Rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> energetic responsesto pulsed flows in the American River,California, assessed by electromyogram telemetry

Although rainbow trout Oncorhynchus mykiss within the American River, California, apparently exhibit minimal upstream or downstream movements in response to hydroelectric-power-generation-related pulsed flows, the associated energetic costs are unknown. We implanted rainbow trout (n = 9, ≥30 cm SL) with electromyogram (EMG)-sensor-equipped radio transmitters to assess the swimming behavior and associated energetic costs associated with their responses to pulsed flows. Using laboratory calibrations in a Brett-type swimming respirometer, the trouts’ swimming speeds and oxygen consumption rates were estimated for their in-river EMG data, through a complete hydroelectric power-generation river pulsed-flow sequence (pre-pulse, increasing flow, peak, and decreasing flow stages), on several (mean: 3.2) sampling dates. Using a mixed-linear model, we found that fish swimming speed estimates increased during the increasing flow stage, while the associated mean oxygen consumption rates also increased at this stage. At river flows near the usual peak (>44 m³s⁻¹), swimming speeds and movement rates decreased, possibly due to the fish using the river’s habitat complexities as hydraulic cover. We conclude that rainbow trout incur increased swimming-related energetic costs during increasing flows and, potentially, decreased foraging opportunities at high flows.     

Metabolic effects of dehydroabietic acid on rainbow trout erythrocytes

Oxygen consumption and ATP concentration were measured in rainbow trout erythrocytes incubated in a physiological saline containing 0, 5, 15, 30 or 60 mg/l dehydroabietic acid. DHAA caused a decrease in cellular ATP level and oxygen consumption at concentrations above 15 mg/l. Haemolysis increased markedly, when the cellular ATP concentration decreased below 1 mM. These data suggest that increased breakdown of red cells may be the primary reason for jaundice which is observed in resin acid-toxicated fish.     

Changes in urine flow rate and haematocrit value of rainbow trout Salmo gairdneri (Richardson) exposed to hypoxia

Measurements were made of urine flow rates and haematocrit of rainbow trout exposed to hypoxic conditions (3 mg O₂/1) for 3, 4, 5 or 24 h. Elevated urine flow rates during short time exposure and concomitant increased haematocrit, followed by lower than normal urine flow rates on return to normal aerated water, suggest that haemoconcentration is the initial response to anoxia. Results from longer exposure to hypoxic conditions suggest that the initial period of haemoconcentration is followed by a period of water retention and a return of the blood volume to normal; the sustained elevated haematocrit is thought to be derived from release of erythrocytes from storage organs. During prolonged exposure rainbow trout also become more permeable to water.     

Oxygen consumption and force development in turtle and trout cardiac muscle during acidosis and high extracellular potassium

Relative to species such as rainbow trout, freshwater turtle shows a high tolerance to challenges involving acidosis and increases in extracellular K+. Therefore, the effects of acidosis or high K+ on twitch force and oxygen consumption were examined in ventricular ring preparations from these two species. The oxygen consumption associated with force development was estimated by net oxygen consumption (oxygen consumption during twitch force development minus that during rest). For turtle, elevation of CO2 from 2% (pH 7.7) to 12% (pH 6.9) in the gas equilibrating the muscle bath decreased twitch force by 20% without any effects on oxygen consumption. Decreasing pH from 7.7 to 6.9 with 22 mM lactic acid had similar effects. For trout, CO2-induced acidosis decreased twitch force by approximately 60%. Furthermore, force development became energetically less efficient as it fell disproportionately more than net oxygen consumption. This was not observed for lactic acidosis. For trout but not for turtle, acidosis resulted in an increase in oxygen consumption during rest. An increase in extracellular K+ from 2.5 mM to 10 mM depressed force and oxygen consumption proportionately for both species. Adrenaline (10 microM) increased twitch force for both species and oxygen consumption for trout; it attenuated the effects of high extracellular K+. Neither adrenaline nor high K+ influenced the ratio of force to net oxygen consumption. As opposed to high extracellular K+, acidosis appears to increase the energetic cost of contractility, particularly for the trout heart.     

Chemically mediated learning in juvenile rainbow trout. Does predator odour pH influence intensity and retention of acquired predator recognition?

The prediction that variability in ambient pH will influence the intensity and retention of learned predator recognition in juvenile rainbow trout Oncorhynchus mykiss was tested under laboratory conditions. Juvenile rainbow trout were conditioned to recognize the odour of a novel predator at pH 6·0 or 7·0 and then tested for learned recognition of the predator odour at pH 6·0 or 7·0 at 2 or 7 days post-conditioning. When tested 2 days post-conditioning, rainbow trout exhibited a significant learned antipredator response regardless of predator odour pH. The response was stronger, however, when the test pH matched the conditioning pH. When tested 7 days post-conditioning, rainbow trout only exhibited a learned response when conditioning and testing pH were the same. These results demonstrate that episodic acidification may impair the strength and retention of acquired predator recognition learning. Given the demonstrated survival benefits associated with learned predator recognition in prey fishes, such impairment will probably have considerable negative impacts at both individual and population levels.     

The effect of monooxygenase inducing agents on the incorporation of [35S]methionine into hepatic microsomal protein of rainbow trout (Salmo gairdneri)

Treatment of rainbow trout (Salmo gairdneri) with 150 mg/kg BNF resulted in an increase in hepatic microsomal monooxygenase activity as assessed by ECOD and EROD when compared to those activities in corn oil-pretreated animals. Administration of 100 mg/kg 2,4,5,2',4',5'-hexachlorobiphenyl (6-CB) to trout had no significant effect on these catalytic activities or on BeND. The amount of radioactivity in hepatic microsomes at 24, 48 or 72 hr following the administration of 75 muCi of [35S]methionine was consistently higher in animals pretreated with BNF than in those treated with corn oil or 6-CB. Autoradiography/fluorography of electrophoretograms demonstrated the appearance of at least three radiolabeled bands in the 50,000-60,000 mol. wt range in solubilized microsomes from BNF-treated fish which were not present in microsomes from control animals or fish treated with 6-CB. These data indicate that the stimulation of hepatic microsomal catalytic activities observed following the administration of 3-MC-type agents to rainbow trout is due, at least in part, to induction of enzyme(s) rather than activation of existing enzyme(s). These results further support the observation that fish appear to be non-responsive to phenobarbital-type inducing agents.     

Physiology and biochemistry of the pseudobranch: an unanswered question?

The structure and function of the pseudobranch has long interested scientists, but its overall role has remained a mystery. Previous studies have attributed respiratory, endocrine, osmoregulatory and sensory roles to the pseudobranch, and the present review concentrates on new findings. Perfusion experiments on the pseudobranch of the rainbow trout (Oncorhynchus mykiss) using both erythrocyte suspensions and Ringer solution have shown that this organ is able to generate values for the respiratory quotient (RQ) greater than 1.0. The release of carbon dioxide into the perfusate was found to be largely independent of flow between perfusion rates of 120-190 microl/min and could be inhibited by acetazolamide (10(-5) M), indicating a role for carbonic anhydrase. Noradrenaline (10(-5) M) had no effect on oxygen consumption or carbon dioxide release of the pseudobranch. The rate of carbon dioxide release was also dependent on the pH of the pre-pseudobranch perfusate, carbon dioxide release being reduced at lower perfusate pH values. Based on the glucose balance of the isolated saline-perfused rainbow trout pseudobranch and on the enzyme profiles for the rainbow trout, cod, swordfish and deep-water grenadier pseudobranch, it is suggested that the pentose phosphate shunt might be a source of carbon dioxide, yielding the high RQ values found for this organ. Most evidence now available indicates that the pseudobranch is integrally linked with the choroid rete and the supply of oxygen to the retina of the fish eye.     

Differences in metabolic response to Loma salmonae infection in juvenile rainbow trout Oncorhynchus mykiss and brook trout Salvelinus fontinalis

Routine and post-exercise metabolic rates were measured for juvenile rainbow trout Oncorhynchus mykiss and brook trout Salvelinus fontinalis infected with the microsporidium gill parasite Loma salmonae under laboratory conditions. Rainbow trout increased routine and post-exercise metabolic rate in response to infection compared with controls. Brook trout, on the other hand, lowered routine metabolic rate without effecting post-exercise metabolic rate compared to controls. The result of these 2 different strategies may either reflect defense of metabolic scope or a difference in the rate of recovery of the excess post-exercise oxygen consumption between the 2 species in response to the same infection.     

Some aspects of sustained training of rainbow trout, Salmo gairdneri Richardson

Groups of 6-7 cm length rainbow trout, Salmo gairdneri Richardson, were simultaneously trained at four water velocities (0, 1·4, 2·2 and 3·5 Ls^-1) for a period of 46 days. Oxygen consumption and swimming ability (fatigue time) were then measured. Only training at 3·5 Ls^-1 increased the swimming ability of the fish. A study of the relative proportion of the white and red muscles indicated that the white muscle was increasing its mass at velocities in excess of 2·2 Ls^-1. The oxygen consumption rate of the trained fish was lower than that of the untrained fish when considered over the whole velocity range.     

Comparative susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease.

The susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease, was assessed following dosed exposures to the infectious stages (triactinomyxons). Parallel groups of age-matched brown trout and rainbow trout were exposed to 10, 100, 1000 or 10,000 triactinomyxons per fish for 2 h and then placed in aquaria receiving single pass 15 degrees C well water. Severity of infection was evaluated by presence of clinical signs (whirling and/or black tail), prevalence of infection, severity of microscopic lesions, and spore counts 5 mo after exposure. Clinical signs of whirling disease, including a darkened caudal region (black tail) and radical tail chasing swimming (whirling), occurred first among rainbow trout at the highest dose at 6 to 7 wk post exposure. Black tail and whirling occurred among rainbow trout receiving 1000 and 100 triactinomyxons per fish at 8 to 9 wk post exposure. Only 1 of 20 fish had a black tail among rainbow trout receiving 10 triactinomyxons per fish, although 30% of the fish were infected at 5 mo post exposure. Black tails were observed in brown trout at 1000 and 10,000 triactinomyxons per fish beginning at 11 and 7 wk post exposure, respectively. There was no evidence of the tail chasing swimming (whirling) in any group of brown trout. The prevalence of infection, spore numbers, and severity of microscopic lesions due to M. cerebralis among brown trout were less at each exposure dose when compared to rainbow trout. Infections were found among rainbow trout at all doses of exposure but only among brown trout exposed to doses of 100 triactinomyxons per fish or greater. Risk of infection analyses showed that rainbow trout were more apt to be infected at each exposure dose than brown trout. Spore counts reached 1.7 x 10(6) per head among rainbow trout at the highest dose of exposure compared to 1.7 x 10(4) at the same exposure dose among brown trout. Spore numbers increased with dose of exposure in rainbow trout but not in brown trout. As microscopic lesion scores increased from mild to moderate, spore numbers increased in rainbow trout but not brown trout. The mechanisms by which brown trout resist infections with M. cerebralis were not determined. Cellular immune functions, including those of eosinophilic granular leukocytes that were more prominent in brown trout than rainbow trout, may be involved.     

Effects of Waterborne Copper, Cyanide, Ammonia, and Nitrite on Stress Parameters and Changes in Susceptibility to Saprolegniosis in Rainbow Trout (Oncorhynchus mykiss)

The effects of toxic exposures on the susceptibility of rainbow trout (Oncorhynchus mykiss) to saprolegniosis were evaluated. Fish were exposed to sublethal concentrations of copper (0.25 mg/liter), cyanide (0.07 mg/liter), ammonia (0.5 mg/liter), and nitrite (0.24 mg/liter) for 24 h. After exposure, the fish were challenged by Saprolegnia parasitica (3.6 x 10(sup6) zoospores per liter) for 10 min. Cortisol and cholesterol were used to indicate stress response. Similar increases of cortisol were found for the four tested chemicals. All fish with cortisol levels higher than 370 ng/ml developed the disease, while only 24% of the fish with cortisol levels lower than 370 ng/ml were infected. Cholesterol levels remained unchanged after toxic exposure. Increased susceptibilities to the pathogen were observed for ammonia (71%), copper (57%), nitrite (50%), and cyanide (33%). The increases in susceptibility as a result of cyanide and nitrite exposure could be explained by the stress response. For copper and ammonia, the combination of two different effects, the stress response and specific impairments of the defense mechanism of trout against saprolegniosis, should be considered.     

Variations in tumor cell growth rates and metabolism with oxygen concentration, glucose concentration, and extracellular pH.

Tumors and multicellular tumor spheroids can develop gradients in oxygen concentration, glucose concentration, and extracellular pH as they grow. In order to calculate these gradients and assess their impact on tumor growth, it is necessary to quantify the effect of these variables on tumor cell metabolism and growth. In this work, the oxygen consumption rates, glucose consumption rates, and growth rates of EMT6/Ro mouse mammary tumor cells were measured at a variety of oxygen concentrations, glucose concentrations, and extracellular pH levels. At an extracellular pH of 7.25, the oxygen consumption rate of EMT6/Ro cells increased by nearly a factor of 2 as the glucose concentration was decreased from 5.5 mM to 0.4 mM. This effect of glucose concentration on oxygen consumption rate, however, was slight at an extracellular pH of 6.95 and disappeared completely at an extracellular pH of 6.60. The glucose consumption rate of EMT6/Ro cells increased by roughly 40% when the oxygen concentration was reduced from 0.21 mM to 0.023 mM and decreased by roughly 60% when the extracellular pH was decreased from 7.25 to 6.95. The growth rate of EMT6/Ro cells decreased with decreasing oxygen concentration and extracellular pH; however, severe conditions were required to stop cell growth (0.0082 mM oxygen and an extracellular pH of 6.60). Empirical correlations were developed from these data to express EMT6/Ro cell growth rates, oxygen consumption rates, and glucose consumption rates, as functions of oxygen concentration, glucose concentration, and extracellular pH. These empirical correlations make it possible to mathematically model the gradients in oxygen concentration, glucose concentration, and extracellular pH in EMT6/Ro multicellular spheroids by solution of the diffusion/reaction equations. Computations such as these, along with oxygen and pH microelectrode measurements in EMT6/Ro multicellular spheroids, indicated that nutrient concentration and pH levels in the inner regions of spheroids were low enough to cause significant changes in nutrient consumption rates and cell growth rates. However, pH and oxygen concentrations measured or calculated in EMT6/Ro spheroids where quiescent cells have been observed were not low enough to cause the cessation of cell growth, indicating that the observed quiescence must have been due to factors other than acidic pH, oxygen depletion, or glucose depletion.     

THE SURVIVAL OF RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON) AND PERCH (PERCA FLUVIATILIS L.) AT VARIOUS CONCENTRATIONS OF DISSOLVED OXYGEN AND CARBON DIOXIDE

The relative importance of dissolved oxygen and dissolved carbon dioxide in determining the lethal effect of an environment for rainbow trout and perch has been investigated with an apparatus which controls the concentrations of these gases in a body of water. It is shown that concentrations of carbon dioxide which sometimes occur in polluted streams can more than double the minimum concentration of dissolved oxygen necessary for the survival of half a population of rainbow trout fingerlings for 24 hr. Increase in temperature between 12·5 and 19·5°C. shortens period of survival in solutions containing up to 67 p. p. m. CO₂. Within the range of dissolved oxygen concentration which is lethal in the presence of 59 p. p. m. CO₂ or more, perch are more resistant than rainbow trout in the lower, but less resistant in the higher, oxygen concentrations. The relation between carbon dioxide concentration and the oxygen tension at which rainbow trout blood is half saturated with oxygen is similar to the relation between carbon dioxide concentration and the oxygen tension at which the median period of survival of this species is I hr.     

Blood sampling techniques and storage duration: effects on the presence and magnitude of the red blood cell beta-adrenergic response in rainbow trout (Oncorhynchus mykiss)

Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pH(i)) in the presence of a stress-induced acidosis such as hypoxia, hypercapnia, or exhaustive exercise. This is accomplished through activation of RBC Na+/H+ exchange (beta-NHE), ultimately minimizing impairment to oxygen transport. Presence and characterization of the RBC beta-NHE in fish is best tested in blood from cannulated, resting animals; however, several studies have used blood from stressed animals drawn from the caudal vein and stored prior to use. The effects of sampling procedures and storage on the beta-NHE response is not known and is the focus of this study. Whole blood drawn from cannulated, resting rainbow trout was compared with RBCs obtained from the caudal vein rinsed and stored at 4 degrees C for 0, 6, 24, 48, 96 or 144 h. Isoproterenol (10(-5) M), a beta-adrenergic agonist, was added to hypoxia/hypercapnia incubated RBCs in vitro. In all treatments, isoproterenol induced a large beta-NHE response, and storage duration (< or =96 h) had a minimal affect, indicating that rinsing and storing is an easy and viable means by which to obtain RBCs and investigate function. Storage for 144 h still resulted in a significant RBC beta-NHE response; however, viability of RBCs may be compromised.     

Intracellular pH regulation in rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) hepatocytes: the activity of sodium/proton exchange is oxygen-dependent

We studied pH regulation in freshly isolated rainbow trout hepatocytes using microspectrofluorometry with the fluorescent dye BCECF. In accordance with earlier data on rainbow trout hepatocytes, ion substitution (N-methyl D-glucamine for sodium and gluconate for chloride) and transport inhibitor [10 microM M methyl isobutyl amiloride (MIA) to inhibit sodium/proton exchange and 100 microM DIDS to inhibit bicarbonate transport] studies in either Hepes-buffered or bicarbonate/carbon dioxide-buffered media (extracellular pH 7.6) indicated a role for sodium/proton exchange, sodium-dependent bicarbonate transport, and sodium-independent anion exchange in the regulation of hepatocyte pH. In Hepes-buffered medium, the activity of the sodium/proton exchanger (i.e. proton extrusion inhibited by MIA) was greater at 1% than at 21% oxygen. The oxygen dependency of the sodium/proton exchange is not caused by hydroxyl radicals, which appear to mediate the oxygen sensitivity of potassium-chloride cotransport in erythrocytes.     

A comparative analysis of the rainbow trout genome with 2 other species of fish (Arctic charr and Atlantic salmon) within the tetraploid derivative Salmonidae family (subfamily: Salmoninae).

We updated the genetic map of rainbow trout (Oncorhynchus mykiss) for 2 outcrossed mapping panels, and used this map to assess the putative chromosome structure and recombination rate differences among linkage groups. We then used the rainbow trout sex-specific maps to make comparisons with 2 other ancestrally polyploid species of salmonid fishes, Arctic charr (Salvelinus alpinus) and Atlantic salmon (Salmo salar) to identify homeologous chromosome affinities within each species and ascertain homologous chromosome relationships among the species. Salmonid fishes exhibit a wide range of sex-specific differences in recombination rate, with some species having the largest differences for any vertebrate species studied to date. Our current estimate of female:male recombination rates in rainbow trout is 4.31:1. Chromosome structure and (or) size is associated with recombination rate differences between the sexes in rainbow trout. Linkage groups derived from presumptive acrocentric type chromosomes were observed to have much lower sex-specific differences in recombination rate than metacentric type linkage groups. Arctic charr is karyotypically the least derived species (i.e., possessing a high number of acrocentric chromosomes) and Atlantic salmon is the most derived (i.e., possessing a number of whole-arm fusions). Atlantic salmon have the largest female:male recombination ratio difference (i.e., 16.81:1) compared with rainbow trout, and Arctic charr (1.69:1). Comparisons of recombination rates between homologous segments of linkage groups among species indicated that when significant experiment-wise differences were detected (7/24 tests), recombination rates were generally higher in the species with a less-derived chromosome structure (6/7 significant comparisons). Greater similarity in linkage group syntenies were observed between Atlantic salmon and rainbow trout, suggesting their closer phylogenetic affinities, and most interspecific linkage group comparisons support a model that suggests whole chromosome arm translocations have occurred in the evolution of this group. However, some possible exceptions were detected and these findings are discussed in relation to their influence on segregation distortion patterns. We also report unusual meiotic segregation patterns in a female parent involving the duplicated (homeologous) linkage group pair 12/16 and discuss several models that may account for these patterns.     

The Effect of Ration on Acclimation to Environmental Acidity in Rainbow Trout

Freshwater salmonids exposed to low environmental pH typically suffer a net loss of ions, primarily Na⁺ and Cl^–, across the gills, resulting in reduced plasma and tissue ion concentrations. However, in recent experiments in our laboratory, juvenile rainbow trout, Oncorhynchus mykiss, fed a ration of 1% body weight d^–1 or greater showed no ionoregulatory disturbance during chronic, sublethal acidification. This raised the possibility that these fish had acclimated to low pH in that they would be better able to withstand further, more severe acidification than fish that had no prior experience of acid conditions: previous studies had concluded that such acclimation does not occur. This hypothesis was tested by measuring unidirectional ion fluxes during a 24h acute acid challenge (pH 4.2) in juvenile rainbow trout that had previously been exposed to either ambient pH 6.2 (naive fish) or sublethal low pH 5.2 (acid pre-exposed fish) for 90 days, and fed a ration of either 1.0 or 0.25% d^–1 (wet basis). No mortalities were observed during the acute acid challenge in the fish fed the higher ration and no differences between the two groups in the response of Na⁺ fluxes were observed. Sodium influx in both groups was significantly inhibited throughout the challenge and Na⁺ net flux was significantly stimulated over the first 6h. Prior to the acute acid challenge, the fish fed the lower ration that had previously been exposed to pH 5.2 had significantly lower plasma ion concentrations than those fish previously exposed to pH 6.2. Both groups suffered mortalities; those of the naive fish (22% by 24h) being markedly lower than those of the acid pre-exposed fish (68% by 24h). However, there were no significant differences in either Na⁺ or Cl^– fluxes between the two groups of fish during the acid challenge: both showed significant inhibition of ion influxes and significantly greater net ion losses, resulting in reduced plasma ion concentrations. These results indicate that rainbow trout are unable to acclimate to environmental acidification irrespective of the availability of dietary salts.     

Trace Metal Levels in Rainbow Trout (Oncorhynchus mykiss) Cultured in Net Cages in a Reservoir and Evaluation of Human Health Risks from Consumption

Although fish consumption has positive health effects, metals accumulated in fish can cause human health risks. In this study, the levels of ten metals in rainbow trout (Oncorhynchus mykiss) farmed in the Keban Dam Reservoir, which has the biggest rainbow trout production capacity in Turkey, were determined and compared with the maximum permissible levels (MPLs). Also, human health risks associated with rainbow trout consumption were assessed. The metal concentrations in rainbow trout were found below the MPLs. The estimated daily intake of each metal was much lower than the respective tolerable daily intake. The target hazard quotient (THQ) for individual metal and total THQ for combined metals did not exceed 1, indicating no health risk for consumers. The cancer risk (CR) value for inorganic arsenic was within the acceptable lifetime risk range of 10⁻⁶ and 10⁻⁴. For carcinogenic and non-carcinogenic effects, the maximum allowable fish consumption rates were high enough to ensure the human health. According to these results, the consumption of rainbow trout farmed in the Keban Dam Reservoir does not pose a risk on human health.

     

Time-dependent changes in protein expression in rainbow trout muscle following hypoxia

Adaptation to hypoxia is a complex process, and individual proteins will be up- or down-regulated in order to address the main challenges at any given time. To investigate the dynamics of the adaptation, rainbow trout (Oncorhynchus mykiss) was exposed to 30% of normal oxygen tension for 1, 2, 5 and 24 h respectively, after which muscle samples were taken. The successful investigation of numerous proteins in a single study was achieved by selectively separating the sarcoplasmic proteins using 2-DE. In total 46 protein spots were identified as changing in abundance in response to hypoxia using one-way ANOVA and multivariate data analysis. Proteins of interest were subsequently identified by MS/MS following tryptic digestion. The observed regulation following hypoxia in skeletal muscle was determined to be time specific, as only a limited number of proteins were regulated in response to more than one time point. The cellular response to hypoxia included regulation of proteins involved in maintaining iron homeostasis, energy levels and muscle structure. In conclusion, this proteome-based study presents a comprehensive investigation of the expression profiles of numerous proteins at four different time points. This increases our understanding of timed changes in protein expression in rainbow trout muscle following hypoxia.     

虎斑乌贼的胚胎耗氧率

为了探究虎斑乌贼胚胎不同发育时期的耗氧率变化和几种生态因子对胚胎发育过程耗氧率的影响,试验采用封闭静水装置,对不同发育时期(12期)的耗氧率进行测定,并研究不同盐度(21、24、27、30、33)、温度(18、21、24、27、30 ℃)和pH(7.0、7.5、8.0、8.5、9.0)对胚胎4个主要发育时期(受精卵期、原肠胚期、器官形成期和内骨骼形成期)耗氧率的影响.结果表明: 胚胎各个发育时期耗氧率不同,随着发育的进程而增大,受精卵期为0.082 mg·(100 eggs)^-1·h^-1,而到原肠胚期的耗氧率显著升高,为0.279 mg·(100 eggs)^-1·h^-1,到孵化期时,耗氧率达到1.367 mg·(100 eggs)^-1·h^-1;盐度对器官形成期和内骨骼形成期的耗氧率均有显著影响(P<0.05),对受精卵期和原肠胚期影响不显著(P>0.05),当盐度为30时,4个发育时期耗氧率均达到最大值,分别为0.082、0.200、0.768和1.301 mg·(100 eggs)^-1·h^-1;温度对原肠胚期、器官形成期和内骨骼形成期的耗氧率有显著影响(P<0.05),对受精卵期无显著性影响(P>0.05),在27 ℃时,胚胎4个发育时期均达到最大值,分别为0.082、0.286、0.806和1.338 mg·(100 eggs)^-1·h^-1;而pH对4个发育时期的耗氧率均无显著性影响(P>0.05),受精卵期在pH 8.0时达到最大值,为0.116 mg·(100 eggs)^-1·h^-1,原肠胚期、器官形成期、内骨骼形成期在pH 8.5时达到最大值,分别为0.281 、0.799和1.130 mg·(100 eggs)^-1·h^-1.