1
|
De Napoli C, Schmidt L, Montesel M, Cussonneau L, Sanniti S, Marcucci L, Germinario E, Kindberg J, Evans AL, Gauquelin-Koch G, Narici M, Bertile F, Lefai E, Krüger M, Nogara L, Blaauw B. Reduced ATP turnover during hibernation in relaxed skeletal muscle. Nat Commun 2025; 16:80. [PMID: 39747078 DOI: 10.1038/s41467-024-55565-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 12/13/2024] [Indexed: 01/04/2025] Open
Abstract
Hibernating brown bears, due to a drastic reduction in metabolic rate, show only moderate muscle wasting. Here, we evaluate if ATPase activity of resting skeletal muscle myosin can contribute to this energy sparing. By analyzing single muscle fibers taken from the same bears, either during hibernation or in summer, we find that fibers from hibernating bears have a mild decline in force production and a significant reduction in ATPase activity. Single fiber proteomics, western blotting, and immunohistochemical analyses reveal major remodeling of the mitochondrial proteome during hibernation. Furthermore, using bioinformatical approaches and western blotting we find that phosphorylated myosin light chain, a known stimulator of basal myosin ATPase activity, is decreased in hibernating and disused muscles. These results suggest that skeletal muscle limits energy loss by reducing myosin ATPase activity, indicating a possible role for myosin ATPase activity modulation in multiple muscle wasting conditions.
Collapse
|
2
|
Elfeky M, Tsubota A, Shimozuru M, Tsubota T, Kimura K, Okamatsu-Ogura Y. Regulation of mitochondrial metabolism by hibernating bear serum: Insights into seasonal metabolic adaptations. Biochem Biophys Res Commun 2024; 736:150510. [PMID: 39121671 DOI: 10.1016/j.bbrc.2024.150510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 08/01/2024] [Accepted: 08/05/2024] [Indexed: 08/12/2024]
Abstract
Hibernating animals undergo a unique and reversible decrease in their whole-body metabolism, which is often accompanied by a suppression of mitochondrial respiration. However, the precise mechanisms underlying these seasonal shifts in mitochondrial metabolism remain unclear. In this study, the effect of the serum from active and hibernating Japanese black bears on mitochondrial respiration was assessed. Stromal-vascular cells were obtained from bear white adipose tissue and cultured with or without an adipocyte differentiation cocktail. When the oxygen consumption was measured in the presence of bear serum, the hibernating bear serum reduced maximal respiration by 15.5 % (p < 0.05) and spare respiratory capacity by 46.0 % (p < 0.01) in the differentiated adipocytes in comparison to the active bear serum. Similar reductions of 23.4 % (p = 0.06) and 40.6 % (p < 0.05) respectively were observed in undifferentiated cells, indicating the effect is cell type-independent. Blue native PAGE analysis revealed that hibernating bear serum suppressed cellular metabolism independently of the assembly of mitochondrial respiratory chain complexes. RNA-seq analysis identified 1094 differentially expressed genes (fold change>1.5, FDR<0.05) related to insulin signaling and glucose metabolism pathways. These findings suggest that the rapid alterations in mitochondrial metabolism during hibernation are likely induced by a combination of reduced insulin signaling and suppressed mitochondrial function, rather than changes in respiratory complex assembly.
Collapse
|
3
|
Silva Rubio C, Kim AB, Milsom WK, Pamenter ME, Smith GR, van Breukelen F. Common tenrecs (Tenrec ecaudatus) reduce oxygen consumption in hypoxia and in hypercapnia without concordant changes to body temperature or heart rate. J Comp Physiol B 2024; 194:869-885. [PMID: 39373763 DOI: 10.1007/s00360-024-01587-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 08/24/2024] [Accepted: 09/05/2024] [Indexed: 10/08/2024]
Abstract
Common tenrecs (Tenrec ecaudatus) are fossorial mammals that use burrows during both active and hibernating seasons in Madagascar and its neighboring islands. Prevailing thought was that tenrecs hibernate for 8-9 months individually, but 13 tenrecs were removed from the same sealed burrow 1 m deep from the surface. Such group hibernation in sealed burrows presumably creates a hypoxic and/or hypercapnic environment and suggests that this placental mammal may have an increased tolerance to hypoxia and hypercapnia. Higher tolerances to hypoxia and hypercapnia have been documented for other mammals capable of hibernation and to determine if this is the case for tenrecs, we exposed them to acute hypoxia (4 h of 16 or 7% O2), progressive hypoxia (2 h of 16, 10 and 4% O2), or progressive hypercapnia (2 h of 2, 5 and 10% CO2) at cold (16 °C) or warm (28 °C) ambient temperatures (Ta). Oxygen equilibrium curves were also constructed on the whole blood of tenrecs at 10, 25, and 37 °C to determine if hemoglobin (Hb)-O2 affinity contributes to hypoxia tolerance. In animals held at 16 °C, normoxic and normocapnic levels of oxygen consumption rate (V ˙ O 2 ), body temperature (Tb), and heart rate (HR) were highly variable between individuals. This inter-individual variation was greatly reduced in animals held at 28 °C for oxygen consumption rate and body temperature. Both hypoxia (acute and progressive) and progressive hypercapnia led to decreases inV ˙ O 2 as well as the variation inV ˙ O 2 between animals held at 16 °C. The fall in oxygen consumption rate in 7% O2 independent of changes in body temperature in tenrecs held at 16 °C is unique and not consistent with the typical hypoxic metabolic response seen in other hibernating species that depends on concomitant falls in Tb. In animals held at 28 °C, exposure to O2 levels as low as 4% and CO2 levels as high as 10% had no significant effect onV ˙ O 2 , HR, or Tb, indicative of high tolerance to both hypoxia and hypercapnia. High variation in heart rate remained between individuals in all gas compositions and at all temperatures. Tenrec Hb-O2 affinity was similar to other homeothermic placental mammals and likely does not contribute to the increased hypoxia tolerance. Ultimately, our results suggest changes in Ta dictate physiological responses to hypoxia or hypercapnia in tenrecs, responses more characteristic of reptiles than of most placental mammals. Given that numerous anatomical and physiological characteristics of tenrecs suggest that they may be representative of an ancestral placental mammal, our findings suggest the typical hypoxic metabolic response evolved later in mammalian evolution.
Collapse
|
4
|
Sadowska J, Carlson KM, Buck CL, Lee TN, Duddleston KN. Microbial urea-nitrogen recycling in arctic ground squirrels: the effect of ambient temperature of hibernation. J Comp Physiol B 2024; 194:909-924. [PMID: 39237834 PMCID: PMC11511772 DOI: 10.1007/s00360-024-01579-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 07/14/2024] [Accepted: 08/13/2024] [Indexed: 09/07/2024]
Abstract
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.
Collapse
|
5
|
Hao Z, Han Y, Zhao Q, Zhu M, Liu X, Yang Y, An N, He D, Lefai E, Storey KB, Chang H, Xie M. Involvement of Melatonin, Oxidative Stress, and Inflammation in the Protective Mechanism of the Carotid Artery over the Torpor-Arousal Cycle of Ground Squirrels. Int J Mol Sci 2024; 25:12888. [PMID: 39684599 DOI: 10.3390/ijms252312888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2024] [Revised: 11/19/2024] [Accepted: 11/20/2024] [Indexed: 12/18/2024] Open
Abstract
Hibernating mammals experience severe hemodynamic changes over the torpor-arousal cycle, with oxygen consumption reaching peaks during the early stage of torpor to re-enter arousal. Melatonin (MT) can improve mitochondrial function and reduce oxidative stress and inflammation. However, the regulatory mechanisms of MT action on the vascular protective function of hibernators are still unclear. Morphology, hemodynamic, mitochondrial oxidative stress, and inflammatory factors of the carotid artery were assessed in ground squirrels who were sampled during summer active (SA), late torpor (LT), and interbout arousal (IBA) conditions. Changes were assessed by methods including hematoxylin and eosin staining, color Doppler ultrasound, ELISA, Western blots, and qPCR. Changes in arterial blood and serum melatonin were also measured by blood gas analyzer and ELISA, whereas mitochondrial oxidative stress and inflammation factors of primary vascular smooth muscle cells (VSMCs) were assessed by qPCR. (1) Intima-media carotid thickness, peak systolic velocity (PSV), end diastolic blood flow velocity (EDV), maximal blood flow rate (Vmax) and pulsatility index (PI) were significantly decreased in the LT group as compared with the SA group, whereas there were no difference between the SA and IBA groups. (2) PO2, oxygen saturation, hematocrit and PCO2 in the arterial blood were significantly increased, and pH was significantly decreased in the LT group as compared with the SA and IBA groups. (3) The serum melatonin concentration was significantly increased in the LT group as compared with the SA and IBA groups. (4) MT treatment significantly reduced the elevated levels of LONP1, NF-κB, NLRP3 and IL-6 mRNA expression of VSMCs under hypoxic conditions. (5) Protein expression of HSP60 and LONP1 in the carotid artery were significantly reduced in the LT and IBA groups as compared with the SA group. (6) The proinflammatory factors IL-1β, IL-6, and TNF-α were reduced in the carotid artery of the LT group as compared with the SA and IBA groups. The carotid artery experiences no oxidative stress or inflammatory response during the torpor-arousal cycle. In addition, melatonin accumulates during torpor and alleviates oxidative stress and inflammatory responses caused by hypoxia in vitro in VSMCs from ground squirrels.
Collapse
|
6
|
Jin F, You Y, Wan J, Zhu H, Peng K, Hu Z, Zeng Q, Hu B, Wang J, Duan J, Hong Y. Analysis of Lipid Metabolism in Adipose Tissue and Liver of Chinese Soft-Shelled Turtle Pelodiscus sinensis During Hibernation. Int J Mol Sci 2024; 25:12124. [PMID: 39596192 PMCID: PMC11595087 DOI: 10.3390/ijms252212124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2024] [Revised: 11/05/2024] [Accepted: 11/07/2024] [Indexed: 11/28/2024] Open
Abstract
Hibernation serves as an energy-conserving strategy that enables animals to withstand harsh environments by reducing their metabolic rate significantly. However, the mechanisms underlying energy adaptation in hibernating ectotherms, such as Pelodiscus sinensis, remain contentious. This paper first reports the decrease in lipid levels and the expression of metabolism-related genes in P. sinensis during hibernation. The results of physiological and biochemical analysis showed that adipocyte cell size was reduced and liver lipid droplet (LD) contents were decreased during hibernation in P. sinensis. Concurrently, serum levels of triglycerides (TGs), total cholesterol (TC), non-esterified fatty acids (NEFAs), high-density lipoprotein cholesterol (HDLC), and low-density lipoprotein cholesterol (LDLC) were diminished (n = 8, p < 0.01), while an increase in serum glucose (Glu) (n = 8, p < 0.01) was noted among hibernating P. sinensis. These observations suggest a shift in energy metabolism during hibernation. To gain insights into the molecular mechanisms, we performed integrated transcriptomic and lipidomic analyses of adipose tissue and livers from summer-active versus overwintering P. sinensis, which revealed downregulation of free fatty acids (FFAs), triglycerides (TGs), diglycerides (DGs), and ceramides (Cers) during hibernation. The results of GSEA analysis showed that metabolic pathways associated with lipid metabolism, including glycerolipid metabolism and regulation of lipolysis in adipocytes, were suppressed significantly. Notably, acute cold exposure induced significant downregulation of genes related to lipolysis such as PNPLA2, ABHD5, LPL, CPT1A, and PPARα. The results indicate that lipolysis is suppressed during hibernation in P. sinensis. Collectively, these findings deepen our understanding of survival mechanisms and elucidate the unique energy adaptation strategies employed by hibernating ectotherms. Future research should explore the implications of these findings for the conservation of ectotherms and the applications for artificially inducing hibernation.
Collapse
|
7
|
Saunders SE, Santin JM. Hibernation reduces GABA signaling in the brainstem to enhance motor activity of breathing at cool temperatures. BMC Biol 2024; 22:251. [PMID: 39497096 PMCID: PMC11533357 DOI: 10.1186/s12915-024-02050-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Accepted: 10/17/2024] [Indexed: 11/06/2024] Open
Abstract
BACKGROUND Neural circuits produce reliable activity patterns despite disturbances in the environment. For this to occur, neurons elicit synaptic plasticity during perturbations. However, recent work suggests that plasticity not only regulates circuit activity during disturbances, but these modifications may also linger to stabilize circuits during future perturbations. The implementation of such a regulation scheme for real-life environmental challenges of animals remains unclear. Amphibians provide insight into this problem in a rather extreme way, as circuits that generate breathing are inactive for several months during underwater hibernation and use compensatory plasticity to promote ventilation upon emergence. RESULTS Using ex vivo brainstem preparations and electrophysiology, we find that hibernation in American bullfrogs reduces GABAA receptor (GABAAR) inhibition in respiratory rhythm generating circuits and motor neurons, consistent with a compensatory response to chronic inactivity. Although GABAARs are normally critical for breathing, baseline network output at warm temperatures was not affected. However, when assessed across a range of temperatures, hibernators with reduced GABAAR signaling had greater activity at cooler temperatures, enhancing respiratory motor output under conditions that otherwise strongly depress breathing. CONCLUSIONS Hibernation reduces GABAAR signaling to promote robust respiratory output only at cooler temperatures. Although frogs do not ventilate lungs during underwater hibernation, we suggest this would be beneficial for stabilizing breathing when the animal passes through a large temperature range during emergence in the spring. More broadly, these results demonstrate that compensatory synaptic plasticity can increase the operating range of circuits in harsh environments, thereby promoting adaptive behavior in conditions that suppress activity.
Collapse
|
8
|
Amaral-Silva L, Santin J. Neural Processing without O 2 and Glucose Delivery: Lessons from the Pond to the Clinic. Physiology (Bethesda) 2024; 39:0. [PMID: 38624246 PMCID: PMC11573265 DOI: 10.1152/physiol.00030.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 04/12/2024] [Accepted: 04/12/2024] [Indexed: 04/17/2024] Open
Abstract
Neuronal activity requires a large amount of ATP, leading to a rapid collapse of brain function when aerobic respiration fails. Here, we summarize how rhythmic motor circuits in the brain stem of adult frogs, which normally have high metabolic demands, transform to produce proper output during severe hypoxia associated with emergence from hibernation. We suggest that general principles underlying plasticity in brain bioenergetics may be uncovered by studying nonmammalian models that face extreme environments, yielding new insights to combat neurological disorders involving dysfunctional energy metabolism.
Collapse
|
9
|
Zhang J, Wang H, Yang H, Kong Y, Xu S, Dang K, Jiang S, Gao Y. IGF-1 and myostatin-mediated co-regulation in skeletal muscle and bone of Daurian ground squirrels (Spermophilus dauricus) during different hibernation stages. Comp Biochem Physiol A Mol Integr Physiol 2024; 297:111716. [PMID: 39097140 DOI: 10.1016/j.cbpa.2024.111716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 06/28/2024] [Accepted: 07/29/2024] [Indexed: 08/05/2024]
Abstract
Muscle and bone are cooperatively preserved in Daurian ground squirrels (Spermophilus dauricus) during hibernation. As such, we hypothesized that IGF-1 and myostatin may contribute to musculoskeletal maintenance during this period. Thus, we systematically assessed changes in the protein expression levels of IGF-1 and myostatin, as well as their corresponding downstream targets, in the vastus medialis (VM) muscle and femur in Daurian ground squirrels during different stages. Group differences were determined using one-way analysis of variance (ANOVA). Results indicated that the co-localization levels of IGF-1 and its receptor (IGF-1R) increased by 50% during the pre-hibernation period (PRE) and by 35% during re-entry into torpor (RET) compared to the summer active period (SA). The phosphorylation level of FOXO1 in the VM muscle increased by 50% in the torpor (TOR) group and by 82% in the inter-bout arousal (IBA) group compared to the PRE group. The phosphorylation level of SGK-1 increased by 54% in the IBA group and by 62% in the RET group compared to the SA group. In contrast, the protein expression of IGF-1 and phosphorylation levels of PI3K, Akt, mTOR, and GSK3β in the VM muscle showed no obvious differences among the different groups. β-catenin protein expression was up-regulated by 84% in the RET group compared to the SA group, while the content of IGF-1 protein, correlation coefficients of IGF-1 and IGF-1R, and phosphorylation levels of PI3K, Akt, and GSK3β in the femur showed no significant differences among groups. Regarding myostatin and its downstream targets, myostatin protein expression decreased by 70% in the RET group compared to the SA group, whereas ActRIIB protein expression and Smad2/3 phosphorylation in the VM muscle showed no obvious differences among groups. Furthermore, Smad2/3 phosphorylation decreased by 58% in the TOR group and 53% in the RET group compared to the SA group, whereas ActRIIB protein expression in the femur showed no obvious differences among groups. Overall, the observed changes in IGF-1 and myostatin expression and their downstream targets may be involved in musculoskeletal preservation during hibernation in Daurian ground squirrels.
Collapse
|
10
|
Yao F, Chen Y, Liu J, Zhang J, Xiao Z, Shi Z, Chen Q, Qin Z. Strategies of invasive snail Pomacea canaliculata during hibernation in rice fields of south China: effects of body size, sex, and soil depth. PEST MANAGEMENT SCIENCE 2024; 80:5929-5940. [PMID: 39087755 DOI: 10.1002/ps.8327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 05/27/2024] [Accepted: 07/08/2024] [Indexed: 08/02/2024]
Abstract
BACKGROUND The invasive freshwater snail Pomacea canaliculata is an agricultural pest with a certain level of tolerance to abiotic stress. After the harvest of late rice, the snails usually burrow themselves into the soil surface layers to overwinter and pose a renewed threat to rice production in the following year. Revealing the response of snails to environmental stresses is crucial for developing countermeasures to control their damage and spread. RESULTS In this study, we conducted a 120-day in situ experiment during the winter to investigate the survival and physiological changes of hibernating snails in 0-5 and 5-10 cm soil depths, aiming to explore their overwintering strategies. Our results showed that 73.61%, 87.50%, and 90.28% of male, female, and juvenile snails survived after hibernation for 120 days in 0-10 cm soil depth, respectively. The differences in survival rates based on sex and size of snails potentially reflect the countermeasures of snails to rapidly reproduce after hibernation. Simultaneously, the hibernating snails exhibited the ability to maintain a certain level of body weight. During this period, the snails increased their antioxidant enzyme activities to cope with oxidative stress, and enhanced their lipid storage. The hibernation survival of snails was not significantly affected by different soil depths, indicating that they have the potential to hibernate into deeper soils. Furthermore, snails were capable of increasing their contents of bound water and glycerol to cope with sudden cold spells during hibernation. CONCLUSION Our findings emphasize the adaptive changes of P. canaliculata snails overwintering in paddy soils. In future studies, the vulnerabilities of P. canaliculata during hibernation (e.g. shell characteristics, nutrient reserves, and dehydration tolerance, etc.,) should be investigated to develop effective control methods for this period. © 2024 Society of Chemical Industry.
Collapse
|
11
|
Wang Z, Wang MD, Wang XC, Chen L, Li LF, Jiang LN, Xu JH, Kai Dang. High levels of mitochondrial dynamics, autophagy, and apoptosis contribute to stable testicular status in hibernating Daurian ground squirrels. Comp Biochem Physiol A Mol Integr Physiol 2024; 297:111705. [PMID: 39032767 DOI: 10.1016/j.cbpa.2024.111705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 06/26/2024] [Accepted: 07/17/2024] [Indexed: 07/23/2024]
Abstract
Daurian ground squirrels (Spermophilus dauricus) experience various stress states during winter hibernation, but the impact on testicular function remains unclear. This study focused on the effects of changes in testicular autophagy, apoptosis, and mitochondrial homeostasis signaling pathways at various stages on the testes of Daurian ground squirrels. Results indicated that: (1) During winter hibernation, there was a significant increase in seminiferous tubule diameter and seminiferous epithelium thickness compared to summer. Spermatogonia number and testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels were higher during inter-bout arousal, suggesting that the testes remained stable during hibernation. (2) An increased number of mitochondria with intact morphology were observed during hibernation, indicating that mitochondrial homeostasis may contribute to testicular stability. (3) DNA fragmentation was evident in the testes during the hibernation and inter-bout arousal stages, with the highest level of caspase3 enzyme activity detected during inter-bout arousal, together with elevated levels of Bax/Bcl-2 and Lc3 II/Lc3 I, indicating an up-regulation of apoptosis and autophagy signaling pathways during hibernation. (4) The abundance of DRP1, MFF, OPA1, and MFN2 proteins was increased, suggesting an up-regulation of mitochondrial dynamics-related pathways. Overall, testicular autophagy, apoptosis, and mitochondrial homeostasis-related signaling pathways were notably active in the extreme winter environment. The well-maintained mitochondrial morphology may favor the production of reproductive hormones and support stable testicular morphology.
Collapse
|
12
|
Fregin B, Hossain MF, Biedenweg D, Friedrichs V, Balkema-Buschmann A, Bokelmann M, Lehnert K, Mokbel D, Aland S, Scholz CC, Lehmann P, Otto O, Kerth G. Thermomechanical properties of bat and human red blood cells-Implications for hibernation. Proc Natl Acad Sci U S A 2024; 121:e2405169121. [PMID: 39401351 PMCID: PMC11513926 DOI: 10.1073/pnas.2405169121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 08/27/2024] [Indexed: 10/30/2024] Open
Abstract
Hibernation is a widespread and highly efficient mechanism to save energy in mammals. However, one major challenge of hibernation is maintaining blood circulation at low body temperatures, which strongly depends on the viscoelastic properties of red blood cells (RBCs). Here, we examined at physiologically relevant timescales the thermomechanical properties of hundreds of thousands of individual RBCs from the hibernating common noctule bat (Nyctalus noctula), the nonhibernating Egyptian fruit bat (Rousettus aegyptiacus), and humans (Homo sapiens). We exposed RBCs to temperatures encountered during normothermia and hibernation and found a significant increase in elasticity and viscosity with decreasing temperatures. Our data demonstrate that temperature adjustment of RBCs is mainly driven by membrane properties and not the cytosol while viscous dissipation in the membrane of both bat species exceeds the one in humans by a factor of 15. Finally, our results show that RBCs from both bat species reveal a transition to a more viscous-like state when temperature decreases. This process on a minute timescale has an effect size that is comparable with fluctuations in RBC viscoelasticity over the course of the year, implying that environmental factors, such as diets, have a lower impact on the capability of RBCs to respond to different temperatures than general physical properties of the cell membrane. In summary, our findings suggest membrane viscoelasticity as a promising target for identifying mechanisms that could be manipulated to ensure blood circulation at low body temperatures in humans, which may be one first step toward safe synthetic torpor in medicine and space flight.
Collapse
|
13
|
Monecke S. From Seasonality to Species Conservation: Chronobiological Research on European Hamsters in Strasbourg, France. J Pineal Res 2024; 76:e13012. [PMID: 39415335 DOI: 10.1111/jpi.13012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Revised: 09/23/2024] [Accepted: 09/27/2024] [Indexed: 10/18/2024]
Abstract
The first monograph on the European hamster from the Strasbourg region dates back to 1765. By the 1930s, a long and continuous chronobiological research tradition was established for this species, starting with the works of Charles Kayser, who published between 1938 and 1971. Another early key researcher in this area was Bernhard Canguilhem with publications from 1966 to 1999. From the 1980s onwards, "the Pévets," Paul Pévet and his wife, Mireille Masson-Pévet, gave new energy to European hamster research. They broadened the research scope from basic hibernation research to mechanistic studies of circannual rhythms and from physiological aspects to molecular details. One main underlying question in their research was the role of melatonin. Thanks to their enthusiasm and vision, the European hamster is today one of the best - if not the best - studied circannual species. At least 73 parameters are described to cycle. Thirty-two of them have been shown to be driven by a circannual clock. Moreover, ground-breaking advances in our understanding of the mechanistic of hibernation, circannual clock functioning, and its entrainment were made. With most of this research being conducted in Strasbourg, Paul Pévet was instrumental in providing the necessary resources that made these innovative and unconventional long-term animal studies possible, contributing to fundamental research and, ultimately, to species conservation.
Collapse
|
14
|
Blanco MB, Greene LK, Welser KH, Ehmke EE, Yoder AD, Klopfer PH. Primate hibernation: The past, present, and promise of captive dwarf lemurs. Ann N Y Acad Sci 2024; 1540:178-190. [PMID: 39137248 DOI: 10.1111/nyas.15206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
The dwarf lemurs (Cheirogaleus spp.) of Madagascar are the only obligate hibernators among primates. Despite century-old field accounts of seasonal lethargy, and more recent evidence of hibernation in the western fat-tailed dwarf lemur (Cheirogaleus medius), inducing hibernation in captivity remained elusive for decades. This included the Duke Lemur Center (DLC), which maintains fat-tailed dwarf lemurs and has produced sporadic research on reproduction and metabolism. With cumulative knowledge from the field, a newly robust colony, and better infrastructure, we recently induced hibernation in DLC dwarf lemurs. We describe two follow-up experiments in subsequent years. First, we show that dwarf lemurs under stable cold conditions (13°C) with available food continued to eat daily, expressed shallower and shorter torpor bouts, and had a modified gut microbiome compared to peers without food. Second, we demonstrate that dwarf lemurs under fluctuating temperatures (12-30°C) can passively rewarm daily, which was associated with altered patterns of fat depletion and reduced oxidative stress. Despite the limitations of working with endangered primates, we highlight the promise of studying hibernation in captive dwarf lemurs. Follow-up studies on genomics and epigenetics, metabolism, and endocrinology could have relevance across multidisciplinary fields, from biomedicine to evolutionary biology, and conservation.
Collapse
|
15
|
Tanwar AK, Dhillon MK, Hasan F, Kumar S, Kirti JS. Lipid composition differs in diapause and nondiapause states of spotted stem borer, Chilo partellus. Comp Biochem Physiol B Biochem Mol Biol 2024; 274:110996. [PMID: 38810773 DOI: 10.1016/j.cbpb.2024.110996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 05/23/2024] [Accepted: 05/25/2024] [Indexed: 05/31/2024]
Abstract
Spotted stem borer, Chilo partellus, undergoes larval diapause (hibernation and aestivation), and depends on the food reserve accumulated during feeding stage for its survival. Lipids are the primary source of energy during diapause, and essential for different cellular, biochemical and physiological functions. However, there is no information on lipid and lipophilic compound contents during different stages of hibernation, aestivation and nondiapause in C. partellus. Thus, we compared the concentration and composition of lipids in pre-diapause, diapause and post-diapause stages of hibernation and aestivation with nondiapause stages of C. partellus. The studies revealed significant differences in total lipids and various lipophilic compounds during different stages of diapause as compared to nondiapause C. partellus. The total lipids were significantly lower during diapause stage of aestivation and hibernation as compared to nondiapause larvae. Further, the linoleic acid, Methyl 3-methoxytetradecanoate, and l-(+)-Ascorbic acid 2,6-dihexadecanoate were significantly lower, and oleic and palmitoleic acids greater during pre-diapause and diapause stages of hibernation and aestivation as compared to nondiapause larvae. The cholesterol content was significantly greater during pre-diapause stage of hibernation, and diapause and post-diapause stages of aestivation as compared to nondiapause stages. The unsaturation ratio was significantly higher in the pre-diapause and diapause stages and lower in post-diapause stage of aestivation than the hibernation and nondiapause states. This study provides insights on differential lipid profiles during different phases of diapause, which could be useful for further understanding biochemical and physiological cross-talk, and develop target-specific technologies for the management of C. partellus.
Collapse
|
16
|
Tejura A, Sun M, McCaig L, Staples J, Veldhuizen R. The effect of temperature and breathing pattern on the surface activity of ground squirrel pulmonary surfactant. J Exp Biol 2024; 227:jeb249280. [PMID: 39263756 PMCID: PMC11491808 DOI: 10.1242/jeb.249280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2024] [Accepted: 09/03/2024] [Indexed: 09/13/2024]
Abstract
This study investigates how hibernation affects the surface activity of pulmonary surfactant with respect to temperature and breathing pattern. Surfactant was isolated from a hibernating species, the 13-lined ground squirrel, and a homeotherm, the rabbit, and analysed for biophysical properties on a constrained sessile drop surfactometer. The results showed that surfactant from ground squirrels reduced surface tension better at low temperatures, including when mimicking episodic breathing, as compared with rabbit surfactant. In addition, low temperature adaptation was also observed using only the hydrophobic components of surfactant from ground squirrels. Overall, the data support the conclusion that ground squirrel surfactant has adapted to maintain surface activity during low temperature episodic breathing patterns, and that temperature adaptation is maintained with the hydrophobic components of the surfactant.
Collapse
|
17
|
Ma Y, Chen Y, Li Y, Chen S, Zhu C, Liu Q, Li L, Cao H, Wu Z, Dong W. Seasonal modulation of the testis transcriptome reveals insights into hibernation and reproductive adaptation in Onychostoma macrolepis. FISH PHYSIOLOGY AND BIOCHEMISTRY 2024; 50:2083-2097. [PMID: 38649597 DOI: 10.1007/s10695-024-01335-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 03/22/2024] [Indexed: 04/25/2024]
Abstract
The Onychostoma macrolepis have a unique survival strategy, overwintering in caves and returning to the river for reproduction in summer. The current knowledge on the developmental status of its testes during winter and summer is still undiscovered. We performed RNA-seq analysis on O. macrolepis testes between January and June, using the published genome (NCBI, ASM1243209v1). Through KEGG and GO enrichment analysis, we were able to identify 2111 differentially expressed genes (DEGs) and demonstrate their functions in signaling networks associated with the development of organism. At the genomic level, we found that during the overwintering phase, genes associated with cell proliferation (ccnb1, spag5, hdac7) were downregulated while genes linked to testicular fat metabolism (slc27a2, scd, pltp) were upregulated. This indicates suppression of both mitosis and meiosis, thereby inhibiting energy expenditure through genetic regulation of testicular degeneration. Furthermore, in January, we observed the regulation of autophagy and apoptosis (becn1, casp13), which may have the function of protecting reproductive organs and ensuring their maturity for the breeding season. The results provide a basis for the development of specialized feed formulations to regulate the expression of specific genes, or editing of genes during the fish egg stage, to ensure that the testes of O. macrolepis can mature more efficiently after overwintering, thereby enhancing reproductive performance.
Collapse
|
18
|
Kravchenko K, Furmankiewicz J. The interplay of temperature and circadian periodicity in winter activity of non-cavernous hibernator, Nyctalusnoctula. J Therm Biol 2024; 125:103999. [PMID: 39514921 DOI: 10.1016/j.jtherbio.2024.103999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 10/09/2024] [Accepted: 10/15/2024] [Indexed: 11/16/2024]
Abstract
Winter activity of hibernating mammals is likely to be influenced by climate change. Our study focuses on Nyctalus noctula, a non-cavernous hibernator using artificial roosts in a recently colonized winter region. Using continuous acoustic monitoring and temperature measurements inside and outside the roosts, we found that bats exhibit a circadian cycle (active at night, resting during the day) even during hibernation season. Activity duration and intensity changed in response to ambient temperature, photoperiod, and hibernation progression. Warm ambient temperatures led to increased nighttime activity, extending the duration of the active phase. As photoperiod increased, the rest phase lengthened, while the overall magnitude of activity decreased from the beginning to the end of the hibernation period. Below 0 °C vocal activity was nearly zero indicating a minimal probability of bat activity during both day and night. The species recent success in extending its hibernation range northward may be attributed to its flexible adjustment to prevailing environmental conditions. Nevertheless, it remains uncertain whether engaging in daily activity at temperatures above 0 °C confers any advantages at northern latitudes to prevent premature energy depletion. The persistence of circadian activity during winter could be a relic behavior, adapted from historical patterns of wintering in insect-rich and warm southern latitudes.
Collapse
|
19
|
Fjelldal MA, Fritzén NR, Suominen KM, Lilley TM. Supersize me: hypotheses on torpor-assisted prehibernation fattening in a boreal bat. Biol Lett 2024; 20:20240291. [PMID: 39288816 PMCID: PMC11407865 DOI: 10.1098/rsbl.2024.0291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2024] [Revised: 07/08/2024] [Accepted: 08/07/2024] [Indexed: 09/19/2024] Open
Abstract
Hibernators face an energetic dilemma in the autumn at northern latitudes; while temperatures and food availability decrease, hibernating species need to build fat deposits to survive the winter. During this critical fattening phase, insectivorous boreal bats use torpor to build and conserve their reserves. However, we still know little about temporal variability in torpor use employed by bats during the prehibernation fattening period and how decreasing temperatures and food availability in combination with increasing individual body mass impact this. Here, we present two general hypotheses for explaining temporal torpor patterns observed in a boreal bat (Eptesicus nilssonii), in which torpor use (i) facilitates rapid mass gain or (ii) conserves stored body mass. Although temporally separated in our dataset, data on temperature, insect abundance and body mass throughout the prehibernation period indicate that E. nilssonii reaches the majority of its overwintering mass before the onset of increasing daytime and night-time torpor use. In combination with low food availability by this point in time, these observations suggest torpor expression may be intended to conserve gained reserves rather than facilitate mass gain. Our study is intended as a first proof of concept for disentangling temporal drivers of torpor in bats during the prehibernation fattening phase.
Collapse
|
20
|
Lammert TL, Müller J, Ferreira SC, Teubenbacher U, Cornils JS, Stalder G, Painer-Gigler J, Ruf T, Bieber C, Pohlin F. No negative effects of intra-abdominal bio-logger implantation under general anaesthesia on spatial cognition learning in a hibernator the edible dormouse. PLoS One 2024; 19:e0307551. [PMID: 39197002 PMCID: PMC11356448 DOI: 10.1371/journal.pone.0307551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Accepted: 07/09/2024] [Indexed: 08/30/2024] Open
Abstract
The effect of hibernation on cognitive capacities of individuals is not fully understood, as studies provide conflicting results. Most studies focus on behavioural observations without taking the physiological state of individuals to account. To mechanistically understand the effect of hibernation on the brain, physiological parameters need to be included. The implantation of bio-loggers can provide insights on i.e. body temperature without further manipulation of the animals. Surgeries and anaesthesia, however, can harm animals' health and cause cognitive dysfunction, potentially biasing data collected through bio-loggers. We investigated the effects of bio-logger implantation surgery on cognitive performance and learning, controlling for animal and study design characteristics. First, juvenile dormice successfully learned to solve a spatial cognition task using a vertical maze. Distance, transitions, velocity, and duration were measured as indicators for performance. After training, bio-loggers were implanted intra-abdominally under general anaesthesia. Animals were re-tested in the maze two weeks after. We found no effect of bio-logger implantation and surgery on performance. This study is the first to show spatial cognition learning in edible dormice and provides a full description of the peri-anaesthetic management and a protocol for bio-logger implantation surgery in dormice. Importantly, measures were taken to mitigate common anaesthetic complications that could lead to post-operative cognitive dysfunction and influence animal behaviour. By pairing physiological measurements through bio-logger implantation with behaviour and cognition measurements, future research will significantly advance the understanding on mechanisms of learning and behaviour.
Collapse
|
21
|
Dori P, Anastasio I, Macchi E, Manenti I, Hones M, Carosi M. Hibernating or not hibernating? Brown bears' response to a mismatch between environmental natural cues and captive management, and its welfare implications. PLoS One 2024; 19:e0306537. [PMID: 39083476 PMCID: PMC11290645 DOI: 10.1371/journal.pone.0306537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 06/19/2024] [Indexed: 08/02/2024] Open
Abstract
In wild brown bears, likely factors triggering hibernation response to harsh environmental conditions are temperature, photoperiod, and food resources availability. In fact, constantly fed captive brown bears are described as skipping hibernation being active all year-round. Is the hibernation response so flexible and subordinate to contingencies, or else is an adaptation that, if dismissed, may negatively impact on bear well-being? This study investigates the potential hibernation response in captive brown bears under unvaried management conditions using an integrative approach simultaneously analyzing multiple animal-based variables together with environmental covariates. Data from a mid-latitude zoo revealed distinct behavioral, fecal glucocorticoids, and body condition score seasonal fluctuations, resembling natural hibernation cycles, despite constant food access. Environmental variables like photoperiod and visitor numbers significantly influenced activity levels. Bears exhibited behaviors indicative of hyperphagia and fall transition, such as appetitive feeding and denning behaviors. Hormonal analyses revealed high fecal cortisol metabolites levels during hyperphagia, suggesting physiological responses to seasonal changes. Findings underscore the importance of environmental cues and food availability in shaping zoo bear behavior and physiology. Considering that the hibernating vs. non-hibernating description might represent an oversimplification, management strategies should deal with captive bear potential need to freely express their adaptive predispositions by accommodating their natural behaviors, such as providing denning spots and adjusting diet composition as soon as typical hyperphagic and predenning behaviors emerge, ultimately enhancing their well-being.
Collapse
|
22
|
van den Berg M, Shi Z, Claassen WJ, Hooijman P, Lewis CTA, Andersen JL, van der Pijl RJ, Bogaards SJP, Conijn S, Peters EL, Begthel LPL, Uijterwijk B, Lindqvist J, Langlais PR, Girbes ARJ, Stapel S, Granzier H, Campbell KS, Ma W, Irving T, Hwee DT, Hartman JJ, Malik FI, Paul M, Beishuizen A, Ochala J, Heunks L, Ottenheijm CAC. Super-relaxed myosins contribute to respiratory muscle hibernation in mechanically ventilated patients. Sci Transl Med 2024; 16:eadg3894. [PMID: 39083588 PMCID: PMC11586073 DOI: 10.1126/scitranslmed.adg3894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 02/12/2024] [Accepted: 07/11/2024] [Indexed: 08/02/2024]
Abstract
Patients receiving mechanical ventilation in the intensive care unit (ICU) frequently develop contractile weakness of the diaphragm. Consequently, they may experience difficulty weaning from mechanical ventilation, which increases mortality and poses a high economic burden. Because of a lack of knowledge regarding the molecular changes in the diaphragm, no treatment is currently available to improve diaphragm contractility. We compared diaphragm biopsies from ventilated ICU patients (N = 54) to those of non-ICU patients undergoing thoracic surgery (N = 27). By integrating data from myofiber force measurements, x-ray diffraction experiments, and biochemical assays with clinical data, we found that in myofibers isolated from the diaphragm of ventilated ICU patients, myosin is trapped in an energy-sparing, super-relaxed state, which impairs the binding of myosin to actin during diaphragm contraction. Studies on quadriceps biopsies of ICU patients and on the diaphragm of previously healthy mechanically ventilated rats suggested that the super-relaxed myosins are specific to the diaphragm and not a result of critical illness. Exposing slow- and fast-twitch myofibers isolated from the diaphragm biopsies to small-molecule compounds activating troponin restored contractile force in vitro. These findings support the continued development of drugs that target sarcomere proteins to increase the calcium sensitivity of myofibers for the treatment of ICU-acquired diaphragm weakness.
Collapse
|
23
|
Mohr SM, Dai Pra R, Platt MP, Feketa VV, Shanabrough M, Varela L, Kristant A, Cao H, Merriman DK, Horvath TL, Bagriantsev SN, Gracheva EO. Hypothalamic hormone deficiency enables physiological anorexia in ground squirrels during hibernation. Nat Commun 2024; 15:5803. [PMID: 38987241 PMCID: PMC11236985 DOI: 10.1038/s41467-024-49996-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 06/19/2024] [Indexed: 07/12/2024] Open
Abstract
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.
Collapse
|
24
|
Park JK, DO Y. The difference and variation of gut bacterial community and host physiology can support adaptation during and after overwintering in frog population. Integr Zool 2024; 19:631-645. [PMID: 38185804 DOI: 10.1111/1749-4877.12798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
The hibernation of amphibians can offer a unique window into overwintering adaptation processes and host-gut microbiota interactions through changes in metabolic availability and homeostasis. We attempted to identify differences in the physiology and gut microbiome during and after hibernation in Japanese wrinkled frogs (Glandirana rugosa), an aquatic overwintering amphibian. After hibernation, the high alpha and beta diversity of the gut bacterial community appears to reflect the more diverse and complex environmental conditions. During winter, Proteobacteria dominated the majority of the gut bacterial community, likely due to high oxygen saturation. After hibernation, Firmicutes and Bacteroidetes increased, which are supportive of host metabolism by gut microbiota. Corticosterone also showed high values and variances after hibernation, presumably allowing the population to remain adaptable across a broad range of environmental gradients. Innate immunity was high after hibernation but exhibited low variation among populations, which supports the idea of a prioritized investment in immunity after hibernation. Blood biochemistry suggests that aquatic overwintering frogs have a mechanism to adapt through overhydration and regulate homeostasis through water excretion associated with the kidney and urine after hibernation. Frog populations exhibit variations and adaptability in gut microbiota and physiology during and after hibernation: Through this, they may demonstrate an adaptive response that regulates metabolic availability in preparation for unpredictable environmental changes. We also propose that the maintenance of Proteobacteria during hibernation can support the colonization of Firmicutes and Bacteroidetes after hibernation, underscoring the need to study the complex effects of gut microbiota across multiple life stages.
Collapse
|
25
|
Findlay-Robinson R, Hill DL. Hibernation nest site selection but not overwinter activity is associated with microclimatic conditions in a hibernating mammal. J Therm Biol 2024; 123:103909. [PMID: 39084175 DOI: 10.1016/j.jtherbio.2024.103909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 06/30/2024] [Accepted: 07/02/2024] [Indexed: 08/02/2024]
Abstract
Fine-scale variation in microclimates between habitats may impact energy consumption for the organisms that inhabit them. This may be particularly important for sedentary species or those unable to change habitats for long periods, such as hibernators. Low ambient temperatures were traditionally thought key to microclimatic selection for hibernation locations, but recent research suggests that other factors may contribute or exceed ambient temperature in importance. We aimed to characterise microclimates at hibernacula of wild hibernating hazel dormice Muscardinus avellanarius, and test how these microclimates differ to those at locations without hibernacula using a microclimatic modelling approach. Dormice hibernated in areas with warmer soil temperatures and lower variability in humidity and relative shortwave radiation. These results add to the growing body of evidence that low ambient temperatures may not be the primary driver of hibernation microclimate selection, although temperature is still likely to play an important role. We also found that ambient temperatures measured at the microclimatic level were substantially buffered compared to point samples taken at the nearest weather station (∼1.6 km away), highlighting the importance of considering microclimates in wildlife conservation in the face of future environmental change.
Collapse
|