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Costanzo JP. Overwintering adaptations and extreme freeze tolerance in a subarctic population of the wood frog, Rana sylvatica. J Comp Physiol B 2018; 189:1-15. [PMID: 30390099 DOI: 10.1007/s00360-018-1189-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/21/2018] [Accepted: 10/29/2018] [Indexed: 12/12/2022]
Abstract
The terrestrially hibernating wood frog (Rana sylvatica) is well-known for its iconic freeze tolerance, an overwintering adaptation that has received considerable investigation over the past 35 years. Virtually, all of this research has concerned frogs indigenous to the temperate regions of its broad range within North America. However, recent investigations have shown that frogs of subarctic populations are extremely cold hardy, being capable of surviving freezing for longer periods and at much lower temperatures as compared to conspecifics from temperate regions. Their exceptional freeze tolerance is partly supported by an enhanced cryoprotectant system that uses very high levels of urea and glucose to limit ice formation, regulate metabolism, and protect macromolecules and cellular structures from freezing/thawing stresses. In the weeks before they begin hibernating, northern frogs undertake radical physiological transitions, such as depletion of fat stores and catabolism of muscle protein, that prime the cryoprotectant system by accruing urea and stockpiling glycogen from which glucose is mobilized during freezing. Concentrations of cryoprotectants ultimately achieved in Alaskan frogs when freezing occurs vary among tissues but generally are higher than those of frogs inhabiting milder climates. This review summarizes the molecular, biochemical, and physiological adaptations permitting this northern phenotype to survive the long and harsh winters of the region.
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Affiliation(s)
- Jon P Costanzo
- Department of Biology, Miami University, 45056, Oxford, OH, USA.
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52
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Abstract
Several amphibian lineages epitomize the faunal biodiversity crises, with numerous reports of population declines and extinctions worldwide. Predicting how such lineages will cope with environmental changes is an urgent challenge for biologists. A promising framework for this involves mechanistic modeling, which integrates organismal ecophysiological features and ecological models as a means to establish causal and consequential relationships of species with their physical environment. Solid frameworks built for other tetrapods (e.g., lizards) have proved successful in this context, but its extension to amphibians requires care. First, the natural history of amphibians is distinct within tetrapods, for it includes a biphasic life cycle that undergoes major habitat transitions and changes in sensitivity to environmental factors. Second, the accumulated data on amphibian ecophysiology is not nearly as expressive, is heavily biased towards adult lifeforms of few non-tropical lineages, and overlook the importance of hydrothermal relationships. Thus, we argue that critical usage and improvement in the available data is essential for enhancing the power of mechanistic modeling from the physiological ecology of amphibians. We highlight the complexity of ecophysiological variables and the need for understanding the natural history of the group under study and indicate directions deemed crucial to attaining steady progress in this field.
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53
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Williams BL, Wiebler JM, Lee RE, Costanzo JP. Nitric oxide metabolites in hypoxia, freezing, and hibernation of the wood frog, Rana sylvatica. J Comp Physiol B 2018; 188:957-966. [PMID: 30209557 DOI: 10.1007/s00360-018-1182-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/31/2018] [Accepted: 09/06/2018] [Indexed: 12/11/2022]
Abstract
Nitric oxide (NO) is a gaseous free radical that in diverse organisms performs many signaling and protective functions, such as vasoregulation, inhibition of apoptosis, antioxidation, and metabolic suppression. Increased availability of NO may be especially important during life-history periods when organisms contend with multiple stresses. We investigated dynamics of the NO metabolites, nitrite (NO2-) and nitrate (NO3-), in the blood plasma, heart, liver, and skeletal muscle of the wood frog (Rana sylvatica), an amphibian that endures chronic cold, freezing, hypoxia, dehydration, and extended aphagia during hibernation. We found elevated concentrations of NO2- and/or NO3- in the plasma (up to 4.1-fold), heart (3.1-fold), and liver (up to 4.1-fold) of frogs subjected to experimental hypoxia (24 h, 4 °C), and in the liver (up to 3.8-fold) of experimentally frozen frogs (48 h, - 2.5 °C), suggesting that increased NO availability aids in survival of these stresses. During a 38-week period of simulated hibernation, NO2- and/or NO3- increased in the plasma (up to 10.4-fold), heart (up to 3.3-fold), and liver (5.0-fold) during an initial 5-week winter-acclimatization regimen and generally remained elevated thereafter. In hibernation, plasma NO2- was higher in frogs indigenous to Interior Alaska than in conspecifics from a temperate locale (southern Ohio), suggesting that NO availability is matched to the severity of environmental conditions prevailing in winter. The comparatively high NO availability in R. sylvatica, a stress-tolerant species, together with published values for other species, suggest that the NO protection system is of general importance in the stress adaptation of vertebrates.
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Affiliation(s)
- Bethany L Williams
- Department of Biology, Miami University, Oxford, OH, 45056, USA
- School of Environment and Natural Resources, The Ohio State University, Columbus, OH, 43202, USA
| | - James M Wiebler
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Richard E Lee
- Department of Biology, Miami University, Oxford, OH, 45056, USA
| | - Jon P Costanzo
- Department of Biology, Miami University, Oxford, OH, 45056, USA.
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Hildebrandt JP, Wiesenthal AA, Müller C. Phenotypic Plasticity in Animals Exposed to Osmotic Stress - Is it Always Adaptive? Bioessays 2018; 40:e1800069. [PMID: 30160800 DOI: 10.1002/bies.201800069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 08/03/2018] [Indexed: 01/03/2023]
Abstract
Hyperplasia and hypertrophy are elements of phenotypic plasticity adjusting organ size and function. Because they are costly, we assume that they are beneficial. In this review, the authors discuss examples of tissue and organ systems that respond with plastic changes to osmotic stress to raise awareness that we do not always have sufficient experimental evidence to conclude that such processes provide fitness advantages. Changes in hydranth architecture in the hydroid Cordylophora caspia or variations in size in the anal papillae of insect larvae upon changes in medium salinity may be adaptive or not. The restructuring of salt glands in ducklings upon salt-loading is an example of phenotypic plasticity which indeed seems beneficial. As the genomes of model species are recently sequenced and the animals are easy to rear, these species are suitable study objects to investigate the biological significance of phenotypic plasticity and to study potential epigenetic and other mechanisms underlying phenotypic changes.
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Affiliation(s)
- Jan-Peter Hildebrandt
- Animal Physiology and Biochemistry, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
| | - Amanda A Wiesenthal
- Animal Physiology and Biochemistry, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
| | - Christian Müller
- Animal Physiology and Biochemistry, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
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55
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Figueras M, Bastarache B, Burke R. Water exchange relationships predict overwintering behavior in hatchling turtles. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neonatal ectotherms face a wide range of environmental hazards because of the diverse habitats that they inhabit and their small body sizes; this is especially true among turtles that live in temperate zones and experience cold winter conditions after hatching. Such hatchlings must balance challenges involving desiccation, freezing, and predation, among other threats. Turtle hatchlings either overwinter in water, terrestrially in relatively shallow nests, terrestrially deep below nests, or terrestrially outside of the nest entirely, and these different microhabitats are associated with different desiccation and freezing risks. We measured desiccation tolerance of individuals of six turtle species, including two (Diamondback Terrapins, Malaclemys terrapin (Schoepff, 1793), and Eastern Box Turtles, Terrapene carolina (Linnaeus, 1758)) that use a strategy that has not previously been explored, along with Wood Turtles (Glyptemys insculpta (Le Conte, 1830)), whose overwintering microhabitat is uncertain. We found additional support for the hypothesis that desiccation resistance is associated with overwintering strategies in hatchling turtles. Further investigation into the overwintering strategies of M. terrapin and T. carolina would be productive.
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Affiliation(s)
- M.P. Figueras
- Department of Biology, Hofstra University, Hempstead, NY 11549, USA
| | - B.A. Bastarache
- Bristol County Agricultural High School, Dighton, MA 02715, USA
| | - R.L. Burke
- Department of Biology, Hofstra University, Hempstead, NY 11549, USA
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56
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Toxopeus J, Sinclair BJ. Mechanisms underlying insect freeze tolerance. Biol Rev Camb Philos Soc 2018; 93:1891-1914. [DOI: 10.1111/brv.12425] [Citation(s) in RCA: 106] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 04/12/2018] [Accepted: 04/17/2018] [Indexed: 12/16/2022]
Affiliation(s)
- Jantina Toxopeus
- Department of Biology; University of Western Ontario; 1151 Richmond Street N, London ON, N6A 5B7 Canada
| | - Brent J. Sinclair
- Department of Biology; University of Western Ontario; 1151 Richmond Street N, London ON, N6A 5B7 Canada
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The cryoprotectant system of Cope's gray treefrog, Dryophytes chrysoscelis: responses to cold acclimation, freezing, and thawing. J Comp Physiol B 2018; 188:611-621. [PMID: 29550887 PMCID: PMC6006228 DOI: 10.1007/s00360-018-1153-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 02/27/2018] [Accepted: 03/08/2018] [Indexed: 12/28/2022]
Abstract
Cope's gray treefrog (Dryophytes chrysoscelis) is one of few freeze-tolerant frogs that mobilize glycerol as a cryoprotectant, yet cold and freezing-induced accumulation of this and other osmolytes has received little attention in this species. This study investigated the development of freeze tolerance in D. chrysoscelis, analyzing the response of the cryoprotectant system to cold acclimation, freezing, and thawing. Glycerol production was low and unresponsive to acclimation temperature, or duration of acclimation to 5 °C, except for one cold-acclimated frog that presented elevated glycerol in plasma, liver, and skeletal muscle. Curiously, glycerol concentration in skeletal muscle was higher than that of plasma and liver, in both warm- and cold-acclimated frogs, suggesting glycerol synthesis in muscle. Urea concentration in plasma doubled in response to cold acclimation but did not change during freezing. Freezing induced hepatic glycogen catabolism and an increase in glycerol and glucose in several tissues, although the mobilization dynamics differed between these cryoprotectants, possibly as a result of different transport mechanisms. Although hepatic glucose mobilization was of considerable magnitude, glucose accumulation in peripheral tissues was low and was surpassed by that of glycerol and urea. The muscle production of glycerol and the cold-induced accumulation of urea imply a role for skeletal muscle metabolism in the mobilization of cryoprotective solutes in D. chrysoscelis. The cryoprotectant system of D. chrysoscelis is complex, highly variable, and unique, with glycerol, glucose, and likely urea serving as cryoprotectants.
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Loehr VJT. Thermoregulatory challenges in the habitat of the world's smallest tortoise, Chersobius signatus. J Therm Biol 2018; 71:62-68. [PMID: 29301701 DOI: 10.1016/j.jtherbio.2017.10.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/28/2017] [Accepted: 10/30/2017] [Indexed: 11/30/2022]
Abstract
Ectotherms have various means of dealing with low environmental temperatures, but relatively few species have been rigorously investigated. Consequently, we have little information to predict how ectotherm populations might respond to global temperature changes. Tortoises from temperate and subtropical regions often overcome periodically cool conditions by hibernation, but speckled dwarf tortoises (Chersobius signatus) need to remain active to exploit ephemeral resources in their arid winter-rainfall habitat. This study investigated how dwarf tortoises cope with low temperatures in winter and spring, by measuring thermal habitat quality and thermoregulation based on differently-sized operative temperature models in sun, shade, and in deep crevices. Investigations continued in summer and autumn to obtain a year-round picture of thermoregulatory challenges. Although large models (i.e., larger than dwarf tortoises) were expected to have lower operative temperatures than smaller models, due to the former's larger thermal inertia, all model sizes had similar temperatures. Hence, the species' small body size does not appear constrained by obtainable body temperatures in cool seasons. Nevertheless, low operative temperatures in winter posed a challenge for the tortoises, which reached their field-preferred body temperature for an average of only 0.8-0.9h per day. Moreover, a low thermoregulation effectiveness suggested that tortoises traded-off physiological benefits of favourable body temperatures against predation risk. Spring and autumn provided higher temperatures, but summer caused the greatest thermoregulatory challenge. Although summer body temperatures were closer to field-preferred body temperature than in any other season, tortoises required rock crevices to avoid overheating. The small size of dwarf tortoises might help them utilise crevices. In summer, maximum operative temperatures in crevices were similar to field-preferred body temperature, indicating that an increase in environmental temperatures might be detrimental to dwarf tortoises. In light of projected temperature rises, future studies should assess if dwarf tortoises can cope with higher environmental temperatures in summer.
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Affiliation(s)
- Victor J T Loehr
- Homopus Research Foundation, Kwikstaartpad 1, 3403ZH IJsselstein, The Netherlands.
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59
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Drake KK, Bowen L, Lewison RL, Esque TC, Nussear KE, Braun J, Waters SC, Miles AK. Coupling gene-based and classic veterinary diagnostics improves interpretation of health and immune function in the Agassiz's desert tortoise ( Gopherus agassizii). CONSERVATION PHYSIOLOGY 2017; 5:cox037. [PMID: 28835840 PMCID: PMC5550616 DOI: 10.1093/conphys/cox037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 05/22/2017] [Accepted: 06/02/2017] [Indexed: 05/30/2023]
Abstract
The analysis of blood constituents is a widely used tool to aid in monitoring of animal health and disease. However, classic blood diagnostics (i.e. hematologic and plasma biochemical values) often do not provide sufficient information to determine the state of an animal's health. Field studies on wild tortoises and other reptiles have had limited success in drawing significant inferences between blood diagnostics and physiological and immunological condition. However, recent research using gene transcription profiling in the threatened Mojave desert tortoise (Gopherus agassizii) has proved useful in identifying immune or physiologic responses and overall health. To improve our understanding of health and immune function in tortoises, we evaluated both standard blood diagnostic (body condition, hematologic, plasma biochemistry values, trace elements, plasma proteins, vitamin A levels) and gene transcription profiles in 21 adult tortoises (11 clinically abnormal; 10 clinically normal) from Clark County, NV, USA. Necropsy and histology evaluations from clinically abnormal tortoises revealed multiple physiological complications, with moderate to severe rhinitis or pneumonia being the primary cause of morbidity in all but one of the examined animals. Clinically abnormal tortoises had increased transcription for four genes (SOD, MyD88, CL and Lep), increased lymphocyte production, biochemical enzymes and organics, trace elements of copper, and decreased numbers of leukocytes. We found significant positive correlations between increased transcription for SOD and increased trace elements for copper, as well as genes MyD88 and Lep with increased inflammation and microbial insults. Improved methods for health assessments are an important element of monitoring tortoise population recovery and can support the development of more robust diagnostic measures for ill animals, or individuals directly impacted by disturbance.
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Affiliation(s)
- K. Kristina Drake
- US Geological Survey, Western Ecological Research Center, Las Vegas Field Station, 160 N. Stephanie Street, Henderson, NV 89074, USA
- Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
- Graduate Group in Ecology, University of California, Davis, One Shields Avenue, Davis, CA 95618, USA
| | - Lizabeth Bowen
- US Geological Survey, Western Ecological Research Center, Davis Field Station, One Shields Avenue, University of California, Davis, CA 95618, USA
| | - Rebecca L. Lewison
- Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
| | - Todd C. Esque
- US Geological Survey, Western Ecological Research Center, Las Vegas Field Station, 160 N. Stephanie Street, Henderson, NV 89074, USA
| | - Kenneth E. Nussear
- Department of Geography, University of Nevada-Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
| | - Josephine Braun
- Wildlife Disease Laboratories, Institute for Conservation Research, San Diego Zoo Global, PO Box 120551, San Diego, CA 92112, USA
| | - Shannon C. Waters
- US Geological Survey, Western Ecological Research Center, Davis Field Station, One Shields Avenue, University of California, Davis, CA 95618, USA
| | - A. Keith Miles
- US Geological Survey, Western Ecological Research Center, Las Vegas Field Station, 160 N. Stephanie Street, Henderson, NV 89074, USA
- Graduate Group in Ecology, University of California, Davis, One Shields Avenue, Davis, CA 95618, USA
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60
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Vo P, Gridi-Papp M. Low temperature tolerance, cold hardening and acclimation in tadpoles of the neotropical túngara frog ( Engystomops pustulosus ). J Therm Biol 2017; 66:49-55. [DOI: 10.1016/j.jtherbio.2017.03.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 03/04/2017] [Accepted: 03/24/2017] [Indexed: 11/28/2022]
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61
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Daily thermal fluctuations to a range of subzero temperatures enhance cold hardiness of winter-acclimated turtles. J Comp Physiol B 2017; 187:1163-1172. [PMID: 28409226 DOI: 10.1007/s00360-017-1099-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 03/21/2017] [Accepted: 04/06/2017] [Indexed: 10/19/2022]
Abstract
Although seasonal increases in cold hardiness are well documented for temperate and polar ectotherms, relatively little is known about supplemental increases in cold hardiness during winter. Because many animals are exposed to considerable thermal variation in winter, they may benefit from a quick enhancement of cold tolerance prior to extreme low temperature. Hatchling painted turtles (Chrysemys picta) overwintering in their natal nests experience substantial thermal variation in winter, and recently, it was found that brief subzero chilling of winter-acclimated hatchlings decreases subsequent chilling-induced mortality, increases blood concentrations of glucose and lactate, and protects the brain from cryoinjury. Here, we further characterize that phenomenon, termed 'cold conditioning', by exposing winter-acclimated hatchling turtles to -3.5, -7.0, or -10.5 °C gradually or repeatedly via daily thermal fluctuations over the course of 5 days and assessing their survival of a subsequent cold shock to a discriminating temperature of -12.7 °C. To better understand the physiological response to cold conditioning, we measured changes in glucose and lactate concentrations in the liver, blood, and brain. Cold conditioning significantly increased cold-shock survival, from 9% in reference turtles up to 74% in cold-conditioned turtles, and ecologically relevant daily thermal fluctuations were at least as effective at conferring cryoprotection as was gradual cold conditioning. Cold conditioning increased glucose concentrations, up to 25 μmol g-1, and lactate concentrations, up to 30 μmol g-1, in the liver, blood, and brain. Turtles that were cold conditioned with daily thermal fluctuations accumulated more glucose in the liver, blood, and brain, and had lower brain lactate, than those gradually cold conditioned. Given the thermal variation to which hatchling painted turtles are exposed in winter, we suggest that the supplemental protection conferred by cold conditioning, especially that induced by daily thermal fluctuations, may be important for their overwinter survival. Investigation into the duration of the cold-conditioning induced protection and its occurrence in natural field conditions is needed to better understand its ecological significance. We suggest that future work exploring the underlying mechanisms of cold conditioning should focus on non-colligative effects of glucose, expression of small Hsps, changes in membrane structure, and ion homeostasis.
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Abstract
Freeze tolerance is an amazing winter survival strategy used by various amphibians and reptiles living in seasonally cold environments. These animals may spend weeks or months with up to ∼65% of their total body water frozen as extracellular ice and no physiological vital signs, and yet after thawing they return to normal life within a few hours. Two main principles of animal freeze tolerance have received much attention: the production of high concentrations of organic osmolytes (glucose, glycerol, urea among amphibians) that protect the intracellular environment, and the control of ice within the body (the first putative ice-binding protein in a frog was recently identified), but many other strategies of biochemical adaptation also contribute to freezing survival. Discussed herein are recent advances in our understanding of amphibian and reptile freeze tolerance with a focus on cell preservation strategies (chaperones, antioxidants, damage defense mechanisms), membrane transporters for water and cryoprotectants, energy metabolism, gene/protein adaptations, and the regulatory control of freeze-responsive hypometabolism at multiple levels (epigenetic regulation of DNA, microRNA action, cell signaling and transcription factor regulation, cell cycle control, and anti-apoptosis). All are providing a much more complete picture of life in the frozen state.
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Affiliation(s)
| | - Janet M. Storey
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
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63
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Iverson JB, Stahl RS, Furcolow C, Kraus F. An evaluation of the use of pentosidine as a biomarker for ageing turtles. CONSERVATION PHYSIOLOGY 2017; 5:cow076. [PMID: 28149519 PMCID: PMC5269512 DOI: 10.1093/conphys/cow076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/10/2016] [Accepted: 12/22/2016] [Indexed: 05/30/2023]
Abstract
Concentrations of the biomarker pentosidine have been shown to be useful measures of age for a number of avian and mammalian species. However, no study has examined its usefulness as an age marker in a long-lived ectotherm despite the fact that such a marker could prove useful in understanding age distributions of populations subject to conservation programmes. Therefore, we evaluated pentosidine concentrations in the interdigital webbing of 117 female yellow mud turtles (Kinosternon flavescens) at a 35 year study site in western Nebraska where nearly all turtles are of known age. Pentosidine concentrations were extraordinarily low and positively correlated with age in this turtle, but concentrations were too variable to permit precise estimates of age for turtles of unknown age. These results may reflect the remarkable physiological adaptations of this turtle to low temperatures and oxygen deprivation in a highly seasonal environment requiring prolonged hibernation. Whether pentosidine concentrations in other ectotherms occupying less seasonal environments would be more highly correlated with age remains to be determined. However, our results suggest that patterns of accumulation of pentosidine in ectotherms may be fundamentally different from those in endotherms.
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Affiliation(s)
- John B. Iverson
- Department of Biology, Earlham College, Richmond, IN 47374, USA
| | - Randal S. Stahl
- APHIS, US Department of Agriculture, 4101 La Porte Avenue, Fort Collins, CO 80521, USA
| | - Carol Furcolow
- APHIS, US Department of Agriculture, 4101 La Porte Avenue, Fort Collins, CO 80521, USA
| | - Fred Kraus
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA
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64
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Thorne MAS, Seybold A, Marshall C, Wharton D. Molecular snapshot of an intracellular freezing event in an Antarctic nematode. Cryobiology 2017; 75:117-124. [PMID: 28082102 DOI: 10.1016/j.cryobiol.2017.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 12/19/2016] [Accepted: 01/08/2017] [Indexed: 10/20/2022]
Abstract
The Antarctic nematode, Panagrolaimus sp. DAW1 (formerly called Panagrolaimus davidi), is the best documented example of an organism able to survive intracellular ice formation in all of its compartments. Not only is it able to survive such extreme physiological disruption, but it is able to produce progeny once thawed from such a state. In addition, under slower rates, or less extreme degrees, of cooling, its body remains unfrozen and the vapour pressure difference between the supercooled body fluids and the surrounding ice leads to a process termed cryoprotective dehydration. In contrast to a fairly large body of work in building up our molecular understanding of cryoprotective dehydration, no comparable work has been undertaken on intracellular freezing. This paper describes an experiment subjecting cultures of Panagrolaimus sp. DAW1 to a range of temperatures including a rapid descent to -10 °C, in a medium just prior to, and after, freezing. Through deep sequencing of RNA libraries we have gained a snapshot of which genes are highly abundant when P. sp. DAW1 is undergoing an intracellular freezing event. The onset of freezing correlated with a high production of genes involved in cuticle formation and subsequently, after 24 h in a frozen state, protease production. In addition to the mapping of RNA sequencing, we have focused on a select set of genes arising both from the expression profiles, as well as implicated from other cold tolerance studies, to undertake qPCR. Among the most abundantly represented transcripts in the RNA mapping is the zinc-metalloenzyme, neprilysin, which also shows a particularly strong upregulated signal through qPCR once the nematodes have frozen.
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Affiliation(s)
| | - Anna Seybold
- Department of Biochemistry, and Genetics Otago, University of Otago, Dunedin, New Zealand
| | - Craig Marshall
- Department of Biochemistry, and Genetics Otago, University of Otago, Dunedin, New Zealand
| | - David Wharton
- Department of Zoology, University of Otago, Dunedin, New Zealand
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65
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Lillywhite HB, Shine R, Jacobson E, DeNardo DF, Gordon MS, Navas CA, Wang T, Seymour RS, Storey KB, Heatwole H, Heard D, Brattstrom B, Burghardt GM. Anesthesia and Euthanasia of Amphibians and Reptiles Used in Scientific Research: Should Hypothermia and Freezing Be Prohibited? Bioscience 2016. [DOI: 10.1093/biosci/biw143] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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66
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Morey AC, Venette RC, Nystrom Santacruz EC, Mosca LA, Hutchison WD. Host-mediated shift in the cold tolerance of an invasive insect. Ecol Evol 2016; 6:8267-8275. [PMID: 27878094 PMCID: PMC5108276 DOI: 10.1002/ece3.2564] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 09/15/2016] [Accepted: 09/30/2016] [Indexed: 11/30/2022] Open
Abstract
While many insects cannot survive the formation of ice within their bodies, a few species can. On the evolutionary continuum from freeze‐intolerant (i.e., freeze‐avoidant) to freeze‐tolerant insects, intermediates likely exist that can withstand some ice formation, but not enough to be considered fully freeze tolerant. Theory suggests that freeze tolerance should be favored over freeze avoidance among individuals that have low relative fitness before exposure to cold. For phytophagous insects, numerous studies have shown that host (or nutrition) can affect fitness and cold‐tolerance strategy, respectively, but no research has investigated whether changes in fitness caused by different hosts of polyphagous species could lead to systematic changes in cold‐tolerance strategy. We tested this relationship with the invasive, polyphagous moth, Epiphyas postvittana (Walker). Host affected components of fitness, such as larval survivorship rates, pupal mass, and immature developmental times. Host species also caused a dramatic change in survival of late‐instar larvae after the onset of freezing—from less than 8% to nearly 80%. The degree of survival after the onset of freezing was inversely correlated with components of fitness in the absence of cold exposure. Our research is the first empirical evidence of an evolutionary mechanism that may drive changes in cold‐tolerance strategies. Additionally, characterizing the effects of host plants on insect cold tolerance will enhance forecasts of invasive species dynamics, especially under climate change.
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Affiliation(s)
- Amy C Morey
- Department of Entomology University of Minnesota St. Paul MN USA
| | - Robert C Venette
- USDA, Forest Service North Central Research Station St. Paul MN USA
| | | | - Laurel A Mosca
- Department of Entomology University of Minnesota St. Paul MN USA
| | - W D Hutchison
- Department of Entomology University of Minnesota St. Paul MN USA
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Cortes PA, Puschel H, Acuña P, Bartheld JL, Bozinovic F. Thermal ecological physiology of native and invasive frog species: do invaders perform better? CONSERVATION PHYSIOLOGY 2016; 4:cow056. [PMID: 27933168 PMCID: PMC5141634 DOI: 10.1093/conphys/cow056] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 10/03/2016] [Accepted: 10/26/2016] [Indexed: 06/04/2023]
Abstract
Biological invasions are recognized as an important biotic component of global change that threatens the composition, structure and functioning of ecosystems, resulting in loss of biodiversity and displacement of native species. Although ecological characteristics facilitating the establishment and spread of non-native species are widely recognized, little is known about organismal attributes underlying invasion success. In this study, we tested the effect of thermal acclimation on thermal tolerance and locomotor performance in the invasive Xenopus laevis and the Chilean native Calyptocephalella gayi. In particular, the maximal righting performance (μMAX), optimal temperature (TO), lower (CTmin) and upper critical thermal limits (CTmax), thermal breadth (Tbr) and the area under the performance curve (AUC) were studied after 6 weeks acclimation to 10 and 20°C. We observed higher values of μmax and AUC in X. laevis in comparison to C. gayi. On the contrary, the invasive species showed lower values of CTmin in comparison to the native one. In contrast, CTmax, TO and Tbr showed no inter-specific differences. Moreover, we found that both species have the ability to acclimate their locomotor performance and lower thermal tolerance limit at low temperatures. Our results demonstrate that X. laevis is a better performer than C. gayi. Although there were differences in CTmin, the invasive and native frogs did not differ in their thermal tolerance. Interestingly, in both species the lower and upper critical thermal limits are beyond the minimal and maximal temperatures encountered in nature during the coldest and hottest month, respectively. Overall, our findings suggest that both X. laevis and C. gayi would be resilient to climate warming expectations in Chile.
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Affiliation(s)
- Pablo A. Cortes
- Departamento de Ecología, Center of Applied Ecology & Sustainability (CAPES), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile
| | - Hans Puschel
- Departamento de Ecología, Center of Applied Ecology & Sustainability (CAPES), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile
| | - Paz Acuña
- Departamento de Ciencias Básicas, Universidad Santo Tomás, Santiago, Chile
| | - José L. Bartheld
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Chile
| | - Francisco Bozinovic
- Departamento de Ecología, Center of Applied Ecology & Sustainability (CAPES), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile
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68
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Enzymatic regulation of seasonal glycogen cycling in the freeze-tolerant wood frog, Rana sylvatica. J Comp Physiol B 2016; 186:1045-1058. [PMID: 27424164 DOI: 10.1007/s00360-016-1012-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 06/20/2016] [Accepted: 07/09/2016] [Indexed: 10/21/2022]
Abstract
Liver glycogen is an important energy store in vertebrates, and in the freeze-tolerant wood frog, Rana sylvatica, this carbohydrate also serves as a major source of the cryoprotectant glucose. We investigated how variation in the levels of the catalytic subunit of protein kinase A (PKAc), glycogen phosphorylase (GP), and glycogen synthase (GS) relates to seasonal glycogen cycling in a temperate (Ohioan) and subarctic (Alaskan) populations of this species. In spring, Ohioan frogs had reduced potential for glycogen synthesis, as evidenced by low GS activity and high PKAc protein levels. In addition, glycogen levels in spring were the lowest of four seasonal samples, as energy input was likely directed towards metabolism and somatic growth during this period. Near-maximal glycogen levels were reached by mid-summer, and remained unchanged in fall and winter, suggesting that glycogenesis was curtailed during this period. Ohioan frogs had a high potential for glycogenolysis and glycogenesis in winter, as evidenced by large glycogen reserves, high levels of GP and GS proteins, and high GS activity, which likely allows for rapid mobilization of cryoprotectant during freezing and replenishing of glycogen reserves during thawing. Alaskan frogs also achieved a near-maximal liver glycogen concentration by summer and displayed high glycogenic and glycogenolytic potential in winter, but, unlike Ohioan frogs, started replenishing their energy reserves early in spring. We conclude that variation in levels of both glycogenolytic and glycogenic enzymes likely happens in response to seasonal changes in energetic strategies and demands, with winter survival being a key component to understanding the regulation of glycogen cycling in this species.
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69
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Variation in winter metabolic reduction between sympatric amphibians. Comp Biochem Physiol A Mol Integr Physiol 2016; 201:110-114. [PMID: 27418441 DOI: 10.1016/j.cbpa.2016.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 06/28/2016] [Accepted: 07/06/2016] [Indexed: 11/23/2022]
Abstract
Distribution and abundance of temperate ectotherms is determined, in part, by the depletion of their limited caloric reserves during wintering. The magnitude of winter energy drain depends on the species-specific capacity to seasonally modify the minimal maintenance costs. We examined seasonal variation of minimum oxygen consumption between two newt species, Ichthyosaura alpestris and Lissotriton vulgaris. Oxygen consumption was measured in both species during their active season (daily temperature range=12-22°C) and wintering period (4°C) at 4°C and 8°C. The seasonal reduction in metabolic rates differed between species and experimental temperatures. Wintering newts reduced their metabolic rates at 4°C and 8°C in I. alpestris, but only at 8°C in L. vulgaris. Both species reduced the thermal sensitivity of oxygen consumption during wintering. Theoretical calculations of winter depletion of caloric reserves under various thermal conditions revealed that seasonal metabolic reduction is more effective in I. alpestris than in L. vulgaris, and its effectiveness will increase with the proportion of warmer days during wintering period. The variation in winter metabolic reduction between sympatric newt species potentially contributes to their distribution patterns and population dynamics under climate change.
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70
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Larson DJ, Barnes BM. Cryoprotectant Production in Freeze-Tolerant Wood Frogs Is Augmented by Multiple Freeze-Thaw Cycles. Physiol Biochem Zool 2016; 89:340-6. [DOI: 10.1086/687305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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71
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72
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O'Connor JH, Rittenhouse TAG. Snow cover and late fall movement influence wood frog survival during an unusually cold winter. Oecologia 2015; 181:635-44. [PMID: 26497126 DOI: 10.1007/s00442-015-3450-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 09/07/2015] [Indexed: 11/25/2022]
Abstract
Understanding how organisms will respond to altered winter conditions is hampered by a paucity of information on the winter ecology for many species. Amphibians are sensitive to environmental temperature and moisture conditions and may be vulnerable to changes in winter climate. We used a combination of radio telemetry and field enclosures to monitor survival of the freeze-tolerant wood frog (Lithobates sylvaticus) during the unusually cold winter of 2013-2014. We experimentally manipulated snow cover to determine the effect of snow removal on winter survival. In addition, we placed a group of untracked frogs at locations used by tracked frogs prior to long-distance late fall movement to investigate whether late fall movement entailed survival consequences. Winter survival was highest (75.3 %) among frogs at post-movement locations that received natural snow cover. The odds of surviving the winter for frogs in the snow removal treatment was only 21.6 % that of frogs in the natural snow treatment. Likewise, paired frogs placed at pre-fall movement locations had only 35.1 % the odds of surviving as tracked frogs at post-fall movement locations. A comparison of a priori models that included microhabitat conditions measured at wood frog overwintering locations revealed that the minimum temperature experienced and the depth of the frog in the substrate explained additional variation in winter survival. Our results suggest that acute exposure to lethal temperature conditions is the most likely cause of mortality during this study, rather than energy exhaustion or desiccation. They also demonstrate the importance of snow cover to the winter survival of wood frogs.
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Affiliation(s)
- Jason H O'Connor
- Department of Natural Resources and the Environment, University of Connecticut, Storrs, CT, 06269-4087, USA. .,Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Holt, FL, 32564, USA.
| | - Tracy A G Rittenhouse
- Department of Natural Resources and the Environment, University of Connecticut, Storrs, CT, 06269-4087, USA
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73
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Sanabria EA, Rodríguez CY, Vergara C, Ontivero E, Banchig M, Navas AL, Herrera-Morata MA, Quiroga LB. Thermal ecology of the post–metamorphic Andean toad (Rhinella spinulosa) at elevation in the monte desert, Argentina. J Therm Biol 2015; 52:52-7. [DOI: 10.1016/j.jtherbio.2015.05.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 10/23/2022]
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74
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Rexer-Huber K, Bishop PJ, Wharton DA. Field ecology of freezing: Linking microhabitat use with freezing tolerance inLitoria ewingii. AUSTRAL ECOL 2015. [DOI: 10.1111/aec.12275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Kalinka Rexer-Huber
- Department of Zoology; University of Otago; PO Box 56 Dunedin 9054 New Zealand
| | - Phillip J. Bishop
- Department of Zoology; University of Otago; PO Box 56 Dunedin 9054 New Zealand
| | - David A. Wharton
- Department of Zoology; University of Otago; PO Box 56 Dunedin 9054 New Zealand
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75
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Rosendale AJ, Lee RE, Costanzo JP. Seasonal variation and freezing response of glucose transporter 2 in liver of the wood frog: implications for geographic variation in freeze tolerance. J Zool (1987) 2015. [DOI: 10.1111/jzo.12255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
| | - R. E. Lee
- Department of Zoology; Miami University; Oxford OH USA
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76
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Driedzic WR. Rainbow smelt: the unusual case of cryoprotection by sustained glycerol production in an aquatic animal. J Comp Physiol B 2015; 185:487-99. [DOI: 10.1007/s00360-015-0903-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/12/2015] [Accepted: 04/19/2015] [Indexed: 12/18/2022]
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77
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Cryoprotectants and extreme freeze tolerance in a subarctic population of the wood frog. PLoS One 2015; 10:e0117234. [PMID: 25688861 PMCID: PMC4331536 DOI: 10.1371/journal.pone.0117234] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 12/19/2014] [Indexed: 01/29/2023] Open
Abstract
Wood frogs (Rana sylvatica) exhibit marked geographic variation in freeze tolerance, with subarctic populations tolerating experimental freezing to temperatures at least 10-13 degrees Celsius below the lethal limits for conspecifics from more temperate locales. We determined how seasonal responses enhance the cryoprotectant system in these northern frogs, and also investigated their physiological responses to somatic freezing at extreme temperatures. Alaskan frogs collected in late summer had plasma urea levels near 10 μmol ml-1, but this level rose during preparation for winter to 85.5 ± 2.9 μmol ml-1 (mean ± SEM) in frogs that remained fully hydrated, and to 186.9 ± 12.4 μmol ml-1 in frogs held under a restricted moisture regime. An osmolality gap indicated that the plasma of winter-conditioned frogs contained an as yet unidentified osmolyte(s) that contributed about 75 mOsmol kg-1 to total osmotic pressure. Experimental freezing to -8°C, either directly or following three cycles of freezing/thawing between -4 and 0°C, or -16°C increased the liver's synthesis of glucose and, to a lesser extent, urea. Concomitantly, organs shed up to one-half (skeletal muscle) or two-thirds (liver) of their water, with cryoprotectant in the remaining fluid reaching concentrations as high as 0.2 and 2.1 M, respectively. Freeze/thaw cycling, which was readily survived by winter-conditioned frogs, greatly increased hepatic glycogenolysis and delivery of glucose (but not urea) to skeletal muscle. We conclude that cryoprotectant accrual in anticipation of and in response to freezing have been greatly enhanced and contribute to extreme freeze tolerance in northern R. sylvatica.
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78
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do Amaral MCF, Lee RE, Costanzo JP. Hepatocyte responses toin vitrofreezing and β-adrenergic stimulation: Insights into the extreme freeze tolerance of subarcticRana sylvatica. ACTA ACUST UNITED AC 2015; 323:89-96. [DOI: 10.1002/jez.1905] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/17/2014] [Accepted: 10/22/2014] [Indexed: 11/05/2022]
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79
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Rosendale AJ, Lee RE, Costanzo JP. Effect of physiological stress on expression of glucose transporter 2 in liver of the wood frog, Rana sylvatica. ACTA ACUST UNITED AC 2014; 321:566-76. [PMID: 25384572 DOI: 10.1002/jez.1885] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 07/18/2014] [Accepted: 07/28/2014] [Indexed: 11/11/2022]
Abstract
Glucose transporters (GLUTs) have been implicated in the survival of various physiological stresses in mammals; however, little is known about the role of these proteins in stress tolerance in lower vertebrates. The wood frog (Rana sylvatica), which survives multiple winter-related stresses by copiously mobilizing hepatic glycogen stores, is an interesting subject for the study of glucose transport in amphibians. We examined the effects of several physiological stresses on GLUT2 protein and mRNA levels in the liver of R. sylvatica. Using immunoblotting techniques to measure relative GLUT2 abundance, we found that GLUT2 numbers increased in response to organismal freezing, hypoxia exposure, and glucose loading; whereas, experimental dehydration and urea loading did not affect GLUT2 abundance. GLUT2 mRNA levels, assessed using quantitative real-time polymerase chain reaction, changed in accordance with protein abundance for most stresses, indicating that transcriptional regulation of GLUT2 occurs in response to stress. Overall, hepatic GLUT2 seems to be important in stress survival in R. sylvatica and is regulated to meet the physiological need to accumulate glucose.
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80
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Hayward SAL, Manso B, Cossins AR. Molecular basis of chill resistance adaptations in poikilothermic animals. ACTA ACUST UNITED AC 2014; 217:6-15. [PMID: 24353199 DOI: 10.1242/jeb.096537] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chill and freeze represent very different components of low temperature stress. Whilst the principal mechanisms of tissue damage and of acquired protection from freeze-induced effects are reasonably well established, those for chill damage and protection are not. Non-freeze cold exposure (i.e. chill) can lead to serious disruption to normal life processes, including disruption to energy metabolism, loss of membrane perm-selectivity and collapse of ion gradients, as well as loss of neuromuscular coordination. If the primary lesions are not relieved then the progressive functional debilitation can lead to death. Thus, identifying the underpinning molecular lesions can point to the means of building resistance to subsequent chill exposures. Researchers have focused on four specific lesions: (i) failure of neuromuscular coordination, (ii) perturbation of bio-membrane structure and adaptations due to altered lipid composition, (iii) protein unfolding, which might be mitigated by the induced expression of compatible osmolytes acting as 'chemical chaperones', (iv) or the induced expression of protein chaperones along with the suppression of general protein synthesis. Progress in all these potential mechanisms has been ongoing but not substantial, due in part to an over-reliance on straightforward correlative approaches. Also, few studies have intervened by adoption of single gene ablation, which provides much more direct and compelling evidence for the role of specific genes, and thus processes, in adaptive phenotypes. Another difficulty is the existence of multiple mechanisms, which often act together, thus resulting in compensatory responses to gene manipulations, which may potentially mask disruptive effects on the chill tolerance phenotype. Consequently, there is little direct evidence of the underpinning regulatory mechanisms leading to induced resistance to chill injury. Here, we review recent advances mainly in lower vertebrates and in arthropods, but increasingly in genetic model species from a broader range of taxa.
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Affiliation(s)
- Scott A L Hayward
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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81
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Rosendale AJ, Philip BN, Lee RE, Costanzo JP. Cloning, characterization, and expression of glucose transporter 2 in the freeze-tolerant wood frog, Rana sylvatica. Biochim Biophys Acta Gen Subj 2014; 1840:1701-11. [DOI: 10.1016/j.bbagen.2013.12.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 12/01/2013] [Accepted: 12/09/2013] [Indexed: 01/22/2023]
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82
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Larson DJ, Middle L, Vu H, Zhang W, Serianni AS, Duman J, Barnes BM. Wood frog adaptations to overwintering in Alaska: new limits to freezing tolerance. ACTA ACUST UNITED AC 2014; 217:2193-200. [PMID: 24737762 DOI: 10.1242/jeb.101931] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the ecological physiology and behavior of free-living wood frogs [Lithobates (Rana) sylvaticus] overwintering in Interior Alaska by tracking animals into natural hibernacula, recording microclimate, and determining frog survival in spring. We measured cryoprotectant (glucose) concentrations and identified the presence of antifreeze glycolipids in tissues from subsamples of naturally freezing frogs. We also recorded the behavior of wood frogs preparing to freeze in artificial hibernacula, and tissue glucose concentrations in captive wood frogs frozen in the laboratory to -2.5°C. Wood frogs in natural hibernacula remained frozen for 193 ± 11 consecutive days and experienced average (October-May) temperatures of -6.3°C and average minimum temperatures of -14.6 ± 2.8°C (range -8.9 to -18.1°C) with 100% survival (N=18). Mean glucose concentrations were 13-fold higher in muscle, 10-fold higher in heart and 3.3-fold higher in liver in naturally freezing compared with laboratory frozen frogs. Antifreeze glycolipid was present in extracts from muscle and internal organs, but not skin, of frozen frogs. Wood frogs in Interior Alaska survive freezing to extreme limits and durations compared with those described in animals collected in southern Canada or the Midwestern United States. We hypothesize that this enhancement of freeze tolerance in Alaskan wood frogs is due to higher cryoprotectant levels that are produced by repeated freezing and thawing cycles experienced under natural conditions during early autumn.
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Affiliation(s)
- Don J Larson
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Luke Middle
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Henry Vu
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Wenhui Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Anthony S Serianni
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - John Duman
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Brian M Barnes
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
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83
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Reynolds AM, Lee RE, Costanzo JP. Membrane adaptation in phospholipids and cholesterol in the widely distributed, freeze-tolerant wood frog, Rana sylvatica. J Comp Physiol B 2014; 184:371-83. [DOI: 10.1007/s00360-014-0805-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 01/08/2014] [Accepted: 01/17/2014] [Indexed: 10/25/2022]
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84
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Kawarasaki Y, Teets NM, Denlinger DL, Lee RE. Alternative overwintering strategies in an Antarctic midge: freezing vs. cryoprotective dehydration. Funct Ecol 2014. [DOI: 10.1111/1365-2435.12229] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Yuta Kawarasaki
- Department of Zoology; Miami University; Oxford OH 45056 USA
| | - Nicholas M. Teets
- Department of Entomology; The Ohio State University; Columbus OH 43210 USA
| | - David L. Denlinger
- Department of Entomology; The Ohio State University; Columbus OH 43210 USA
- Department of Evolution, Ecology, and Organismal Biology; The Ohio State University; Columbus OH 43210 USA
| | - Richard E. Lee
- Department of Zoology; Miami University; Oxford OH 45056 USA
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85
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do Amaral MCF, Lee RE, Costanzo JP. Enzymatic regulation of glycogenolysis in a subarctic population of the wood frog: implications for extreme freeze tolerance. PLoS One 2013; 8:e79169. [PMID: 24236105 PMCID: PMC3827335 DOI: 10.1371/journal.pone.0079169] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 09/25/2013] [Indexed: 11/19/2022] Open
Abstract
The wood frog, Rana sylvatica, from Interior Alaska survives freezing at –16°C, a temperature 10–13°C below that tolerated by its southern conspecifics. We investigated the hepatic freezing response in this northern phenotype to determine if its profound freeze tolerance is associated with an enhanced glucosic cryoprotectant system. Alaskan frogs had a larger liver glycogen reserve that was mobilized faster during early freezing as compared to conspecifics from a cool-temperate region (southern Ohio, USA). In Alaskan frogs the rapid glucose production in the first hours of freezing was associated with a 7-fold increase in glycogen phosphorylase activity above unfrozen frog levels, and the activity of this enzyme was higher than that of frozen Ohioan frogs. Freezing of Ohioan frogs induced a more modest (4-fold) increase in glycogen phosphorylase activity above unfrozen frog values. Relative to the Ohioan frogs, Alaskan frogs maintained a higher total protein kinase A activity throughout an experimental freezing/thawing time course, and this may have potentiated glycogenolysis during early freezing. We found populational variation in the activity and protein level of protein kinase A which suggested that the Alaskan population had a more efficient form of this enzyme. Alaskan frogs modulated their glycogenolytic response by decreasing the activity of glycogen phosphorylase after cryoprotectant mobilization was well under way, thereby conserving their hepatic glycogen reserve. Ohioan frogs, however, sustained high glycogen phosphorylase activity until early thawing and consumed nearly all their liver glycogen. These unique hepatic responses of Alaskan R. sylvatica likely contribute to this phenotype’s exceptional freeze tolerance, which is necessary for their survival in a subarctic climate.
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Affiliation(s)
- M. Clara F. do Amaral
- Department of Zoology, Miami University, Oxford, Ohio, United States of America
- * E-mail:
| | - Richard E. Lee
- Department of Zoology, Miami University, Oxford, Ohio, United States of America
| | - Jon P. Costanzo
- Department of Zoology, Miami University, Oxford, Ohio, United States of America
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86
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Costanzo JP, do Amaral MCF, Rosendale AJ, Lee RE. Hibernation physiology, freezing adaptation and extreme freeze tolerance in a northern population of the wood frog. J Exp Biol 2013; 216:3461-73. [DOI: 10.1242/jeb.089342] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
We investigated hibernation physiology and freeze tolerance in a population of the wood frog, Rana sylvatica, indigenous to Interior Alaska, USA, near the northernmost limit of the species' range. Winter acclimatization responses included a 233% increase in the hepatic glycogen depot that was subsidized by fat body and skeletal muscle catabolism, and a rise in plasma osmolality that reflected accrual of urea (to 106±10 μmol ml−1) and an unidentified solute (to ~73 μmol ml−1). In contrast, frogs from a cool-temperate population (southern Ohio, USA) amassed much less glycogen, had a lower uremia (28±5 μmol ml−1) and apparently lacked the unidentified solute. Alaskan frogs survived freezing at temperatures as low as −16°C, some 10–13°C below those tolerated by southern conspecifics, and endured a 2-month bout of freezing at −4°C. The profound freeze tolerance is presumably due to their high levels of organic osmolytes and bound water, which limits ice formation. Adaptive responses to freezing (−2.5°C for 48 h) and subsequent thawing (4°C) included synthesis of the cryoprotectants urea and glucose, and dehydration of certain tissues. Alaskan frogs differed from Ohioan frogs in retaining a substantial reserve capacity for glucose synthesis, accumulating high levels of cryoprotectants in brain tissue, and remaining hyperglycemic long after thawing. The northern phenotype also incurred less stress during freezing/thawing, as indicated by limited cryohemolysis and lactate accumulation. Post-glacial colonization of high latitudes by R. sylvatica required a substantial increase in freeze tolerance that was at least partly achieved by enhancing their cryoprotectant system.
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Affiliation(s)
- Jon P. Costanzo
- Department of Zoology, Miami University, Oxford, OH 45056, USA
| | | | | | - Richard E. Lee
- Department of Zoology, Miami University, Oxford, OH 45056, USA
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