Considering ultraviolet radiation in experimental biology: a neglected pervasive stressor.

Ultraviolet radiation (UVR) is a pervasive factor that has shaped the evolution of life on Earth. Ambient levels of UVR mediate key biological functions but can also cause severe lethal and sublethal effects in a wide range of organisms. Furthermore, UVR is a powerful modulator of the effects of other environmental factors on organismal physiology, such as temperature, disease, toxicology and pH, among others.

Atlantic salmon Salmo salar do not prioritize digestion when energetic budgets are constrained by warming and hypoxia.

During summer, farmed Atlantic salmon (Salmo salar) can experience prolonged periods of warming and low aquatic oxygen levels due to climate change. This often results in a drop in feed intake; however, the physiological mechanism behind this behaviour is unclear. Digestion is a metabolically expensive process that can demand a high proportion of an animal's energy budget and might not be sustainable under future warming scenarios.

Dramatic genome-wide reprogramming of mRNA in hypometabolic muscle.

In response to seasonal droughts, the green striped burrowing frog Cyclorana alboguttata enters a reversible hypometabolic state called aestivation where heart rate and oxygen consumption can be reduced despite warm (>25C°) ambient temperatures. With a view to understanding molecular mechanisms we profiled aestivating versus control gastrocnemius muscle using mRNA sequencing. This indicated an extensive metabolic reprogramming, with nearly a quarter of the entire transcriptome (3996 of 16,960 mRNA) exhibiting a nominal >2-fold change.

Cold-induced skin darkening does not protect amphibian larvae from UV-associated DNA damage.

Amphibian declines are sometimes correlated with increasing levels of ultraviolet radiation (UVR). While disease is often implicated in declines, environmental factors such as temperature and UVR play an important role in disease epidemiology. The mutagenic effects of UVR exposure on amphibians are worse at low temperatures.

The interactive impacts of a constant reef stressor, ultraviolet radiation, with environmental stressors on coral physiology.

Reef-building corals create one of the most biodiverse and economically important ecosystems on the planet. Unfortunately, global coral reef ecosystems experience threats from numerous natural stressors, which are amplified by human activities. One such threat is ultraviolet radiation (UVR) from the sun; a genotoxic stressor that is a double-edged sword for corals as they rely on sunlight for energy.

Thermal compensation reduces DNA damage from UV radiation.

Increases in ultraviolet radiation (UVR) correlate spatially and temporally with global amphibian population declines and interact with other stressors such as disease and temperature. Declines have largely occurred in high-altitude areas associated with greater UVR and cooler temperatures. UVR is a powerful mutagenic harming organisms largely by damaging DNA.

Sublethal consequences of ultraviolet radiation exposure on vertebrates: Synthesis through meta-analysis.

Ultraviolet radiation (UVR) from the sun is a natural daytime stressor for vertebrates in both terrestrial and aquatic ecosystems. UVR effects on the physiology of vertebrates manifest at the cellular level, but have bottom-up effects at the tissue level and on whole-animal performance and behaviours. Climate change and habitat loss (i.

Carryover effects from environmental change in early life: An overlooked driver of the amphibian extinction crisis?

Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of individual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life-history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short-term studies limited to single life-history stages.

Biological mechanisms matter in contemporary wildlife conservation.

Given limited resources for wildlife conservation paired with an urgency to halt declines and rebuild populations, it is imperative that management actions are tactical and effective. Mechanisms are about how a system works and can inform threat identification and mitigation such that conservation actions that work can be identified. Here, we call for a more mechanistic approach to wildlife conservation and management where behavioral and physiological tools and knowledge are used to characterize drivers of decline, identify environmental thresholds, reveal strategies that would restore populations, and prioritize conservation actions.

Body size dictates physiological and behavioural responses to hypoxia and elevated water temperatures in Murray cod ().

Increasing drought frequency and duration pose a significant threat to fish species in dryland river systems. As ectotherms, fish thermal and hypoxia tolerances directly determine the capacity of species to persist in these environments during low flow periods when water temperatures are high and waterbodies become highly stratified. Chronic thermal stress can compound the impacts of acute hypoxic events on fish resulting in significant fish mortality; however, it is not known if all size classes are equally susceptible, or if the allometric scaling of physiological processes means some size classes are disproportionately affected.

Temperature causes species-specific responses to UV-induced DNA damage in amphibian larvae.

Anthropogenic ozone depletion has led to a 2-5% increase in ultraviolet B radiation (UVBR) levels reaching the earth's surface. Exposure to UVBR causes harmful DNA damage in amphibians, but this is minimized by DNA repair enzymes such as thermally sensitive cyclobutane pyrimidine dimer (CPD)-photolyase, with cool temperatures slowing repair rates. It is unknown whether amphibian species differ in the repair response to a given dose of UVBR across temperatures.

Early exposure to UV radiation causes telomere shortening and poorer condition later in life.

Determining the contribution of elevated ultraviolet-B radiation (UVBR; 280-315 nm) to amphibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life-history stages might affect post-metamorphic stages via long-term carryover effects. We acutely exposed tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a multi-factorial laboratory experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners.

UV exposure causes energy trade-offs leading to increased chytrid fungus susceptibility in green tree frog larvae.

Levels of ultraviolet (UV) radiation have increased in many parts of the world due to the anthropogenic destruction of the ozone layer. UV radiation is a potent immunosuppressant and can increase the susceptibility of animal hosts to pathogens. UV radiation can directly alter immune function via immunosuppression and photoimmunotolerance; however, UV may also influence pathogen defences by affecting the distribution of energy resources among competing physiological processes.

The role of environmental calcium in the extreme acid tolerance of northern banjo frog (Limnodynastes terraereginae) larvae.

Many aquatically respiring animals acutely exposed to low pH waters suffer inhibition of ion uptake and loss of branchial (gill) epithelial integrity, culminating in a fatal loss of body Na+. Environmental calcium levels ([Ca2+]e) are pivotal in maintaining branchial junction integrity, with supplemental Ca2+ reversing the negative effects of low pH in some animals. Tolerance of some naturally acidic environments by aquatic animals is further complicated by low [Ca2+]e, yet many of these environments are surprisingly biodiverse.

Can slowing the rate of water temperature decline be utilized to reduce the impacts of cold water pollution from dam releases on fish physiology and performance?

Cold water pollution (CWP) is caused by releases of unseasonably cold water from large, thermally stratified dams. Rapid and prolonged decreases in water temperature can have depressive effects on the metabolism, growth and swimming performance of fish. However, it is unknown if reducing the rate of temperature decrease could mitigate these negative effects by allowing thermal acclimation/acclimatization to occur.

Fire and rain: A systematic review of the impacts of wildfire and associated runoff on aquatic fauna.

Climate and land-use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events.

Applied ecoimmunology: using immunological tools to improve conservation efforts in a changing world.

Ecoimmunology is a rapidly developing field that explores how the environment shapes immune function, which in turn influences host-parasite relationships and disease outcomes. Host immune defence is a key fitness determinant because it underlies the capacity of animals to resist or tolerate potential infections. Importantly, immune function can be suppressed, depressed, reconfigured or stimulated by exposure to rapidly changing environmental drivers like temperature, pollutants and food availability.

Ultraviolet-B irradiance and cumulative dose combine to determine performance and survival.

Despite decades of research, the role of elevated solar ultraviolet-B radiation (UVBR; 280-315 nm) in shaping amphibian populations remains ambiguous. These difficulties stem partly from a poor understanding of which parameters of UVBR exposure - dose, irradiance, and time interval - determine UVBR exposure health risk, and the potentially erroneous assumption that effects are proportional to the dose of exposure, irrespective of the administered regime (Bunsen-Roscoe Law of Reciprocity; BRL). We tested if the BRL holds with respect to UVBR-induced physiological effects in amphibians by acutely exposing tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a fully factorial experiment.

Exposure to Nitrate Increases Susceptibility to Hypoxia in Fish.

AbstractAquatic hypoxic events are increasing in frequency and intensity as concentrations of nutrients, such as nitrate, continue to rise from human activities. Many fish species can alter their behavior and physiology to cope with drops in oxygen, but these compensatory strategies may be compromised under high levels of nitrate pollution. Hence, we investigated whether exposure to elevated nitrate concentrations affects key behavioral (avoidance and aquatic surface respiration [ASR]) and physiological (hemoglobin and hematocrit levels, ventilation frequency, and burst and prolonged swimming performance) responses of fish to mitigate the impacts of acute hypoxia.

Conservation physiology and the COVID-19 pandemic.

The COVID-19 pandemic and associated public health measures have had unanticipated effects on ecosystems and biodiversity. Conservation physiology and its mechanistic underpinnings are well positioned to generate robust data to inform the extent to which the Anthropause has benefited biodiversity through alterations in disturbance-, pollution- and climate change-related emissions. The conservation physiology toolbox includes sensitive biomarkers and tools that can be used both retroactively (e.

Thermal plasticity of the cardiorespiratory system provides cross-tolerance protection to fish exposed to elevated nitrate.

Exposure to nitrate is toxic to aquatic animals due to the formation of methaemoglobin and a subsequent loss of blood-oxygen carrying capacity. Yet, nitrate toxicity can be modulated by other stressors in the environment, such as elevated temperatures. Acclimation to elevated temperatures has been shown to offset the negative effects of nitrate on whole animal performance in fish, but the mechanisms underlying this cross-tolerance interaction remain unclear.

Low light intensities increase avoidance behaviour of diurnal fish species: implications for use of road culverts by fish.

Inadequately designed culverts can be physical barriers to fish passage if they increase the velocity of water flow in the environment, alter natural turbulence patterns or fail to provide adequate water depth. They may also act as behavioural barriers to fish passage if they affect the willingness of fish species to enter or pass through the structure due to altered ambient light conditions. To understand how reduced light intensity might affect fish behaviour in culverts, the authors performed a behavioural choice experiment quantifying the amount of time individual fish spent in dark and illuminated areas of a controlled experimental channel.