Maternal age has a negative effect on offspring lifespan in a range of taxa and is hypothesized to influence the evolution of aging. However, the mechanisms of maternal age effects are unknown, and ...it remains unclear if maternal age alters offspring response to therapeutic interventions to aging. Here, we evaluate maternal age effects on offspring lifespan, reproduction, and the response to caloric restriction, and investigate maternal investment as a source of maternal age effects using the rotifer, Brachionus manjavacas, an aquatic invertebrate. We found that offspring lifespan and fecundity decline with increasing maternal age. Caloric restriction increases lifespan in all offspring, but the magnitude of lifespan extension is greater in the offspring from older mothers. The trade-off between reproduction and lifespan extension under low food conditions expected by life history theory is observed in young-mother offspring, but not in old-mother offspring. Age-related changes in maternal resource allocation to reproduction do not drive changes in offspring fitness or plasticity under caloric restriction in B. manjavacas. Our results suggest that the declines in reproduction in old-mother offspring negate the evolutionary fitness benefits of lifespan extension under caloric restriction.
Improvising Out Loud Corey, Jeff; Corey, Emily; Nimoy, Leonard ...
05/2017
eBook
Jeff Corey (1914--2002) made a name for himself in the 1940s as a character actor in films likeSuperman and the Mole Men(1951),Joan of Arc(1948), andThe Killers(1946). Everything changed in 1951, ...when he was summoned before the House Un-American Activities Committee. Corey refused to name names and was promptly blacklisted, which forced him to walk away from a vibrant livelihood as an actor and embark on a career as one of the industry's most revered acting instructors.
InImprovising Out Loud: My Life Teaching Hollywood How to Act, Corey recounts his extraordinary story. Among the actors who would soon fill his classes were James Dean, Kirk Douglas, Jane Fonda, Rob Reiner, Jack Nicholson, and Leonard Nimoy. In 1962, when the blacklist ended, Corey was one of the industry's first trailblazers to seamlessly reboot his acting career and secure roles in some of the classic films of the era, includingButch Cassidy and the Sundance Kid(1969),True Grit(1969), andLittle Big Man(1970), in which he starred as the infamous Wild Bill Hickok.
Throughout his life, Corey sought to capture the human heart: in conflict, in terror, in love, and in all of its small triumphs. His memoir, which he wrote with his daughter Emily Corey, provides a unique and personal perspective on the man whose teaching inspired some of Hollywood's biggest names to star in the roles that made them famous.
Lifespan extension under low temperature is well conserved across both endothermic and exothermic taxa, but the mechanism underlying this change in aging is poorly understood. Low temperature is ...thought to decrease metabolic rate, thus slowing the accumulation of cellular damage from reactive oxygen species, although recent evidence suggests involvement of specific cold-sensing biochemical pathways. We tested the effect of low temperature on aging in 11 strains of Brachionus rotifers, with the hypothesis that if the mechanism of lifespan extension is purely thermodynamic, all strains should have a similar increase in lifespan. We found differences in change in median lifespan ranging from a 6% decrease to a 100% increase, as well as differences in maximum and relative lifespan extension and in mortality rate. Low temperature delays reproductive senescence in most strains, suggesting an extension of healthspan, even in strains with little to no change in lifespan. The combination of low temperature and caloric restriction in one strain resulted in an additive lifespan increase, indicating these interventions may work via non- or partially-overlapping pathways. The known low temperature sensor TRPA1 is present in the rotifer genome, but chemical TRPA1 agonists did not affect lifespan, suggesting that this gene may be involved in low temperature sensation but not in chemoreception in rotifers. The congeneric variability in response to low temperature suggests that the mechanism of low temperature lifespan extension is an active genetic process rather than a passive thermodynamic one and is dependent upon genotype.
•Congeneric strains displayed variable lifespan change in response to lower temperature.•Low temperature reduced reproductive senescence suggesting healthspan extension.•The cold-sensor TRPA1 does not mediate chemoreception in Brachionus rotifers.•Results suggest that lifespan extension under low temperature is an active genetic process.
Thermal refuges are becoming increasingly influential for dictating the population status and spatial distribution of cold-water stenotherm salmonids in the mid- to southern extent of their range. ...The global climate is predicted to continue to warm, and therefore, the overall thermal suitability of freshwater habitats for stream salmonids is predicted to decline in concert. However, stream and river thermal heterogeneity will offer considerable resiliency for these populations. Thermal refuges are formed by many physical processes; common natural refuges include cold tributary plumes, groundwater springs, alcoves, and hyporheic upwellings. However, many anthropogenically formed refuges (such as stratified reservoirs or cold-water tailrace outflows) also exist in hydropower-regulated rivers. The significance of these refuges to stream salmonids depends on their size and temperature differential, but also other habitat characteristics such as their depth, flow velocity, Froude number, and many biotic factors within the refuges. Modern technologies such as drone-mounted thermal infrared cameras and other remote sensing techniques allow for the efficient identification of such refuges, and inexpensive options include the identification of refuges during ice cover using orthophotographs. Behavioural thermoregulation, i.e., salmonids aggregating in cold-water refuges, can be either facultative or obligate and the timing of these events is governed by life stage, species, and population-specific physiologically regulated cumulative thresholds that are inherently related to the recent thermal history, or hysteresis, of each individual. Salmonids appear to have an excellent spatial cognition for locating and relocating cold-water refuges, and their spatial distribution is largely affected by the availability of the cold-water refuges during the warm-water period in many thermally stressed rivers. Gregarious behaviour is the norm for salmonid fishes within the thermal refuges; however, the size/microhabitat hierarchy appears to dictate the within-refuge distribution at the micro-scale. There continues to be a great impetus for protecting—and in carefully determined cases creating—cold-water refuges in the future. A thorough understanding of what a “goldilocks” refuge is for various salmonids and their different life stages will be imperative as cold-water restoration is gaining popularity. Finally, disentangling the roles of the climate-induced and landscape activity-induced warming potential of fluvial freshwater will be important to ensure continued environmentally responsible landscape activities in future waterscapes.
Broadening our understanding of river thermal variability is of paramount importance considering the role temperature plays in aquatic ecosystem health. At the catchment scale, spatial statistical ...river network models (SSN) are popular for analyses of river temperature, as these are less “data hungry” than other modeling methods, and have offered invaluable insights into how thermal habitats of salmonids may change with climate warming. However, recent work has demonstrated that hydrogeological complexity can disrupt river temperature spatial autocorrelation. We test the prediction that the non‐linearity of hydrological processes inherent in a hydrogeologically complex setting, such as the Miramichi River, invalidates the SSN approach, and a Random Forest (RF) model can overcome these complexities. In all instances, RFs outperformed SSNs when predicting average (TwA) and maximum (TwM) August river temperature during 2017, and were quite robust (TwA and TwM: R2 = 0.93; RMSE = 0.6°C; R2 = 0.91; RMSE = 1.0°C, respectively). We conclude that RF models can capture the inherent non‐linearity of hydrological processes in complex hydrogeologic settings. We examined thermal habitat change for adult and 1+/2+ Atlantic salmon—AS—(Salmo salar), and all age classes of brook trout—BKT—(Salvelinus fontinalis), during August 2017, with thresholds of behavioral thermoregulation specific to the catchment. We assumed a baseline = TwA and investigated river network contraction (km) for TwM. During TwA, all habitat was suggested to be thermally suitable for 1+/2+ AS (<23°C), but 4.2% was unsuitable for adult AS and BKT of all ages (>20°C). For TwM, ~80% of the catchment was predicted to be unsuitable for adult AS and BKT. We examined two boundaries for behavorial thermoregulation in 1+/2+ AS: >23°C and >27°C. For the >23°C boundary, ~27.7% of the catchment is thermally unsuitable during TwM, and 4.9% is thermally unsuitable for the >27°C boundary. TwA in August 2017 was identical to long‐term (1970–1999) July–August TwA, as such these thermal maps will be useful for resource managers.
Studies on the temporal aspects of when thermal refuges are used by stenothermic fishes remain limited. We found the temperatures that induce thermal refuge use by Atlantic salmon juveniles are ...dynamic across a summer. Our results illustrate that these temperatures can vary by #x007E;#x2009;2.8#x00B0;C within an 11-day window.
Abstract
The role of temperature on biological activities and the correspondent exponential relationship with temperature has been known for over a century. However, lacking to date is knowledge relating to (a) the recovery of ectotherms subjected to extreme temperatures in the wild, and (b) the effects repeated extreme temperatures have on the temperatures that induce behavioural thermoregulation (aggregations). We examined these questions by testing the hypothesis that thermal thresholds which initiate aggregations in juvenile Atlantic salmon (AS) (Salmo salar) are not static, but are temporally dynamic across a summer and follow a hysteresis loop. To test our hypothesis, we deployed custom-made underwater camera (UWC) systems in known AS thermal refuges to observe the timing of aggregation events in a natural system and used these data to develop and test models that predict the temperatures that induce thermal aggregations. Consistent with our hypothesis our UWC observations revealed a range of aggregation onset temperatures (AOT) ranging from 24.2°C to 27.1°C, thus confirming our hypothesis that AOTs are dynamic across summer. Our models suggest it take ~ 11 days of non-thermally taxing temperatures for the AOT to rebound in the study river. Conversely, we found that as the frequency of events increased, the AOT declined, from 27.1°C to 24.2°C. Integrating both model components led to more robust model performance. Further, when these models were tested against an independent data set from the same river, the results remained robust. Our findings illustrate the complexity underlying behavioural thermoregulation in AS—a complexity that most likely extends to other salmonids. The frequency of extreme heat events is predicted to increase, and this has the capacity to decrease AOT thresholds in AS, ultimately reducing their resilience to extreme temperature events.
Summer water temperatures within many temperate rivers regularly surpass the incipient lethal temperature for juvenile Atlantic salmon (c. 27°C), causing widescale abandonment of territory in favour ...of areas of cooler water (thermal refuges). This study aims to highlight the influence of thermal refuges on river‐scale abundance patterns. That is, do salmon parr adjust their distribution over time according to proximity to thermal refuges?
Twelve reaches (seven reference: five refuge) were chosen along a 17‐km section of the Little Southwest Miramichi River in Canada. Reaches were sampled throughout the 2011 and 2012 summer periods; high temperature events were recorded during summer 2012 but not summer 2011.
Multivariate principal component analyses indicated no discernible difference in habitat characteristics between the reach‐types under normal thermal conditions. However, reaches containing a thermal refuge had a significant increase in relative abundance of parr immediately after a series of high temperature events (water temperature >26°C) in 2012 (p = 0.034). This increase in relative abundance in refuge reaches was not present during the summer of 2011 when no temperature events occurred (p = 0.088), prior to the event of 2012 (p = 0.999), or at the late autumn survey following the 2012 event (p = 0.999).
Difference in temperature between refuge and mainstem reaches significantly influenced the suitability of a tributary as a thermal refuge habitat (R2 = 0.84), with preference shown for cooler refuges. River‐wide thermal heterogeneity therefore plays a critical role in survival of juvenile salmon throughout summer months and is likely to become necessary under future climate change scenarios.
Abstract
River temperatures often surpass the thermal limits of juvenile Atlantic salmon (Salmo salar). Using thermal monitoring data to replicate a natural heat event, we investigated how cooler ...nighttime temperatures would affect how juvenile salmon cope with several days of heat cycling.
Abstract
The frequency of extreme thermal events in temperate freshwater systems is expected to increase alongside global surface temperature. The Miramichi River, located in eastern Canada, is a prominent Atlantic salmon (Salmo salar) river where water temperatures can exceed the proposed upper thermal limit for the species (~27°C). Current legislation closes the river to recreational angling when water temperatures exceed 20°C for two consecutive nights. We aimed to examine how natural thermal variation, representative of extreme high thermal events, affected the thermal tolerance and physiology of wild, juvenile Atlantic salmon. We acclimated fish to four thermal cycles, characteristic of real-world thermal conditions while varying daily thermal minima (16°C, 18°C, 20°C or 22°C) and diel thermal fluctuation (e.g. Δ5°C–Δ9°C). In each cycling condition, we assessed the role that thermal minima played on the acute thermal tolerance (critical thermal maximum, (CTMax)), physiological (e.g. heat shock protein 70 (HSP70), ubiquitin) and energetic (e.g. hepatic glycogen, blood glucose and lactate) status of juvenile Atlantic salmon throughout repeated thermal cycles. Exposure to 16–21°C significantly increased CTMax (+0.9°C) compared to a stable acclimation temperature (16°C), as did exposure to diel thermal fluctuations of 18–27°C, 20–27°C and 22–27°C, yet repeated exposure provided no further increases in acute thermal tolerance. In comparison to the reference condition (16–21°C), consecutive days of high temperature cycling with different thermal minima resulted in significant increases in HSP70 and ubiquitin, a significant decrease in liver glycogen, and no significant cumulative effect on either blood glucose or lactate. However, comparison between thermally taxed treatments suggested the diel thermal minima had little influence on the physiological or energetic response of juvenile salmon, despite the variable thermal cycling condition. Our results suggest that relatively cooler night temperatures in the summer months may play a limited role in mitigating physiological stress throughout warm diel cycle events.
Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon ...(Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (Tonset = 28.3°C) than in the LSWM (Tonset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R2 = 0.61 & 0.65; P50 = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies.
Standard metabolic rates (SMRs) for Atlantic salmon (Salmo salar) have been calculated independently for different life stages and populations, but the absence of a comprehensive SMR model limits its ...application for modelling the energy use or life stage-specific growth. Atlantic salmon respiration data were compiled from a meta-analysis of 26 publications, and exponential or optimal relationships were fitted to the metadata to estimate respiration equation parameters and generate confidence intervals dependent on temperature and body mass. While model parameters were significant for both models, mass-corrected standard metabolic rates (g O
2
·day
−1
) increased as a function of water temperature (°C) and decreased beyond ∼16 °C following an optimal relationship (AIC
optimal
= –9185.50 versus AIC
exponential
= –8948.95; ΔAIC = 236.55). Juvenile Atlantic salmon growth (cohorts 1 and 2) from bioenergetics simulations did not vary between Little Southwest Miramichi and Northwest Miramichi rivers; however, variation between simulations using the different respiration models (i.e., exponential versus optimal) led to differences in the way fish allocate energy throughout the year. Results from this analysis will inform conservation efforts for the species throughout its current range and predict the energetic requirements at juvenile life stages.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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