Upper thermal limits are 'hard-wired' across body mass but not populations of an estuarine fish.

Climate warming is seeing temperatures breach exceptional thresholds as the frequency and intensity of heat waves increase. Efforts to forecast species vulnerability to climate warming often focus on upper thermal limits threatening survival, overlooking the role of intraspecific variation in determining vulnerability. Using an estuarine fish (black bream, Acanthopagrus butcheri) as a model, we explore how intraspecific variation in body mass and among populations affects upper thermal tolerance.

Deteriorating waterways: The effect of nitrate pollution on the development and physiology of the endangered southern bell frog (Litoria raniformis).

Nitrogen-based fertilizers can increase agricultural yields and crop quality, but this comes at the risk of contaminating nearby waterways. Nitrate is the most stable and abundant form of inorganic nitrogen in the environment and chronic exposure can impair performance and fitness in aquatically respiring species. But it remains unknown if these impairments are linked to disruptions in energy homeostasis.

Metabolic consequences of sex reversal in two lizard species: a test of the like-genotype and like-phenotype hypotheses.

Vertebrate sex is typically determined genetically, but in many ectotherms sex can be determined by genes (genetic sex determination, GSD), temperature (temperature-dependent sex determination, TSD), or interactions between genes and temperature during development. TSD may involve GSD systems with either male or female heterogamety (XX/XY or ZZ/ZW) where temperature overrides chromosomal sex determination to cause a mismatch between genetic sex and phenotypic sex (sex reversal). In these temperature-sensitive lineages, phylogenetic investigations point to recurrent evolutionary shifts between genotypic and temperature-dependent sex determination.

The mechanistic basis and adaptive significance of cross-tolerance: a 'pre-adaptation' to a changing world?

Protective responses are pivotal in aiding organismal persistence in complex, multi-stressor environments. Multiple-stressor research has traditionally focused on the deleterious effects of exposure to concurrent stressors. However, encountering one stressor can sometimes confer heightened tolerance to a second stressor, a phenomenon termed 'cross-protection'.

Harnessing the potential of cross-protection stressor interactions for conservation: a review.

Conservation becomes increasingly complex as climate change exacerbates the multitude of stressors that organisms face. To meet this challenge, multiple stressor research is rapidly expanding, and the majority of this work has highlighted the deleterious effects of stressor interactions. However, there is a growing body of research documenting cross-protection between stressors, whereby exposure to a priming stressor heightens resilience to a second stressor of a different nature.

Stress history affects heat tolerance in an aquatic ectotherm (Chinook salmon, Oncorhynchus tshawytscha).

The stress history of an ectotherm may be a pivotal predictor of how they cope with rapid spikes in environmental temperature. An understanding of how stressors in habitats and commercial operations affect ectotherm heat tolerance is urgently required so that management actions can be informed by thermal physiology. We hypothesised that brief exposure to mild stress would heighten tolerance to subsequent heat stress, indicative of a cross-tolerance interaction, whereas exposure to severe stress would reduce heat tolerance, reflecting a cross-susceptibility interaction.

Exercise training does not affect heat tolerance in Chinook salmon (Oncorhynchus tshawytscha).

The progression of climate warming will expose ectotherms to transient heatwave events and temperatures above their tolerance range at increased frequencies. It is therefore pivotal that we understand species' physiological limits and the capacity for various controls to plastically alter these thresholds. Exercise training could have beneficial impacts on organismal heat tolerance through improvements in cardio-respiratory capacity, but this remains unexplored.

Adding climate change to the mix: responses of aquatic ectotherms to the combined effects of eutrophication and warming.

The threat of excessive nutrient enrichment, or eutrophication, is intensifying across the globe as climate change progresses, presenting a major management challenge. Alterations in precipitation patterns and increases in temperature are increasing nutrient loadings in aquatic habitats and creating conditions that promote the proliferation of cyanobacterial blooms. The exacerbating effects of climate warming on eutrophication are well established, but we lack an in-depth understanding of how aquatic ectotherms respond to eutrophication and warming in tandem.

Diving in hot water: a meta-analytic review of how diving vertebrate ectotherms will fare in a warmer world.

Diving ectothermic vertebrates are an important component of many aquatic ecosystems, but the threat of climate warming is particularly salient to this group. Dive durations typically decrease as water temperatures rise; yet, we lack an understanding of whether this trend is apparent in all diving ectotherms and how this group will fare under climate warming. We compiled data from 27 studies on 20 ectothermic vertebrate species to quantify the effect of temperature on dive durations.

Double whammy: Nitrate pollution heightens susceptibility to both hypoxia and heat in a freshwater salmonid.

Species persistence in a changing world will depend on how they cope with co-occurring stressors. Stressors can interact in unanticipated ways, where exposure to one stressor may heighten or reduce resilience to another stressor. We examined how a leading threat to aquatic species, nitrate pollution, affects susceptibility to hypoxia and heat stress in a salmonid, the European grayling (Thymallus thymallus).

Aerobic scope and climate warming: Testing the "plastic floors and concrete ceilings" hypothesis in the estuarine crocodile (Crocodylus porosus).

Ectotherms are predicted to show a reduction in absolute aerobic scope (AAS = maximum - standard metabolic rates) if habitat temperatures surpass optima. However, thermal phenotypic plasticity may play a protective role in the maintenance of AAS. In fishes, resting physiological rates ("physiological floors," e.

Synergism between elevated temperature and nitrate: Impact on aerobic capacity of European grayling, Thymallus thymallus in warm, eutrophic waters.

Climate warming and nitrate pollution are pervasive aquatic stressors that endanger the persistence of fishes prevailing in anthropogenically disturbed habitats. Individually, elevated nitrate and temperature can influence fish energy homeostasis by increasing maintenance costs and impairing oxygen transport capacity. However, it remains unknown how fish respond to simultaneous exposure to elevated temperature and nitrate pollution.

Nitrite-induced reductions in heat tolerance are independent of aerobic scope in a freshwater teleost.

Nitrite is a widespread form of pollution that directly lowers the blood oxygen carrying capacity of aquatically respiring species. It is unknown if this impairment of oxygen transport translates into an increased susceptibility to elevated temperatures. We hypothesised that nitrite exposure would lower blood oxygen carrying capacity and decrease both aerobic scope (maximum-standard metabolic rate) and heat tolerance.

Integrating physiological data with the conservation and management of fishes: a meta-analytical review using the threatened green sturgeon ().

Reversing global declines in the abundance and diversity of fishes is dependent on science-based conservation solutions. A wealth of data exist on the ecophysiological constraints of many fishes, but much of this information is underutilized in recovery plans due to a lack of synthesis. Here, we used the imperiled green sturgeon () as an example of how a quantitative synthesis of physiological data can inform conservation plans, identify knowledge gaps and direct future research actions.

Effect of water pH and calcium on ion balance in five fish species of the Mekong Delta.

Acidic freshwater habitats disrupt ion-homeostasis in fishes, yet the often acidic waters of the Mekong host the second highest diversity of freshwater fish in the world. To investigate how five Mekong fish species tolerate water acidity, we measured: time to loss of equilibrium (LOE) at sustained (4 days) low pH (3.5) and net ion flux in acute low pH (3.

Diving beyond Aerobic Limits: Effect of Temperature on Anaerobic Support of Simulated Predator Avoidance Dives in an Air-Breathing Ectotherm.

Diving optimality models predict air breathers to routinely dive within aerobic limits, but predator avoidance dives may be an exception. Lengthening submergence times during a predation threat may enhance survival probability, and we therefore hypothesized that predator avoidance dives in juvenile estuarine crocodiles (Crocodylus porosus) would be partially anaerobically fueled. We also predicted that reliance on anaerobic metabolism would increase at elevated temperatures to offset the faster depletion of body oxygen stores.

Plastic responses to diel thermal variation in juvenile green sturgeon, Acipenser medirostris.

Human-induced thermal variability can disrupt energy balance and performance in ectotherms; however, phenotypic plasticity may play a pivotal protective role. Ectotherm performance can be maintained in thermally heterogeneous habitats by reducing the thermal sensitivity of physiological processes and concomitant performance. We examined the capacity of juvenile green sturgeon (Acipenser medirostris) to respond to daily thermal variation.

Physiological mechanisms constraining ectotherm fright-dive performance at elevated temperatures.

Survival of air-breathing, diving ectotherms is dependent on their capacity to optimise the time available for obligate underwater activities, such as predator avoidance. Submergence times are thermally sensitive, with dive durations significantly reduced by increases in water temperature, deeming these animals particularly vulnerable to the effects of climate change. The physiological mechanisms underlying this compromised performance are unclear but are hypothesised to be linked to increased oxygen demand and a reduced capacity for metabolic depression at elevated temperatures.

Substrate roughening improves swimming performance in two small-bodied riverine fishes: implications for culvert remediation and design.

Worldwide declines in riverine fish abundance and diversity have been linked to the fragmentation of aquatic habitats through the installation of instream structures (e.g. culverts, dams, weirs and barrages).

Finding our way: On the sharing and reuse of animal telemetry data in Australasia.

The presence and movements of organisms both reflect and influence the distribution of ecological resources in space and time. The monitoring of animal movement by telemetry devices is being increasingly used to inform management of marine, freshwater and terrestrial ecosystems. Here, we brought together academics, and environmental managers to determine the extent of animal movement research in the Australasian region, and assess the opportunities and challenges in the sharing and reuse of these data.

Diving in a warming world: the thermal sensitivity and plasticity of diving performance in juvenile estuarine crocodiles (Crocodylus porosus).

Air-breathing, diving ectotherms are a crucial component of the biodiversity and functioning of aquatic ecosystems, but these organisms may be particularly vulnerable to the effects of climate change on submergence times. Ectothermic dive capacity is thermally sensitive, with dive durations significantly reduced by acute increases in water temperature; it is unclear whether diving performance can acclimate/acclimatize in response to long-term exposure to elevated water temperatures. We assessed the thermal sensitivity and plasticity of 'fright-dive' capacity in juvenile estuarine crocodiles (Crocodylus porosus; n = 11).

Same temporal niche, opposite rhythmicity: two closely related bioluminescent insects with opposite bioluminesce propensity rhythms.

Arachnocampa species, commonly called glowworms, are flies whose larvae use light to attract prey. Here we compare rhythmicity in two of the nine described species: the Tasmanian species, Arachnocampa tasmaniensis, which inhabits caves and wet forest, and the eastern Australian mainland species, A. flava, primarily found in subtropical rainforest.