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).     

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.     

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.     

Inter‐individual differences in rates of routine energy loss and growth in young‐of‐the‐year juvenile Atlantic cod

Inter‐individual differences in rates of routine (non‐feeding) metabolism and growth were evaluated in young‐of‐the‐year (YOY) juvenile Atlantic cod Gadus morhua . Rates of O₂ consumption, CO₂ production and ammonia (TAN) excretion were measured in 64, 25–43 mm standard length ( L _S) YOY growing at different rates (0·27–0·47 mm day⁻¹) in a common rearing tank. Parameter rates ( y ) increased allometrically ( y = a·M^b ) with increasing body mass ( M ) with b ‐values for O₂ production, CO₂ consumption and TAN excretion equal to 0·81, 0·89 and 0·56, respectively. In some cases, residuals from these regressions were significantly negatively correlated to fish growth rate. In no cases did residuals of parameter rates increase with increasing growth rate. These data suggest that, during unfed periods, relatively fast‐growing fish were more metabolically efficient than slower‐growing fish from the same cohort. The fish condition factor, derived from     , also significantly decreased with increasing growth rate. Results indicated differences in both the rates of routine energy loss and the patterns of growth allocation among YOY Atlantic cod. Since these physiological attributes were positively correlated with growth rate, they may be indicative of 'survivors' in field populations.     

Survival of largemouth bass, bluegill and channel catfish embryos after electroshocking

Survival to hatching was determined after electroshocking embryos of largemouth bass Micropterus salmoides , bluegill Lepomis macrochirus and channel catfish Ictalurus punctatus . Embryos at different developmental stages were exposed for 20 s to homogeneous electric fields (4–16 V cm⁻¹) of direct current (DC) or 60 or 120 Hz pulsed direct current (PDC) in water of 100 μS cm⁻¹ ambient conductivity. For all species, DC reduced survival of embryos at developmental stages before, during, or soon after epiboly; but survival did not differ from controls during later developmental stages. Survival of largemouth bass and bluegill was not reduced by 60 or 120 Hz PDC except for bluegill exposed at 12 h post‐fertilization. Channel catfish embryo survival was <5% when exposed to 60 or 120 Hz PDC at 8 h post‐fertilization, survival improved for embryos exposed at 67 h to 60 Hz but not to 120 Hz, and all embryos survived exposure to PDC at 150 h post‐fertilization. Exposure durations as short as 5 s resulted in <10% survival of largemouth bass during sensitive stages. All bluegill embryos aged 22 h post‐fertilization hatched prematurely after exposure to 16 V cm⁻¹ DC, but survival was not affected. The use of PDC for electroshocking near largemouth bass and bluegill nests could reduce the negative effects on survival of these species; however, PDC can reduce survival of channel catfish embryos.     

Effects of temperature, body size and feeding on rates of metabolism in young‐of‐the‐year haddock

The mean rate of oxygen consumption (routine respiration rate, R _R, mg O₂ fish⁻¹ h⁻¹), measured for individual or small groups of haddock Melanogrammus aeglefinus (3–12 cm standard length, L _S) maintained for 5 days within flow‐through respiratory chambers at four different temperatures, increased with increasing dry mass ( M _D). The relationship between R _R and M _D was allometric ( R _R = α  M ^b ) with b values of 0·631, 0·606, 0·655 and 0·650 at 5·0, 8·0, 12·0 and 15·0° C, respectively. The effect of temperature ( T ) and M _D on mean R _R was described by     indicating a Q ₁₀ of 2·27 between 5 and 15° C. Juvenile haddock routine metabolic scope, calculated as the ratio of the mean of highest and lowest deciles of R _R measured in each chamber, significantly decreased with temperature such that the routine scope at 15° C was half that at 5° C. The cost of feeding ( R _SDA) was c . 3% of consumed food energy, a value half that found for larger gadoid juveniles and adults.     

Endurance swimming of European eel

A long‐term swim trial was performed with five female silver eels Anguilla anguilla of 0·8–1·0 kg ( c . 80 cm total length, L _T) swimming at 0·5 body lengths (BL) s⁻¹, corresponding to the mean swimming speed during spawning migration. The design of the Blazka‐type swim tunnel was significantly improved, and for the first time the flow pattern of a swim tunnel for fish was evaluated with the Laser‐Doppler method. The velocity profile over three different cross‐sections was determined. It was observed that 80% of the water velocity drop‐off occurred over a boundary layer of 20 mm. Therefore, swim velocity errors were negligible as the eels always swam outside this layer. The fish were able to swim continuously day and night during a period of 3 months in the swim tunnel through which fresh water at 19° C was passed. The oxygen consumption rates remained stable at 36·9 ± 2·9 mg O₂ kg⁻¹ h⁻¹ over the 3 months swimming period for all tested eels. The mean cost of transportation was 28·2 mg O₂ kg⁻¹ km⁻¹. From the total energy consumption the calculated decline in fat content was 30%. When extrapolating to 6000 km this would have been 60%, leaving only 40% of the total energy reserves for reproduction after arriving at the spawning site. Therefore low cost of transport combined with high fat content are crucial for the capacity of the eel to cross the Atlantic Ocean and reproduce.     

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.     

Effect of feeding level and feeding frequency on specific dynamic action in Silurus meridionalis

The effect of feeding level ( F _L; 0·5 to 4% dry diet mass per wet fish body mass) and feeding frequency (once every 4 days to twice per day) on postprandial metabolic response was investigated in southern catfish Silurus meridionalis at 27·5° C. The results showed that there was no significant difference in the specific dynamic action (SDA) coefficient among the groups of different feeding levels ( P  > 0·05). The duration increased from 26·0 to 40·0 h and the peak metabolic rate increased from 207·8 to 378·8 mg O₂ kg⁻¹ h⁻¹ when the feeding level was increased from 0·5 to 4%. The relationship between the peak metabolic rate ( R _P, mg O₂ kg⁻¹ h⁻¹) and F _L could be described as: R _P = 175·4 + 47·3 F _L( r ² = 0·943, n  = 40, P  < 0·001). The relationship between the SDA duration ( D , h) and F _L could be described as D =30·97 F _L^0·248 ( r ²=0·729, n =40, P  < 0·001).     

Effect of body size, temperature, and salinity on the routine metabolism of larval and juvenile spotted seatrout

Routine oxygen consumption rates of young spotted seatrout Cynoscion nebulosus (Sciaenidae) were measured over a range of temperatures (24, 28, 30 and 32° C) and salinities (5, 10, 20, 35 and 45). Larvae and juveniles, 4·1–39·5 mm standard length ( L _S), ranging several orders of magnitude in dry body mass were used to estimate the mass–metabolism relationship. Oxygen consumption (μl O₂ larva⁻¹ h⁻¹) scaled isometrically with body mass for larvae <5·8 mm L _S(phase I, slope = 1·04) and allometrically thereafter (phase II, slope = 0·78). The inflection in the mass–metabolism relationship coincided with the formation of the hypural plate and an increase in the relative tail size of larvae. Salinity did not have a significant effect on routine metabolism during phase I. Temperature and salinity significantly affected routine metabolism during phase II of the mass–metabolism relationship. The effect of salinity was temperature dependent, and was significant only at 30° C. Response surfaces describing the environmental influences on routine metabolism were developed to provide a bioenergetic basis for modelling environmental constraints on growth.     

Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon

Routine oxygen consumption ( M o ₂) was 35% higher in 1 day starved and 21% higher in 4 day starved adult transgenic coho salmon Oncorhynchus kisutch relative to end of migration ocean-ranched coho salmon. Critical swimming speed ( U _crit) and M o ₂ at U _crit ( M o _2max) were significantly lower in 4 day starved transgenic coho salmon (1·25 BL s⁻¹; 8·79 mg O₂ kg⁻¹ min⁻¹) compared to ocean-ranched coho salmon (1·60 BL s⁻¹; 9·87 mg O₂ kg⁻¹ min⁻¹). Transgenic fish swam energetically less efficiently than ocean-ranched fish, as indicated by a poorer swimming economy at U _crit ( M o _2max     ). Although M o _2max was lower in transgenic coho salmon, the excess post-exercise oxygen consumption (EPOC) measured during the first 20 min of recovery was significantly larger in transgenic coho salmon (44·1 mg O₂ kg⁻¹) compared with ocean-ranched coho salmon (34·2 mg O₂ kg⁻¹), which had a faster rate of recovery.     

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.     

Control of seed development in Arabidopsis thaliana by atmospheric oxygen

Seed development is known to be inhibited completely when plants are grown in oxygen concentrations below 5·1 kPa, but apart from reports of decreased seed weight little is known about embryogenesis at subambient oxygen concentrations above this critical level. Arabidopsis thaliana (L.) Heynh. plants were grown full term under continuous light in premixed atmospheres with oxygen partial pressures of 2·5, 5·1, 10·1, 16·2 and 21·3 kPa O₂, 0·035 kPa CO₂ and the balance nitrogen. Seeds were harvested for germination tests and microscopy when siliques had yellowed. Seed germination was depressed in O₂ treatments below 16·2 kPa, and seeds from plants grown in 2·5 kPa O₂ did not germinate at all. Fewer than 25% of the seeds from plants grown in 5·1 kPa oxygen germinated and most of the seedlings appeared abnormal. Light and scanning electron microscopic observation of non-germinated seeds showed that these embryos had stopped growing at different developmental stages depending upon the prevailing oxygen level. Embryos stopped growing at the heart-shaped to linear cotyledon stage in 5·1 kPa O₂, at around the curled cotyledon stage in 10·1 kPa O₂, and at the premature stage in 16·2 kPa O₂. Globular and heart-shaped embryos were observed in sectioned seeds from plants grown in 2·5 kPa O₂. Tissue degeneration caused by cell autolysis and changes in cell structure were observed in cotyledons and radicles. Transmission electron microscopy of mature seeds showed that storage substances, such as protein bodies, were reduced in subambient oxygen treatments. The results demonstrate control of embryo development by oxygen in Arabidopsis .     

Respiration of steelhead trout sperm: sensitivity to pH and carbon dioxide

Steelhead trout Oncorhynchus mykiss sperm held in seminal plasma or sperm-immobilizing buffer (pH 8·6) at 10° C consumed O₂ at the rate of c . 2 nmol O₂ min⁻¹ 10⁻⁹ sperm; the rate of O₂ consumption was not different in sperm held for 4 or 24 h. Decreasing the extracellular pH from 8·5 to 7·5 either by diluting semen with buffer titrated with HCl or by increasing the partial pressure of CO₂ in the incubation atmosphere resulted in c . a 40% decrease in the rate of sperm respiration. The data did not, however, support the hypothesis that the precipitous reduction in the capacity for sperm motility that occurs as external pH is reduced is a result of a decrease in cellular metabolism. The rate of O₂ consumption of freshly collected semen from different males was not correlated to cellular ATP content or to the proportion of sperm that were motile upon activation; the initial ATP content and sperm motility were positively correlated. The rate of O₂ consumption was not significantly increased following sperm activation or by the addition of an uncoupler of oxidative phosphorylation, carbonyl cyanide p -trifluoromethoxyphenylhydrazone, suggesting that these sperm have little, if any, capacity for increased oxidative metabolism.     

Growth, CO2 consumption and H2 production of Anabaena variabilis ATCC 29413-U under different irradiances and CO2 concentrations

Aims:  The objective of this study is to develop kinetic models based on batch experiments describing the growth, CO₂ consumption, and H₂ production of Anabaena variabilis ATCC 29413-U^TM as functions of irradiance and CO₂ concentration.
Methods and Results:  A parametric experimental study is performed for irradiances from 1120 to 16100 lux and for initial CO₂ mole fractions from 0·03 to 0·20 in argon at pH 7·0 ± 0·4 with nitrate in the medium. Kinetic models are successfully developed based on the Monod model and on a novel scaling analysis employing the CO₂ consumption half-time as the time scale.
Conclusions:  Monod models predict the growth, CO₂ consumption and O₂ production within 30%. Moreover, the CO₂ consumption half-time is an appropriate time scale for analysing all experimental data. In addition, the optimum initial CO₂ mole fraction is 0·05 for maximum growth and CO₂ consumption rates. Finally, the saturation irradiance is determined to be 5170 lux for CO₂ consumption and growth whereas, the maximum H₂ production rate occurs around 10 000 lux.
Significance and Impact of the Study:  The study presents kinetic models predicting the growth, CO₂ consumption and H₂ production of A. variabilis . The experimental and scaling analysis methods can be generalized to other micro-organisms.     

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.     

Reproductive biology of the milk shark Rhizoprionodon acutus and the bigeye houndshark Iago omanensis in the coastal waters of Oman

Female Rhizoprionodon acutus were found to mature between 62 and 74 cm total length ( L _T) whereas males matured between 63 and 71 cm L _T. The L _T at 50% maturity was 64·3 cm for females and 64·7 cm for males. Litter size varied from one to six embryos, and was positively correlated with maternal L _T. Female embryos outnumbered males by a ratio of 2·3:1. The size at birth was c . 37 cm L _T. Full‐term embryos and post‐partum females were observed during all seasons although their occurrence was highest in spring. Spermatozoa were rarely recorded in the oviducal gland, indicating that this species does not store sperm. It was not possible to generate maturity curves for Iago omanensis but it was evident that females matured by the time they reached 35 cm and males were mature by 31 cm L _T. This species displayed a clearly defined reproductive cycle with parturition occurring primarily in spring, after a gestation period of c . 1 year. Maximal embryo size was 19 cm L _T while maximal litter size was 24 embryos. The oviducal gland appeared to act as a seminal receptacle and it appeared that females may utilize these stores by not mating every year.     

Changes in growth performance and proximate composition in Japanese flounder during metamorphosis

Morphological changes are described in Japanese flounder Paralichthys olivaceus larvae and juveniles with emphasis on growth during the period of metamorphosis. Ontogenetic changes in condition factor and lipid, glycogen and protein levels were also analysed to determine the utilization of stored energy. Fish grew from 6·6 to 20·3 mm L _T(1·15 to 84·4 mg in mass, M ) during the period from 11 to 40 days after hatching (DAH) at 19·3° C. Per cent specific growth rate per day (% G day⁻¹) for wet mass was lowest during the metamorphic phase (21–30 DAH) compared to pre‐(11–20 DAH) and post‐metamorphic (31–40 DAH) phases. When L _T and M were expressed as     , the b value was highest during the pre‐metamorphic phase and lowest during the metamorphic phase. These findings indicate that the developmental changes that occur during metamorphosis of Japanese flounder are closely related to the growth pattern. Moisture, lipid and glycogen contents were also at the lowest level during metamorphosis compared to pre‐ and post‐metamorphosis, which suggest that Japanese flounder use their energy reserves to accomplish metamorphosis due to an apparent decline in feeding during this period.     

Early development of milkfish: effects of salinity on embryonic and larval metabolism, yolk absorption and growth

During embryogenesis of Chanos chanos , more than half of the yolk was consumed and the majority of it was converted into larval tissue. Salinity affected both yolk absorption and embryonic and larval growth. Larvae hatched in 20% had larger yolk reserves but were smaller and grew more slowly than larvae in 35 and 50%. Larvae hatched in 35 and 50% had equal amounts of yolk but those from 35% were larger. Oxygen consumption rates increased during development (from 0.06 ± 0.01 μl O₂ egg^–1 h^–1 by blastulae to 0.37 ± 0-01 μl O₂ egg^–1 h^–1 by prehatch embryos and 0–43 ± 0–03 μl O₂ larva ^–1 h ^–1 by newly-hatched larvae) and were significantly affected by salinity. Eggs and yolk-sac larvae incubated in 35% consumed more oxygen than those in the low and high salinities. Salinity affected both the rate and pattern of yolk utilization but salinity-related differences in metabolism, yolk absorption, and growth were not related directly to the osmotic gradient. Low salinity retarded yolk absorption while high salinity reduced yolk utilization efficiencies. Differences in oxygen consumption rates were probably related to variations in the relative amounts of metabolically active embryonic and larval tissue and/or higher activity levels rather than differential osmoregulatory costs. 35% is probably the most suitable salinity for incubation and larval rearing of milkfish.     

Scaling of oxygen consumption of Lake Magadi tilapia, a fish living at 37°C

Rates of oxygen consumption were measured in the geothermal, hot spring fish, Oreochromis alcalicus grahami by stopped flow respirometry. At 37° C, routine oxygen consumption followed the allometric relationship: V o₂=0.738 M ^0.75, where V o₂ is ml O₂ h ⁻¹ and M is body mass (g). This represents a routine metabolic rate for a 10 g fish at 37° C of 0.415 ml O₂ g⁻¹ h ⁻¹ (16.4 μmol O₂ g ⁻¹ h ⁻¹). Acutely increasing the temperature from 37 to 42° C significantly elevated the rate of O₂ consumption from 0.739 to 0.970 ml O₂ g ⁻¹ h ⁻¹ ( Q ₁₀=l.72). In the field, O. a. grahami was observed to be 'gulping' air from the surface of the water especially in hot springs that exceeded 40° C. O. a. grahami may utilize aerial respiration when O₂ requirements are high.