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Torpor encompasses diverse adaptations to extreme environmental stressors such as hibernation, aestivation, brumation, and daily torpor. Here we introduce StrokeofGenus, an analytic pipeline that identifies distinct transcriptomic states and shared gene expression patterns across studies, tissues, and species. We use StrokeofGenus to study multiple and diverse forms of torpor from publicly-available RNA-seq datasets that span eight species and two classes. We identify three transcriptionally distinct states during the cycle of heterothermia: euthermia, torpor, and interbout arousal. We also identify torpor-specific gene expression patterns that are shared both across tissues and between species with over three hundred million years of evolutionary divergence. We further demonstrate the general sharing of gene expression patterns in multiple forms of torpor, implying a common evolutionary origin for this process. Although here we apply StrokeofGenus to analysis of torpor, it can be used to interrogate any other complex physiological processes defined by transient transcriptomic states. [ABSTRACT FROM AUTHOR]

The divide between the rich and poor in the European housing market is fast rising. Latest research indicates that Europe is dealing with an increasing number of homeless people. Every city in Europe has them—homeless people compelled to live on street corners, frequently hiding themselves with cardboard. Rain, snow, and temperatures below zero pose a threat to their lives on a daily basis. There are many varied kinds of services that have been discovered, but it is difficult to keep track of everyone and guarantee that they have a warm night's sleep in the winter. The current article suggests accommodation as a workaround until they can receive high-intensity support, a way to keep a single person warm and safe during the winter. The focus is on devising a strategy that not only ensures the warmth and safety of individuals during the harsh winter months but also seeks to industrialize the construction of shelters, ensuring affordability below the cost of winter hospitalization for a homeless person. Crucially, the article introduces an additional layer to this initiative by highlighting the dual purpose of these individual shelters. Beyond being a means to provide respite for the homeless during severe weather, these shelters are envisioned as immediate response units in the event of emergencies such as earthquakes in urban areas. The article explores the potential impact of this multi-layered approach on transforming urban landscapes and fostering resilient communities. [ABSTRACT FROM AUTHOR]

The search for biomarkers for the early diagnosis of neurodegenerative diseases is a growing area. Numerous investigations are exploring minimally invasive and cost-effective biomarkers, with the detection of phosphorylated Tau (pTau) protein emerging as one of the most promising fields. pTau is the main component of the paired helical filaments found in the brains of Alzheimer's disease cases and serves as a precursor in the formation of neurofibrillary tangles (NFTs). Recent research has revealed that analysis of p-Tau181, p-Tau217 and p-Tau231 in blood may be an option for detecting the preclinical stage of Alzheimer's disease. In this study, we have analyzed the values of pTau 181 in the serum of Syrian hamsters during hibernation. Naturally, over the course of hibernation, these animals exhibit a reversible accumulation of pTau in the brain tissue, which rapidly disappears upon awakening. A biosensing system based on the interferometric optical detection method was used to measure the concentration of pTau181 protein in serum samples from Syrian hamsters. This method eliminates the matrix effect and amplifies the signal obtained by using silicon dioxide nanoparticles (SiO2 NPs) biofunctionalized with the αpTau181 antibody. Our results indicate a substantial increase in the serum concentration of pTau in threonine-181 during hibernation, which disappears completely 2–3 h after awakening. Investigating the mechanism by which pTau protein appears in the blood non-pathologically may enhance current diagnostic techniques. Furthermore, since this process is reversible, and no tangles are detected in the brains of hibernating hamsters, additional analysis may contribute to the discovery of improved biomarkers. Additionally, exploring drugs targeting pTau to prevent the formation of tangles or studying the outcomes of any pTau-targeted treatment could be valuable. [ABSTRACT FROM AUTHOR]

Fat-tailed dwarf lemurs (Cheirogaleus medius), primates endemic to Madagascar, are obligate hibernators that form stable, lifelong pairs in the wild. Given the temporal constraints imposed by seasonal hibernation, infant dwarf lemurs must grow, develop, and wean within the first two months of life. Maternal as well as paternal infant care, observed in the wild, has been deemed critical for infant survival. Given the importance of fathers' involvement in early infant care, we expect this behavior to persist even under captive conditions. At the Duke Lemur Center, in Durham NC, we observed two families of fat-tailed dwarf lemurs and focused on the behavior of adult males within the first two months of the infants' lives. We report evidence of paternal involvement, including babysitting, co-feeding, grooming, accompanying, and leading infants, consistent with observations from the wild. As expected, paternal babysitting decreased as infants gained independence, while co-feeding increased. Supplemental anecdotes, video recorded by observers, also highlight clear cases of involvement by both parents, and even older siblings, in safeguarding and socializing new infants. We argue that maintaining captive fat-tailed dwarf lemur populations under socially and ecologically relevant conditions facilitates the full expression of physiological and behavioral repertoires. Most importantly, it also allows dwarf lemurs to realize their species' potential and become robust proxies of their wild kin. [ABSTRACT FROM AUTHOR]

Energy conservation associated with hibernation is maximized at the intersection of low body temperature (Tb), long torpor bouts, and few interbout arousals. In the arctic ground squirrel (Urocitellus parryii), energy conservation during hibernation is best achieved at ambient temperatures (Ta) around 0 °C; however, they spend the majority of hibernation at considerably lower Ta. Because arctic ground squirrels switch to mixed fuel metabolism, including protein catabolism, at extreme low Ta of hibernation, we sought to investigate how microbial urea-nitrogen recycling is used under different thermal conditions. Injecting squirrels with isotopically labeled urea (13C/15N) during hibernation at Ta's of − 16 °C and 2 °C and while active and euthermic allowed us to assess the ureolytic activity of gut microbes and the amount of liberated nitrogen incorporated into tissues. We found greater incorporation of microbially-liberated nitrogen into tissues of hibernating squirrels. Although ureolytic activity appears higher in euthermic squirrels, liberated nitrogen likely makes up a smaller percentage of the available nitrogen pool in active, fed animals. Because non-lipid fuel is a limiting factor for torpor at lower Ta in this species, we hypothesized there would be greater incorporation of liberated nitrogen in animals hibernating at − 16 °C. However, we found higher microbial-ureolytic activity and incorporation of microbially-liberated nitrogen, particularly in the liver, in squirrels hibernating at 2 °C. Likely this is because squirrels hibernating at 2 °C had higher Tb and longer interbout arousals, a combination of factors creating more favorable conditions for gut microbes to thrive and maintain greater activity while giving the host more time to absorb microbial metabolites. [ABSTRACT FROM AUTHOR]

Demography of herbivorous mammal populations may be affected by changes in predation, population density, harvesting, and climate. Whereas numerous studies have focused on the effect of single environmental variables on individual demographic processes, attempts to integrate the consequences of several environmental variables on numerous functional traits and demographic rates are rare. Over a 32-year period, we examined how forage availability (vegetation assessed through NDVI) and population density affected the functional traits and demographic rates of a population of Columbian ground squirrels (Urocitellus columbianus), a herbivorous hibernating rodent. We focused on mean population phenology, body mass, breeding success, and survival. We found a negative effect of population density on demographic rates, including on breeding success and pup and adult survival to the next year. We found diverging effects of vegetation phenology on demographic rates: positive effects of a later start of the growing season on adult and yearling female survival, and juvenile survival, but no clear effect on male survival. Interestingly, neither population density nor vegetation affected population phenology or body condition in the following year. Vegetative growth rate had a positive influence on female mass gain (somatic investment) over a season, but both vegetative growth rate and biomass, surprisingly, had negative effects on the survival of young through their first hibernation. Thus, ground squirrels appeared to benefit more from later timing of vegetation than increases in vegetative biomass per se. Our study provides evidence for complex ecological effects of vegetation and population density on functional traits and demographic rates of small mammal populations. [ABSTRACT FROM AUTHOR]

We comment on a recent study (Vasenkov et al. in Dokl Biol Sci 513:395–399, 2023, https://doi.org/10.1134/S0012496623700746) presenting the movement paths of three greater noctule bats (Nyctalus lasiopterus), two juveniles and an adult, tracked from Russia in September–October 2020 and 2021, with particular emphasis on the unprecedented straight-line migration of a juvenile male to Italy. Notably, the juvenile's extraordinary 2515 km migration marks the longest recorded (as the crow flies) movement in a bat species. We argue that the two juveniles may represent cases of dispersal. Despite the attention garnered by Vasenkov et al.'s findings, caution is warranted in interpreting the broader migration picture. The paper's dissemination underscores a potential oversimplification, neglecting key insights from recent work conducted in Italy that documented the year-round presence, hibernation, and parturition of N. lasiopterus in an area of the Friuli Venezia-Giulia region where the juvenile male tracked from Russia stopped over. Besides, inferring the existence of migratory routes based on small numbers of tracked bats is insufficient. The oversight of these findings may imply a misleading narrative about the species' behaviour, likely representing a case of partial migration, a pattern widespread among migratory bat species. [ABSTRACT FROM AUTHOR]

Whether an invasive species thrives in cold ecosystems depends on its response to winter weather. A potential threat to these ecosystems in Europe is the invasive raccoon dog (Nyctereutes procyonoides). The survival of this mesopredator is supported in cold weather, because it can periodically use winter sleep, but its winter activity levels compared to native mesopredators remain unclear. We investigated the winter behaviour of raccoon dogs in Finland, near the edge of their invasion front, and compared their activity to native red foxes and badgers. Using wildlife cameras, we found that raccoon dogs do reduce activity during the coldest months, but camera observations did not strongly correlate with temperature perhaps due to feeding at camera sites. That is, artificial food sources may have increased raccoon dogs' winter activity. Nevertheless, they responded more clearly to temperature drops than red foxes, but were more active than badgers that were mostly dormant and thus absent from our data. GPS-tracked raccoon dogs remained at some level active through winter, even near subarctic regions, but the cold and snowy weather clearly decreased activity and individuals stayed close to their nests during the coldest periods. Overall, these findings suggest that raccoon dogs can maintain some winter activity even in extremely cold environments, and they readily exploit human-provided resources. This potential ability to thrive in cold regions highlights the invasive potential of raccoon dogs. As winters become milder due to climate change, their numbers could increase significantly within cold-adapted ecosystems, impacting native species and posing conservation challenges. [ABSTRACT FROM AUTHOR]

Mammalian hibernators survive prolonged periods of cold and resource scarcity by temporarily modulating normal physiological functions, but the mechanisms underlying these adaptations are poorly understood. The hibernation cycle of thirteen-lined ground squirrels (Ictidomys tridecemlineatus) lasts for 5–7 months and comprises weeks of hypometabolic, hypothermic torpor interspersed with 24–48-h periods of an active-like interbout arousal (IBA) state. We show that ground squirrels, who endure the entire hibernation season without food, have negligible hunger during IBAs. These squirrels exhibit reversible inhibition of the hypothalamic feeding center, such that hypothalamic arcuate nucleus neurons exhibit reduced sensitivity to the orexigenic and anorexigenic effects of ghrelin and leptin, respectively. However, hypothalamic infusion of thyroid hormone during an IBA is sufficient to rescue hibernation anorexia. Our results reveal that thyroid hormone deficiency underlies hibernation anorexia and demonstrate the functional flexibility of the hypothalamic feeding center. Hibernating ground squirrels have negligible hunger despite a months-long period of food deprivation and cold exposure. Here, authors show that prolonged anorexia is enabled by inhibition of the hypothalamic feeding center due to central hypothyroidism. [ABSTRACT FROM AUTHOR]

The temperature coefficients of heart rate (Q10HR) or oxygen consumption (Q10Ox) were analyzed upon arousal from natural hibernation in long-tailed ground squirrels Urocitellus undulatus and during the rewarming of artificially precooled adult rats and rat pups. The Q10Ox value was calculated using a standard equation, whereas for calculating Q10HR, the equation was empirically modified to track changes in this parameter over a wide range of body temperatures (Tb). It was found that during the initial period of arousal from torpor, at Th ≤ 10°C, ground squirrels demonstrated a sharp increase in the temperature coefficients up to Q10HR = 40–50 and Q10Ox = 6–7. Even higher values of Q10HR (>100) were recorded at the onset of rewarming of rat pups, although they had a low level of Q10Ox (1.2). Adult rats could not tolerate cooling below 16°C and demonstrated a moderate variability of both Q10HR = 2.0–4.0 and Q10Ox = 2.0–2.2. During the recovery of normal Tb, the Q10HR values in all animals approximated to ~2.0, as predicted by the van't Hoff–Arrhenius rule for chemical reactions in both living and inanimate nature. We assume that high values of Q10HR and Q10Ox, detected in the early period of ground squirrel's arousal from hibernation, may indicate the functioning of adaptive processes aimed at accelerating body warming. Resistance to cooling and a high Q10HR in rat pups may suggest the rudimentary adaptability to hibernation in the juvenile period of rats as representatives of the order Rodentia, which also includes such natural hibernators as ground squirrels. [ABSTRACT FROM AUTHOR]

The stability of host plant resistance to insects, and efficacy of insecticides against the insect pests is influenced by several inherent traits of the target insects in addition to the environmental factors. Spotted stem borer, Chilo partellus (Swinhoe) is a key pest of maize and sorghum. It undergoes both hibernation and aestivation depending upon the prevailing climatic conditions. We studied the host preference and damage potential of this pest in maize and sorghum, and its susceptibility to different insecticides in F1 progenies of hibernating, aestivating and nondiapausing strains of C. partellus. The larvae from hibernating strain resulted in greater leaf damage and deadhearts, and had greater larval weight and better survival on maize and sorghum than those from the aestivating and nondiapausing strains, although there were a few exceptions. The susceptible maize and sorghum genotypes were highly preferred by the hibernating larvae, while the resistant genotypes were preferred most by the aestivating strain. Maize was least preferred, while sorghum was most preferred by the larvae from hibernating as compared to aestivating and nondiapausing strains of C. partellus. The larvae from aestivating strain were least susceptible to cypermethrin and thiamethoxam, but highly susceptible to deltamethrin and imidacloprid as compared to the other strains. The present studies showed significant differences in preference and damage potential in the host crops, and susceptibility to insecticides in diapausing and nondiapausing strains of C. partellus. Identification of stem borer resistant genotypes of sorghum and maize, and the insecticides with stable efficacy will be useful for integrated management of this pest. [ABSTRACT FROM AUTHOR]

During the period of hibernation, mammals periodically go through cold (torpor) and warm (аrousal) phases. Previously, a sharp decrease in the levels of blood leukocytes and platelets in the torpid state was found; however, the dynamics of their changes during аrousal remains unknown. We studied the content and composition of circulating cells of the little ground squirrel during аrousal. The number of all types of leukocytes and platelets in a torpid state is significantly reduced. The restoration of leukocyte level in the blood during аrousal occurs in two phases: fast (Tb 10–20○C) and slow (Tb 20–37○C). Unlike other cell types, the content of neutrophils after temperature restoration remains below the control. During аrousal, the platelet level increases linearly in the range of Tb 10–30○C; at the same time, no normalization of the P-LCR parameter occurs. [ABSTRACT FROM AUTHOR]

The baseboard management controller (BMC) is a specialized processor installed on the motherboard of a server. The BMC operates independently from the server and provides administrators with functionalities for managing the server. In the event of a power outage or system failure causing server downtime, administrators should promptly access the server remotely to identify the cause and take necessary actions. To facilitate this, fast BMC booting is crucial. This paper proposes the concept of hybrid booting with the incremental hibernation technique. The proposed technique periodically stores the state of the BMC and offers various recovery options based on the saved state. It also employs an incremental backup technique for the efficient management of stored states and a hybrid booting technique to guarantee fast booting. In order to evaluate the performance of the proposed technique, the proposed technique is implemented on a development board where the BMC chipset operates and compared to the existing hibernation technique in terms of execution time, disk usage, and booting time. The experimental results show that the proposed technique efficiently enables BMC backup and reduces the booting times. [ABSTRACT FROM AUTHOR]

Winter energy stores are finite and factors influencing patterns of activity are important for overwintering energetics and survival. Hibernation patterns (e.g., torpor bout duration and arousal frequency) often depend on microclimate, with more stable hibernacula associated with greater energy savings than less stable hibernacula. We monitored hibernation patterns of individual big brown bats (Eptesicus fuscus; Palisot de Beauvois, 1796) overwintering in rock-crevices that are smaller, drier, and less thermally stable than most known cave hibernacula. While such conditions would be predicted to increase arousal frequency in many hibernators, we did not find support for this. We found that bats were insensitive to changes in hibernacula microclimate (temperature and humidity) while torpid. We also found that the probability of arousal from torpor remained under circadian influence, likely because throughout the winter during arousals, bats commonly exit their hibernacula. We calculated that individuals spend most of their energy on maintaining a torpid body temperature a few degrees above the range of ambient temperatures during steady-state torpor, rather than during arousals as is typical of other small mammalian hibernators. Flight appears to be an important winter activity that may expedite the benefits of euthermic periods and allow for short, physiologically effective arousals. Overall, we found that big brown bats in rock crevices exhibit different hibernation patterns than conspecifics hibernating in buildings and caves. Summary statement: In a population of prairie-living bats, we show an uncommon hibernation pattern consisting of short, infrequent arousals, and estimate the majority of their energy stores are expended while torpid rather than euthermic. [ABSTRACT FROM AUTHOR]

Disuse-induced muscular atrophy is frequently accompanied by iron overload. Hibernating animals are a natural animal model for resistance to disuse muscle atrophy. In this paper, we explored changes in skeletal muscle iron content of Daurian ground squirrels (Spermophilus dauricus) during different periods of hibernation as well as the regulatory mechanisms involved. The results revealed that compared with the summer active group (SA), iron content in the soleus muscle (SOL) decreased (− 65%) in the torpor group (TOR), but returned to normal levels in the inter-bout arousal (IBA); splenic iron content increased in the TOR group (vs. SA, + 67%), decreased in the IBA group (vs. TOR, − 37%). Expression of serum hepcidin decreased in the TOR group (vs. SA, − 22%) and returned to normal levels in the IBA groups; serum ferritin increased in the TOR group (vs. SA, + 31%), then recovered in the IBA groups. Soleus muscle transferrin receptor 1 (TfR1) expression increased in the TOR group (vs. SA, + 83%), decreased in the IBA group (vs. TOR, − 30%); ferroportin 1 increased in the IBA group (vs. SA, + 55%); ferritin increased in the IBA group (vs. SA, + 42%). No significant differences in extensor digitorum longus in iron content or iron metabolism-related protein expression were observed among the groups. Significantly, all increased or decreased indicators in this study returned to normal levels after the post-hibernation group, showing remarkable plasticity. In summary, avoiding iron overload may be a potential mechanism for hibernating Daurian ground squirrels to avoid disuse induced muscular atrophy. In addition, the different skeletal muscle types exhibited unique strategies for regulating iron homeostasis. [ABSTRACT FROM AUTHOR]

Hibernation is a widespread metabolic strategy among mammals for surviving periods of food scarcity. During hibernation, animals naturally alternate between metabolically depressed torpor bouts and energetically expensive arousals without ill effects. As a result, hibernators are promising models for investigating mechanisms that buffer against cellular stress, including telomere protection and restoration. In non-hibernators, telomeres, the protective structural ends of chromosomes, shorten with age and metabolic stress. In temperate hibernators, however, telomere shortening and elongation can occur in response to changing environmental conditions and associated metabolic state. We investigate telomere dynamics in a tropical hibernating primate, the fat-tailed dwarf lemur (Cheirogaleus medius). In captivity, these lemurs can hibernate when maintained under cold temperatures (11–15 °C) with limited food provisioning. We study telomere dynamics in eight fat-tailed dwarf lemurs at the Duke Lemur Center, USA, from samples collected before, during, and after the hibernation season and assayed via qPCR. Contrary to our predictions, we found that telomeres were maintained or even lengthened during hibernation, but shortened immediately thereafter. During hibernation, telomere lengthening was negatively correlated with time in euthermia. Although preliminary in scope, our findings suggest that there may be a preemptive, compensatory mechanism to maintain telomere integrity in dwarf lemurs during hibernation. Nevertheless, telomere shortening immediately afterward may broadly result in similar outcomes across seasons. Future studies could profitably investigate the mechanisms that offset telomere shortening within and outside of the hibernation season and whether those mechanisms are modulated by energy surplus or crises. [ABSTRACT FROM AUTHOR]

The complete blood count (CBC) dynamics was investigated in long-tailed ground squirrels Urocitellus undulatus (n = 100) during different periods of their annual activity. While blood cell (WBC), platelet (PLT), and red blood cell (RBC) counts were determined in summer (normothermia, June–July), fall (preparatory period, October), winter torpor (hypothermia, December–February) and winter active (euthermia, interbout arousals, December–February) periods. In fall, PLT and WBC counts increased by ~40% compared to summer. Under winter torpor, thrombocytosis and leukocytosis were replaced by extreme thrombocytopenia (↓ ~90%), as well as leukopenia in all WBC subpopulations (↓ ~80%). During brief interbout arousals, PLT and WBC counts reached the summer values except for a slightly increased MPV (mean platelet volume). As fall approached, there was an insignificant erythrocytosis (↑ ~10%), which together with changes in other indices could have suggested a mild fall-time hypoxia. During winter torpid and euthermic periods, RBC counts were almost indistinguishable from the summer control values, however, atypical RBC forms occurred both in the fall preparatory period and during hibernation itself. The results are discussed in the context of blood cell adaptation to harsh conditions of hibernation in ground squirrels, and can be useful in studying the adaptive abilities of homoeotherms, including humans. [ABSTRACT FROM AUTHOR]

During the hibernation season, Arctic ground squirrels (AGS) experience extreme temperature fluctuations (body temperature, Tb, as low as − 3 °C), during which they are mostly physically inactive. Once Tb reaches ~ 15 °C during interbout arousals, hibernators recruit skeletal muscle (SkM) for shivering thermogenesis to reach Tb of ~ 35 °C. Polyunsaturated fatty acids (PUFA) in the diet are known to influence SkM function and metabolism. Recent studies in the cardiac muscle of hibernators have revealed that increased levels of ω-6 and the ω-6:ω-3 PUFA ratio correlate with sarco/endoplasmic reticulum calcium ATPase (SERCA) activity and hibernation status. We hypothesized that diet (increased ω-6:ω-3 PUFA ratio) and torpor status are important in the regulation of the SERCA pump and that this may improve SkM performance during hibernation. Ex vivo functional assays were used to characterize performance changes in SkM (diaphragm) from AGS fed the following diets. (1) Standard rodent chow with an ω-6:ω-3 ratio of 5:1, or (2) a balanced diet with an ω-6:ω-3 ratio of 1:1 that roughly mimics wild diet. We collected diaphragms at three different stages of hibernation (early torpor, late torpor, and arousal) and evaluated muscle function under hypothermic temperature stress at 4 °C, 15 °C, 25 °C, and 37 °C to determine functional resilience. Our data show that torpid animals fed standard rodent chow have faster SkM relaxation when compared to the balanced diet animals. Furthermore, we discovered that standard rodent chow AGS during torpor has higher SkM relaxation kinetics, but this effect of torpor is eliminated in balanced diet AGS. Interestingly, neither diet nor torpor influenced the rate of force development (rate of calcium release). This is the first study to show that increasing the dietary ω-6:ω-3 PUFA ratio improves skeletal muscle performance during decreased temperatures in a hibernating animal. This evidence supports the interpretation that diet can change some functional properties of the SkM, presumably through membrane lipid composition, ambient temperature, and torpor interaction, with an impact on SkM performance. [ABSTRACT FROM AUTHOR]

Mus musculus enters a torpid state in response to caloric restriction in sub-thermoneutral ambient temperatures. This torpid state is characterized by an adaptive and controlled decrease in metabolic rate, heart rate, body temperature, and activity. Previous research has identified the paraventricular nucleus (PVN) within the hypothalamus, a region containing oxytocin neurons, as a location that is active during torpor onset. We hypothesized that oxytocin neurons within the PVN are part of this neural circuit and that activation of oxytocin neurons would deepen and lengthen torpor bouts. We report that activation of oxytocin neurons alone is not sufficient to induce a torpor-like state in the fed mouse, with no significant difference in body temperature or heart rate upon activation of oxytocin neurons. However, we found that activation of oxytocin neurons prior to the onset of daily torpor both deepens and lengthens the subsequent bout, with a 1.7 ± 0.4 °C lower body temperature and a 135 ± 32 min increase in length. We therefore conclude that oxytocin neurons are involved in the neural circuitry controlling daily torpor in the mouse. [ABSTRACT FROM AUTHOR]

Hibernating mammals have annual cycles with strict timing of all processes including reproduction, yet female reproductive physiology is only poorly studied in such species. We investigated the estrous cycle in yellow ground squirrels (Spermophilus fulvus), which hibernate up to 9 months. Using vaginal cytology and serum progesterone and estradiol profiles, we identified proestrus, estrus, metestrus, and anestrus in the cycle. As in other rodents, predominance of cornified cells marked estrus, and an increase in the leukocyte number reflected metestrus. The only estrus in a year started, and then, pregnancy occurred mostly within 3 days after spring emergence. In one female, we noticed a copulatory plug for the first time for this species. The progesterone level increased from proestrus/estrus to pregnancy and decreased in the postlactation period. Estradiol concentration did not change significantly throughout the estrous cycle but varied among females and was consistently high in some of them. The hormone levels did not vary with female age despite smaller body size in yearling females than in older ones. During postlactation, progesterone concentration diminished toward hibernation, and we could not detect signs of prehibernation activation of the female reproductive system. Probably, gonadal preparation in S. fulvus females proceeds at periodic arousals during hibernation. Our data showed fast transitions between phases of the female estrous cycle and early maturation of juvenile females, consistently with the hypothesis of the fast life-history strategy of S. fulvus. [ABSTRACT FROM AUTHOR]

This study continues our previous research aimed at investigating changes in the pools of amino acids in the myocardium of the ground squirrel during winter torpor. Neurochemical profiles of amino acids and the secondary metabolites (taurine, phosphoserine, and cysteic acid) were explored in the neocortex of the ground squirrel at different stages of torpor: in the beginning of torpor (2–3 days) and during prolonged torpor (9–10 days), as well as during short-term winter arousal (winter activity, euthermia). Reduced excitatory neurotransmitter levels (glutamate by 7% and 14%; aspartate by 25% and 52% in a coordinated manner and the increased level of GABA, the main transmission inhibitor (by 50% and 67%) were observed from the onset of the torpor entry and at the end of the torpor arousal, respectively. Alanine, which was formed in negligible amounts in the neocortex in the summer season, increased at the initial stage of hibernation and after multiday torpor bout (by 98% and 126%, respectively), indicating a partial switch to anaerobic glycolysis. Short-term interbout euthermia returned levels of these substances back to normal. The behavior of glutamate and aspartate, the anaplerotic substrates, that supported cycling of the tricarboxylic acid cycle during torpor and winter activity periods was like their responses in the myocardium, though differed quantitatively. The responses of the neuromodulators such as glycine, threonine, and lysine differed radically when compared to their responses in the myocardium. No changes in taurine and phosphoserine pools were detected, but the level of cysteic acid decreased compared to the summer control from 0.51 ± 0.06 μmol/g to 0.07 ± 0.01 μmol/g at the end of torpor, while during winter euthermia it became 2 times lower than the summer level. Our data suggest that metabolic pathways involving anaplerotic amino acids of the neocortex are more active than the myocardium during winter torpor, while the pools of neuromodulators that regulate inhibition processes, increase. [ABSTRACT FROM AUTHOR]

One of the principal consequences of climate warming on hibernating mammals could be the loss of optimal conditions for hibernation. Although hibernating mammals, like bats, may be particularly vulnerable to climate warming due to a potential reduction of energy saving during the hibernation, there is a lack of knowledge regarding how they will be affected and how they will respond to this impact. Here, we examine the variation in the body condition of Schreiber's bent-winged bat (Miniopterus schreibersii) to investigate changes in the optimization energy demand. Using a 20-year dataset (1998–2017), we analyse the temporal trends of body condition in three key stages of the hibernation period: onset and end of hibernation and early activity. Our results indicate that body condition at the onset and end of hibernation have decreased significantly over these 20 years. However, despite this lower body condition, the decrease of mass loss rate in the last decade (although not significant) indicate a greater saving of fat reserves. The significant increase in winter temperatures did not affect body condition or reserve depletion, instead, lower body condition was observed with a higher number of days below 0 °C. Unlike other hibernating bat species, the females had lower fat reserves than males in all three periods considered. This study indicates that hibernation energy requirements could be changing as an adaptation to a warmer climate and that hibernating bats can survive the winter by optimizing their lower accumulation of reserves. [ABSTRACT FROM AUTHOR]

Ribosome hibernation is a key survival strategy bacteria adopt under environmental stress, where a protein, hibernation promotion factor (HPF), transitorily inactivates the ribosome. Mycobacterium tuberculosis encounters hypoxia (low oxygen) as a major stress in the host macrophages, and upregulates the expression of RafH protein, which is crucial for its survival. The RafH, a dual domain HPF, an orthologue of bacterial long HPF (HPFlong), hibernates ribosome in 70S monosome form, whereas in other bacteria, the HPFlong induces 70S ribosome dimerization and hibernates its ribosome in 100S disome form. Here, we report the cryo- EM structure of M. smegmatis, a close homolog of M. tuberculosis, 70S ribosome in complex with the RafH factor at an overall 2.8 Å resolution. The N- terminus domain (NTD) of RafH binds to the decoding center, similarly to HPFlong NTD. In contrast, the C- terminus domain (CTD) of RafH, which is larger than the HPFlong CTD, binds to a distinct site at the platform binding center of the ribosomal small subunit. The two domain-connecting linker regions, which remain mostly disordered in earlier reported HPFlong structures, interact mainly with the anti-Shine Dalgarno sequence of the 16S rRNA. Ribosome hibernation is a key survival strategy bacteria adapt under stress. Here, cryo- EM structure of mycobacterial 70S ribosome with hypoxia stress-induced factor RafH suggests the molecular mechanism of RafH-induced ribosome hibernation. [ABSTRACT FROM AUTHOR]

Torpor and arousal cycles, both daily and seasonal (e.g. hibernation), are crucial for small mammals, including bats, to maintain the energy and water balance. The alternation between torpor and arousal leads to metabolic changes, leaving traceable evidence of metabolic wastes in urine. In this study we investigated urinary creatinine and acetoacetate (a ketone body) in the Eastern bent-wing bat (Miniopterus fuliginosus) in Mungyeong, South Korea. We found an increase in urinary creatinine during torpor in summer, indicating changes in renal water reabsorption rates during the active season. Although we could not confirm ketonuria in hibernating bats due to a methodological limitation caused by the small amount of urine, we verified an increase in urinary creatinine concentration during hibernation. This finding suggests that managing water stress resulting from evaporative water loss is one of key reasons for arousal during hibernation in Eastern bent-wing bats. A study on metabolic markers in urine from Eastern bent-winged bats demonstrates seasonal and individual variations in water-stress that suggest an association between water-stress and winter arousal. [ABSTRACT FROM AUTHOR]

Many studies assume that it is beneficial for individuals of a species to be heavier, or have a higher body condition index (BCI), without accounting for the physiological relevance of variation in the composition of different body tissues. We hypothesized that the relationship between BCI and masses of physiologically important tissues (fat and lean) would be conditional on annual patterns of energy acquisition and expenditure. We studied three species with contrasting ecologies in their respective natural ranges: an obligate hibernator (Columbian ground squirrel, Urocitellus columbianus), a facultative hibernator (black-tailed prairie dog, Cynomys ludovicianus), and a food-caching non-hibernator (North American red squirrel, Tamiasciurus hudsonicus). We measured fat and lean mass in adults of both sexes using quantitative magnetic resonance (QMR). We measured body mass and two measures of skeletal structure (zygomatic width and right hind foot length) to develop sex- and species-specific BCIs, and tested the utility of BCI to predict body composition in each species. Body condition indices were more consistently, and more strongly correlated, with lean mass than fat mass. The indices were most positively correlated with fat when fat was expected to be very high (pre-hibernation prairie dogs). In all cases, however, BCI was never better than body mass alone in predicting fat or lean mass. While the accuracy of BCI in estimating fat varied across the natural histories and annual energetic patterns of the species considered, measuring body mass alone was as effective, or superior in capturing sufficient variation in fat and lean in most cases. [ABSTRACT FROM AUTHOR]

A review summarizing the data, both original and literature, on the development of the urban environment by smaller mammals is presented, the common hamster serving as an example. Initially, having predominantly inhabited the forested steppe zone, this species first essentially became a hemi-agrophile and, along with the development of agriculture, it occupied the margins of fields, this providing it with good food supply throughout the year. Changes in farming culture (fragmentary fields replaced with vast areas of arable land occupied by monocultures and the use of poisons and fertilizers) led to a shift in the ecological optimum of the species to areas occupied by gardens, kitchen gardens, and urban ecosystems. This has provoked changes in the genetic structure of populations, a greater (compared to suburbs) diversity of alleles of the main histocompatibility complex responsible for the resistance to pathogens, a reduced hibernation period up to its complete abandonment, and a decreased aggressiveness to conspecifics which allows for more burrows to be arranged in a limited space and the general storage to be consumed. Using food wastes as additional food resources has appeared possible, and this may have led to changes in the digestive and other systems. All this has allowed the common hamster to exist successfully in urbanized environments, despite the reduction of life expectancy due to a large number of stressors (parasitic load, pollution, etc.). Not all of the above traits are assumed to have been formed in the process of synurbization. Many previously acquired adaptations could have turned out to be effective along with the development of urban areas. Obviously, the way the common hamster has developed from a noncommensal species to an agrophile and a synurbist is not unique, as many other mammalian and bird species have passed or are passing through it at present. [ABSTRACT FROM AUTHOR]

Most of the information on animal circadian activity is based on laboratory data. To obtain information from a natural population, we conducted for the first time an instrumental study of daily activity in yellow ground squirrels, which are large hibernating rodents. Eight individuals were fitted with glued-on radio transmitters that contained accelerometers and light sensors in summer 2021. Our data showed that yellow ground squirrels left their burrows only during daytime; the squirrels rested when they entered their burrows. As hibernation approached, the duration of aboveground activity decreased. In contrast to similar species with two peaks of activity, the aboveground activity of yellow ground squirrels was single-phased. Most likely, prolonged hibernation and, therefore, time deficiency motivated yellow ground squirrels to use daylight hours as effectively as possible. [ABSTRACT FROM AUTHOR]

Hibernation confers resistance to ischemia–reperfusion injury in tissue, but the underlying mechanisms remain unclear. Suppression of mitochondrial respiration during torpor may contribute to this tolerance. To explore this concept, we subjected isolated liver mitochondria from torpid, interbout euthermic (IBE) and summer 13-lined ground squirrels (Ictidomys tridecemlineatus) to 5 min of anoxia, followed by reoxygenation (A/R). We also included rat liver mitochondria as a non-hibernating comparison group. Maximum respiration rates of mitochondria from torpid ground squirrels were not affected by A/R, but in IBE and summer, these rates decreased by 50% following A/R and in rats they decreased by 80%. Comparing net ROS production rates among groups, revealed seasonal differences; mitochondria from IBE and torpor produced 75% less ROS than summer ground squirrels and rats. Measurements of oxidative damage to these mitochondria, both freshly isolated, as well as pre- and post-A/R, demonstrated elevated damage to protein, but not lipids, in all groups. Hibernation likely generates oxidative stress, as freshly isolated mitochondria had greater protein damage in torpor and IBE than in summer and rats. When comparing markers of damage pre- and post-A/R, we found that when RET was active, rat macromolecules were more damaged than when RET is inhibited, but in TLGS markers of damage were similar. This result suggests that suppression of RET during hibernation, both in torpor and IBE, lessens oxidative stress produced during arousal. Taken together our study suggests that ischemia–reperfusion tolerance at the mitochondrial level is associated with metabolically suppressed oxidative phosphorylation during hibernation. [ABSTRACT FROM AUTHOR]

Hibernation is a highly seasonal physiological adaptation that allows brown bears (Ursus arctos) to survive extended periods of low food availability. Similarly, daily or circadian rhythms conserve energy by coordinating body processes to optimally match the environmental light/dark cycle. Brown bears express circadian rhythms in vivo and their cells do in vitro throughout the year, suggesting that these rhythms may play important roles during periods of negative energy balance. Here, we use time-series analysis of RNA sequencing data and timed measurements of ATP production in adipose-derived fibroblasts from active and hibernation seasons under two temperature conditions to confirm that rhythmicity was present. Culture temperature matching that of hibernation body temperature (34 °C) resulted in a delay of daily peak ATP production in comparison with active season body temperatures (37 °C). The timing of peaks of mitochondrial gene transcription was altered as were the amplitudes of transcripts coding for enzymes of the electron transport chain. Additionally, we observed changes in mean expression and timing of key metabolic genes such as SIRT1 and AMPK which are linked to the circadian system and energy balance. The amplitudes of several circadian gene transcripts were also reduced. These results reveal a link between energy conservation and a functioning circadian system in hibernation. [ABSTRACT FROM AUTHOR]

Purpose of Review: We aim to reevaluate how the assessment of myocardial viability can guide optimal treatment strategies for patients with ischemic cardiomyopathy (ICM) based on a more contemporary understanding of the mechanism of benefit of revascularization. Recent Findings: The assessment of viability in left ventricular (LV) segments with diminished contraction has been proposed as key to predict the benefit of revascularization and, therefore, as a requisite for the selection of patients to undergo this form of treatment. However, data from prospective trials have diverged from earlier retrospective studies. Summary: Traditional binary viability assessment may oversimplify ICM's complexity and the nuances of revascularization benefits. A conceptual shift from the traditional paradigm centered on the assessment of viability as a dichotomous variable to a more comprehensive approach encompassing a thorough understanding of ICM's complex pathophysiology and the salutary effect of revascularization in the prevention of myocardial infarction and ventricular arrhythmias is required. [ABSTRACT FROM AUTHOR]

Hibernation enables many species of the mammalian kingdom to overcome periods of harsh environmental conditions. During this physically inactive state metabolic rate and body temperature are drastically downregulated, thereby reducing energy requirements (torpor) also over shorter time periods. Since blood cells reflect the organism´s current condition, it was suggested that transcriptomic alterations in blood cells mirror the torpor-associated physiological state. Transcriptomics on blood cells of torpid and non-torpid Djungarian hamsters and QIAGEN Ingenuity Pathway Analysis (IPA) revealed key target molecules (TMIPA), which were subjected to a comparative literature analysis on transcriptomic alterations during torpor/hibernation in other mammals. Gene expression similarities were identified in 148 TMIPA during torpor nadir among various organs and phylogenetically different mammalian species. Based on TMIPA, IPA network analyses corresponded with described inhibitions of basic cellular mechanisms and immune system-associated processes in torpid mammals. Moreover, protection against damage to the heart, kidney, and liver was deduced from this gene expression pattern in blood cells. This study shows that blood cell transcriptomics can reflect the general physiological state during torpor nadir. Furthermore, the understanding of molecular processes for torpor initiation and organ preservation may have beneficial implications for humans in extremely challenging environments, such as in medical intensive care units and in space. [ABSTRACT FROM AUTHOR]

Hibernation is an adaptive strategy that allows animals to enter a hypometabolic state, conserving energy and enhancing their fitness by surviving harsh environmental conditions. However, addressing the adaptive value of hibernation, at the individual level and in natural populations, has been challenging. Here, we applied a non-invasive technique, body composition analysis by quantitative magnetic resonance (qMR), to calculate energy savings by hibernation in a population of hibernating marsupials (Dromiciops gliroides). Using outdoor enclosures installed in a temperate rainforest, and measuring qMR periodically, we determined the amount of fat and lean mass consumed during a whole hibernation cycle. With this information, we estimated the daily energy expenditure of hibernation (DEEH) at the individual level and related to previous fat accumulation. Using model selection approaches and phenotypic selection analysis, we calculated linear (directional, β), quadratic (stabilizing or disruptive, γ) and correlational (ρ) coefficients for DEEH and fat accumulation. We found significant, negative directional selection for DEEH (βDEEH = − 0.58 ± 0.09), a positive value for fat accumulation (βFAT = 0.34 ± 0.07), and positive correlational selection between both traits (ρDEEH × FAT = 0.24 ± 0.07). Then, individuals maximizing previous fat accumulation and minimizing DEEH were promoted by selection, which is visualized by a bi-variate selection surface estimated by generalized additive models. At the comparative level, results fall within the isometric allometry known for hibernation metabolic rate in mammals. Thus, by a combination of a non-invasive technique for body composition analysis and semi-natural enclosures, we were characterized the heterothermic fitness landscape in a semi-natural population of hibernators. [ABSTRACT FROM AUTHOR]

Changes in the content of heat shock protein 90 (HSP90) in m. soleus (contains mainly fibers expressing the "slow" isoform I MyHC) and m. gastrocnemius (contains mainly fibers expressing the "fast" isoforms II MyHC) of a true hibernant, the long-tailed ground squirrel (Urocitellus undulatus), during different periods of the annual cycle, summer activity (seasonal control), hypothermia/winter torpor, and winter (interbout) activity, were studied. It was found that despite the development of atrophic changes that were more pronounced in the "fast" m. gastrocnemius, the content of HSP90 in both muscles did not change throughout the hibernation period. The role of HSP90 in maintaining the stability of the titin giant sarcomeric protein molecules during the periods of the animal's entry into and exit from hypothermia, when the activity of calpain proteases increased due to the increased content of Ca2+ in the cytosol of muscle cells, as well as during hypothermia, when the activity of calpains most likely was not completely inhibited, was discussed. During the winter/interbout activity, when there was an increased titin turnover in the striated ground squirrel muscles, a constant content of HSP90 was apparently necessary for the correct folding of newly synthesized titin molecules and their embedding into sarcomeres, as well as for the removal of improperly folded and old titin molecules/fragments, as well as other proteins. Thus, HSP90 proteostasis in skeletal muscles of the long-tailed ground squirrel could contribute to maintaining a stable level of titin and, possibly, other sarcomeric proteins during hibernation, which, in turn, would contribute to maintaining a highly ordered sarcomeric structure and the necessary level of contractile muscle activity in different phases of the hibernation–wakefulness cycle. [ABSTRACT FROM AUTHOR]

During the hibernation season, the values for the parameters of the cell cycle of red bone marrow cells in the hibernating ground squirrels Urocitellus undulatus, when they return to an active-like state between periods of torpor and interbout arousal, do not differ from those observed in summer-active animals. In animals that enter a state of torpor, the cumulative percentage of cells in the resting phase (G0 phase) and pre-synthesis phase (G1 phase) increased from 71.8 to 76.0%, the percentage of cells in the synthesis phase (S phase) decreased from 19.3 to 15.3% compared to those animals that return to an active-like state between periods of torpor and interbout arousal. The cumulative percentage of cells in the post DNA synthesis phase (G2 phase) and mitosis (M) does not change, but (G2 + M)/S ratio increases. When animals enter a state of torpor, changes in parameter values are observed when the animal's body temperature drops below 25°C; this effect refers to a system whose thermal relaxation time is a nonmonotonic function of the initial temperature. The activity of the key enzyme of polyamine synthesis ornithine decarboxylase, a marker of cell activation and proliferation during interbout arousal does not significantly differ from that observed in summer-active animals; the enzymatic activity decreases sharply, when animals decrease their body temperature below 25°C and enter the state of torpor, and this activity remains at a low level during hibernation and arousal until body temperature reaches 30°C. The role of changes in the parameter values associated with proliferative activity in adaptation of hematopoietic tissue during hibernation of the Yakutian ground squirrel is discussed. [ABSTRACT FROM AUTHOR]

Previously, it has been shown that a series of physiological and biochemical changes occur in Yakutian long-tailed ground squirrels during autumn (the pre-hibernation period), involving the brain, heart, skeletal muscles, and other organs. This study was conducted to analyze the composition of peripheral blood cells obtained from Yakutian ground squirrels in autumn. For the first time, an increase in the total number of leukocytes, particularly granulocytes, and a decrease in the number of lymphocytes were observed when compared with samples obtained in summer; a leukogram shift from the lymphocytic to the granulocytic fraction was revealed. Significant increase in platelet counts and thrombocrit with preservation of the percentage ratio of mature and young cell fractions was shown. To date, information on the cellular components of blood during the autumn season when hibernators prepare for winter months of hibernation remains scarce. Nonetheless, the results of our study indicate that very significant adaptive changes occur in leukocytes and platelets of ground squirrels in this period. Possible causes of these changes are discussed. [ABSTRACT FROM AUTHOR]

The hazel dormouse is predominantly an arboreal species that moves down to the ground to hibernate in the autumn in temperate parts of its distributional ranges at locations not yet well understood. The main objective of this study is to test whether environmental characteristics surrounding hazel dormouse hibernacula can be identified using high-resolution remote sensing and data collected in situ. To achieve this, remotely sensed variables, including canopy height and cover, topographic slope, sky view, solar radiation and cold air drainage, were modelled around 83 dormouse hibernacula in England (n = 62) and the Netherlands (n = 21), and environmental characteristics that may be favoured by pre-hibernating dormice were identified. Data on leaf litter depth, temperature, canopy cover and distance to the nearest tree were collected in situ and analysed at hibernaculum locations in England. The findings indicated that remotely sensed data were effective in identifying attributes surrounding the locations of dormouse hibernacula and when compared to in situ information, provided more conclusive results. This study suggests that remotely sensed topographic slope, canopy height and sky view have an influence on hazel dormice choosing suitable locations to hibernate; whilst in situ data suggested that average daily mean temperature at the hibernaculum may also have an effect. Remote sensing proved capable of identifying localised environmental characteristics in the wider landscape that may be important for hibernating dormice. This study proposes that this method can provide a novel progression from habitat modelling to conservation management for the hazel dormouse, as well as other species using habitats where topography and vegetation structure influence fine-resolution favourability. [ABSTRACT FROM AUTHOR]

Histological and cytological changes in the liver and small intestine tissues of Spermophilus citellus (S. citellus) during and post-hibernation were examined. Microphotographs were taken under the light and electron microscope for this purpose. During hibernation, it was determined that the number of Kupffer cells in the liver increased, and the areas of PAS-negative staining increased. In the small intestine, it was determined that the length of the villi was shortened and the surface area was reduced, and there was a decrease in the crypt depth. In post-hibernation, a decrease in the number of Kupffer cells and an increase in PAS-positive areas were observed in the liver. In post-hibernation, in the small intestine, an increase in villus lengths, villus surface area, and crypt depth was determined. An independent samples t-test was performed to analyze the data obtained about the small intestine. The results will reference studies on the liver and digestive tract. [ABSTRACT FROM AUTHOR]

Torpor is used in small sized birds and mammals as an energy conservation trait. Considerable effort has been put towards elucidating the mechanisms underlying its entry and maintenance, but little attention has been paid regarding the exit. Firstly, we demonstrate that the arousal phase has a stereotyped dynamic: there is a sharp increase in metabolic rate followed by an increase in body temperature and, then, a damped oscillation in body temperature and metabolism. Moreover, the metabolic peak is around two-fold greater than the corresponding euthermic resting metabolic rate. We then hypothesized that either time or energy could be crucial variables to this event and constructed a model from a collection of first principles of physiology, control engineering and thermodynamics. From the model, we show that the stereotyped pattern of the arousal is a solution to save both time and energy. We extended the analysis to the scaling of the use of torpor by endotherms and show that variables related to the control system of body temperature emerge as relevant to the arousal dynamics. In this sense, the stereotyped dynamics of the arousal phase necessitates a certain profile of these variables which is not maintained as body size increases. [ABSTRACT FROM AUTHOR]

Hibernating amphibians are suitable for the research on the adaptation of gut microbiota to long-term fasting and cold stresses. However, the previous studies mainly focus on the large or whole gut microbiota but not the small gut microbiota. To test the structural discrepancy between the small and large gut microbiota during hibernation, we performed two independent batches of 16S rRNA gene amplicon sequencing to profile the small and large gut microbiota of hibernating Asiatic toad (Bufo gargarizans) from two wild populations. Both batches of data revealed that Proteobacteria, Bacteroidetes, and Firmicutes were the three most dominant phyla in the small and large gut microbiota. Three core OTUs with 100% occurrence in all gut microbiotas were annotated as Pseudomonas. A significant structural discrepancy was detected between the small and large gut microbiota. For instance, Proteobacteria assembled in the small intestine with a higher proportion than it did in the large intestine, but Bacteroidetes and Firmicutes assembled in the large intestine with a higher proportion than they did in the small intestine. The large gut microbiota exhibited higher diversity than the small gut microbiota. Nevertheless, a severe batch effect existed in the structural analysis of the gut microbiotas. The large gut microbiota showed a better resistance to the batch effect than the small gut microbiota did. This study provides preliminary evidence that microbes assemble in the small and large intestines of amphibians with discrepant patterns during hibernation. [ABSTRACT FROM AUTHOR]

The state of hibernation is characterized by an increased tolerance to long-term deep hypothermia, hypoxia, lack of food and water. At the same time, even a short-term reorganization of the adaptive mechanisms at low temperatures causes significant metabolic changes in animals, reflected in the amino acid profile. Metabolic changes in myocardial free amino acids during hibernation have not actually been studied, although the knowledge of these processes is important for deeper insight into the mechanisms of hibernation, relevant for clinical medicine. The aim of this work was to study the changes in the composition of myocardial free amino acids in a ground squirrel Urocitellus undulatus at different stages of hibernation. A negative interdependence of glutamic acid and alanine pools was revealed at different stages of torpor. The level of glutamic acid, as compared to the summer control (5.08 ± 0.44 µmol/g of wet weight), began to decline in the first (December) torpor bout, continued throughout prolonged torpor (down to 1.57 ± 0.14 µmol/g), and was accompanied by an increase in the alanine pool. During winter arousal, the glutamic acid pool rose above the summer level, while the alanine pool fell below that, with their total level remaining unchanged. Aspartic acid and glycine pools declined in parallel with the decrease in glutamate and aspartate pools, however, during winter arousal, glycine was not detected whatsoever. Given the involvement of glutamic acid and aspartate in anaplerotic reactions of the tricarboxylic acid (TCA) cycle and the reciprocal relationship of glutamic acid and alanine, it is concluded that the changes in the level of these metabolites at different stages of hibernation bouts reflect a gradual transition from aerobic (TCA cycle and oxidative phosphorylation) to anaerobic glycolysis, and vice versa during euthermia. [ABSTRACT FROM AUTHOR]

Armadillos are considered important reservoir hosts for Trypanosoma cruzi, the causative agent of Chagas disease. The first report of T. cruzi infection in pichis (Zaedyus pichiy), a small armadillo species endemic to central Argentina and Chile, dates back to 1935. However, more recent reports on T. cruzi in this species are scarce. The objective of this study was to assess T. cruzi infection and parasite load in Z. pichiy from Mendoza Province, an area endemic to human Chagas disease. Blood samples were obtained in 2014–2016 from pichis from Lavalle (low Monte), Malargüe (Patagonian steppe), and San Carlos (ecotone) departments, Mendoza Province, Argentina. The detection and quantification of T. cruzi was performed through qPCR amplification using satellite primers. Of the 265 analyzed samples, 201 (76%) were positive for T. cruzi. Parasite loads varied between < 0.1–55.8 parasite-equivalents/mL (par-eq/mL), with a median of 1.1 par-eq/mL in quantifiable samples. The prevalence was similar in Malargüe and Lavalle (85–94%), but significantly lower in pichis from San Carlos (50%). Animals from Lavalle captured after hibernation had significantly higher parasite loads (median 2.0 par-eq/mL). In Malargüe, T. cruzi infection and parasite loads were significantly lower before than after hibernation in 2016. The high prevalence and low median parasite load suggest a chronic and persistent infection of T. cruzi in pichis. Regional differences and a marked increase in precipitation during 2015–2016 could have influenced annual and seasonal infection rates of this vector-borne disease. [ABSTRACT FROM AUTHOR]

Mammalian and avian torpor is highly effective in reducing energy expenditure. However, the extent of energy savings achieved and thus long-term survival appear to differ between species capable of multiday hibernation and species restricted to daily heterothermy, which could, however, be due to thermal effects. We tested how long-term survival on stored body fat (i.e. time to lean body mass), crucial for overcoming adverse periods, is related to the pattern of torpor expressed under different ambient temperatures (Ta: 7 °C typical of hibernation, 15 and 22 °C typical of daily torpor) in the small marsupial hibernator the pygmy-possum (Cercartetus nanus). Possums expressed torpor at all Tas and survived without food for 310 days on average at Ta 7 °C, 195 days at Ta 15 °C, and 127 days at Ta 22 °C. At Ta 7 and 15 °C, torpor bout duration (TBD) increased from < 1–3 to ~ 5–16 days over 2 months, whereas at Ta 22 °C, TBD remained at < 1 to ~ 2 days. At all Tas daily energy use was substantially lower and TBD and survival times of possums much longer (3–12 months) than in daily heterotherms (~ 10 days). Such pronounced differences in torpor patterns and survival times even under similar thermal conditions provide strong support for the concept that torpor in hibernators and daily heterotherms are physiologically distinct and have evolved for different ecological purposes. [ABSTRACT FROM AUTHOR]

Loss of bone mass can occur in mammals after prolonged disuse but the situation for hibernators that are in a state of torpor for many months of the year is not yet fully understood. The present study assesses the bone remodeling mechanisms present in Daurian ground squirrels (Spermophilus dauricus) during hibernation as compared with a model of hindlimb disuse. Differences in microstructure, mechanical properties, bone remodeling-related proteins (Runx2, OCN, ALP, RANKL, CTK and MMP-9) and key proteins of Wnt/β-catenin signaling pathway (GSK-3β and phospho-β-catenin) were evaluated in ground squirrels under 3 conditions: summer active (SA) vs. hibernation (HIB) vs. hindlimb unloaded (HLU). The results indicated that the body weight in HLU ground squirrels was lower than the SA group, and the middle tibia diameter in the HLU group was lower than that in SA and HIB groups. The thickness of cortical and trabecular bone in femurs from HLU ground squirrels was lower than in SA and HIB groups. Most parameters of the tibia in the HLU group were lower than those in SA and HIB groups, which indicated cortical bone loss in ground squirrels. Moreover, our data showed that the changes in microscopic parameters in the femur were more obvious than those in the tibia in HLU and HIB ground squirrels. The levels of Runx2 and ALP were lower in HLU ground squirrels than SA and HIB groups. The protein levels of OCN were unchanged in the three groups, but the protein levels of ALP were lower in the HLU group than in SA and HIB groups. RANKL, CTK and MMP-9 protein levels were significantly decreased in tibia of HLU ground squirrels as compared with SA and HIB groups. In addition, the protein expression levels of RANKL, CTK and MMP-9 showed no statistical difference between SA and HIB ground squirrels. Thus, the mechanisms involved in the balance between bone formation and resorption in hibernating and hindlimb unloading ground squirrels may be different. The present study showed that in femur, the Wnt signaling pathway was inhibited, the protein level of GSK-3β was increased, and the protein expression of phospho-β-catenin was decreased in the HIB group as compared with the SA group, which indicates that the Wnt signaling pathway has a great influence on the femur of the HIB group. In conclusion, the natural anti-osteoporosis properties of Daurian ground squirrels are seasonal. The squirrels do not experience bone loss when they are inactive for a long time during hibernation, but the mechanisms of anti-osteoporosis did not work in HLU summer active squirrels. [ABSTRACT FROM AUTHOR]

Although gut seasonal plasticity has been extensively reported, studies on physiological flexibility, such as water-salt transportation and motility in reptiles, are limited. Therefore, this study investigated the intestinal histology and gene expression involved in water-salt transport (AQP1, AQP3, NCC, and NKCC2) and motility regulation (nNOS, CHRM2, and ADRB2) in desert-dwelling Eremias multiocellata during winter (hibernating period) and summer (active period). The results showed that mucosal thickness, the villus width and height, the enterocyte height of the small intestine, and the mucosal and submucosal thicknesses of the large intestine were greater in winter than in summer. However, submucosal thickness of the small intestine and muscularis thickness of the large intestine were lower in winter than in summer. Furthermore, AQP1, AQP3, NCC, nNOS, CHRM2, and ADRB2 expressions in the small intestine were higher in winter than in summer; AQP1, AQP3, and nNOS expressions in the large intestine were lower in winter than in summer, with the upregulation of NCC and CHRM2 expressions; no significant seasonal differences were found in intestinal NKCC2 expression. These results suggest that (i) intestinal water-salt transport activity is flexible during seasonal changes where AQP1, AQP3 and NCC play a vital role, (ii) the intestinal motilities are attenuated through the concerted regulation of nNOS, CHRM2, and ADRB2, and (iii) the physiological flexibility of the small and large intestine may be discrepant due to their functional differences. This study reveals the intestinal regulation and adaptation mechanisms in E. multiocellata in response to the hibernation season. [ABSTRACT FROM AUTHOR]

Primate encounter rates often vary throughout the year due to seasonal differences in activity, ecology, and behaviour. One notably extreme behaviour is continuous hibernation. Although a rare adaptation in primates, the dwarf lemurs of Madagascar (genus Cheirogaleus) enter obligate hibernation each year during the dry season, after spending the wet season consuming high-energy foods. Whilst seasonal changes in activity in some Cheirogaleus populations are well-known, many species remain little-studied, and there is no specific information on their encounter rates, nor when they enter and emerge from hibernation. This uncertainty critically affects reliable calculation of population density estimates for these highly threatened lemurs. In this study, we assessed how encounter rates of the fat-tailed dwarf lemur (C. medius) vary seasonally in the transitional forests of the Sahamalaza-Iles Radama National Park, northwest Madagascar, during a 4-year period. We established a system of line transects (N = 60) throughout our study area, on which we conducted distance sampling of C. medius. We then used our distance sampling data to calculate encounter rate and population density data. We found encounter rates of C. medius to be significantly higher during the wet season compared with the dry season. Furthermore, encounter rates of C. medius were particularly low from May–August. These results provide some evidence to suggest the time period that C. medius hibernate in Sahamalaza-Iles Radama National Park. These findings underpin the importance of careful study design when surveying threatened species with seasonal differences in activity, such as those that hibernate. This study also demonstrates the importance of species-specific behavioural data for accurate population density assessment, which is required to inform conservation action. [ABSTRACT FROM AUTHOR]

Snake fungal disease, caused by Ophidiomyces ophidiicola, is recognized as a potential concern for North American snakes. We tested skin swabs from Northern Pine Snakes (Pituophis melanoleucus melanoleucus) in the New Jersey pinelands for the presence of O. ophidiicola before emergence from hibernation. We used qPCR to test the collected swabs for the presence of O. ophidiicola, then determined pathogen prevalence as a function of sampling year, sampling location (skin lesion, healthy ventral skin, healthy head skin) sex, and age. There were no temporal trends in O. ophidiicola detection percentages on snakes, which varied from 58 to 83% in different years. Ophidiomyces ophidiicola detection on snakes was highest in swabs of skin lesions (71%) and lowest in head swabs (29%). Males had higher prevalence than females (82% versus 62%). The fungus was not detected in hatchling snakes (age 0) in the fall, but 75% of juveniles tested positive at the end of hibernation (age 1 year). We also screened hibernacula soil samples for the presence of O. ophidiicola. Where snakes hibernated, 69% of soil samples were positive for O. ophidiicola, and 85% of snakes lying on positive soil samples also tested positive for the pathogen. Although a high proportion of snakes (73%) tested positive for O. ophidiicola during our 4-year study, the snakes appeared healthy except for small skin lesions. We conclude that O. ophidiicola prevalence is high on hibernating Northern Pine Snakes and in the hibernacula soil, with a strong association between snakes and positive adjacent soil. This is the first demonstration that snakes likely become infected during hibernation. [ABSTRACT FROM AUTHOR]

Hibernating mammals are able to reduce their body temperature almost to 0°C. During this process, their heart is highly resistant to arrythmogenesis caused by temperature reduction. In this work, we studied for the first time potassium currents and their dynamics during hibernation in the myocardium of a hibernating mammal, long-tailed ground squirrel Citellus undulates. Using patch clamp technique, we studied the transient outward potassium current Ito and background inward rectifier current IK1 in isolated ventricular and atrial myocytes of summer (active) and winter (hibernating) ground squirrels. It was found that at room temperature and positive holding potentials, the peak amplitude of Ito in cardiomyocytes of hibernating animals was lower than in their active conspecifics. Ito downregulation during hibernation was more pronounced in the ventricular myocardium than in the atrial. The background IK1 in the ventricular myocardium of winter animals increased during adaptation to hibernation. In the atrial myocardium, no statistically significant intergroup differences in IK1 were revealed. We also recorded action potentials in isolated ventricular cardiomyocytes. The duration of action potentials at 50% and 90% repolarization levels was indistinguishable between the groups, nor were detected any significant differences in the action potential maximum upstroke velocity and the level of resting membrane potential. Taken together, the revealed differences in the amplitude of Ito and IK1 between active and hibernating ground squirrels may promote the increase of the refractory period duration and contribute to maintaining of the resting membrane potential level at low temperatures. [ABSTRACT FROM AUTHOR]

The cranial and mandibular remains of a large serotine bat Eptesicus praeglacialis Kormos, 1930 are described from the Lower Pleistocene deposits of the Taurida cave in the central Crimea. This is the first finding of the skull material of E. praeglacialis and the first record of the species in Crimea. Judging by the tooth wear stages, the remains of both young and adult specimens are present in the taphocenosis. The small mammal tooth marks on the bones (caused by eating the remnants of soft tissues) in the absence of signs of digestion, characterizing materials from the predatory bird pellets, indicate that the taphocenosis includes the remains of E. praeglacialis individuals that used the cave as a shelter and died there. This corresponds to the idea of appearance of hibernation in caves as a climatically determined ecological adaptation in some European forest-dwelling bats (including Eptesicus) at the Pliocene–Pleistocene transition. [ABSTRACT FROM AUTHOR]

NADP-dependent isocitrate dehydrogenase (NADP-IDH, EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate with the concomitant production of NADPH. NADPH plays important roles in many biosynthesis pathways, maintenance of proper oxidation–reduction balance, and protection against oxidative damage. This present study investigated the dynamic nature of NADP-IDH during hibernation by purifying it from the skeletal muscle of Richardson's ground squirrel (Urocitellus richardsonii) and analyzing its structural and functional changes in response to hibernation. Kinetic parameters of purified NADP-IDH from euthermic and hibernating ground squirrel skeletal muscle were characterized at 22 °C and 5 °C. Relative to euthermic muscle, -NADP-IDH in hibernating muscle had a higher affinity for its substrate, isocitrate at 22 °C, whereas at 5 °C, there was a significant decrease in isocitrate affinity. Western blot analysis revealed greater serine and threonine phosphorylation in hibernator NADP-IDH as compared to euthermic NADP-IDH. In addition, Bioinformatic analysis predicted the presence of 18 threonine and 21 serine phosphorylation sites on squirrel NADP-IDH. The structural and functional changes in NADP-IDH indicate the ability of the organism to reduce energy consumption during hibernation, while emphasizing increased NADPH production, and thus antioxidant activity, during torpor arousal cycles. [ABSTRACT FROM AUTHOR]

Introduction: The steep population decline of the emblematic monarch butterfly is caused mainly by the reduction of food sources for caterpillars and adults, as well as disturbance in its overwintering forests. Although feeding at the overwintering sites in Mexico has long been considered unimportant, observations show that butterflies feed inside and outside of their forests on sunny days. Nectaring close to the hibernation colonies may be relevant for their conservation, as their reserves decline faster in disturbed forests. However, there are no systematic studies on nectar sources in the Monarch Butterfly Biosphere Reserve, Michoacán, Mexico. Aims: In this study, we identified and quantified the main plant species visited by butterflies for nectaring in the Reserve. Methods: We collected systematic observational data on the flora and butterfly visits in three sanctuaries, around colonies formed between February and March of the 2019–2020 season. Results: Butterflies fed on 29 plant species from 10 families. Most had white, yellow or blue flowers, were somewhat synanthropic and had their main flowering season in winter. The most visited species were Salvia mexicana and S. plurispicata, which were also the most abundant. By individual plant, Prunus serotina, Crataegus mexicana, Buddleja sessiliflora, Verbesina oncophora and Roldana albonervia were the most visited. Discussion/Implications for insect conservation: The results point to possible interventions in support of the butterflies. The visited species are generally easy to encourage or cultivate and could be promoted in the surrounding agricultural areas. [ABSTRACT FROM AUTHOR]