Gender differences in the associations of psychosocial trauma and acute medical stressors with immune system activation and dementia risk.

Objective: The purpose of this article is to provide a narrative review synthesizing the literature on differences between women and men in relationships among certain stressors associated with immune system activation and their relationship to cognitive dysfunction and dementia. Method: We review the cycle of stress leading to neuroinflammation via cortisol and neurochemical alterations, cell-mediated immune system activation, and pro-inflammatory cytokines, and how this is implicated in the development of dementia. We follow this by discussing sex differences in stress physiology and immune function. We then review the work on early life adversity (ELA) and adverse childhood experiences (ACEs), post-traumatic stress disorder, acute medical stressors, and their associations with cognitive dysfunction and dementia. Throughout, we emphasize women's presentations and issues unique to women (e.g. trauma disorder prevalence). Conclusions: There is a need for more mechanistic and longitudinal studies that consider trauma accumulation, both physical and emotional, as well as a greater focus on traumas more likely to occur in women (e.g. sexual abuse), and their relationship to early cognitive decline and dementia.

War-Time Stress and Sexual Well-Being in Israel.

Objective: This study explored the relationship between war-related stressors and sexual well-being among a civilian population during the 2023 Israel-Hamas War, emphasizing a comprehensive assessment of sexual satisfaction, function, and distress. We aimed to investigate how direct exposure, media exposure, and acute stress symptoms during the war contribute to various dimensions of sexual well-being using a quasi-longitudinal online survey method. Methods: An online survey with a convenience sample of 1033 Israeli adults, utilizing measures of direct and media exposure to war stress, acute stress symptoms, and various aspects of sexual well-being, both pre-war and present was distributed. Data analysis involved Pearson correlations and hierarchical regression. Results: There were significant associations between stress-related variables and sexual well-being, highlighting the differential contribution of direct exposure, media exposure, and acute stress symptoms. Direct exposure to stress was uniquely associated with sexual dysfunction, while media exposure and acute stress symptoms contributed significantly to predicting various aspects of sexual well-being. Conclusions: Recognizing the multifaceted impact of stress during wartime on sexual well-being is crucial for developing comprehensive mental health interventions that address individual and societal factors. This study contributes valuable insights into the relationships between stress-related variables and sexual well-being during wartime, emphasizing the need for holistic approaches in addressing the intimate challenges individuals face during times of conflict.

Racial discrimination in healthcare services among Black individuals in Canada as a major threat for public health: its association with COVID-19 vaccine mistrust and uptake, conspiracy beliefs, depression, anxiety, stress, and community resilience.

OBJECTIVES: To examine the prevalence of major racial discrimination (MRD) in healthcare services and its association with COVID-19 vaccine mistrust and uptake, conspiracy theories, COVID-19-related stressors, community resilience, anxiety, depression, and stress symptoms. STUDY DESIGN: The study used a population-based cross-sectional design. METHODS: Data from the BlackVax dataset on COVID-19 vaccination in Black individuals in Canada was analyzed (n = 2002, 51.66% women). Logistic regression analyses were performed to examine the association between MRD and independent variables. RESULTS: 32.55% of participants declared having experienced MRD in healthcare services. Participants with MRD were less vaccinated against COVID-19, presented higher scores of vaccine mistrust, conspiracy beliefs, COVID-19 related stressors, depression, anxiety, and stress, and had lower scores of community resilience. They were more likely to experience depression (AOR = 2.13, P < 0.001), anxiety (AOR = 2.00, P < 0.001), and stress symptoms (AOR = 2.15, P < 0.001). Participants who experienced MRD were more likely to be unvaccinated (AOR = 1.35, P = 0.009). CONCLUSIONS: Racial discrimination experienced by Black individuals in health services is a major public health concern and threat to population health in Canada. Federal, provincial, and municipal public health agencies should adapt their programs, strategies, tools, and campaigns to address the mistrust created by racial discrimination.

Multistress Interplay: Time and Duration of Ocean Acidification Modulate the Toxicity of Mercury and Other Metals.

The current understanding of multistress interplay assumes stresses occur in perfect synchrony, but this assumption is rarely met in the natural marine ecosystem. To understand the interplay between nonperfectly overlapped stresses in the ocean, we manipulated a multigenerational experiment (F0-F3) to explore how different temporal scenarios of ocean acidification will affect mercury toxicity in a marine copepod Pseudodiaptomus annandalei. We found that the scenario of past acidification aggravated mercury toxicity but current and persistent acidification mitigated its toxicity. We specifically performed a proteomics analysis for the copepods of F3. The results indicated that current and persistent acidification initiated the energy compensation for development and mercury efflux, whereas past acidification lacked the barrier of H+ and had dysfunction in the detoxification and efflux system, providing a mechanistic understanding of mercury toxicity under different acidification scenarios. Furthermore, we conducted a meta-analysis on marine animals, demonstrating that different acidification scenarios could alter the toxicity of several other metals, despite evidence from nonsynchronous scenarios remaining limited. Our study thus demonstrates that time and duration of ocean acidification modulate mercury toxicity in marine copepods and suggests that future studies should move beyond the oversimplified scenario of perfect synchrony in understanding multistress interaction.

COVID-19-Related Stressors and Psychophysical Health Conditions among Italian University Students: A Post Pandemic Insight.

The COVID-19 medical emergency has ended worldwide, yet the psychological impact of these years of unprecedented changes on students' lives still needs to be deepened. METHODS: This study aims to assess and compare COVID-19-related stressors (relationships and academic life; isolation; and fear of contagion) and psychophysical symptoms reported by 637 university students at three times, i.e., April 2020 (n = 197), April 2021 (n = 200), and April 2022 (n = 240). The impact of COVID-19-related stressors on psychophysical symptoms within each time was also tested. RESULTS: In April 2022, perceived isolation and fear of contagion decreased from the peak registered in April 2021, but stress related to relationships and academic life remained high. An ongoing increase in psychophysical symptoms was found. More than 50% of students reported clinical levels of sleep disorders, depression, psychoticism, and interpersonal sensitivity. In April 2022, students still perceiving stress related to relationships and academic life and isolation were at risk for anxiety, somatization, and sleep disorders. Students still perceiving stress related to fear of contagion were also at risk for depression, obsessive-compulsive symptoms, and psychoticism. CONCLUSION: The findings emphasized the long-lasting effects of COVID-19-related stress on students' psychophysical health. Interventions must aim at supporting students in dealing with the complex post-pandemic adjustment process.

War-related stress scale.

BACKGROUND: The current war in Ukraine has affected the well-being of people worldwide. In order to understand how difficult the situation is, specific stressors associated with war need to be measured. In response, an inventory of war-related stressors including its short form, has been developed. METHODS: A list of potential war-related stressors was created, and the content validity of each item assessed. The list, along with other validated scales, was administered to a representative sample of the Slovak population (effective N = 1851). Exploratory factor analysis, confirmatory factor analysis, convergent validity analysis and network analysis were carried out to determine the optimal scale (long and short form) focused on war-related stressors. RESULTS: The full version of the scale consists of 21 items, further divided into three factors: society-related stressors, person-related stressors, and security-related stressors. The short version of the scale comprises nine items loaded onto one factor. These items cover concerns for one's safety and future, access to necessities, potential worsening of the economic situation, and the risk of conflict escalation, including a nuclear threat. The results of the network analysis indicate that concern about escalation and fear of an economic crisis play a central role. CONCLUSIONS: The scale attempts to encompass a wide spectrum of areas that are affected by war and its potential consequences on individuals who reside outside the conflict zone. Given the complexity of the issue, researchers are invited to modify the scale, tailoring it to specific cultural, geographical, and temporal contexts.

Pilot Study Focused on Knowledge, Attitudes, and Health Access Behaviors of Psychiatric-Mental Health Nurses Regarding Suicide Prevention.

OBJECTIVE: The purpose of this pilot study was to evaluate the effect of a web-based education module on the knowledge, attitudes, and ratings of willingness to access help related to suicide prevention in psychiatric-mental health nurses. METHODS: A quasi-experimental pretest-posttest design was employed. Registered nurses from two academic health center units and a 239-bed Psychiatric Hospital were invited to participate. Scores on knowledge of suicide risk and prevention, attitudes, subjective norms, perceived behavioral control, and intent to seek help upon experiencing suicidal ideations were obtained before and after administering a 25-min web-based training. RESULTS: Twenty-nine participants completed the pre-survey, web-based education module, and post-survey. Significant increases from baseline in the scores on knowledge, attitudes, subjective norms, and intentions related to help-seeking behaviors for nurse suicide prevention were noted. Perceived behavioral control median scores increased but were not statistically significant. More than 40% of the participants reported having experienced suicidal thoughts. CONCLUSIONS: Further study is needed to determine contributors to this higher rate. Understanding the effectiveness of strategies to reduce nurse suicide can provide insights into building better nurse suicide prevention programs.

Can exposure to Gymnodinium catenatum toxic blooms influence the impacts induced by Neodymium in Mytilus galloprovincialis mussels? What doesn't kill can make them stronger?

The presence in marine shellfish of toxins and pollutants like rare earth elements (REEs) poses a major threat to human well-being, coastal ecosystems, and marine life. Among the REEs, neodymium (Nd) stands out as a widely utilized element and is projected to be among the top five critical elements by 2025. Gymnodinum catenatum is a phytoplankton species commonly associated with the contamination of bivalves with paralytic shellfish toxins. This study evaluated the biological effects of Nd on the mussel species Mytilus galloprovincialis when exposed to G. catenatum cells for fourteen days, followed by a recovery period in uncontaminated seawater for another fourteen days. After co-exposure, mussels showed similar toxin accumulation in the Nd and G. catenatum treatment in comparison with the G. catenatum treatment alone. Increased metabolism and enzymatic defenses were observed in organisms exposed to G. catenatum cells, while Nd inhibited enzyme activity and caused cellular damage. Overall, this study revealed that the combined presence of G. catenatum cells and Nd, produced positive synergistic effects on M. galloprovincialis biochemical responses compared to G. catenatum alone, indicating that organisms' performance may be significantly modulated by the presence of multiple co-occurring stressors, such those related to chemical pollution and harmful algal blooms. ENVIRONMENTAL IMPLICATIONS: Neodymium (Nd) is widely used in green technologies like wind turbines, and this element's potential threats to aquatic environments are almost unknown, especially when co-occurring with other environmental factors such as blooms of toxic algae. This study revealed the cellular impacts induced by Nd in the bioindicator species Mytilus galloprovincialis but further demonstrated that the combination of both stressors can generate a positive defense response in mussels. The present findings also demonstrated that the impacts caused by Nd lasted even after a recovery period while a previous exposure to the toxins generated a faster biochemical improvement by the mussels.

Honey bee stressor networks are complex and dependent on crop and region.

Honey bees play a major role in crop pollination but have experienced declining health throughout most of the globe. Despite decades of research on key honey bee stressors (e.g., parasitic Varroa destructor mites and viruses), researchers cannot fully explain or predict colony mortality, potentially because it is caused by exposure to multiple interacting stressors in the field. Understanding which honey bee stressors co-occur and have the potential to interact is therefore of profound importance. Here, we used the emerging field of systems theory to characterize the stressor networks found in honey bee colonies after they were placed in fields containing economically valuable crops across Canada. Honey bee stressor networks were often highly complex, with hundreds of potential interactions between stressors. Their placement in crops for the pollination season generally exposed colonies to more complex stressor networks, with an average of 23 stressors and 307 interactions. We discovered that the most influential stressors in a network-those that substantively impacted network architecture-are not currently addressed by beekeepers. Finally, the stressor networks showed substantial divergence among crop systems from different regions, which is consistent with the knowledge that some crops (e.g., highbush blueberry) are traditionally riskier to honey bees than others. Our approach sheds light on the stressor networks that honey bees encounter in the field and underscores the importance of considering interactions among stressors. Clearly, addressing and managing these issues will require solutions that are tailored to specific crops and regions and their associated stressor networks.

The role of the macroalgae Ulva lactuca on the cellular effects of neodymium and mercury in the mussel Mytilus galloprovincialis.

Rare earth elements (REEs) are increasingly being studied mainly due to their economic importance and wide range of applications, but also for their rising environmental concentrations and potential environmental and ecotoxicological impacts. Among REEs, neodymium (Nd) is widely used in lasers, glass additives, and magnets. Currently, NdFeB-based permanent magnets are the most significant components of electronic devices and Nd is used because of its magnetic properties. In addition to REES, part of the environmental pollution related to electrical and electronic equipment, fluorescent lamps and batteries also comes from mercury (Hg). Since both elements persist in ecosystems and are continuously accumulated by marine organisms, a promising approach for water decontamination has emerged. Through a process known as sorption, live marine macroalgae can be used, especially Ulva lactuca, to accumulate potential toxic elements from the water. Therefore, the present study aimed to evaluate the cellular toxicity of Nd and Hg in Mytilus galloprovincialis, comparing the biochemical effects induced by these elements in the presence or absence of the macroalgae U. lactuca. The results confirmed that Hg was more toxic to mussels than Nd, but also showed the good capability of U. lactuca in preventing the onset of cellular disturbance and homeostasis disruption in M. galloprovincialis by reducing bioavailable Hg levels. Overall, the biochemical parameters evaluated related to metabolism, antioxidant and biotransformation defences, redox balance, and cellular damage, showed that algae could prevent biological effects in mussels exposed to Hg compared to those exposed to Nd. This study contributes to the advancement of knowledge in this field, namely the understanding of the impacts of different elements on bivalves and the crucial role of algae in the protection of other aquatic organisms.

The positive side of stress: Investigating the impact of challenge stressors on innovative behavior in higher education.

Stress can be a double-edged sword. Given the intricacy of the innovation process, the link between job stress and individual innovation behavior remains uncertain. To clarify the relationship between challenge stressors and the innovative behavior of higher education teachers, this study was based on the conservation of resources (COR) theory and adopted the structural equation modeling method to explore the impact of challenge stressors on the innovative behavior of higher education teachers and reveal its influencing mechanism and boundary conditions. By analyzing the data from 208 questionnaires of higher education teachers, the findings reveal that challenge stressors positively influence innovative behavior, with task crafting serving as a critical bridge. Additionally, a favorable employment relationship climate enhances the positive impact of challenge stressors. Gender dynamics are also explored, adding nuance to the understanding of this relationship. These results shed light on the inherent mechanisms governing the relationship between challenge stressors and innovative behavior among higher education teachers, and underscore the significance of task crafting. In addition, the discoveries provided fresh insights and ideas for investigating how organizational climate affects individual innovative behavior.

Unveiling the Rising Threat of Cadmium Pollution and Alarming Health Risks Associated with the Consumption of 15 Commercially Important Fish Species in the Middle Stretch of River Ganga, at Patna, India.

Among environmental contaminants, the rising level of cadmium in freshwater ecosystems is one of the most significant global concerns. The study addresses the current pollution status of cadmium in the middle stretch of River Ganga and explores the potential hazard associated with the consumption of 15 commercially important fish species by the inhabitants. Together 72 water and sediment samples were analyzed from the four representative sampling sites of River Ganga after the surveillance of major anthropogenic stressors. The concentration of cadmium ranges from 0.003 to 0.011 mg/l and 0.2 to 3.48 mg/kg in water and sediment respectively in 2022. The average concentration of cadmium was recorded to be the highest in Channa punctatus (1.35 mg/kg), followed by Rita rita = Johnius coitor (1.15 mg/kg), and the lowest in Labeo bata (0.2 mg/kg). The finding highlights greater exposure duration and feeding preferences of fish species have played a significant role in the bioaccumulation of the metal in the riverine system. Notably, the domestic effluents, agricultural runoffs, and pollutants brought along by the tributaries of River Ganga are identified as the main anthropogenic stressors for the moderate to considerably polluted status of the River Ganga. The target hazard quotient (THQ) and target carcinogenic risk (TCR) have revealed a higher susceptibility to cadmium contamination in children followed by females, and males. In addition, hierarchical cluster analysis (HCA) has noted intake of Rita rita, Channa punctata, Puntius sophore, and Johnius coitor could be more detrimental to children's health than adults.

Sequential Treatment Application Robot (STAR) for high-replication marine experimentation.

Marine organisms are often subject to numerous anthropogenic stressors, resulting in widespread ecosystem degradation. Physiological responses to these stressors, however, are complicated by high biological variability, species-specific sensitivities, nonlinear relationships, and countless permutations of stressor combinations. Nevertheless, quantification of these relationships is paramount for parameterizing predictive tools and ultimately for effective management of marine resources. Multi-level, multi-stressor experimentation is therefore key, yet the high replication required has remained a logistical challenge and a financial barrier. To overcome these issues, we created an automated system for experimentation on marine organisms, the Sequential Treatment Application Robot (STAR). The system consists of a track-mounted robotic arm that sequentially applies precision treatments to independent aquaria via syringe and peristaltic pumps. The accuracy and precision were validated with dye and spectrophotometry, and stability was demonstrated by maintaining corals under treatment conditions for more than a month. The system is open source and scalable in that additional treatments and replicates may be added without incurring multiplicative costs. While STAR was designed for investigating the combined impacts of nutrients, warming, and disease on reef-building corals, it is highly customizable and may be used for experimentation involving a diverse array of treatments and species.

A longitudinal study of risk and protective factors for symptoms of adjustment disorder during the COVID-19 pandemic.

Background: The COVID-19 pandemic caused multiple stressors that may lead to symptoms of adjustment disorder.Objective: We longitudinally examined relationships between risk and protective factors, pandemic-related stressors and symptoms of adjustment disorder during the COVID-19 pandemic, as well as whether these relationships differed by the time of assessment.Method: The European Society for Traumatic Stress Studies (ESTSS) ADJUST Study included N = 15,169 participants aged 18 years and above. Participants from 11 European countries were recruited and screened three times at 6-month intervals from June 2020 to January 2022. Associations between risk and protective factors (e.g. gender), stressors (e.g. fear of infection), and symptoms of adjustment disorder (AjD, ADNM-8) and their interaction with time of assessment were examined using mixed linear regression.Results: The following predictors were significantly associated with higher AjD symptom levels: female or diverse gender; older age; pandemic-related news consumption >30 min a day; a current or previous mental health disorder; trauma exposure before or during the pandemic; a good, satisfactory or poor health status (vs. very good); burden related to governmental crisis management and communication; fear of infection; restricted social contact; work-related problems; restricted activity; and difficult housing conditions. The following predictors were associated with lower AjD levels: self-employment or retirement; working in healthcare; and face-to-face contact ≥ once a week with loved ones or friends. The effects of the following predictors on AjD symptoms differed by the time of assessment in the course of the pandemic: a current or previous mental disorder; burden related to governmental crisis management; income reduction; and a current trauma exposure.Conclusions: We identified risk factors and stressors predicting AjD symptom levels at different stages of the pandemic. For some predictors, the effects on mental health may change at different stages of a pandemic.

We longitudinally examined predictors of symptoms of adjustment disorder in 15,563 adults during the COVID-19 pandemic.We found stressors, risk, and protective factors predicting adjustment disorder symptom levels at different stages of the pandemic.For some predictors, the effects appear to change in different phases of a pandemic.

Interaction of acetamiprid, Varroa destructor, and Nosema ceranae in honey bees.

Health of honey bees is threatened by a variety of stressors, including pesticides and parasites. Here, we investigated effects of acetamiprid, Varroa destructor, and Nosema ceranae, which act either alone or in combination. Our results suggested that interaction between the three factors was additive, with survival risk increasing as the number of stressors increased. Although exposure to 150 µg/L acetamiprid alone did not negatively impact honey bee survival, it caused severe damage to midgut tissue. Among the three stressors, V. destructor posed the greatest threat to honey bee survival, and N. ceranae exacerbated intestinal damage and increased thickness of the midgut wall. Transcriptomic analysis indicated that different combinations of stressors elicited specific gene expression responses in honey bees, and genes involved in energy metabolism, immunity, and detoxification were altered in response to multiple stressor combinations. Additionally, genes associated with Toll and Imd signalling, tyrosine metabolism, and phototransduction pathway were significantly suppressed in response to different combinations of multiple stressors. This study enhances our understanding of the adaptation mechanisms to multiple stressors and aids in development of suitable protective measures for honey bees. ENVIRONMENTAL IMPLICATION: We believe our study is environmentally relevant for the following reasons: This study investigates combined effects of pesticide, Varroa destructor, and Nosema ceranae. These stressors are known to pose a threat to long-term survival of honey bees (Apis mellifera) and stability of the ecosystems. The research provides valuable insights into the adaptive mechanisms of honey bees in response to multiple stressors and developing effective conservation strategies. Further research can identify traits that promote honey bee survival in the face of future challenges from multiple stressors to maintain the overall stability of environment.

Stream macroinvertebrate communities in restored and impacted catchments respond differently to climate, land-use, and runoff over a decade.

Identifying which environmental drivers underlie degradation and improvements of ecological communities is a fundamental goal of ecology. Achieving this goal is a challenge due to diverse trends in both environmental conditions and ecological communities across regions, and it is constrained by the lack of long-term parallel monitoring of environmental and community data needed to study causal relationships. Here, we identify key environmental drivers using a high-resolution environmental - ecological dataset, an ensemble of the Soil and Water Assessment Tool (SWAT+) model, and ecological models to investigate effects of climate, land-use, and runoff on the decadal trend (2012-2021) of stream macroinvertebrate communities in a restored urban catchment and an impacted catchment with mixed land uses in Germany. The decadal trends showed decreased precipitation, increased temperature, and reduced anthropogenic land-uses, which led to opposing runoff trends - with decreased runoff in the restored catchment and increased runoff in the impacted catchment. The two catchments also varied in decadal trends of taxonomic and trait composition and metrics. The most significant improvements over time were recorded in communities of the restored catchment sites, which have become wastewater free since 2007 to 2009. Within the restored catchment sites, community metric trends were primarily explained by land-use and evaporation trends, while community composition trends were mostly associated with precipitation and runoff trends. Meanwhile, the communities in the impacted catchment did not undergo significant changes between 2012 and 2021, likely influenced by the effects of prolonged droughts following floods after 2018. The results of our study confirm the significance of restoration and land-use management in fostering long-term improvements in stream communities, while climate change remains a prodigious threat. The coupling of long-term biodiversity monitoring with concurrent sampling of relevant environmental drivers is critical for preventative and restorative management in ecology.

Military affected by the first wave of COVID-19 in Senegal: stress and resilience factors during care.

COVID-19 had a psychological impact on the population, particularly those affected. Our objective was to investigate stress and resilience factors in the Senegalese soldiers affected during the first wave of COVID-19. Our retrospective and qualitative study included military personnel listed as contacts, suspects, or positive cases and supported by the Armed Forces Psychological Support Program during the period of isolation. The stress factors were health-related, sociological, and occupational. The conditions and the experience of isolation, stigmatization, and suspension of their professional projects were concerns for the soldiers. They had relied on personal, familial, and professional resources to cultivate resilience during the quarantine. Isolation during the pandemic showed psychological consequences, the foundations of which have been found in our study.

Epigenetic arsenal for stress mitigation in plants.

Plant's ability to perceive, respond to, and ultimately adapt to various stressors is a testament to their remarkable resilience. In response to stresses, plants activate a complex array of molecular and physiological mechanisms. These include the rapid activation of stress-responsive genes, the manufacturing of protective compounds, modulation of cellular processes and alterations in their growth and development patterns to enhance their chances of survival. Epigenetic mechanisms play a pivotal role in shaping the responses of plants to environmental stressors. This review explores the intricate interplay between epigenetic regulation and plant stress mitigation. We delve into the dynamic landscape of epigenetic modifications, highlighting their influence on gene expression and ultimately stress tolerance. This review assembles current research, shedding light on the promising strategies within plants' epigenetic arsenal to thrive amidst adverse conditions.

The effects of role stressors and smartphone interactions on delivery riders' unsafe behaviors during the delivery process in China.

Objectives. Although some studies have shown role stressors can lead to unsafe behaviors, it is unclear how role stressors induce delivery riders' unsafe behaviors. We found that delivery riders suffered from tremendous role stressors during the delivery process and had to conduct frequent smartphone interactions. This study aimed to explore the effects of role stressors and smartphone interactions on delivery riders' unsafe behaviors. Methods. First, a questionnaire survey (N = 326) was used to collect data, and correlation and regression analyses were conducted to explore the relationship between role stressors, smartphone interaction frequency and delivery riders' unsafe behaviors. Second, a scenario survey (N = 35) was conducted, and comparative analysis was used to further explore how smartphone interactions affect delivery riders' unsafe behaviors. Results. The questionnaire survey revealed that role stressors, smartphone interaction frequency and delivery riders' unsafe behaviors were positively correlated. In addition, the role stressors forced delivery riders to conduct necessary and unnecessary smartphone interactions. The scenario survey found that smartphone interactions reduced delivery riders' motion speed and motion ability, and increased their psychology, so they had a risk-taking mentality, which led to an increase in unsafe behaviors.

Thermal tolerance and survival are modulated by a natural gradient of infection in differentially acclimated hosts.

Wild ectotherms are exposed to multiple stressors, including parasites, that can affect their responses to environmental change. Simultaneously, unprecedented warm temperatures are being recorded worldwide, increasing both the average and maximum temperatures experienced in nature. Understanding how ectotherms, such as fishes, will react to the combined stress of parasites and higher average temperatures can help predict the impact of extreme events such as heat waves on populations. The critical thermal method (CTM), which assesses upper (CTmax) and lower (CTmin) thermal tolerance, is often used in acclimated ectotherms to help predict their tolerance to various temperature scenarios. Despite the widespread use of the CTM across taxa, few studies have characterized the response of naturally infected fish to extreme temperature events or how acute thermal stress affects subsequent survival. We acclimated naturally infected pumpkinseed sunfish (Lepomis gibbosus) to four ecologically relevant temperatures (10, 15, 20 and 25°C) and one future warming scenario (30°C) for 3 weeks before measuring CTmax and CTmin. We also assessed individual survival the week following CTmax. Parasites were counted and identified following trials to relate infection intensity to thermal tolerance and survival. Interestingly, trematode parasites causing black spot disease were negatively related to CTmax, suggesting that heavily infected fish are less tolerant to acute warming. Moreover, fish infected with yellow grub parasites showed decreased survival in the days following CTmax implying that the infection load has negative survival consequences on sunfish during extreme warming events. Our findings indicate that, when combined, parasite infection and high prolonged average temperatures can affect fish thermal tolerance and survival, emphasizing the need to better understand the concomitant effects of stressors on health outcomes in wild populations. This is especially true given that some parasite species are expected to thrive in warming waters making host fish species especially at risk.