Pengaruh Padat Tebar terhadap Konsumsi Oksigen dan Respons Stres Ikan Cupang Alam (Betta imbellis)

<strong>Effect of Stocking Density on Oxygen Consumption and Stress Response in Crescent Betta (<em>Betta imbellis</em>)</strong>. Stocking density is one of the determinant parameters for fish growth optimization in aquaculture systems due to its relationship with fish metabolism. Information about the impact of different stocking densities on crescent betta (<em>Betta imbellis</em>) metabolism was not available yet. This study was aimed to analyze the effect of stocking density on oxygen consumption, critical oxygen level, and stress responses in crescent betta.The study was carried out under three different stocking density treatments: 5, 10, and 15 fish/L with three replications using 2.74 ± 0.23 cm total length and 0.22 ± 0.05 g body weight tested fishes.The parameters observed were oxygen consumption, ventilation rate, blood glucose level, cortisol, and critical oxygen level. The result showed that the highest oxygen consumption was found at 5 fish/L stocking density treatment (3.01 ± 0.28 mg O₂/g/h), which was significantly different from 10 fish/L (1.01 ± 0.21 mg O₂/g/h) and 15 fish/L (0.92 ± 0.08 mg O₂/g/h) stocking density treatments. Oxygen consumptions under hypoxic condition was not significantly different compared to normoxic condition.The ventilation rate tends to increase significantly along with the increasing of stocking densities. Critical oxygen levels were not significantly different among the treatments,with the value of 3.31 ± 0.65 mg/L, 3.14 ± 0.29 mg/L, and 2.83 ± 0.19 mg/L for stocking density of 5, 10, and 15 fish/L, respectively. The blood glucose level at 15 fish/L stocking density was significantly higher than others, whereas the cortisol levels was not significantly different among the treatments. The results of this study provided information that the increasing stocking density of cressent betta will decrease their metabolism activity and increase ventilation rate. However, the increase of ventilation rate was negatively correlated with oxygen consumption per breath at higher stocking densities due to decrease in fish activity; and higher stocking densities will decrease oxygen consumption. Based on the results, it can be concluded that the ideal stocking density for crescent betta is 5 fish/L. The increasing of stocking density will decrease oxygen consumption rates and increase the stress level of crescent betta.

Oxygen supply capacity breathes new life into critical oxygen partial pressure (Pcrit)

ABSTRACT The critical oxygen partial pressure (Pcrit), typically defined as the PO2 below which an animal's metabolic rate (MR) is unsustainable, is widely interpreted as a measure of hypoxia tolerance. Here, Pcrit is defined as the PO2 at which physiological oxygen supply (α0) reaches its maximum capacity (α; µmol O2 g−1 h−1 kPa−1). α is a species- and temperature-specific constant describing the oxygen dependency of the maximum metabolic rate (MMR=PO2×α) or, equivalently, the MR dependence of Pcrit (Pcrit=MR/α). We describe the α-method, in which the MR is monitored as oxygen declines and, for each measurement period, is divided by the corresponding PO2 to provide the concurrent oxygen supply (α0=MR/PO2). The highest α0 value (or, more conservatively, the mean of the three highest values) is designated as α. The same value of α is reached at Pcrit for any MR regardless of previous or subsequent metabolic activity. The MR need not be constant (regulated), standardized or exhibit a clear breakpoint at Pcrit for accurate determination of α. The α-method has several advantages over Pcrit determination and non-linear analyses, including: (1) less ambiguity and greater accuracy, (2) fewer constraints in respirometry methodology and analysis, and (3) greater predictive power and ecological and physiological insight. Across the species evaluated here, α values are correlated with MR, but not Pcrit. Rather than an index of hypoxia tolerance, Pcrit is a reflection of α, which evolves to support maximum energy demands and aerobic scope at the prevailing temperature and oxygen level.

Effects of Different Amounts of Nb Doping on Electrical, Optical and Structural Properties in Sputtered TiO2−x Films

Highly conductive TiO2 films with different Nb doping levels (up to 5 at%) were prepared by reactive DC magnetron sputtering under precise control of the oxygen partial pressure. They were deposited on unheated substrates, covered with a protective Si3N4 layer, and subsequently annealed at 300 °C. The doping efficiency of Nb is greater than 90%. Conductivity is a maximum for a partly oxidized target in the transition range. The best films exhibit a resistivity of 630 µΩ cm and a mobility of 7.6 cm2/Vs combined with a high transparency above 70%. Comparing the behavior of undoped and Nb-containing films, intrinsic limits of the conductivity in the TiO2−x:Nb system could be observed, and a consistent model explaining these findings is presented. The conductivity is limited—by decreasing electron density due to Nb oxidation—by increasing incorporation formation of Nb2O5 clusters as scattering centers with increasing oxygen partial pressure and Nb concentration, by a transition from the crystalline to the amorphous state of the films below a critical oxygen partial pressure.

Effects of acute hypoxia on auditory pathway of Wistar albino rats

Background/aim: Ischemia is insufficient blood flow to provide adequate oxygenation. In the present study, we aimed to show whether acute hypoxia has a critical oxygen value that may lead to the deterioration of cochlear function.Materials and methods: Under general anesthesia, prehypoxic signal-to-noise ratios were determined by distortion product otoacoustic emissions (DPOAE). The oxygen saturation (SaO2) values of rats were monitored with an oxygen saturation probe. Rats were injected with an extra dose of anesthetic agent, and SaO2 was reduced. DPOAE values in SaO2 100–90, 90–80, 80–70, and 70–60 posthypoxic values were measured and compared statistically with prehypoxic values.Results: At 3000 and 4000 Hz, SaO2 70–60 values measured after the hypoxia were observed to be statistically significantly lower than the values measured before the hypoxia. At 6000 and 8000 Hz, SaO2 80–70 and 70–60 values measured after the hypoxia were observed to be statistically significantly lower than the values measured before the hypoxia. At 10,000 Hz, all of the values measured after the hypoxia were observed to be statistically significantly lower than the values obtained before the hypoxia.Conclusion: Many studies have been conducted on the effects of hypoxia on the inner ear. It remains unclear how fluctuations in DPOAE levels affect hearing in clinical trials when the SaO2 starts to decrease. Although hypoxia has been implicated in the etiology of sudden hearing loss and tinnitus, the effects of acute hypoxia on the cochlea are still uncertain. Further studies are needed on this subject.

Breathing new life into the critical oxygen partial pressure (Pcrit): a new definition, interpretation and method of determination

The critical oxygen partial pressure (Pcrit) is most commonly defined as the oxygen partial pressure below which an animal’s standard metabolic rate can no longer be maintained. It is widely interpreted as measure of hypoxia tolerance, which influences a species’ aerobic scope and, thus, constrains biogeography. However, both the physiology underlying that interpretation and the methodology used to determine Pcrit remain topics of active debate. The debate remains unresolved in part because Pcrit, as defined above, is a purely descriptive metric that lacks a clear mechanistic basis. Here we redefine Pcrit as the PO2 at which physiological oxygen supply is maximized and refer to these values, thus determined, as Pcrit-α. The oxygen supply capacity (α) is a species- and temperature-specific coefficient that describes the slope of the relationship between the maximum achievable metabolic rate and PO2. This α is easily determined using respirometry and provides a precise and robust estimate of the minimum oxygen pressure required to sustain any metabolic rate. To determine α, it is not necessary for an individual animal to maintain a consistent metabolic rate throughout a trial (i.e. regulation) nor for the metabolic rate to show a clear break-point at low PO2. We show that Pcrit-α can be determined at any metabolic rate as long as the organisms’ oxygen supply machinery reaches its maximum capacity at some point during the trial. We reanalyze published representative Pcrit trials for 40 species across five phyla, as well as complete datasets from six additional species, five of which have not previously been published. Values determined using the Pcrit-α method are strongly correlated with Pcrit values reported in the literature. Advantages of Pcrit-α include: 1) Pcrit-α is directly measured without the need for complex statistics that hinder measurement and interpretation; 2) it makes clear that Pcrit is a measure of oxygen supply, which does not necessarily reflect hypoxia tolerance; 3) it alleviates many of the methodological constraints inherent in existing methods; 4) it provides a means of predicting the maximum metabolic rate achievable at any PO2, 5) Pcrit-α sheds light on the temperature- and size-dependence of oxygen supply and metabolic rate and 6) Pcrit-α can be determined with greater precision than traditional Pcrit.

An efficient Turing-type Ag2Se-CoSe2 multi-interfacial oxygen-evolving electrocatalyst

Although the Turing structures, or stationary reaction-diffusion patterns, have received increasing attention in biology and chemistry, making such unusual patterns on inorganic solids is fundamentally challenging. We report a simple cation exchange approach to produce Turing-type Ag2Se on CoSe2 nanobelts relied on diffusion-driven instability. The resultant Turing-type Ag2Se-CoSe2 material is highly effective to catalyze the oxygen evolution reaction (OER) in alkaline electrolytes with an 84.5% anodic energy efficiency. Electrochemical measurements show that the intrinsic OER activity correlates linearly with the length of Ag2Se-CoSe2 interfaces, determining that such Turing-type interfaces are more active sites for OER. Combing X-ray absorption and computational simulations, we ascribe the excellent OER performance to the optimized adsorption energies for critical oxygen-containing intermediates at the unconventional interfaces. Our work offers opportunities for creating Turing structures in other inorganic nanomaterials with unexplored catalytic abilities.