On the importance of trait interrelationships for understanding environmental responses of stream macroinvertebrates

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The roles of elevation and local environmental factors as drivers of diatom diversity in subarctic streams

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Seed dormancy and control of germination in Sisymbrella dentata (L.) O.E. Schulz (Brassicaceae)

• Seed germination responsiveness to environmental cues is crucial for plant species living in changeable habitats and can vary among populations within the same species as a result of adaptation or modulation to local climates. Here, we investigate the germination response to environmental cues of Sisymbrella dentata (L.) O.E. Schulz, an annual endemic to Sicily living in Mediterranean Temporary Ponds (MTP), a vulnerable ecosystem.
• Germination of the only two known populations, Gurrida and Pantano, was assessed over a broad range of conditions to understand the role of temperatures, nitrate, hormones (abscisic acid – ABA and gibberellins – GA) and after‐ripening in dormancy release in this species.
• Seed germination responsiveness varied between the two populations, with seeds from Gurrida germinating under a narrower range of conditions. Overall, this process in S. dentata consisted of testa and endosperm rupture as two sequential events, influenced by ABA and GA biosynthesis. Nitrate addition caused an earlier testa rupture, after‐ripening broadened the thermal conditions that allow germination, and alternating temperatures significantly promoted germination of non‐after‐ripened seeds.
• Primary dormancy in S. dentata seeds likely allows this plant to form a persistent seed bank that is responsive to specific environmental cues characteristic of MTP habitats.

     

Applying life-history strategies for freshwater macroinvertebrates to lentic waters

• 1 Effective environmental management requires a sound understanding of the causal mechanisms underlying the relationship of species with their environment. Mechanistic explanations linking species and environment are ultimately based on species traits. Many tools for ecological assessment and biomonitoring lack such explanations. Elsewhere, we have defined life‐history strategies, based on the interrelations between species traits and their functional implications.
• 2 This study tests the hypothesis that life‐history strategies represent different solutions to particular ecological problems, thus connecting species and their environment through species traits. Data on aquatic macroinvertebrates in a variety of waterbodies were analysed in terms of life‐history strategies. These waterbodies differed in environmental conditions and macroinvertebrate assemblages. Solutions to the ecological problems present in each type of water body were expected to be reflected in the abundance of (species exhibiting) different life‐history strategies.
• 3 Results show clear differences in strategy composition between the different water types, which could be related to the prevailing environmental conditions through mechanistic explanations. For example, species with a long period of juvenile development and a synchronized emergence of short‐lived adults were most dominant in large mesotrophic waterbodies with stable and predictable environmental conditions. In contrast, species that have a rapid development and spread successive reproduction attempts over a longer time period were most abundant in waterbodies with fluctuating and less predictable environmental conditions.
• 4 Differences in strategy composition provide insight into the prevailing environmental conditions related to temporal predictability, and habitat favourability, from the perspective of the species themselves. By reducing diverse species assemblages to a small number of strategies, representing easily interpretable relationships, this approach may be useful in environmental quality assessment programmes, including those required by the European Water Framework Directive. Based on mechanistic explanations, life‐history strategies may generate testable predictions and guide future research. Further research may focus on expanding life‐history strategies to include other species groups and ecosystems.

     

Hawaiian picture‐winged Drosophila exhibit adaptive population divergence along a narrow climatic gradient on Hawaii Island

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Genetic Control and Mechanisms of Salt and Hyperosmotic Stress Resistance in Cyanobacteria

Exposure to high concentrations of environmental NaCl exerts two stress effects on living cells, increasing the osmotic pressure and the concentration of inorganic ions. Salt stress dramatically suppresses the photosynthetic activity in cells of phototrophic organisms, such as cyanobacteria. During salt adaptation, cyanobacterial cells accumulate osmoprotectors, export excessive Na⁺ with the help of Na⁺/H⁺ antiporters, and actively absorb K⁺ with the help of K⁺-transporting systems. These physiological processes are accompanied by induction or suppression of several genes involved in salt adaptation. The review considers the main mechanisms responsible for the resistance of cyanobacterial cells to salt and hyperosmotic stresses. Special emphasis is placed on recent achievements in studying the genetic control of salt resistance and regulation of gene expression during adaptation of cyanobacteria to salt and hyperosmotic stresses.     

Assessment of Free‐Living Physical Activity in Humans: An Overview of Currently Available and Proposed New Measures

The number of physical activity measures and indexes used in the human literature is large and may result in some difficulty for the average investigator to choose the most appropriate measure. Accordingly, this review is intended to provide information on the utility and limitations of the various measures. Its primary focus is the objective assessment of free‐living physical activity in humans based on physiological and biomechanical methods. The physical activity measures have been classified into three categories:

• 1 . Measures based on energy expenditure or oxygen uptake, such as activity energy expenditure, activity‐related time equivalent, physical activity level, physical activity ratio, metabolic equivalent, and a new index of potential interest, daytime physical activity level.
• 2 . Measures based on heart rate monitoring, such as net heart rate, physical activity ratio heart rate, physical activity level heart rate, activity‐related time equivalent, and daytime physical activity level heart rate.
• 3 . Measures based on whole‐body accelerometry (counts/U time).

Quantification of the velocity and duration of displacement in outdoor conditions by satellites using the Differential Global Positioning System may constitute a surrogate for physical activity, because walking is the primary activity of man in free‐living conditions. A general outline of the measures and indexes described above is presented in tabular form, along with their respective definition, usual applications, advantages, and shortcomings. A practical example is given with typical values in obese and non‐obese subjects. The various factors to be considered in the selection of physical activity methods include experimental goals, sample size, budget, cultural and social/environmental factors, physical burden for the subject, and statistical factors, such as accuracy and precision. It is concluded that no single current technique is able to quantify all aspects of physical activity under free‐living conditions, requiring the use of complementary methods. In the future, physical activity sensors, which are of low‐cost, small‐sized, and convenient for subjects, investigators, and clinicians, are needed to reliably monitor, during extended periods in free‐living situations, small changes in movements and grade as well as duration and intensity of typical physical activities.     

Petrosia ficiformis (Poiret, 1789): an excellent model for holobiont and biotechnological studies

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The aggregation of prokaryotic and eukaryotic cells has resulted in evolution of organisms with remarkable abilities to synthetize natural bioactive compounds of biotechnological relevance. Marine sponges such as Petrosia ficiformis are examples of this evolutionary strategy. The P. ficiformis microbiome, which produces a diversity of chemical compounds, plays a fundamental role in this sponge’s extraordinary adaptation to various ecological conditions. The microbial community of P. ficiformis seems representative of sponge microbiomes, but it has an unusual exclusively horizontal transmission. This uncommon feature, together with its wide environmental distribution, its ability to generate 3D cell cultures that host symbionts, and the availability of meta-omics and physiology information make this sponge an effective model to study the complexity of holobionts.     

Lateral hydrological connectivity differentially affects the community characteristics of multiple groups of aquatic invertebrates in tropical wetland pans in South Africa

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Oxidants and antioxidants in aquatic animals

• 1.1. Oxidative stress, potentially, is experienced by all aerobic life when antioxidant defenses are overcome by prooxidant forces, and is the basis of many physiological abberations.
• 2.2. Environmental contaminants may enhance oxidative stress in aquatic organisms, e.g. highly elevated rates of ideopathic lesions and neoplasia among fish inhabiting polluted environments is increasingly related to oxidative stress associated with environmental pollution.
• 3.3. Metabolism of redox cycling xenobiotics in aquatic organisms is very similar to that of mammals suggesting similarities in the health consequences of exposure to such compounds.
• 4.4. The expression of specific lesions known to arise specifically from oxidative stress, e.g. lipid peroxidation, oxidized bases in DNA and accumulation of lipofuscin pigments are present in many aquatic animals exposed to contaminants.
• 5.5. Aquatic organisms contain the major antioxidant enzymes SOD, catalase and glutathione peroxidase, albeit there are marked quantitative differences among the various species reported.

     

Reflections on Organisms: Examples from the Neurobiology of Insect Rhythmic Movements

Consideration of organisms is necessary for neurobiologistsinterested in the neural bases of behavior, because a behavioralact performed by an intact animal defines the problem to besolved and also constitutes the context in which the nervoussystem operates. In addition, observations of behaving organismscan introduce new preparations for study of general questions.Examples are given from rhythmic gill movements of Corydaluscornutus, insect flight, and development of the moth flightmotor. In a concluding section, questions are raised about possiblephilosophical and judgmental influences on the current tensionsbetween holistic approaches expressed in organismic biologyand reductionist approaches expressed in biotechnology.     

The importance of biogeographical history and extant environmental conditions as drivers of freshwater decapod distribution in southern South America

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Environmental heterogeneity shapes physiological traits in tropical direct‐developing frogs

1. Tropical ectotherm species tend to have narrower physiological limits than species from temperate areas. As a consequence, tropical species are considered highly vulnerable to climate change since minor temperature increases can push them beyond their physiological thermal tolerance. Differences in physiological tolerances can also be seen at finer evolutionary scales, such as among populations of ectotherm species along elevation gradients, highlighting the physiological sensitivity of such organisms.
2. Here, we analyze the influence of elevation and bioclimatic domains, defined by temperature and precipitation, on thermal sensitivities of a terrestrial direct‐developing frog (Craugastor loki) in a tropical gradient. We address the following questions: (a) Does preferred temperature vary with elevation and among bioclimatic domains? (b) Do thermal tolerance limits, that is, critical thermal maximum and critical thermal minimum vary with elevation and bioclimatic domains? and (c) Are populations from high elevations more vulnerable to climate warming?
3. We found that along an elevation gradient body temperature decreases as environmental temperature increases. The preferred temperature tends to moderately increase with elevation within the sampled bioclimatic domains. Our results indicate that the ideal thermal landscape for this species is located at midelevations, where the thermal accuracy (d_b) and thermal quality of the environment (d_e) are suitable. The critical thermal maximum is variable across elevations and among the bioclimatic domains, decreasing as elevation increases. Conversely, the critical thermal minimum is not as variable as the critical thermal maximum.
4. Populations from the lowlands may be more vulnerable to future increases in temperature. We highlight that the critical thermal maximum is related to high temperatures exhibited across the elevation gradient and within each bioclimatic domain; therefore, it is a response to high environmental temperatures.

     

Diving deeper into the underlying white shark behaviors at Guadalupe Island,Mexico

1. Fine‐scale movement patterns are driven by both biotic (hunting, physiological needs) and abiotic (environmental conditions) factors. The energy balance governs all movement‐related strategic decisions.
2. Marine environments can be better understood by considering the vertical component. From 24 acoustic trackings of 10 white sharks in Guadalupe Island, this study linked, for the first time, horizontal and vertical movement data and inferred six different behavioral states along with movement states, through the use of hidden Markov models, which allowed to draw a comprehensive picture of white shark behavior.
3. Traveling was the most frequent state of behavior for white sharks, carried out mainly at night and twilight. In contrast, area‐restricted searching was the least used, occurring primarily in daylight hours.
4. Time of day, distance to shore, total shark length, and, to a lesser extent, tide phase affected behavioral states. Chumming activity reversed, in the short term and in a nonpermanent way, the behavioral pattern to a general diel vertical pattern.

     

Hormone‐mediated foraging strategies in an uncertain environment: Insights into the at‐sea behavior of a marine predator

1. Hormones are extensively known to be physiological mediators of energy mobilization and allow animals to adjust behavioral performance in response to their environment, especially within a foraging context.
2. Few studies, however, have narrowed focus toward the consistency of hormonal patterns and their impact on individual foraging behavior. Describing these relationships can further our understanding of how individuals cope with heterogeneous environments and exploit different ecological niches.
3. To address this, we measured between‐ and within‐individual variation of basal cortisol (CORT), thyroid hormone T3, and testosterone (TEST) levels in wild adult female Galápagos sea lions (Zalophus wollebaeki) and analyzed how these hormones may be associated with foraging strategies. In this marine predator, females exhibit one of three spatially and temporally distinct foraging patterns (i.e., “benthic,” “pelagic,” and “night” divers) within diverse habitat types.
4. Night divers differentiated from other strategies by having lower T3 levels. Considering metabolic costs, night divers may represent an energetically conservative strategy with shorter dive durations, depths, and descent rates to exploit prey which migrate up the water column based on vertical diel patterns.
5. Intriguingly, CORT and TEST levels were highest in benthic divers, a strategy characterized by congregating around limited, shallow seafloors to specialize on confined yet reliable prey. This pattern may reflect hormone‐mediated behavioral responses to specific risks in these habitats, such as high competition with conspecifics, prey predictability, or greater risks of predation.
6. Overall, our study highlights the collective effects of hormonal and ecological variation on marine foraging. In doing so, we provide insights into how mechanistic constraints and environmental pressures may facilitate individual specialization in adaptive behavior in wild populations.

     

Burrowing behavior and burrowing energetics of a bioindicator under human disturbance

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Emerging sex allocation research in mammals: marsupials and the pouch advantage

• 1 Adaptive adjustments in offspring sex ratios in mammals have long been reported, but the conditions and mechanisms that prompt shifts in the proportion of sons and daughters born are still unclear.
• 2 Empirical evidence indicates that offspring sex in mammals can be related to a diversity of environmental and maternal traits. However, the underlying assumptions regarding offspring and maternal fitness are rarely tested.
• 3 Physiological mechanisms of maternal selection of offspring sex may occur at many stages during the prolonged maternal investment stage, and a pluralistic approach to studying mechanisms might prove fruitful.
• 4 This review highlights the apparent frequency, in marsupial mammals, of sex ratio bias, which has largely been recorded as conforming to one of a few hypotheses.
• 5 Marsupials are ideally suited to experiments involving cross‐fostering of offspring, which can allow rigorous tests of the fitness consequences of rearing one sex vs. the other. The reproductive biology of marsupials lends the group to detailed studies of the timing and physiological correlates of offspring sex biases.
• 6 Many components of metatherian biology may prove advantageous in experimental studies of sex allocation in mammals, and together may provide a prosperous avenue for examining adaptive and mechanistic hypotheses in mammalian sex allocation.

     

Fish recruitment in rivers with modified discharge depends on the interacting effects of flow and thermal regimes

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