Acclimation Time Research Articles

Effect of different cold acclimation methods on the exercise capacity of mice in low-temperature environments.

This study aimed to evaluate the effects of different cold acclimation strategies on exercise performance in male mice exposed to low-temperature environments. Male mice were subjected to five distinct acclimation regimens over 8 weeks: immersion at 10°C (10 °CI) or 20°C (20 °CI), swimming at 10°C (10 °CS), 20°C (20 °CS), or 34°C (34 °CS). During the first 2 weeks, the acclimation time progressively decreased from 30min to 3min per day, and the water temperatures were lowered from 34°C to the target levels, followed by 6 weeks of consistent exposure. Body weight, food intake, and rectal temperature were monitored throughout the study. Post-acclimation assessments included low-temperature exhaustion exercise ability testing; 16S rDNA sequencing of gut microbiota; and quantification of gene expression related to brown adipose thermogenesis, skeletal muscle synthesis, and degradation. (1) After 8 weeks of acclimation, neither serum adrenaline nor angiotensin II levels significantly increased in mice exposed to 10°C or 20°C water. (2) Cold acclimation extended the endurance time under low-temperature conditions, notably in the 20 °CI, 10 °CS, and 20°CS groups. (3) Compared with the control (C) group, the 20 °CI and 10°CS groups showed significantly increased UCP1, IGF-1, AKT, and mTOR gene expression levels (P<0.05). The expression levels of MAFbx and MuRF1 genes in the 10°CS and 20°CS groups significantly decreased compared with those in the C group (P<0.05). (4) Compared with the C group, the 20 °CI, 10 °CS, and 20°CS groups demonstrated significant changes in intestinal microbiota diversity. Specifically, the abundance of Akkermansia strains significantly increased in the 20 °CI and 10°CS groups. The abundance of Ruminococcus and Prevotellaceae_UCG-001 significantly increased in the 20°CS group. Exercise in cold environments can activate genes related to heat production and skeletal muscle synthesis and increase the abundance of beneficial bacteria producing short-chain fatty acids, thereby modulating host metabolism, accelerating the formation of cold acclimation, and enhancing exercise capacity in low-temperature environments.

Testing for thermal acclimation in zoospores of an amphibian pathogen.

Thermal acclimation effects on locomotory performance have been widely documented for macroscopic organisms, but such responses remain largely unexplored in microorganisms. Metabolic theory of ecology (MTE) predicts faster responses in smaller organisms, with potential consequences for host-parasite interactions in variable temperature environments. We investigated thermal acclimation effects on zoospores of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd), quantifying (1) thermal performance for maximum zoospore velocity and (2) high temperatures needed to immobilize 50% (CT50max) or 100% (CT100max) of zoospores. We obtained measurements within 18 min following a temperature shift. We found significant curvilinear acclimation effects on maximum zoospore velocity and CT50max, although the latter pattern might have been driven by confoundment with zoospore density. We also observed a significant positive effect of the trial start temperature on CT50max, consistent with a rapid acclimation response to the start temperature on a time scale of ~1-6 min (i.e. too rapid for our experimental acclimation treatments to detect), implying that zoospores either have constitutive heat tolerance (i.e. no acclimation) or fully acclimate CTmax to new temperatures within ~10 min. To explore the plausibility of such a rapid response, we analyzed published CTmax acclimation times for macroscopic eukaryotes, resulting in a predicted interquartile range of 3.11-25.98 min when mass-scaled to the size of a Bd zoospore. Taken together, these results suggest that Bd zoospores do exhibit thermal acclimation response on the rapid time scale predicted by MTE, possibly giving Bd an advantage over slower-acclimating hosts in variable-temperature environments.

Light exposure induces phenotypic plasticity of the upside-down jellyfish Cassiopea sp. and its endosymbiotic dinoflagellates

The upside-down jellyfish, Cassiopea, is an increasingly popular model organism gaining prominence for both its endosymbiotic dinoflagellates from the family Symbiodiniaceae and its behavioral changes of bell pulsations associated with environmental cues. Pulsation provides a unique window into the host's response to environmental conditions, a typically difficult to access component of other symbiotic cnidarians. Pulsation has also been hypothesized to play a regulatory role on the endosymbiotic assemblage, but the magnitude of this regulatory effect is not well understood. Here, we used two light-acclimation experiments to help disentangle the complex phenotypic responses of the cnidarian host and its endosymbiotic dinoflagellates. The first experiment examined the phenotypic plasticity (size, behavior, color) of Cassiopea sp. in response to repeated ambient light acclimation trials to determine the rate and magnitude of phenotypic plasticity. The second experiment compared the acclimation response of jellyfish across three experimental groups to test whether a short acclimation time destabilized the host-endosymbiont relationship. Our goal was to identify covarying host-endosymbiont phenotypes to gain new insights into the dynamics of this relationship. We employed flow cytometric phenotypic profiling for high-throughput phenotypic characterization of endosymbiotic dinoflagellates in addition to pulse-amplitude modulated (PAM) fluorometry to characterize photosynthetic efficiency (Fv/Fm). Host phenotypes responded predictably to light-dark cycles and stabilized after nine to twelve days of exposure to consistent light conditions. However, disruption of this acclimation period affected the holobiont's phenotypic profile. We also found evidence that phenotypic responses of the host and endosymbionts were generally decoupled, indicating a stronger regulatory response of light conditions on phenotypes than possible host-regulatory strategies on the endosymbiotic assemblage. This study provides unique insights into the acclimation strategies of upside-down jellyfish, an emerging model for the study of cnidarian-dinoflagellate symbiosis.

Microbial community acclimation during anaerobic digestion of high-oil food waste

Anaerobic digestion is one of the most promising options for the disposal of biodegradable food waste. However, the relatively high content of oil in food waste inhibits the conversion efficiency of anaerobic digestion because of the accumulation of long-chain fatty acids (LCFAs). In this study, activated anaerobic sludge was acclimated to accommodate high-oil conditions. The methane yield of high-oil food waste digested by the acclimated sludge increased by 24.9% compared to that digested by the raw sludge. To determine the internal changes in the acclimated sludge, the shifts in the microbial communities during the acclimation period were investigated via high-throughput sequencing (HTS) based on the 16 S rRNA gene. The results indicated that Bacteroidetes, Firmicutes, Chloroflexi and Proteobacteria were the dominant bacteria at the phylum level. The acclimation time allows some functional bacterial taxa to proliferate, such as Clostridium and Longilinea, which are able to degrade LCFAs and turn them into small organic molecules that also have nutrient value for other bacteria. Among the archaeal communities, the hydrogenotrophic methanogen Methanobacterium nearly supplanted the acetotrophic methanogen Methanosaeta. The time profiles of volatile fatty acids (VFAs) and pH during this period provided additional evidence for the success of the acclimation. This study demonstrated the effectiveness of acclimation and the dynamic of microbial communities, which further contributed to the management and resource utilization of high-oil food waste.

Feasibility of simultaneous optimization of Anammox start-up and nitrogen removal performance by intermittent dosing of nanoscale zero-valent iron

The long acclimation period and sensitivity to environmental conditions of Anammox are the bottlenecks for its promotion and application. An innovative strategy was adopted to accelerate functional microbial enhancement and improve nitrogen removal performance by inoculating cryopreserved Anammox sludge and activated sludge with intermittent dosing of nanoscale zero-valent iron (nZVI). The acclimation time was shortened by 76 days with nitrogen removal efficiency (NRE) reaching up to 91.07 %. Anammox, NDFO (nitrate/nitrite-dependent Fe(II) oxidation), Feammox (Fe(III) reduction coupled with anaerobic ammonium oxidation) and abiotic reactions were coupled in the system with nZVI, contributing to 69.79 %, 15.14 %, 9.84 % and 0.25 % of nitrogen removal, respectively. Further microbial analysis demonstrated significant enrichment of functional microorganisms, such as Candidatus Jettenia, Acidovorax and Comamonas. High-efficient nitrogen removal was attribute to the increase of functional genes involved in Anammox, electronic transfer, heme C synthesis and iron metabolism. This work provides an inspiring idea for the mainstream Anammox application.

Strong acclimation effect of temperature and humidity on heat tolerance of the Arctic collembolan Megaphorura arctica.

The Arctic is a highly variable environment in which extreme daily and seasonal temperature fluctuations can occur. With climate change, an increase in the occurrence of extreme high temperatures and drought events is expected. While the effects of cold and dehydration stress on polar arthropods are well studied in combination, little is known about how these species respond to the combined effects of heat and dehydration stress. In this paper, we investigated how the heat tolerance of the Arctic collembola Megaphorura arctica is affected by combinations of different temperature and humidity acclimation regimes under controlled laboratory conditions. The effect of acclimation temperature was complex and highly dependent on both acclimation time and temperature, and was found to have a positive, negative or no effect depending on experimental conditions. Further, we found marked effects of the interaction between temperature and humidity on heat tolerance, with lower humidity severely decreasing heat tolerance when the acclimation temperature was increased. This effect was more pronounced with increasing acclimation time. Lastly, the effect of acclimation on heat tolerance under a fluctuating temperature regime was dependent on acclimation temperature and time, as well as humidity levels. Together, these results show that thermal acclimation alone has moderate or no effect on heat tolerance, but that drought events, likely to be more frequent in the future, in combination with high temperature stress can have large negative impacts on heat tolerance of some Arctic arthropods.

Cytotoxicity of pharmaceuticals and their mixtures toward scaffold-free 3D spheroid cultures of rainbow trout (Oncorhynchus mykiss) hepatocytes

Pharmaceutical residues are widely detected in surface waters all around the world, causing a range of adverse effects on environmental species, such as fish. Besides population level effects (mortality, reproduction), pharmaceutical residues can bioaccumulate in fish tissues resulting in organ-specific toxicities. In this study, we developed in vitro 3D culture models for rainbow trout (Oncorhynchus mykiss) liver cell line (RTH-149) and cryopreserved, primary rainbow trout hepatocytes (RTHEP), and compared their spheroid formation and susceptibility to toxic impacts of pharmaceuticals. The rapidly proliferating, immortalized RTH-149 cells were shown to form compact spheroids with uniform morphology in just three days, thus enabling higher throughput toxicity screening compared with the primary cells that required acclimation times of about one week. In addition, we screened the cytotoxicity of a total of fourteen clinically used human pharmaceuticals toward the 3D cultures of both RTH-149 cells (metabolically inactive) and primary RTHEP cells (metabolically active), to evaluate the impacts of the pharmaceuticals’ own metabolism on their hepatotoxicity in rainbow trout in vitro. Among the test substances, the azole antifungals (clotrimazole and ketoconazole) were identified as the most cytotoxic, with hepatic metabolism indicatively amplifying their toxicity, followed by fluoxetine, levomepromazine, and sertraline, which were slightly less toxic toward the metabolically active primary cells than RTH-149 spheroids. Besides individual pharmaceuticals, the 3D cultures were challenged with mixtures of the eight most toxic substances, to evaluate if their combined mixture toxicities can be predicted based on individual substances’ half-maximal effect (EC50) concentrations. As a result, the classical concentration addition approach was concluded sufficiently accurate for preliminarily informing on the approximate effect concentrations of pharmaceutical mixtures on a cellular level. However, direct read-across from human data was proven challenging and inexplicit for prediction of hepatotoxicity in fish in vitro.

Acclimation capacity to global warming of amphibians and freshwater fishes: Drivers, patterns, and data limitations.

Amphibians and fishes play a central role in shaping the structure and function of freshwater environments. These organisms have a limited capacity to disperse across different habitats and the thermal buffer offered by freshwater systems is small. Understanding determinants and patterns of their physiological sensitivity across life history is, therefore, imperative to predicting the impacts of climate change in freshwater systems. Based on a systematic literature review including 345 experiments with 998 estimates on 96 amphibian (Anura/Caudata) and 93 freshwater fish species (Teleostei), we conducted a quantitative synthesis to explore phylogenetic, ontogenetic, and biogeographic (thermal adaptation) patterns in upper thermal tolerance (CTmax) and thermal acclimation capacity (acclimation response ratio, ARR) as well as the influence of the methodology used to assess these thermal traits using a conditional inference tree analysis. We found globally consistent patterns in CTmax and ARR, with phylogeny (taxa/order), experimental methodology, climatic origin, and life stage as significant determinants of thermal traits. The analysis demonstrated that CTmax does not primarily depend on the climatic origin but on experimental acclimation temperature and duration, and life stage. Higher acclimation temperatures and longer acclimation times led to higher CTmax values, whereby Anuran larvae revealed a higher CTmax than older life stages. The ARR of freshwater fishes was more than twice that of amphibians. Differences in ARR between life stages were not significant. In addition to phylogenetic differences, we found that ARR also depended on acclimation duration, ramping rate, and adaptation to local temperature variability. However, the amount of data on early life stages is too small, methodologically inconsistent, and phylogenetically unbalanced to identify potential life cycle bottlenecks in thermal traits. We, therefore, propose methods to improve the robustness and comparability of CTmax/ARR data across species and life stages, which is crucial for the conservation of freshwater biodiversity under climate change.

Warming-induced “plastic floors” improve hypoxia vulnerability, not aerobic scope, in red drum (Sciaenops ocellatus)

Ocean warming is a prevailing threat to marine ectotherms. Recently the “plastic floors, concrete ceilings” hypothesis was proposed, which suggests that a warmed fish will acclimate to higher temperatures by reducing standard metabolic rate (SMR) while keeping maximum metabolic rate (MMR) stable, therefore improving aerobic scope (AS). Here we evaluated this hypothesis on red drum (Sciaenops ocellatus) while incorporating measures of hypoxia vulnerability (critical oxygen threshold; Pcrit) and mitochondrial performance. Fish were subjected to a 12-week acclimation to 20 °C or 28 °C. Respirometry was performed every 4 weeks to obtain metabolic rate and Pcrit; mitochondrial respirometry was performed on liver and heart samples at the end of the acclimation. 28 °C fish had a significantly higher SMR, MMR, and Pcrit than 20 °C controls at time 0, but SMR declined by 36.2 % over the 12-week acclimation. No change in SMR was observed in the control treatment. Contrary to expectations, SMR suppression did not improve AS relative to time 0 owing to a progressive decline in MMR over acclimation time. Pcrit decreased by 27.2 % in the warm-acclimated fishes, which resulted in temperature treatments having statistically similar values by 12-weeks. No differences in mitochondrial traits were observed in the heart – despite a Δ8 °C assay temperature – while liver respiratory and coupling control ratios were significantly improved, suggesting that mitochondrial plasticity may contribute to the reduced SMR with warming. Overall, this work suggests that warming induced metabolic suppression offsets the deleterious consequences of high oxygen demand on hypoxia vulnerability, and in so doing greatly expands the theoretical range of metabolically available habitats for red drum.

Performance of a modified and intermittently operated slow sand filter with two different mediums in removing turbidity, ammonia, and phosphate with varying acclimatization periods

The present study investigated the utilization of blood clam shells as a potential substitute for conventional media, as well as the influence of the acclimation time on the efficacy of an intermittent slow sand filter (ISSF) in the treatment of real domestic wastewater. ISSF was operated with 16 h on and 8 h off, focusing on the parameters of turbidity, ammonia, and phosphate. Two media combinations (only blood clam shells [CC] and sand + blood clam shells [SC]) were operated under two different acclimatization periods (14 and 28 d). Results showed that SC medium exhibited significantly higher removal of turbidity (p < 0.05) as compared to CC medium (45.99 ± 26.84 % vs. 3.79 ± 9.35 %), while CC exhibited slightly higher (p > 0.05) removal of ammonia (23.12 ± 20.2 % vs. 16.77 ± 16.8 %) and phosphate (18.03 ± 11.96 % vs 13.48 ± 12 %). Comparing the acclimatization periods, the 28 d of acclimatization period showed higher overall performances than the 14 d. Further optimizations need to be conducted to obtain an effluent value below the national permissible limit, since the ammonia and phosphate parameters are still slightly higher. SEM analysis confirmed the formation of biofilm on both mediums after 28 d of acclimatization; with further analysis of schmutzdecke formation need to be carried out to enrich the results.

Internet-delivered psychological interventions for older adults with depression: A scoping review

BackgroundDepression is prevalent among older adults, and internet-delivered psychological interventions (IDPIs) have emerged as a promising solution. AimTo explore the landscape of IDPIs for late-life depression, examining current characteristics, psychotherapies, intervention strategies, facilitators, and barriers. MethodGuided by a PRISMA-guided scoping review, we systematically searched five electronic databases. Results25 relevant studies were identified. IDPIs were used for treatment, prevention, and assessment. Internet-based cognitive behavioral therapy was the most common psychotherapy. Seven strategies to provide tailored services include psychotherapy courses, professional involvement, mood and progress tracking, virtual community, timed reminders, additional learning resources, and gamification elements. Barriers contained cognitive impairment, low digital literacy, device inaccessibility, limited depression awareness, adherence issues, and acclimation time, while facilitators included prior treatment experience, real-life character stories, strong client-worker bonds, and integration into daily care routines. ConclusionIDPIs present an accessible and convenient avenue for older adults. Future directions suggest exploring minimalist interventions, diverse strategies, and optimized implementation to amplify IDPIs impact among this vulnerable group.

Controlled Elicitation and Greenhouse Acclimation Time Effects on Morphological and Biochemical Variables in Collections of Heliopsis longipes from Central México

Controlled Elicitation and Greenhouse Acclimation Time Effects on Morphological and Biochemical Variables in Collections of Heliopsis longipes from Central México

Towards intelligent workstations: Investigating the feasibility of Doppler radar sensors for personal respiratory quantification in thermal comfort

Along the line of research efforts utilizing occupant thermophysiological responses in operation of Heating, Ventilation, and Air-Conditioning (HVAC), this study assessed feasibility of Doppler Radar Sensors (DRSs) in quantifying respiration. Respiration has been known as one of the physiological processes which gets adjusted based on metabolic rate and DRSs are capable of capturing characteristics of periodic movements of chest/abdomen area induced by respiration. Accordingly, we have devised two approaches of quantifying respiration in context of thermoregulation states – by checking (1) frequency and intensity of the signal representing respiration (i.e., respiration state) and (2) ratio between exhale and inhale (i.e., respiratory ratio). With these, two experimental studies have been conducted with human subjects to evaluate reliability, applicability/sensitivity. Results showed that 60 s of a measurement time could provide reliability, which opens a chance to eliminate a validation process and respiration might not be a physiological response that rapidly gets activated for heat adjustment. Also, it has been shown that, with sufficient acclimation time (20 min), five out of eight participants increased respiration states in a high temperature setup and seven out of eight participants raised their respiratory ratios. In other words, individuals have different ways of utilizing respiration to deal with heat adjustment and acclimation time plays a key role in the use of respiration. Given DRSs' conventional application is occupancy detection, the versatility of DRSs has been shown and it contributes to realizing an intelligent workstation that is capable of contextualizing user's behaviors and perceptions.

Comparison between batch aerobic biodegradation of paracetamol and glucose with open mixed microbial cultures: Experimental data and kinetic modelling

Biodegradation of man-made chemicals (xenobiotics) in biological wastewater treatment processes is essential to avoid the accumulation of these substances with negative effects on the environment and on human health. This study investigated the aerobic biodegradation of paracetamol as sole carbon and energy source and compared it to a model biogenic substrate (glucose). Batch experiments with unacclimated open mixed cultures from soil were carried out with glucose or paracetamol in a range of concentrations (100–2000 mg/L), measuring the rate of substrate removal, the acclimation time, the oxygen consumption and the COD (chemical oxygen demand) removal. The experimental data were used for kinetic modelling, using several different models based on the Monod kinetics with modifications for inhibition or for acclimation. Paracetamol was biodegraded as sole carbon and energy source at all concentrations (90–97 % COD removal), with slower degradation rate and longer acclimation time than for glucose. From the COD balance, a slightly higher production of microorganisms per unit of substrate COD was calculated for paracetamol than for glucose. The kinetic modelling of the experimental data achieved a good fit with the simple Monod model, but with different parameters for each substrate concentration. Combined fitting of all the experiments with the same set of parameters was attempted, and overall the best fitting was observed with a new model that includes an empirical time constant for acclimation. Compared to glucose, microbial growth on paracetamol was characterised by lower maximum specific growth rate, slightly higher growth yield and higher time constant for acclimation.

Long-term CO2 Enrichment Increases Biomass but Results in Rapid Physiological Acclimation of Petunia and Pansy

Although crops often respond immediately to enriched CO2 concentrations (e.g., increased photosynthesis), this initial response is often not sustained throughout production, thus reducing the benefit of this input. For horticulture species, the timing and extent of these acclimation responses are still widely uncertain. Therefore, the objective of this research was to determine species-specific acclimation responses to elevated CO2 concentrations for pansy (Viola ×wittrockiana ‘Matrix Blue Blotch Improved’) and petunia (Petunia ×hybrida ‘Dreams Midnight’). Seedlings were transplanted to 11.5-cm pots and placed in growth chambers with air temperature, relative humidity, and radiation intensity setpoints of 21 °C, 55%, and 250 μmol⋅m−2⋅s−1, respectively. Carbon dioxide treatments were established using the two growth chambers with setpoints of either 400 (ambient) or 1000 μmol⋅mol−1 (elevated) maintained during a 16-hour photoperiod. In addition to data collected through destructive harvest, the rate of photosynthesis (A) in response to increasing internal leaf CO2 concentration (A-Ci) and at the operating CO2 concentration (A-Ca) were measured weekly with a portable leaf photosynthesis system at saturating [A-Ci (1000 μmol⋅m−2⋅s−1)] or production [A-Ca (250 μmol⋅m−2⋅s−1)] radiation intensities. For both pansy and petunia, elevated CO2 produced greater total shoot dry mass than ambient CO2 after 4 weeks. However, the decreased maximum rate of photosynthetic electron transport, maximum rate of Rubisco carboxylase, and triose phosphate utilization rate of both species were also observed under elevated CO2. Similarly, A measured at 400 and 1000 μmol⋅mol−1 was reduced for both pansy and petunia grown under the elevated compared with ambient CO2 concentration based on A-Ca responses after 7 days, indicating quick physiological acclimation to this input. These results provide information regarding the timing and extent of physiological acclimation in response to elevated CO2 concentrations. However, because of physiological acclimation potentially occurring within 7 days of treatment initiation, additional research is necessary to develop species-specific recommendations for controlled environment production.

Changes in Larval Oyster Swimming Behavior with Salinity and Larval Age.

AbstractEastern oysters (Crassostrea virginica) are sessile, relying on a larval phase to disperse in estuaries. Oyster larval swimming behavior can alter dispersal trajectories and patterns of population connectivity. Experiments were conducted to test how both (1) acclimation time to new environmental conditions and (2) larval swimming behavior change with salinity and larval age. Acclimation time to changes in salinity was longest in lower salinity (6 ppt) and decreased with age. To test changes in behavior with salinity, larvae were placed into four salinities (6, 10, 16, and 22 ppt) where swimming was recorded. To test changes in behavior with age, larvae aged 6, 12, and 15 days were recorded. In both experiments, swimming paths were mapped in two dimensions, behavior of each path was categorized, and speed, direction, and acceleration were calculated. The frequency of upward, neutral, and downward swimming behaviors did not differ across salinity treatments but did vary with age, whereas the frequency of behavior types varied with both salinity and ontogeny. As an example, diving was observed more frequently in low salinity, and more downward helices were observed in moderate salinity, while younger larvae swam upward with more frequency than older larvae. Surprisingly, diving was observed in 10%-15% of all larvae across all ages. Given the consequence of larval behavior to marine invertebrate dispersal, changes in swimming over larval age and in response to environmental changes have important implications to marine population stability and structure.

Effects of acclimation temperature and exposure time on the scope for growth of the blackfoot Pāua (Haliotis iris)

Context Climate change and increased seawater temperatures can greatly affect physiological processes and growth of marine ectotherms, including the blackfoot haliotid, Pāua (Haliotis iris). Scope for growth (SFG) is a laboratory-derived measure of the energy available for growth but this has not been examined in Pāua. Aims To measure SFG of seasonally collected Pāua and their haemolymph parameters at constant acclimation temperatures of 12, 15, 18 and 21°C for 28 days. Methods Energy available for growth was measured from kelp food and losses due to respiration and ammonia excretion calculated on Days 1, 14, 21 and 28 of acclimation. Haemolymph parameters were also measured. Key results After 3 days of acclimation, SFG was highly variable. Following 2 weeks of acclimation, SFG was positive for all temperatures. Respiration and excretion energies depended on both acclimation temperature and time. Haemolymph parameters were affected by acclimation temperature. Conclusion Pāua have limited ability to acclimate to a temperature 21°C suggesting that they would not grow effectively at this temperature. Implications This research suggests that adult Pāua can be adversely affected by increased seawater temperature, resulting from climate change and this could affect their future growth and distribution.

Digestibility of bacterial protein by Atlantic salmon (Salmo salar) is affected by both inclusion level and acclimation time

The impact of acclimation time and inclusion level of a bacterial protein (BP) meal on the digestibility of protein and amino acids to post-smolt Atlantic salmon (Salmo salar) was examined using a factorial experimental design that compared acclimation over five time points (3-days, 10-days, 17-days, 24-days, and 35-days) and five BP inclusion levels (0 g/kg, 100 g/kg, 200 g/kg, 300 g/kg and 400 g/kg). An additional test diet with soy protein concentrate (300 g/kg) was included as a comparison. Each of the diets were prepared from the same basal mash and using the same processing methods. Feed intake was measured daily. The results of the study showed that diet apparent digestibility coefficients (DADC) changed markedly over the time-course of the study, initially being low and variable before stabilizing at higher values from day-17 onwards. However, the effect on temporal variability of DADC values was consistent across all diets. This consistency translated to comparatively stable ingredient apparent digestibility coefficients (IADC) across each of the time points assessed, though there was a significant decline in all IADC values over time. Additionally, the IADC data was less reliable at the 10% inclusion level with higher variability and significantly differed from the other values determined at the higher inclusion levels. Furthermore, there was not always consistency in the IADC values for nitrogen and sum of amino acids, although both are often used as measures of protein. There were also significant differences among the different amino acids in terms of their IADC values. Although there was a trend towards poorer feed intake with the higher inclusion levels of the BP, this was no worse than that observed for the soy protein concentrate. In recognition of the findings of this study we are suggesting that digestibility studies with Atlantic salmon post-smolt should acclimate for a minimum of 14-days prior to faecal collection and that test ingredient inclusion should be 200 g/kg or greater to obtain reliable data.

Sampling biases and reproducibility: experimental design decisions affect behavioural responses in hermit crabs

How important are sampling and experimental design decisions in shaping test subject behaviour under laboratory conditions? We examined the effects of circatidal rhythm, time held in captivity, sampling location (open or covered areas of habitat), acclimation period and water depth on activity and emergence latency in hermit crabs ( Pagurus bernhardus ). We found that subjects held in captivity for 1 month and those collected from the open were faster to emerge from their shells after disturbance compared, respectively, to those tested after 1 day in captivity or collected from beneath cover. We also found that subjects tested after shorter acclimation periods were more active than those tested following longer acclimation periods. Our findings reveal that sampling and study design decisions can have pronounced influences on subject behaviour measured under otherwise common conditions, with potentially important implications for interpretation and reproducibility of findings. As researchers we should take care to explicitly consider how sampling biases and effects arising from our experimental protocols might affect the behavioural responses of test subjects. Doing so can help us make more reasonable generalizations beyond our subject pool, draw better-informed comparisons between studies and achieve greater reproducibility of findings. • Do decisions we routinely make regarding experimental design affect outcomes? • Are animals we test representative of the wider populations we aim to understand? • We asked if subtle design decisions affected behaviour under laboratory conditions. • Time in captivity, acclimation time and location of collection affected behaviour. • We should declare and discuss potential for bias arising from experimental designs.

In-situ removal of odorous NH3 and H2S by loess modified with biologically stabilized leachate

The loess regions distribute widely in Northwestern China, North America and Eastern Europe. For these regions, landfill is a suitable technology for solid waste treatment. However, as a landfill cover material, loess is not very effective in controlling the emission of malodorous gases. The present study modified loess with biologically stabilized leachate, and investigated the capacities and mechanisms of the modified loess to remove odorous NH3 and H2S. The removal rates of NH3 and H2S at different acclimation time, targeted gas concentrations and temperatures were measured. It was found that the NH3 removal rate of the modified loess was up to 0.08 μmol/(g·hr), which was 1.8 times that of the virgin loess. The H2S removal rate of the modified loess was up to 1.74 μmol/(g·hr), which was 1.25 times that of the virgin loess. The half-meter loess layer modified by biologically stabilized leachate achieved nearly 100% removal of H2S. The improvement of NH3 and H2S removal ability was mainly due to the enrichment of relevant microorganisms. This work proposed a novel method for in-situ control of malodorous pollutants in landfills in the loess regions, and proved that the in-situ removal of NH3 and H2S using the loess modified with biologically stabilized leachate is feasible and cost-effective.