Salinity stress occurs when salt concentration in the environment changes rapidly, for example because of tidal water flow, rainstorms, drought, or evaporation from small bodies of water. However, gradual changes in salt concentration can also cause osmotic stress in aquatic habitats if levels breach thresholds that reduce the fitness of resident organisms. The latter scenario is exemplified by climate change driven salinization of estuaries and by dilution of ocean surface salinity through changes in the water cycle. In this review, we discuss how fish employ the evolutionarily conserved cellular stress response (CSR) to cope with these different forms of salinity stress. Macromolecular damage is identified as the cause of impaired physiological performance during salinity stress and serves as the signal for inducing a CSR. Basic aspects of the CSR have been observed in fish exposed to salinity stress, including repair and protection of cellular macromolecules, reallocation of energy, cell cycle arrest, and in severe cases, programmed cell death. Osmosensing and signal transduction events that regulate these aspects of the CSR provide a link between environmental salinity and adaptive physiological change required for survival. The CSR has evolved to broaden the range of salinities tolerated by certain euryhaline fish species, but is constrained in stenohaline species that are sensitive to changes in environmental salinity. Knowledge of how the CSR diverges between euryhaline and stenohaline fish enables understanding of physiological mechanisms that underlie salt tolerance and facilitates predictions as to the relative vulnerabilities of different fish species to a rapidly changing hydrosphere.
The cellular stress response (CSR) is pervasive to all domains of life. It has shaped the interaction between organisms and their environment since the origin of the first cell. Although the CSR has been subject to a myriad of nuanced modifications in the various branches of life present today, its core features remain preserved. The scientific literature covering the CSR is enormous and the broad scope of this brief overview was challenging. However, it is critical to conceptually understand how cells respond to stress in a holistic sense and to point out how fundamental aspects of the CSR framework are integrated. It was necessary to be extremely selective and not feasible to even mention many interesting and important developments in this expansive field. The purpose of this overview is to sketch out general and emerging CSR concepts with an emphasis on the initial cellular strain resulting from stress (macromolecular damage) and the evolutionarily most highly conserved elements of the CSR. Examples emphasize fish and aquatic invertebrates to highlight what is known in organisms beyond mammals, yeast, and other common models. Nonetheless, select pioneering studies using canonical models are also considered and the concepts discussed are applicable to all cells. More detail on important aspects of the CSR in aquatic animals is provided in the accompanying articles of this special issue.
more » « less- Award ID(s):
- 1656371
- NSF-PAR ID:
- 10131671
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Experimental Zoology Part A: Ecological and Integrative Physiology
- Volume:
- 333
- Issue:
- 6
- ISSN:
- 2471-5638
- Page Range / eLocation ID:
- p. 359-378
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Stress represents a multi‐faceted force that is central for the evolution of life. Organisms evolve while adapting to stress and stressful contexts often represent selective bottlenecks. To understand stress effects on biological systems and corresponding coping strategies it is imperative to properly define stress and the resulting strain that triggers compensatory responses in cells and organisms. Here I am deriving such definitions for biological systems based on principles that are established in physics. The relationship between homeostasis of critical biological variables, the elastic limit, the cellular stress response (CSR), cellular homeostasis response (CHR), system dysregulation, and the breaking point (death of the system) is outlined. Dysregulation of homeostatic set‐points of biological variables perturbs the functional properties of the system, shifting them out of the evolutionarily optimized range. Such shifts are accompanied by elevated rates of macromolecular damage, which represents a nonspecific signal for induction of a universal response, the CSR. The CSR complements the CHR in re‐establishing homeostasis of the system as a whole. Moreover, the CSR is essential for coping with suboptimal conditions while the system is in a dysregulated state and for removing excessive damage that accumulates during such periods. The extreme complexity of biological systems and their emergent properties often necessitate monitoring stress effects on many biological variables simultaneously to properly deduce stress effects on the system as a whole. Therefore, increased utilization of systems biology (omics) approaches for characterizing cellular and organismal stress responses facilitates the reductionist dissection of biological stress response mechanisms.
-
more » « less
Abstract Climate change is expected to increase weather extremes and variability, including more frequent weather whiplashes or extreme swings between severe drought and extraordinarily wet years. Shifts in precipitation patterns will alter stream flow regimes, affecting critical life history stages of sensitive aquatic organisms. Understanding how threatened fish species, such as steelhead/rainbow trout (
Oncorhynchus mykiss ), are affected by stream flows in years with contrasting environmental conditions is important for their conservation. Here, we report how extreme wet and dry years, from 2015 to 2018, affected stream flow patterns in two tributaries to the South Fork Eel River, California,USA , and aspects ofO. mykiss ecology, including over‐summer fish growth and body condition as well as spring out‐migration timing. We found that stream flow patterns differed across years in the timing and magnitude of large winter–spring flow events and in summer low‐flow levels. We were surprised to find that differences in stream flows did not impact growth, body condition, or timing of out‐migration ofO. mykiss . Fish growth was limited in the late summer in these streams (average of 0.02 ± 0.05 mm/d), but was similar across dry and wet years, and so was end‐of‐summer body condition and pool‐specific biomass loss from the beginning to the end of the summer. Similarly,O. mykiss migrated out of tributaries during the last week of March/first week of April regardless of the timing of spring flow events. We suggest that the muted response to inter‐annual hydrologic variability is due to the high quality of habitat provided by these unimpaired, groundwater‐fed tributaries. Similar streams that are likely to maintain cool temperatures and sufficient base flows, even in the driest years, should be a high priority for conservation and restoration efforts. -
more » « less
Summary Stress is ubiquitous and disrupts homeostasis, leading to damage, decreased fitness, and even death. Like other organisms, mycorrhizal fungi evolved mechanisms for stress tolerance that allow them to persist or even thrive under environmental stress. Such mechanisms can also protect their obligate plant partners, contributing to their health and survival under hostile conditions. Here we review the effects of stress and mechanisms of stress response in mycorrhizal fungi. We cover molecular and cellular aspects of stress and how stress impacts individual fitness, physiology, growth, reproduction, and interactions with plant partners, along with how some fungi evolved to tolerate hostile environmental conditions. We also address how stress and stress tolerance can lead to adaptation and have cascading effects on population‐ and community‐level diversity. We argue that mycorrhizal fungal stress tolerance can strongly shape not only fungal and plant physiology, but also their ecology and evolution. We conclude by pointing out knowledge gaps and important future research directions required for both fully understanding stress tolerance in the mycorrhizal context and addressing ongoing environmental change.
-
more » « less
Abstract An important component of life history theory is understanding how natural variation arises in populations. Both endogenous and exogenous factors contribute to organism survival and reproduction, and therefore, it is important to understand how such factors are both beneficial and detrimental to population dynamics. One ecologically relevant factor that influences the life history of aquatic organisms is ultraviolet (UV) radiation. While the majority of research has focused on the potentially detrimental effects that UV radiation has on aquatic organisms, few studies have evaluated hormetic responses stimulated by radiation under select conditions. The goal of this study was to evaluate the impact of UV‐A/B irradiation on life history characteristics in
Tigriopus californicus copepods. After exposing copepods to UV‐A/B irradiation (control, 1‐, and 3‐hr UV treatments at 0.5 W/m2), we measured the impact of exposure on fecundity, reproductive effort, and longevity. We found that UV irradiation increased the size of the first clutch among all reproducing females in both the 1‐ and 3‐hr experimental groups and decreased longevity among all females that mated in the 1‐hr treatment. UV irradiation had no effect on the number of clutches females produced. These findings indicate a potential benefit of UV irradiation on reproductive performance early in life, although the same exposure came at a cost to longevity.
