Months Of Acclimation Research Articles

Photoacclimation and photophysiology of four species of toxigenic Dinophysis

This study aimed to explore the effects of different light intensities on the ecophysiology of eight new Dinophysis isolates comprising four species (D. acuminata, D. ovum, D. fortii, and D. caudata) collected from different geographical regions in the US. After six months of acclimation, the growth rates, photosynthetic efficiency (Fv/Fm ratio), toxin content, and net toxin production rates of the Dinophysis strains were examined. The growth rates of D. acuminata and D. ovum isolates were comparable across light intensities, with the exception of one D. acuminata strain (DANY1) that was unable to grow at the lowest light intensity. However, D. fortii and D. caudata strains were photoinhibited and grew at a slower rate at the highest light intensity, indicating a lower degree of adaptability and tolerance to such conditions. Photosynthetic efficiency was similar for all Dinophysis isolates and negatively correlated with exposure to high light intensities. Multiple toxin metrics, including cellular toxin content and net production rates of DSTs and PTXs, were variable among species and even among isolates of the same species in response to light intensity. A pattern was detected, however, whereby the net production rates of PTXs were significantly lower across all Dinophysis isolates when exposed to the lowest light intensity. These findings provide a basis for understanding the effects of light intensity on the eco-physiological characteristics of Dinophysis species in the US and could be employed to develop integrated physical-biological models for species and strains of interest to predict their population dynamics and mitigate their negative effects.

Postprandial metabolism of Australian hybrid abalone (Haliotis laevigata × H. rubra) in relation to temperature and dietary protein manipulation

Understanding the physiological responses of abalone to culture conditions and nutritional inputs is paramount to maintain optimal performance under densely stocked farming conditions. High water temperature (>24 °C) is widely accepted as a key contributor to elevated summer mortality. High crude protein levels in modern abalone diets may interact with elevated water temperature to produce detrimental effects on abalone physiological processes but have received scant attention. This study measured the energy used in the digestion, absorption, and assimilation (i.e., specific dynamic action (SDA)) of hybrid abalone (Haliotis laevigata x H. rubra) after four months of acclimation to three protein levels (32, 38 and 44%) at three culture temperatures (12, 17 and 22 °C). Hybrid abalone exhibited significant stepwise increases in meal size as temperature increased from 12 through to 22 °C, contributing to significantly different SDA between the temperature treatments. Resting (standard) aerobic metabolic rate and peak metabolism (peak ṀO2) during SDA both increased with temperature, while SDA duration was lowest at 17 °C. No effect of dietary protein was observed within the temperature treatments for the SDA metrics. Abalone held at 12 °C exhibited significantly higher rates of gonad maturation, particularly among females. When 22 °C-acclimated abalone were exposed to a simulated summer heatwave up to 26 °C, they exhibited similar mortality and metabolic responses across protein treatment groups and there was a trend of steadily decreasing ṀO2 with sustained 26 °C water temperature, probably due to fasting. These results help to inform best farming practices to ensure optimal diet, growth, metabolic performance, and survival of hybrid abalone in the dynamic farm environment.

Triisobutyl phosphate biodegradation by enriched activated sludge consortia: Degradation mechanism and bioaugmentation potential

This study investigated the ability of activated sludge (AS) to biodegrade triisobutyl phosphate (TiBP) after acclimation in an AS bioreactor by adding 50 mg/L TiBP. The bioreactor significantly increased the biotransformation rate of TiBP (2.15–12.7 d−1) over two months of acclimation. Seven transformation products (TPs) of TiBP were identified by high-resolution mass spectrometry, and hydrolysis, hydroxylation and dehydrogenation were the major biodegradation pathways of TiBP. TiBP degradation solutions at 0, 3, 7, and 10 h showed significantly toxic effects on zebrafish embryos, while the toxicity of TiBP degradation solutions at 24 h significantly decreased. Pseudomonas was inferred to be a specific bacterial population in the TiBP metabolic microbial consortium (TMMC) that degrades TiBP (p < 0.001). When TMMC (0.5, 1, and 2 gss/L) was introduced into AS, the TiBP biotransformation rates (1.97, 2.05, and 2.26 d−1 at 1.0 mg/L TiBP, and 0.09, 0.11, and 0.83 d−1 at 30.0 mg/L TiBP) were significantly enhanced compared to the control (0.31 and 0.07 d−1) without TMMC inoculation. In general, this study provides new insights into the key species populations that accelerate TiBP degradation and promote the development of TiBP reduction biotechnology in WWTPs.

Chronic experimental hyperoxia elevates aerobic scope: a valid method to test for physiological oxygen limitations in fish.

Experimental hyperoxia has been shown to enhance the maximum oxygen uptake capacity of fishes under acute conditions, potentially offering an avenue to test prominent physiological hypotheses attempting to explain impacts of climate warming on fish populations (e.g., gill-oxygen limitation driving declines in fish size). Such benefits of experimental hyperoxia must persist under chronic conditions if it is to provide a valid manipulation to test the relevant hypotheses, yet the long-term benefits of experimental hyperoxia to oxygen uptake capacity have not been examined. Here, the authors measured aerobic metabolic performance of Galaxias maculatus upon acute exposure to hyperoxia (150% air saturation) and after 5months of acclimation, at both 15°C and 20°C. Acute hyperoxia elevated aerobic scope by 74%-94% relative to normoxic controls, and an elevation of 58%-73% persisted after 5months of hyperoxia acclimation. When hyperoxia-acclimated fish were acutely transitioned back to normoxia, they maintained superior aerobic performance compared with normoxic controls, suggesting an acclimation of the underlying metabolic structures/processes. In demonstrating the long-term benefits of experimental hyperoxia on the aerobic performance of a fish, the authors encourage the use of such approaches to disentangle the role of oxygen in driving the responses of fish populations to climate warming.

Long-time enrofloxacin processing with microbial fuel cells and the influence of coexisting heavy metals (Cu and Zn)

Antibiotics and heavy metals always coexist in livestock wastewater, and the effect of their coexistence on antibiotic degradation by microbial fuel cells (MFCs) remains unclear. In this study, enrofloxacin served as an electron donor for MFCs that had operated for 10 months with Cu and Zn in the influent. After 10 months of acclimation, the MFCs showed good performance for electricity production and enrofloxacin degradation, with a maximum power density of 244.2 ± 20.3 mW/m2, chemical oxygen demand (COD) removal efficiency of 87.3 ± 1.5%, and enrofloxacin degradation rate of 67.6 ± 7.1%. The presence of Zn and enrofloxacin contributed to improving the power output of the MFCs to different extents, while Cu addition and electrical stimulation could strengthen the capability of the MFCs towards antibiotics removal. The coexistence of heavy metals can stabilise the performance of MFCs in response to changes in COD or enrofloxacin concentrations. Comamonas has high adaptability to wastewater with heavy metals and antibiotics coexisting and may be a functional bacterium for MFCs to produce electricity and degrade antibiotics.

Methane production and microbial community acclimation of five manure inocula during psychrophilic anaerobic digestion of swine manure

For small-scale farms, the development of rustic and cheap psychrophilic anaerobic digestion systems appears as an opportunity to treat manure, mitigate gaseous emissions and promote decentralized renewable energy production. However, the development of such processes is limited by our understanding of their start-up. In this research, we tested the ability of one mesophilic digestate and four different manure to be used as inoculum for the start-up of psychrophilic anaerobic digestion of swine slurry at 13 °C. The most efficient inoculum appeared to be a swine manure that had been stored for 2 months in a pit. After 9 months of acclimation, the corresponding reactor produced a maximum methane yield of 42L of CH4/kg Volatile Solidesubstrate/day and a CH4 volume of 125L of CH4/kg-Chemical Oxygen Demandadded. The maximum methane production expressed at 13 °C was between 55% and 68% of that obtained at 37 °C. Monitoring of the microbial community dynamics by high throughput 16S rDNA sequencing showed the smooth adaptation of manure microbial species, underlining the transient dominance of the acetogen syntroph candidatus Cloacimonas during acclimation and the enrichment in the Methanosaeta and Methanosarcina methanogens for an efficient methane production.

EFFECT OF SYSTEMIC RESISTANCE INDUCTORS ON PR´S ENZYMATIC ACTIVITIES AND SEVERITY OF MANGO ANTHRACNOSE

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; anthracnose (&lt;em&gt;Colletotrichum gloeosporioides&lt;/em&gt;) is an important disease in mango (&lt;em&gt;Mangifera indica&lt;/em&gt;) due to its worldwide distribution and inducting of severe epidemics in vegetative and reproductive states, causing significant losses. In nature, plants produce defense mechanisms to protect themselves from biotic and abiotic factors by increasing the synthesis of secondary metabolites and enzymes involving processes such as the accumulation of phenolic compounds, β-1, 3-glucanases and chitinases. &lt;strong&gt;Objective:&lt;/strong&gt; in the present work, the increase in the accumulation of phenolic compounds and enzymes related to pathogenesis β-1, 3-glucanases and chitinases was evaluated as a function of inducers of systemic resistance acquired: acibenzolar-S-methyl, salicylic acid and sodium phosphonate (phosphite). &lt;strong&gt;Methodology:&lt;/strong&gt; the applications of treatments were initiated when the plants were approximately 2 years old (6 months of acclimation), the treatments were applied via foliage, the foliage sampling for the enzymatic analysis was performed taken at 0, 5, 10, 20, and 30 days after inoculations (dai) and the variables evaluated were: phenolic compounds concentration, enzymatic activity of β-1,3-glucanasess (GLU) and chitinases (CHI) by chromatographic methods, also the incubation period, incidence, severity were evaluated. &lt;strong&gt;Results:&lt;/strong&gt; analysis of variance, growth dynamics and correlation showed that those treatments where a resistance inducer was applied had significantly lower incidence and severity levels than the control, as well longer incubation periods. The dynamics of phenolic compound concentration and enzymatic activity were similar in all treatments except for control, observing peaks at 5 and 20 days after application. In addition, a significant correlation between the variables: area under the progress curve of the accumulation of phenolic compounds and activity of β-1, 3-glucanases and chitinases with the anthracnose incidence, severity and incubation period could be observed. &lt;strong&gt;Implications:&lt;/strong&gt; in future studies it is recommended to analyze the behavior of treatments in multiple cultivars. &lt;strong&gt;Conclusion:&lt;/strong&gt; these results contribute to the mango agronomic management in the region as precedent in the search to low environmental impact alternatives for diseases management, also contributing to the determination of disease’s etiology.&lt;/p&gt;

Activated sludge-degrading analgesic drug acetaminophen: Acclimation, microbial community dynamics, degradation characteristics, and bioaugmentation potential

This study identified specific bacterial populations that play a key role in detoxifying acetaminophen (N-acetyl-p-aminophenol, APAP) in activated sludge (AS) microbial communities. An AS bioreactor was established by feeding 100 mg/L of APAP as a sole carbon, nitrogen, and energy source. While the bioreactor increased APAP biotransformation rates significantly (0.7 d−1 to 6.1 d−1) over a month of acclimation, it selected for Pseudomonas by significantly reducing community diversity by 40% and richness by 47%. A Pseudomonas population (designated PCO) isolated from the APAP-degrading community was phylogenetically distinct from other Pseudomonas spp. previously reported as APAP-degrading isolates. PCO could remove APAP at levels up to 590 mg/L without inhibition and could also metabolize APAP-derived metabolites, 4-aminophenol, hydroquinone, and 1,4-benzoquinone at varying levels. PCO was introduced to AS at various volumes (5, 25, and 50% of the total), showing significantly enhanced APAP transformation rates (1.5, 1.9, and 2.3 d−1) compared to the control (1.2 d−1) without PCO inoculation. Overall, our study provides new insights into the phylogenetic and metabolic features of a key species population predominantly accelerating APAP breakdown in the context of AS microbial communities, which will help in the design of a biological means (bioaugmentation) of treating APAP-bearing waste streams.

Long-term acclimation to near-future ocean acidification has negligible effects on energetic attributes in a juvenile coral reef fish

Increased levels of dissolved carbon dioxide (CO2) drive ocean acidification and have been predicted to increase the energy use of marine fishes via physiological and behavioural mechanisms. This notion is based on a theoretical framework suggesting that detrimental effects on energy use are caused by plasma acid-base disruption in response to hypercapnic acidosis, potentially in combination with a malfunction of the gamma aminobutyric acid type A (GABAA) receptors in the brain. However, the existing empirical evidence testing these effects primarily stems from studies that exposed fish to elevated CO2 for a few days and measured a small number of traits. We investigated a range of energetic traits in juvenile spiny chromis damselfish (Acanthochromis polyacanthus) over 3months of acclimation to projected end-of-century CO2 levels (~ 1000µatm). Somatic growth and otolith size and shape were unaffected by the CO2 treatment across 3months of development in comparison with control fish (~ 420µatm). Swimming activity during behavioural assays was initially higher in the elevated CO2 group, but this effect dissipated within ~ 25min following handling. The transient higher activity of fish under elevated CO2 was not associated with a detectable difference in the rate of oxygen uptake nor was it mediated by GABAA neurotransmitter interference because treatment with a GABAA antagonist (gabazine) did not abolish the CO2 treatment effect. These findings contrast with several short-term studies by suggesting that end-of-century levels of CO2 may have negligible direct effects on the energetics of at least some species of fish.

Evidence of stress imprinting with population-level differences in two moss species.

Plants are often repeatedly exposed to stresses during their lives and have a mechanism called stress imprinting that provides “memories” of stresses they experience and increases their ability to cope with later stresses. To test hypotheses that primed bryophytes can preserve their stress imprinting after 6 days of recovery and induce higher levels of osmolytes and ROS‐scavenging activities upon later stress exposure, and there exist population‐level differentiation in their desiccation defenses, we transplanted samples of two populations of each of two moss species, Hypnum plumaeforme and Pogonatum cirratum, in a nature reserve in southern China. After 16 months of acclimation, sets of each population were subjected to control, one‐time desiccation stress, duplicated desiccation stress and cross‐stress (low temperature stress followed by desiccation stress) treatments. Levels of oxidant enzymes, osmolytes, and phytohormones in the samples were then determined. The desiccation stress generally led to increases in activities or contents of superoxide dismutase, guaiacol peroxidase, catalase, proline, soluble sugars, soluble proteins, and stress hormones including abscisic acid (ABA), jasmonates (JA), and salicylic acid (SA), with differences between both species and populations. After a 6‐day recovery period, contents of phytohormones (including ABA, JA, SA, and cytokinins) in stressed H. plumaeforme had substantially fallen toward control levels. The duplicated and cross‐stress treatments generally led to further accumulation of proline, soluble sugars, and soluble proteins, with further increases in activities of antioxidant enzymes in some cases. Furthermore, significant differences between allochthonous and native populations were found in contents of malondialdehyde and osmolytes, as well as antioxidant enzyme activities. Our results confirm the hypotheses and highlight the importance of osmolytes in mosses' stress responses.

More than just the numbers-contrasting response of snake erythrocytes to thermal acclimation.

Acclimation to lower temperatures decreases energy expenditure in ectotherms but increases oxygen consumption in most endotherms, when dropped below thermoneutrality. Such differences should be met by adjustments in oxygen transport through blood. Changes in hematological variables in correspondence to that in metabolic rates are, however, not fully understood, particularly in non-avian reptiles. We investigated the effect of thermal acclimation on a snake model, the grass snakes (Natrix natrix). After 6months of acclimation to either 18°C or 32°C hematocrit, hemoglobin concentration, erythrocyte number, and size were assessed. All variables revealed significantly lower values under warm compared to cold ambient temperature. Our data suggest that non-avian reptiles, similarly as birds, reduce erythrocyte fraction under energy-demanding temperatures. Due to low deformability of nucleated erythrocytes in sauropsids, such reduced fraction may be important in decreasing blood viscosity to optimize blood flow. Novel findings on flexible erythrocyte size provide an important contribution to this optimization process.

Synthesis of Short-Chain-Length and Medium-Chain-Length Polyhydroxyalkanoate Blends from Activated Sludge by Manipulating Octanoic Acid and Nonanoic Acid as Carbon Sources.

The effects of octanoic acid/nonanoic acid and acclimation time on the synthesis of short-chain-length and medium-chain-length PHA blends from activated sludge were investigated. An increased concentration (847-1366 mg/L) of PHAs resulted from 4-month acclimation compared with the concentration derived from 2-month acclimation (450-1126 mg/L). The content of octanoic acid had a positive linear relationship with the content of even-numbered carbon monomers among the PHAs. The blending products were identified mainly with scl-PHAs during the 2-month acclimation period and were thereafter dominated by mcl-PHAs until 4 months of acclimation. Thermal properties analysis demonstrated that the products derived from 4-month acclimation were a mixture of scl-PHAs and mcl-PHAs rather than a copolymer of scl-PHAs and mcl-PHAs. High-throughput sequencing results indicated that Pseudofulvimonas, Paracoccus, and Blastocatella were the dominant genera that might be responsible for scl-PHAs production during the 2-month acclimation period, whereas Comamonas and Pseudomonas that were responsible for mcl-PHAs production then became the dominant genera after 4-months acclimation.

Negative effects of climate change on upland grassland productivity and carbon fluxes are not attenuated by nitrogen status

Effects of climate change on managed grassland carbon (C) fluxes and biomass production are not well understood. In this study, we investigated the individual and interactive effects of experimental warming (+3 °C above ambient summer daily range of 9–12 °C), supplemental precipitation (333 mm +15%) and drought (333 mm −23%) on plant biomass, microbial biomass C (MBC), net ecosystem exchange (NEE) and dissolved organic C (DOC) flux in soil cores from two upland grasslands of different soil nitrogen (N) status (0.54% and 0.37%) in the UK. After one month of acclimation to ambient summer temperature and precipitation, five replicate cores of each treatment were subjected to three months of experimental warming, drought and supplemental precipitation, based on the projected regional summer climate by the end of the 21st Century, in a fully factorial design. NEE and DOC flux were measured throughout the experimental duration, alongside other environmental variables including soil temperature and moisture. Plant biomass and MBC were determined at the end of the experiment. Results showed that warming plus drought resulted in a significant decline in belowground plant biomass (−29 to −37%), aboveground plant biomass (−35 to −77%) and NEE (−13 to −29%), regardless of the N status of the soil. Supplemental precipitation could not reverse the negative effects of warming on the net ecosystem C uptake and plant biomass production. This was attributed to physiological stress imposed by warming which suggests that future summer climate will reduce the C sink capacity of the grasslands. Due to the low moisture retention observed in this study, and to verify our findings, it is recommended that future experiments aimed at measuring soil C dynamics under climate change should be carried out under field conditions. Longer term experiments are recommended to account for seasonal and annual variability, and adaptive changes in biota.

Continuous nitrogen removal by a single-stage reactor packed with ring-laced string medium

The efficiency of nitrogen removal by a partial-nitritation/anammox (PNA) reaction was investigated using a packed-bed reactor in which ring-laced strings were used as the supporting medium. A stable population of PNA microorganisms was established from typical activated sludge, after less than two months of acclimation in the packed-bed reactor, by applying a high nitrogen-loading rate (NLR: 0.53kg/m3/d) and short hydraulic retention time (HRT: 1.8h). The stability of reactor performance was confirmed in industrial wastewater (IW), demonstrating a nitrogen removal efficiency (NRE) of greater than 77% during 260 days of continuous operation, between 0.19 and 0.53kg/m3/d of NLR. Partial nitrification was adequately controlled by low-level oxygen supply to the reactor. Pyro-tag sequencing analysis of the biofilm revealed a clear abundance of anammox bacteria in the inner part of the biofilm and ammonium-oxidizing bacteria in the outer part. In the synthetic inorganic medium (SIM), the microbial community structure did not change drastically between the early and late phases of the experiment's continuous operation, which lasted over 200 days. In IW, however, the existence ratio of anammox bacteria decreased to 4% on day 249 of continuous operation. The number of detected operational taxonomic units (OTUs) increased in the IW, implying that the community structure was widely diversified. However, anammox bacteria could propagate sufficiently to catalyze nitrogen removal under this condition because the NRE was stable at approximately 88%.

Improvement of Dextransucrase Activity by Glucose Acclimation Cultivation and Kinetics of Sucrose Consumption

Dextransucrase is the enzyme that catalyzes the synthesis of dextran from sucrose. Though dextran is an unwanted deterioration product in the sugar industry, it is being widely used in medicine, cosmetics, and several food areas. Currently, the natural enzyme activity of dextransucrase is low. Thus, it is of great interest to understand how to improve the dextransucrase activity. In the study, Leuconostoc mesenteroides (L.M.CICC-20724) were cultured in a glucose-based solid medium (glucose was the sole carbon source) and then transferred to a sucrose-based solid medium (sucrose was the sole carbon source) for rejuvenation. It was observed that the dextransucrase production was inhibited when L.M.CICC-20724 using the glucose-based solid medium. After 3 months of acclimation, the activity of dextransucrase produced by the acclimated L. mesenteroides (Glu-L.M.) achieved a stable level at approximately 4.20 U/mL. The dextransucrase activity (approximately 1–2 U/mL) increased more than two times with L.M.CICC-20724 in comparision with original one. Dextran products generated from Glu-L.M. and L.M.CICC-20724 were studied using Fourier transform infrared spectroscopy and results showed that both dextrans had a consistent structural composition. The kinetics of sucrose consumption was studied. Under the condition of 0.5 U/mL dextransucrase activity, the consumption of relative low initial sucrose concentrations (0.1, 0.2 and 0.4 M) more fitted to the first-order reaction kinetics, while the consumption of relative high initial sucrose concentrations (0.6 and 0.8 M) was fitted better to the second-order reaction kinetics.

Effects of thermal stress on the expression of glucocorticoid receptor complex linked genes in Senegalese sole (Solea senegalensis): Acute and adaptive stress responses

The present study examined the short and mid-term effects of a rise in temperature from 18°C to 24°C on the expression of genes related to the stress response regulation in juveniles of Senegalese sole, Solea senegalensis. The animals were exposed to a temperature increase of 6°C, after 1month of acclimation at 18°C. After this process, samples of different tissues were collected from a total of 96 fish at four sampling points: 1h, 24h, 3days and 1week. The transcript levels of a set of genes involved in the stress response such as glucocorticoid receptors 1 and 2, corticotrophin-releasing factor, corticotrophin-releasing factor binding proteins, proopiomelanocortin A and B, and cellular stress defense (heat shock protein 70, 90AA and 90AB) were quantified at these sampling points. Additionally, blood samples were also taken to measure the circulating plasma cortisol concentration.Thermal stress induced by increasing temperature prompted an elevation of plasma cortisol levels in juvenile Senegalese sole after 1h as a short-term response, and a consecutive increase after one week, as a mid-term response. Senegalese sole seemed to respond positively in terms of adaptive mechanisms, with a rapid over-expression of grs and hsps in liver and brain, significantly higher after one hour post stress, denoting the fast and acute response of those tissues to a rapid change on temperature. The ratio hsp90/gr also increased 24h after thermal shock, ratio proposed to be an adaptive mechanism to prevent proteosomal degradation of GR. As a mid-term response, the elevation of brain crfbp gene expression one week after thermal shock could be an adaptive mechanism of negative feedback on HPI axis.Taken together, these data suggested an initial up-regulation of the glucocorticoid receptor complex linked genes in response to a temperature increase in Senegalese sole, with heat shock protein 90 potentially being a regulatory factor for the glucocorticoid receptor in the presence of cortisol.

Simulated global warming increases usnic acid but reduces perlatolic acid in the mat-forming terricolous lichenCladonia stellaris

AbstractLichens as sessile and slow-growing symbiotic associations have evolved various carbon-based secondary compounds (CBSCs) to mitigate the effects of some stressors in the extreme environments in which they often grow. The mat-forming lichenCladonia stellaris, an important fodder for reindeer, produces usnic acid in the outermost layer and perlatolic acid in the medulla. Here, we studied effects of simulated global warming on these CBSCs inC. stellariscultivated in climate chambers with: 1) ambient conditions as control or 2) ambient conditions +4°C. The chambers simulated, at an hourly resolution, an averaged 10-year growing season dynamic from a long-term monitored boreal mire in northern Sweden. After two months of acclimation, +4°C warming in one simulated growing season increased the concentration of usnic acid by 31% compared with ambient conditions, whereas the warming decreased the concentration of perlatolic acid by 14%. Since lichen CBSCs play important roles in ecosystem processes such as lichenivory and decomposition, these changes may profoundly affect lichen-dominated ecosystems.

Seasonal acclimation and latitudinal adaptation are of the same magnitude in Mytilus edulis and Mytilus trossulus mitochondrial respiration

Species distribution models often assume homogeneous physiological performance within a species distribution range. This assumption potentially underestimates the distribution as it neglects physiological plasticity and adaptation among species and populations. Better knowledge on the physiological variation is, therefore, needed to better predict the effects of global warming on species distribution. Mussels in the genus Mytilus are known to display latitudinal variation in whole animal aerobic metabolism. Here we test the hypothesis that latitudinal variation in whole animal metabolic rate of two congeners of Mytilus (Mytilus edulis collected 56°N, and Mytilus trossulus collected 77°N) is related to differences in mitochondrial respiration. We further investigated the changes in mitochondrial respiration following long-term cold-water acclimation of M. edulis. We assessed mitochondrial respiration after five months of acclimation to 1 and 15 °C. At similar experimental temperatures, mitochondrial respiration in animals acclimated to 1 °C was higher compared to those acclimated to 15 °C. After five months of acclimation, 1 °C-acclimated M. edulis had similar mitochondrial respiration as 1 °C-acclimated M. trossulus despite their different geographical origin. Our data indicate that mitochondrial capacity does not support latitudinal observed differences in whole animal metabolism between M. edulis and M. trossulus. However, we reveal that mitochondrial respiration in M. edulis can increase by 283% after cold acclimation. Combined, our results show that seasonal variation in mitochondrial respiration is of the same magnitude as large-scale (>1000 km) latitudinal variation. The high respiratory plasticity in Mytilus spp. improves fitness in changing temperature environments and supports their large biogeographic distribution.

Stress response or beneficial temperature acclimation: transcriptomic signatures in Antarctic fish (Pachycara brachycephalum).

Research on the thermal biology of Antarctic marine organisms has increased awareness of their vulnerability to climate change, as a flipside of their adaptation to life in the permanent cold and their limited capacity to acclimate to variable temperatures. Here, we employed a species-specific microarray of the Antarctic eelpout, Pachycara brachycephalum, to identify long-term shifts in gene expression after 2months of acclimation to six temperatures between -1 and 9°C. Changes in cellular processes comprised signalling, post-translational modification, cytoskeleton remodelling, metabolic shifts and alterations in the transcription as well as translation machinery. The magnitude of transcriptomic responses paralleled the change in whole animal performance. Optimal growth at 3°C occurred at a minimum in gene expression changes indicative of a balanced steady state. The up-regulation of ribosomal transcripts at 5°C and above was accompanied by the transcriptomic activation of differential protein degradation pathways, from proteasome-based degradation in the cold towards lysosomal protein degradation in the warmth. From 7°C upwards, increasing transcript levels representing heat-shock proteins and an acute inflammatory response indicate cellular stress. Such patterns may contribute to a warm-induced energy deficit and a strong weight loss at temperatures above 6°C. Together, cold or warm acclimation led to specific cellular rearrangements and the progressive development of functional imbalances beyond the optimum temperature. The observed temperature-specific expression profiles reveal the molecular basis of thermal plasticity and refine present understanding of the shape and positioning of the thermal performance curve of ectotherms on the temperature scale.

Mental Health and Substance Use Considerations in the Care of Returning Veterans

Since September 11, 2001, approximately 2.5 million men and women have been deployed in the Global War on Terror. Nearly half have spent between 6 to 24 months in direct service to combat zones in Afghanistan (Operation Enduring Freedom [OEF]) or Iraq (Operation Iraqi Freedom [OIF]). 1 While on active duty, our military constantly faces life-threatening situations. Upon their return home, the majority of these soldiers and Marines successfully move forward with their lives, after an initial few months of acclimation.