 30 to 250 mg O₂ m⁻² h⁻¹ during the year, with a maximum uptake in August. The oxygen uptake per year was calculated to 860 g O₂ m⁻². The oxygen uptake rate was correlated to lake temperature and Kjeldahl nitrogen content of the sediment. The oxygen uptake rate, however, showed no correlation with loss on ignition of the sediment. A Q₁₀-value of 2.2 was found for lake measurements in the temperature interval of 5–15°C. The corresponding O₁₀-value in the laboratory was 2.6. A high microbial biomass indicated by the maximum content of Kjeldahl nitrogen and the lowest ratio of loss on ignition on Kjeldahl nitrogen appeared in late August, when the maximum oxygen uptake occurred. The oxygen uptake rate increased during the time interval from sampling to the start of the experiments.     

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.     

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.     

Sequence of gonadal events and oestradiol levels in Sparus aurata (L.) under two photoperiod regimes

Individually tagged Sparus aurata were kept in tanks with running sea water (21°± 2°C) during their second and third years of life. Gonads were biopsied and blood was sampled at monthly intervals. Thirteen of 50 fish in the second year and 24 of 35 fish in the third year were phenotypically females. Fish kept under 16L/8D photoperiod from July 1981 to August 1982 did not reach maturation; waves of initial ovarian growth alternated with waves of atresia. When photoperiod was shortened as from August 1982, gonadal development commenced within a month and proceeded at a rate higher than that of the control fish reared under natural photoperiod. Under natural photoperiod oestradiol serum levels (E₂) were relatively low during the resting phase, May-October (108 ± 11 pg ml⁻¹), and during the late vitellogenic phase (502 ± 76 pg ml⁻¹). High levels (1669 ± 312 and 1240 ± 172pg ml⁻¹) occurred during the early vitellogenic and the maturational phases. The high level of E₂ during the spawning season of S. aurata is explained by earlier reports indicating a prolonged breeding season with daily release of eggs, and alternating daily surges of E₂ and 17α, 20β, dihydroxy-4-pregnen-3-one, possibly a 'maturational progestin' in this fish. In phenotypic males, E₂ was highest during early spermatogenic phases (745 ± 142pg ml⁻¹) but was low (155 ± 11 pg ml⁻¹) in males with running sperm.     

Photoautotrophic growth in suspension culture of cells from the moss, Barbula unguiculata

Chlorophyllous cells in suspension culture from the moss, Barbula unguculata Hedw., grown under photoheterotrophic conditions were transferred to photoautotrophic conditions. The cells started to grow photoautotrophically without selection. Maximum growth was observed under irradiances of more than 5 W m² and in an atmosphere enriched with 1% (v/v) CO₂. Under optimum growth conditions, dry weight and chlorophyll content in the culture had increased 20-fold after 20 days of cell growth. High concentration of chlorophyll [10–20 μg (mg dry weight)⁻¹] and high photosynthetic actively [30–70 μmol O₂ evolved (mg chlorophyll)⁻¹ h⁻¹] were observed throughout the culture period. In sugar-free culture medium, cell growth did not occur in the dark or in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) under light, although cell growth was observed in glucose-containing medium under those conditions. When cells that were grown photoautotrophically for one year were transferred to glucose-containing medium under ordinary air, they started to grow heterotrophically both in the light and in the dark.     

Bacterivory by starved marine heterotrophic nanoflagellates of two species which feed differently, estimated by uptake of dual radioactive-labelled bacteria

Abstract: The rates of ingestion of bacteria and of accumulation of bacterial biomass by hungry Pteridomonas danica and Paraphysomonas imperforata were measured using dual radioactive-labelled bacteria in experiments lasting 4–8 h. Pteridomonas continuously consumed 4–5 bacteria h⁻¹ throughout experiments lasting 8 h, irrespective of bacterial concentration above a threshold of about 5 × 10⁵ bacteria ml⁻¹, and continued to catch bacteria even below this density. The clearance rate of about 1 nl cell⁻¹ h⁻¹ at higher bacterial concentrations increased three or four times as bacterial numbers fell. Paraphysomonas cells, with only half the biomass of Pteridomonas , ingested up to 10 bacteria h⁻¹ at high bacterial concentrations, and gradually reduced the feeding rate, effectively ceasing to feed at 10⁶ bacteria ml⁻¹; their initial clearance rate of 1–2.5 nl cell⁻¹ h⁻¹ subsequently fell as low as 0.1 nl cell⁻¹ h⁻¹. Estimation of feeding rate by extrapolation from short-term experiments on such flagellates requires extreme caution. These flagellates, starved to levels typical of the natural environment, accumulated ingested bacterial biomass at an efficiency of between 16 and 21%, indicating that in nature they would recycle 80% or more of the nutrients contained in their food.