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.     

Effects of social and visual contact on the oxygen consumption of juvenile sea bass measured by computerized intermittent respirometry

The resting metabolic rate (RMR) of juvenile European sea bass Dicentrarchus labrax L. (47·5±1·5 g, 15–18 cm) was 126·2±2·5 mgO₂ kg⁻¹ h⁻¹, and temporal patterns of oxygen consumption were not affcted by visual contact or social interaction with conspecifics. The results suggest that a group effect is not present in juvenile D. labrax , thus no selective advantage of shoaling is gained through lowered metabolism in this facultative schooling species.     

Elevated oxygen uptake and high rates of nitrogen excretion in early life stages of the cobia Rachycentron canadum (L.), a fast-growing subtropical fish

Physiological energetics of cobia Rachycentron canadum were quantified for 18 to 82 days post-hatch (dph) hatchery-reared juveniles to better understand energy transformation and its implications in growth and survival. Mean oxygen consumption rates ( ; mg O₂ h⁻¹) of fish fed ad libitum and fish that were starved significantly increased with increasing wet mass (M; g), = 1·4291 M ^0·8119 and = 1·1784 M ^0·7833, respectively, with a significant reduction in mean metabolic rates of starved fish (19 to 27% specific dynamic action; SDA). Total ammonia nitrogen excretion rates ( A _MM, μmol h⁻¹) also scaled with M and significantly decreased after starvation. Mean mass-specific A _MM and urea excretion rates are the highest reported in the literature, with urea accounting for approximately half the total nitrogen excretion measured in both fed and starved fish. Relatively high energetic rates may allow cobia to develop rapidly into pre-juveniles and be less susceptible to predation and starvation at a comparatively early age.     

The respiration of young coho Oncorhynchus kisutch at gradually declining oxygen levels and during recovery from oxygen deprivation

The respiration of coho salmon, Oncorhynchus kisutch , weighing between 15 and 50 g was measured at gradually declining oxygen levels and at temperatures ranging between 14 and 17°C. The maximum and minimum oxygen concentrations tested were 250 and 40 μmol L⁻¹, respectively. Respiration rates were measured for 1 h periods before oxygen concentration was lowered by 12.5 or 25.0 μmol oxygen L⁻¹. At the end of these endurance tests the oxygen level was returned to normoxic conditions and respiration rates were determined for the recovery period. Under normoxic conditions (> 200 μmol L⁻¹) the respiration of coho levelled around 5.1 μmol g⁻¹ wet weight h⁻¹. At intermediate levels between 150 and 200 μmol oxygen L⁻¹, the average rate increased to 5.8 μmol g⁻¹ h⁻¹, which could be attributed to higher spontaneous activity of the test animals. At low oxygen levels (< 150 μmol⁻¹) average respiration rates dropped to values between 5.5 and 5.7 μmol g⁻¹ h⁻¹, reaching a minimum of 3.8 μmol g⁻¹ h⁻¹ at oxygen levels below 50 μmol L^μ. First mortality was observed in this range. After exposure to reduced oxygen levels the fish maintained a higher respiration rate when again exposed to normoxic oxygen levels above 200 μmol L⁻¹. Increased respiration rates were observed for a recovery period of 6 h.     

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.     

Generation of a reproducible nutrient-depleted biofilm of Escherichia coli and Burkholderia cepacia

An in vitro method of growing bacteria as a defined nutrient-depleted biofilm is proposed. The medium was defined nutritionally in terms of the quantitative composition and by the total amount of nutrient required to achieve a defined population size. Escherichia coli and Burkholderia cepacia were incubated on a filter support placed on a defined volume of solid medium. The change of biomass of the biofilm population was compared with the change in a planktonic culture. The size of the population in stationary phase was proportional to the concentration of limiting substrate up to 40 μmol cm⁻² glucose for E. coli and up to 2·7 × 10⁻⁹ mol cm⁻² iron for B. cepacia . Escherichia coli growing exponentially had a growth rate of μ = 0·30 h⁻¹ in a biofilm and μ = 0·96 h⁻¹ in planktonic culture. The growth rate, μ, for exponentially growing B. cepacia in a biofilm was 1·12 h⁻¹ and in planktonic culture 0·78 h⁻¹. This method allows the limitation of the size of a biofilm population to a chosen value.     

Individual variation in the rate of oxygen consumption by zebrafish embryos

A sensitive microsensor‐based method was used to measure oxygen consumption of individual zebrafish Danio rerio embryos at 6 h intervals from 24 to 75 h post‐fertilization. An increase in oxygen consumption rates from 4·54 to 8·29 nmol O₂ h⁻¹ was found during this period. At the individual level the differences in oxygen consumption rates caused the total oxygen consumption from 24 to 75 h post‐fertilization to vary between 0·261 and 0·462 μmol O₂ per individual with a mean of 0·379 μmol O₂ per individual. A separate carbon mass balance study corroborated the mean total oxygen consumption obtained by yielding a respiratory quotient of 0·80 for this period. These results suggest that there is significant intraspecific variation in the metabolic rate of developing zebrafish embryos, which may influence other early life‐history traits such as growth and starvation resistance.     

Morphometry of some structural parameters affecting oxgyen diffusion in body trunk red muscle at different sizes of a tilapia, Oreochromis niloticus

Morphometric measurements were carried out on some of the structural parameters affecting oxygen diffusing capacity in red muscle of 15 specimens of O. niloticus body weight (b.w.) 0.65–812.3 g. Total capillary length and surface area and total morphometric oxygen diffusing capacity in body trunk red muscle had average values of 4792·7 (± 1740.7 s.e.) m, 415·4 (± 157·3 s.e.) cm² and 0·0213 (± 0·0075 s.e.) ml⁻¹ min⁻¹ cm⁻² mmHg respectively. When expressed as functions of b.w. these parameters had scaling values of 1·02, 1·07 and 0·993 respectively. These figures show a slight increase or almost no change in these structural parameters (which affect diffusion of oxygen to mitochondria in red muscle) per unit weight of fish. This should be important as the role of sustained swimming (by red muscle) becomes more important in larger tilapia. Oxygen diffusion distances were short [3·11 (±0·16 s.e.) μm] which facilitates diffusion of oxygen to mitochondria. The scaling value for oxygen diffusion distances of 0·067 (with respect to body weight) shows a slight increase in this parameter with development. This value is significantly different from zero.     

Oxygen consumption rates of tilapia in fresh water, sea water, and hypersaline sea water

Whole animal oxygen consumption rates and plasma constituents were determined in the tilapia O. mossambicus , acclimated for 1 month in fresh water, sea water, and 1·6 × sea water. Oxygen consumption rates for the three water salinities were: 177·2 ± 16·86, 78·6 ± 2·32, and 195·4 ± 15·39 mg O₂ kg⁻¹ h⁻¹ (means ± 1 s.e.), respectively. Plasma prolactin (tPRL₁₈₈) concentration was significantly lower in 1·6 × sea water compared to fresh and sea water. There were no significant differences among mean plasma cortisol concentration and lysozyme activity. Ventilation was significantly higher in fish in sea water compared to the fish in fresh and 1·6 × sea water. The lowest oxygen consumption rates were found in fish acclimated to sea water. That salinity is probably closest to the brackish waters from which they were captured in the wild, and this agreement likely reflects the selection for optimal morphological and physiological characteristics to live in that environment.     

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.     

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.     

Effects of cadmium chloride on the development of rainbow trout Oncorhynchus mykiss early life stages

The sub-chronic (28–56 days) effects of exposure to low concentrations of cadmium (Cd; 0·05, 0·25, 0·50 and 2·50 μg l⁻¹) shortly following fertilization on embryos, larvae and juvenile rainbow trout Oncorhynchus mykiss were examined. Premature hatching occurred at lower concentrations (0·05 and 0·25 μg l⁻¹ Cd), however, delayed hatching was seen in the 2·50 μg l⁻¹ Cd group, with >90% of hatching occurring on the last day of the hatching period. Larval growth was negatively affected by Cd exposure in a concentration-dependent manner. Larvae exposed to 2·50 μg l⁻¹ Cd were 13·9 ± 0·8% shorter in total length ( L _T) and weighed 22·4 ± 3·5% (mean ± s . e .) less than controls at the end of the exposure period. Plasma sex steroid concentrations (oestradiol in juvenile females and 11-ketotestosterone in juvenile males) were elevated (four- to 10-fold over controls) in exposed fish in both males and females, following 28 days of exposure to 0·05, 0·25 and 0·50 μg l⁻¹ Cd, respectively. These results suggest that environmentally realistic concentrations (in the μg l⁻¹ range) of Cd can affect the development of O. mykiss impacting embryos, larvae and juvenile fish.     

The effects of water hardness upon the uptake, accumulation and excretion of zinc in the brown trout, Salmo trutta L.

The effects of water hardness (9 and 220 mgl⁻¹ as CaCO₃) upon zinc exchange in brown trout exposed to 0.77 μmol Zn 1⁻¹ have been investigated using artificial soft water (<49.9 μmol Ca ^l-1, <40.1 μmol Mg 1⁻¹) and mains hard water (1671.7 μmol Ca 1⁻¹, 493.6 μmol Mg 1⁻¹) of known composition. Both hard and soft water-adapted fish exhibited a bimodal pattern of net zinc influx. Net zinc influxes during both fast and slow uptake phases were significantly greater ( P <0.001) in soft (82.9 and 6.2 μmol Zn 100 g⁻¹ h⁻¹) than in hard water (46.3 and 2.4 μmol Zn 100 g h⁻¹). Zinc efflux (- 0.2 μmol Zn 100 g⁻¹ h⁻¹) was enhanced only in hard water during the slow net influx phase.
Brown trout exposed to zinc in hard water and placed in metal-free media exhibited a greater net efflux (- 25.6 μmol Zn 100 g⁻¹ h⁻¹) of the metal than did fish in soft water (-4.2 μmol Zn 100 g⁻¹ h⁻¹) treated in the same manner. Tissue ⁶⁵Zn activities reflected both the differences in uptake and excretion rates of the metal between hard and soft water fish. During zinc exposure (0.77 μmol Zn 1⁻¹) high water hardness reduced tissue burdens of the metal by reducing net branchial influx, and enhancing efflux of the metal in hard water fish.     

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.     

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.     

Exposure to low concentrations of dissolved ammonia promotes growth rate in walleye Sander vitreus

The objective of the current study was to examine whether sublethal (moderate) levels of dissolved ammonia may be beneficial to growth in juvenile walleye Sander vitreus (recent evidence in juvenile rainbow trout Oncorhynchus mykiss has shown significant increases in protein synthesis in the presence of moderately elevated concentrations of dissolved ammonia). Moderately elevated dissolved ammonia concentrations between 100 and 300 μmol l⁻¹ suppressed routine aerobic metabolic activity by 20% during acute trials (2 h), while promoting specific growth rate (>50%) and elevating whole body soluble protein content by 20% in the early stages (14–42 days) in chronic ammonia exposure experiments. Juvenile S. vitreus held at ammonia concentrations between 107·6 ± 5·5 and 225·5 ± 4·7 μmol l⁻¹ (mean ± s . e .) grew significantly faster than control fish and significantly reduced plasma cortisol levels (<3 μg dl⁻¹). Results from this study suggest that chronic exposure to moderate amounts of dissolved ammonia significantly increase growth rates in juvenile S. vitreus by increasing nitrogen accessible for supplementary protein deposition leading to somatic development.     

Impact of clay particles on the cutaneous exchange of oxygen across the chorion of Atlantic salmon eggs

Rates of oxygen consumption for Atlantic salmon Salmo salar embryos approaching hatching were determined. Values were recorded using a 'closed system' experimental set‐up. A magnetic stirrer was used to ensure that zones of oxygen depletion did not develop in the micro‐environment surrounding the respiring eggs. Recorded values of oxygen consumption ranged from 0·0024 to 0·0038 mg O₂ egg⁻¹ h⁻¹, with a mean consumption rate of 0·0032 mg O₂ egg⁻¹ h⁻¹. The values of oxygen consumption were similar to those reported in other studies using a closed system experimental set‐up, however, they were lower than those reported in a study adopting a flow‐through system. The introduction of clay‐sized sediment to the incubation chamber created a thin film (<1 mm) of sediment on the egg surface, and resulted in reduced rates of oxygen consumption. The additional 0·3 g of clay sediment reduced oxygen consumption by an average of 41% and the addition of a further 0·2 g of clay sediment reduced consumption by an average of 98%. Two explanations for the recorded reduction in consumption were proposed: (i) the creation of a low permeability seal around the eggs restricted the availability of oxygen to the incubating embryos and (ii) the clay‐sized fine sediment physically blocked the micro‐pore canals in the egg membrane, thereby restricting oxygen uptake.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Morphological and functional alterations induced in trout intestine by dietary cadmium and lead

Effects of oral administration of lead and cadmium on structure and function of trout intestine were investigated in Salmo gairdneri. Fish were fed either cadmium (5 mg kg*¹ fish per day) or lead (10 mg kg⁻¹ fish p er day) and sacrificed after a 15 or 30 day treatment.
Levels of cadmium and lead in kidney, liver and spleen were significantly increased by the 15th day of treatment.
Following both cadmium and lead treatment, morphological observations showed an increased mucous cell activity, a disruption of intestinal brush border and an increased renewal rate of absorptive cells.
Influx (J_ms), outflux (J_sm) of chlorine and sodium ion and net fluxes were measured on perfused intestinal segments and ouabain-sensitive sodium, potassium-ATPase (Na, K-ATPase) activity was determined on intestinal scrapings. Cadmium did not alter either sodium chlorine transepithelial fluxes or sodium, potassium-ATPase activity, but lead did. In the middle intestine, lead modified significantly transepithelial sodium and chlorine fluxes (J_ms Na: 3.21 ± 0.34 to 1.79 ± 0.29 and J_ms Cl: 3.32 ± 0.34 to 1.86 ± 0.22μmol h⁻¹ cm⁻², n = 6) after 30-day diet. J_net remain unchanged and Na, K-ATPase activity decreased. In the posterior intestine, lead altered only J_ms Na (1.95 ± 0.31 to 0.37 ± 0.09μmol h⁻¹ cm⁻²) and J_ms Cl. Consequently J_nes were also decreased.
So, although both cadmium and lead induce morphological disorders in the middle and in the posterior intestine of the trout, they have different effects on the absorption mechanisms of ions.     

Activity of methanotrophic bacteria in Green Bay sediments

Abstract Sediment pore water samples obtained from a 19 m station in Green Bay in Lake Michigan were examined for levels of ambient dissolved methane and copper, and for the potential for in situ methane oxidation by methanotrophs found within surface sediments. The in situ methane concentration in the upper oxic sediment layer ranged from 20–150 μmol · 1⁻¹ at this station. The activity of methanotrophs and the kinetics of methane oxidation in these sediments were demonstrated by the uptake of radiolabeled methane. K_s values varied between 4.1–9.6 nmol · cm³ of sediment slurry. High V_max values (12.7–35.2 nmol · cm⁻³ · h⁻¹) suggest a large population of methanotrophs in the sediments. An average methane flux to the oxic sediments of 0.24 mol · m⁻² · year⁻¹ was calculated from the pore water methane gradients. Pore water concentrations of copper in the upper sediment layer ranged from 10–120 nmol · 1⁻¹. Based upon the copper concentration, other measured parameters, and equilibrium conditions defined by WATEQF4, an estimate for dissolved free Cu²⁺ concentration of 5–38 nmol · 1⁻¹ pore water was obtained. Several factors control the rate of methane oxidation, including oxygen, methane, and the bioavailability of free Cu²⁺.