Periods Of Nutritional Stress Research Articles

Exploring Adaptive Phenotypes for the Human Calcium-Sensing Receptor Polymorphism R990G.

Rainforest hunter-gatherers from Southeast Asia are characterized by specific morphological features including a particularly dark skin color (D), short stature (S), woolly hair (W), and the presence of steatopygia (S)-fat accumulation localized in the hips (DSWS phenotype). Based on previous evidence in the Andamanese population, we first characterized signatures of adaptive natural selection around the calcium-sensing receptor gene in Southeast Asian rainforest groups presenting the DSWS phenotype and identified the R990G substitution (rs1042636) as a putative adaptive variant for experimental follow-up. Although the calcium-sensing receptor has a critical role in calcium homeostasis by directly regulating the parathyroid hormone secretion, it is expressed in different tissues and has been described to be involved in many biological functions. Previous works have also characterized the R990G substitution as an activating polymorphism of the calcium-sensing receptor associated with hypocalcemia. Therefore, we generated a knock-in mouse for this substitution and investigated organismal phenotypes that could have become adaptive in rainforest hunter-gatherers from Southeast Asia. Interestingly, we found that mouse homozygous for the derived allele show not only lower serum calcium concentration but also greater body weight and fat accumulation, probably because of enhanced preadipocyte differentiation and lipolysis impairment resulting from the calcium-sensing receptor activation mediated by R990G. We speculate that such differential features in humans could have facilitated the survival of hunter-gatherer groups during periods of nutritional stress in the challenging conditions of the Southeast Asian tropical rainforests.

Integrated diagnosis and time-series sensitivity evaluation of nutrient deficiencies in medicinal plant (Ligusticum chuanxiong Hort.) based on UAV multispectral sensors.

Nitrogen(N), phosphorus(P), and potassium(K) are essential elements that are highly deficient during plant growth. Existing diagnostic methods are not suitable for rapid diagnosis of large-scale planting areas. Near-ground remote sensing technology based on unmanned aerial vehicle (UAV) and sensor is often applied to crop growth condition monitoring and agricultural management. It has been proven to be used for monitoring plant N, P, and K content. However, its integrated diagnostic model has been less studied. In this study, we collected UAV multispectral images of Ligusticum chuanxiong Hort. in different periods of nutritional stress and constructed recognition models with different heights and algorithms. The optimal model variables were selected, and the effects of different sampling heights and modeling algorithms on the model efficiency under the time span were evaluated. At the same time, we evaluated the timeliness of the model based on leaf element content determination and SPAD. It was also validated in field crop production. The results showed that the LR algorithm's model had optimal performance at all periods and flight altitudes. The optimal accuracy of N-deficient plants identification reached 100%, P/K-deficient plants reached 92.4%, and normal plants reached 91.7%. The results of UAV multispectral diagnosis, chemical diagnosis, and SPAD value diagnosis were consistent in the diagnosis of N deficiency, and the diagnosis of P and K deficiency was slightly lagging behind that of chemical diagnosis. This research uses UAV remote sensing technology to establish an efficient, fast, and timely nutritional diagnosis method for L. Chuanxiong, which is applied in production. Meanwhile, the standardized production of medicinal plant resources provides new solutions.

Osteophagia of sea turtle bones by white-tailed deer (Odocoileus virginianus) in Santa Rosa National Park, northwestern Costa Rica

Herbivores obtain nutrients mostly from the vegetation they consume, but may obtain additional minerals during periods of nutritional stress by consuming bones (osteophagia), a behavioral strategy that has been reported for many wild ungulate species, including the white-tailed deer (Odocoileus virginianus). Here we document multiple records (n = 183 camera-trap records) of osteophagia by white-tailed deer chewing sea turtle remains (resulting from jaguar [Panthera onca] predation) near a nesting beach in Santa Rosa National Park, Costa Rica during January-September 2017. Females with fawns, males with hard and velvet-covered antlers, and non-spotted fawns reached a peak of sea turtle bone consumption during June to August. We hypothesize that seasonality, sex, age, and individual growth stage influence the frequency of osteophagy as a strategy to cope with environmental changes and food resource scarcity. Finally, these observations highlight the role of an apex predator as indirectly influencing rare but important ecological processes.

Rapidly declining body size in an insectivorous bat is associated with increased precipitation and decreased survival.

Reduced food availability is implicated in declines in avian aerial insectivores, but the effect of nutritional stress on mammalian aerial insectivores is unclear. Unlike birds, insectivorous bats provision their young through lactation, which might protect nursing juveniles when prey availability is low but could increase the energetic burden on lactating females. We analyzed a 15-year capture-mark-recapture data set from 5312 individual little brown myotis (Myotis lucifugus) captured at 11 maternity colonies in northwestern Canada, to test the hypothesis that nutritional stress is impacting these mammalian aerial insectivores. We used long-bone (forearm [FA]) length as a proxy for relative access to nutrition during development, and body mass as a proxy for access to nutrition prior to capture. Average FA length and body mass both decreased significantly over the study period in adult females and juveniles, suggesting decreased access to nutrition. Effect sizes were very small, similar to those reported for declining body size in avian aerial insectivores. Declines in juvenile body mass were only observed in individuals captured in late summer when they were foraging independently, supporting our hypothesis that lactation provides some protection to nursing young during periods of nutritional stress. Potential drivers of the decline in bat size include one or both of (1) declining insect (prey) abundance, and (2) declining prey availability. Echolocating insectivorous bats cannot forage effectively during rainfall, which is increasing in our study area. The body mass of captured adult females and juveniles in our study was lower, on average, after periods of high rainfall, and higher after warmer-than-average periods. Finally, survival models revealed a positive association between FA length and survival, suggesting a fitness consequence to declines in body size. Our study area has not yet been impacted by bat white-nose syndrome (WNS), but research elsewhere has suggested that fatter bats are more likely to survive infection. We found evidence for WNS-independent shifts in the body size of little brown myotis, which can inform studies investigating population responses to WNS. More broadly, the cumulative effects of multiple stressors (e.g., disease, nutritional stress, climate change, and other pressures) on mammalian aerial insectivores require urgent attention.

Harnessing solar power: photoautotrophy supplements the diet of a low-light dwelling sponge

The ability of organisms to combine autotrophy and heterotrophy gives rise to one of the most successful nutritional strategies on Earth: mixotrophy. Sponges are integral members of shallow-water ecosystems and many host photosynthetic symbionts, but studies on mixotrophic sponges have focused primarily on species residing in high-light environments. Here, we quantify the contribution of photoautotrophy to the respiratory demand and total carbon diet of the sponge Chondrilla caribensis, which hosts symbiotic cyanobacteria and lives in low-light environments. Although the sponge is net heterotrophic at 20 m water depth, photosynthetically fixed carbon potentially provides up to 52% of the holobiont’s respiratory demand. When considering the total mixotrophic diet, photoautotrophy contributed an estimated 7% to total daily carbon uptake. Visualization of inorganic 13C- and 15N-incorporation using nanoscale secondary ion mass spectrometry (NanoSIMS) at the single-cell level confirmed that a portion of nutrients assimilated by the prokaryotic community was translocated to host cells. Photoautotrophy can thus provide an important supplemental source of carbon for sponges, even in low-light habitats. This trophic plasticity may represent a widespread strategy for net heterotrophic sponges hosting photosymbionts, enabling the host to buffer against periods of nutritional stress.

Changes in prey fields increase the potential for spatial overlap between gentoo penguins and a krill fishery within a marine protected area

AbstractAIMManagement of competition with predators is an important consideration for fisheries, particularly within marine protected areas (MPAs) where conservation is a primary objective. We aimed to test whether static no‐take zones within a large, sustainable‐use MPA prevented overlap between gentoo penguins and a krill fishery during two winters with contrasting prey fields.LOCATIONSouth Georgia, Southwest Atlantic Ocean.METHODWe used satellite tracking (N = 16, June–September 2018) to describe gentoo penguin movements and distribution and quantified their overlap with the MPA’s no‐take zone (NTZ) and the krill fishing grounds. DNA metabarcoding of scats (N = 220, April–September 2018) was used to quantify diet.RESULTSWhen krill were at moderate densities and evenly distributed in 2001, gentoo penguins would have spent all of their time within the 12 NM NTZ, but when availability was low in 2018, they spent 46.3% of their time outside the NTZ and 9.6% within the krill fishing grounds. The extension of the NTZ to 30 km in response to this finding would have produced a 14.9% increase in protection for penguins and displaced 4% of fishery hauls. Gentoo penguin diet comprised 25.8% krill, which is lower than in the late 1980s but more than in 2009.MAIN CONCLUSIONSGentoo penguins extend their foraging range when krill is scarce, which increases the potential for spatial overlap with the krill fishery during periods of nutritional stress. Current regulations allow for expansion of both extent and catches by the krill fishery and, should this occur, gentoo penguins may face heightened risks from competition. A dynamic ocean management framework, that extends closed areas in response to near real‐time data on penguin movements and krill density estimates, may reduce the potential for competition in this sustainable‐use MPA while allowing a profitable krill fishery.

Long-term reproductive success is predicted by sexual behavior and impaired by temporary nutritional stress during sexual maturation

Nutritional stress during the earliest stages of an animal’s life can have long-term effects on its behavior and reproductive performance, but the effects of brief periods of nutritional stress later in life are less well-studied. We manipulated female diet in Narnia femorata (Hemiptera: Coreidae) and investigated to what extent nutritional stress during sexual maturation affects subsequent sexual behavior and long-term offspring production. We show that nutritional stress at this key point during early adulthood can have lasting effects on reproduction, impairing long-term offspring production despite the subsequent return of good nutrition. These results demonstrate that nutritional availability during late stages of development, in young adults, can be crucial to future fitness. We found no effect of temporary nutritional stress on female receptivity to mating or attractiveness to males; although females that were less receptive also produced fewer offspring in the next month. Overall, we demonstrate that even brief periods of nutritional deprivation late in development can have drastic long-term effects, apparently beyond compensation, and despite a good early nutritional environment.

Bariatric surgery as a proxy for nutritional stress in stable isotope investigations of archaeological populations

Pathophysiological fractionation of stable nitrogen and carbon isotopes during periods of nutritional stress has the potential to bias investigations of ancient diets using such methods, particularly when no corroborating evidence of stress is apparent. More stable isotope analyses of human proxies for nutritional stress are therefore necessary to resolve this issue of diet vs. stress. We show here that individuals undergoing bariatric surgery are an ideal proxy for studying pathophysiological fractionation among humans. Using sequential samples of hair from two individuals, we construct an isotopic timeline demonstrating a 1‰ enrichment in δ15N values immediately following bariatric surgery, reflecting the catabolism of body tissues. Stable carbon isotopes show little systematic change with tissue catabolism.

Onset of feeding in juvenile sea urchins and its relation to nutrient signalling

ABSTRACTThe purple sea urchin, Strongylocentrotus purpuratus, has been the focus of extensive ecological and developmental research over the years. Strongylocentrotus purpuratus larvae transition into the juvenile stage after an extensive planktonic period. The metamorphic transition is characterized by dramatic changes in morphology and physiology of the juvenile compared to the larval form and mechanisms underlying this process, especially the early days post-settlement, remain poorly understood. We used SEM and phalloidin stain analysis as well as whole mount in situ hybridization to gain a detailed understanding of juvenile development in relation to nutrient signalling [insulin-like growth factor (IIS), FoxO (forkhead box, sub-group ‘O’) and TOR (target of rampamycin), also known as IIS/TOR/FoxO signalling]. Our results show that the majority of juvenile feeding features are fully developed only after 8-days of juvenile development, leaving an extensive period of nutritional stress. We found that FoxO gene expression increases during that time period and is localized in juvenile tube feet, potentially associated with sensory structures involved in nutrient signalling. Our data complement existing work on sea urchin juvenile development and shed new light on the perimetamorphic period of Strongylocentrotus purpuratus, with respect to nutrient signalling and the potential stressful pre-feeding period of juvenile sea urchins.

Intensity of Mutualism Breakdown Is Determined by Temperature Not Amplification of Wolbachia Genes.

Wolbachia are maternally transmitted intracellular bacterial symbionts that infect approximately 40% of all insect species. Though several strains of Wolbachia naturally infect Drosophila melanogaster and provide resistance against viral pathogens, or provision metabolites during periods of nutritional stress, one virulent strain, wMelPop, reduces fly lifespan by half, possibly as a consequence of over-replication. While the mechanisms that allow wMelPop to over-replicate are still of debate, a unique tandem repeat locus in the wMelPop genome that contains eight genes, referred to as the “Octomom” locus has been identified and is thought to play an important regulatory role. Estimates of Octomom locus copy number correlated increasing copy number to both Wolbachia bacterial density and increased pathology. Here we demonstrate that infected fly pathology is not dependent on an increased Octomom copy number, but does strongly correlate with increasing temperature. When measured across developmental time, we also show Octomom copy number to be highly variable across developmental time within a single generation. Using a second pathogenic strain of Wolbachia, we further demonstrate reduced insect lifespan can occur independently of a high Octomom locus copy number. Taken together, this data demonstrates that the mechanism/s of wMelPop virulence is more complex than has been previously described.

Predation shapes the movement of a well-defended species, the North American porcupine, even when nutritionally stressed

Animals reduce their exposure to predation often at the cost of nutritional inputs. A variety of predator avoidance strategies exist, but species generally exist along a spectrum with some primarily utilizing behavioral responses to avoid predation and others relying more on morphological defenses to deter predation. North American porcupines (Erethizon dorsatum) possess a well-developed predator deterrent strategy (i.e., quills). During the winter, porcupines enter a nutritional bottleneck where they principally rely on endogenous stores to survive winter. We hypothesized that porcupine behavior in winter would, then, be primarily driven by nutritional demands rather than predation risk. To test this trade-off between perceived risk of predation and nutritional stress, we analyzed the length and sinuosity of movement patterns, relative to nutritional condition (urinary urea: creatinine), snow conditions (depth, density), and a risk landscape (predation risk and refuges). As predicted, the sinuosity of movement paths was unrelated to any of our variables, but we detected a strong correlation between lengths of movements with risk landscape. Specifically, the length of porcupine movement declined as the average risk of predation increased, and the presence of refuge trees in their movement path was positively related to path length. Thus, even for animals possessing extreme morphological defenses effective at deterring predation, and during a period of nutritional stress, movement and behavior are nevertheless driven by perceived predation risk.

The Endosymbiont Hamiltonella Increases the Growth Rate of Its Host Bemisia tabaci during Periods of Nutritional Stress

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) harbors several bacterial symbionts. Among the secondary (facultative) symbionts, Hamiltonella has high prevalence and high infection frequencies, suggesting that it may be important for the biology and ecology of its hosts. Previous reports indicated that Hamiltonella increases whitefly fitness and, based on the complete sequencing of its genome, may have the ability to synthesize cofactors and amino acids that are required by its host but that are not sufficiently synthesized by the host or by the primary endosymbiont, Portiera. Here, we assessed the effects of Hamiltonella infection on the growth of B. tabaci reared on low-, standard-, or high-nitrogen diets. When B. tabaci was reared on a standard-nitrogen diet, no cost or benefit was associated with Hamiltonella infection. But, if we reared whiteflies on low-nitrogen diets, Hamiltonella-infected whiteflies often grew better than uninfected whiteflies. Furthermore, nitrogen levels in field-collected whiteflies indicated that the nutritional conditions in the field were comparable to the low-nitrogen diet in our laboratory experiment. These data suggest that Hamiltonella may play a previously unrecognized role as a nutritional mutualist in B. tabaci.

Effects of Body Condition on Buoyancy in Endangered North Atlantic Right Whales

Buoyancy is an important consideration for diving marine animals, resulting in specific ecologically relevant adaptations. Marine mammals use blubber as an energy reserve, but because this tissue is also positively buoyant, nutritional demands have the potential to cause considerable variation in buoyancy. North Atlantic right whales Eubalaena glacialis are known to be positively buoyant as a result of their blubber, and the thickness of this layer varies considerably, but the effect of this variation on buoyancy has not been explored. This study compared the duration and rate of ascending and descending glides, recorded with an archival tag, with blubber thickness, measured with an ultrasound device, in free-swimming right whales. Ascending whales with thicker blubber had shorter portions of active propulsion and longer passive glides than whales with thinner blubber, suggesting that blubber thickness influences buoyancy because the buoyant force is acting in the same direction as the animal's movement during this phase. Whales with thinner layers also used similar body angles and velocities when traveling to and from depth, while those with thicker layers used shallower ascent angles but achieved higher ascent velocities. Such alterations in body angle may help to reduce the cost of transport when swimming against the force of buoyancy in a state of augmented positive buoyancy, which represents a dynamic response to reduce the energetic consequences of physiological changes. These results have considerable implications for any diving marine animal during periods of nutritional stress, such as during seasonal migrations and annual variations in prey availability.

Visitations by Snowshoe Hares (<em>Lepus americanus</em>) to and Possible Geophagy of Materials from an Iron-Rich Excavation in North-Central British Columbia

Fecal pellet samples and photo data were collected and analyzed to investigate the suspected occurrence of geophagy of soils by Snowshoe Hares (Lepus americanus) at a small iron-rich mineral excavation in north-central British Columbia. Pellet samples from Snowshoe Hares collected near the excavation site in both February 2004 and 2005 showed higher levels of iron (II) sulphate in pellets than in samples from control areas (P < 0.05). Using remote wildlife camera technology, we determined that Snowshoe Hares accounted for 72% of visits by mammals to the site. Ninety percent of these visits occurred at night; this timing corresponds with the use of mineral licks by several other species of mammals in North America. Use occurred in winter (49%) and spring (47%), but was rare in summer and autumn, and may have coincided with periods of nutritional stress in Snowshoe Hares.

Measuring the costs of alternative reproductive tactics in horseshoe crabs, Limulus polyphemus

Trade-offs are inherent to alternative reproductive tactics (ARTs), and identifying the costs and benefits of tactics is essential to understanding their evolution and maintenance within a population. Male horseshoe crabs exhibit two condition-dependent ARTs: males that are in better condition arrive on spawning beaches attached to a female, while males in poorer condition join spawning pairs as satellites and engage in sperm competition. Previous research has identified several benefits to the attached tactic, but the costs are less well understood. We examined a previously uninvestigated potential cost to the attached male tactic: nutritional stress caused by a restricted ability to feed. We found that field-caught attached males produced 57% less faeces in a 12 h period than satellite males, and had 2.5 times emptier digestive tracts than satellite males. We further examined this cost using stable isotopes because nutritionally stressed animals are predicted to have higher δ15N levels. We found that field-caught attached males had higher δ15N values than satellite males. However, higher δ15N values could result from nutritional stress or from feeding on higher trophic levels. We tested this experimentally and found that starved animals had higher post-treatment δ15N values compared to animals that were fed. Furthermore, the digestive tracts of field-caught attached males contained three times more sea grass (lower tropic levels have lower δ15N values) than satellite males. These findings mean that the higher δ15N values of field-caught attached males likely result from fasting rather than differences in diet. Taken together, our results indicate that a period of nutritional stress caused by reduced food consumption is a novel cost of the attached tactic. This study provides a key piece of information to explain why ARTs in horseshoe crabs take the form they do and provides a novel method for studying costs associated with ARTs in other species.

Autophosphorylation Within the Atg1 Activation Loop Is Required for Both Kinase Activity and the Induction of Autophagy in Saccharomyces cerevisiae

Autophagy is an evolutionarily conserved degradative pathway that has been implicated in a number of physiological events important for human health. This process was originally identified as a response to nutrient deprivation and is thought to serve in a recycling capacity during periods of nutritional stress. Autophagy activity appears to be highly regulated and multiple signaling pathways are known to target a complex of proteins that contains the Atg1 protein kinase. The data here extend these observations and identify a particular phosphorylation event on Atg1 as a potential control point within the autophagy pathway in Saccharomyces cerevisiae. This phosphorylation occurs at a threonine residue, T226, within the Atg1 activation loop that is conserved in all Atg1 orthologs. Replacing this threonine with a nonphosphorylatable residue resulted in a loss of Atg1 protein kinase activity and a failure to induce autophagy. This phosphorylation required the presence of a functional Atg1 kinase domain and two known regulators of Atg1 activity, Atg13 and Atg17. Interestingly, the levels of this modification were found to increase dramatically upon exposure to conditions that induce autophagy. In addition, T226 phosphorylation was associated with an autophosphorylated form of Atg1 that was found specifically in cells undergoing the autophagy process. In all, these data suggest that autophosphorylation within the Atg1 activation loop may represent a point of regulatory control for this degradative process.

Energy Reallocation during and after Periods of Nutritional Stress in Steller Sea Lions: Low‐Quality Diet Reduces Capacity for Physiological Adjustments

Two groups of female Steller sea lions (groups H and P) were subjected to periods of energy restriction and subsequent refeeding during winter and summer to determine changes in energy partitioning among principal physiological functions and the potential consequences to their fitness. Both sea lion groups consumed high-quality fish (herring) before and after the energy restrictions. During restrictions, group H was fed a lower quantity of herring and group P a caloric equivalent of low-quality fish (pollock). Quantitative estimates of maintenance and production energies and qualitative estimates of thermoregulation, activity, and basal metabolic rate were measured. During summer, all animals compensated for the imposed energy deficit by releasing stored energy (production energy). Group H also optimized the energy allocation to seasonal conditions by increasing activity during summer, when fish are naturally abundant (foraging effort), and by decreasing thermoregulation capacity when waters are warmer. During winter, both groups decreased the energy allocated to overall maintenance functions (basal metabolic rate, thermoregulation, and activity together) in addition to releasing stored energy, but they preserved thermoregulatory capacity. Group H also decreased activity levels in winter, when foraging in the wild is less efficient, unlike group P. Overall, sea lions fed pollock did not change energy allocation to suit environmental conditions as readily as those fed herring. This implies that a low energy-density diet may further reduce fitness of animals in the wild during periods of nutritional stress.

The Influence of Spatio-Temporal Variation in Food Availability and Nest-Predation Risk on Clutch-Size Decisions

The role of both temporal and spatial variability in nest predation and food availability in influencing birds' decisions about clutch size has not been studied. I examine patterns in nest-predation risk and food availability across a range of severity of wildfire to investigate their relationship to clutch size in the Dark-eyed Junco (Junco hyemalis), which breeds commonly in burned forests. Spatial variation in burn severity led to lower risk of nest predation in patches of intermediate severity in the first two years after the fire, while food availability was inversely related to burn severity during only the first year post-fire. Spatial variation in risk of nest predation explained variation in clutch size only during the first year post-fire when food was limited, consistent with parents investing less in risky nest locations during periods of nutritional stress. Nest-predation risk increased seasonally during both year 1 and year 2 post-fire. Clutch size rose dramatically over the first breeding season post-fire, paralleling a unique seasonal increase in food availability in year 1, consistent with juncos tracking temporal variation in food availability by investing more in eggs. Results are consistent with parents balancing spatio-temporal variation in resource limitation with predation risk in their investment in eggs. Disagreement between existing studies as to the relative importance of food and nest predation further highlights the need for carefully designed experimental approaches that integrate explanations for both temporal and spatial trends in sources of selection likely to shape the evolution of clutch-size decisions.

Evidence for Metabolic Provisioning by a Common Invertebrate Endosymbiont, Wolbachia pipientis, during Periods of Nutritional Stress

Wolbachia are ubiquitous inherited endosymbionts of invertebrates that invade host populations by modifying host reproductive systems. However, some strains lack the ability to impose reproductive modification and yet are still capable of successfully invading host populations. To explain this paradox, theory predicts that such strains should provide a fitness benefit, but to date none has been detected. Recently completed genome sequences of different Wolbachia strains show that these bacteria may have the genetic machinery to influence iron utilization of hosts. Here we show that Wolbachia infection can confer a positive fecundity benefit for Drosophila melanogaster reared on iron-restricted or -overloaded diets. Furthermore, iron levels measured from field-collected flies indicated that nutritional conditions in the field were overall comparable to those of flies reared in the laboratory on restricted diets. These data suggest that Wolbachia may play a previously unrecognized role as nutritional mutualists in insects.

Winter Use of Senescent Herbaceous Plants by White-Tailed Deer in Minnesota

During winter in northern North America, white-tailed deer (Odocoileus virginianus) have been reported to consume non-woody browse items such as dried leaves (of woody plants), lichens, and evergreen herbaceous plants. We report use of five species of senescent (dead) herbaceous perennial plants in winter by a high density white-tailed deer herd in south-central Minnesota during a winter of average snow depths and below average temperatures. While low in digestible energy, senescent herbaceous material may present deer with a forage item higher in digestible protein than larger diameter woody twigs during periods of nutritional stress.