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Davis CG, Weaver SJ, Taylor EN. Cutaneous Evaporative Water Loss in Lizards Changes Immediately with Temperature. ECOLOGICAL AND EVOLUTIONARY PHYSIOLOGY 2024; 97:118-128. [PMID: 38728691 DOI: 10.1086/730423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
AbstractCutaneous evaporative water loss (CEWL) makes up a significant portion of total evaporative water loss in many terrestrial vertebrates. CEWL changes on evolutionary and acclimatory timescales in response to temperature and humidity. However, the lability of CEWL on acute timescales is unknown. To examine this, we increased or decreased body temperatures of western fence lizards (Sceloporus occidentalis) over a 15-min period while continuously recording CEWL with a handheld evaporimeter. CEWL increased in response to heating and decreased in response to cooling on the order of seconds. However, CEWL was different between heating and cooling groups at a common body temperature. We observed the same positive relationship between CEWL and body temperature, as well as the difference in CEWL between treatments, for deceased lizards that we opportunistically measured. However, deceased lizards had more extreme CEWL values for any given body temperature and treatment. Overall, our results suggest that both structural traits and active physiological processes likely influence the rates and plasticity of CEWL.
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Reher S, Rabarison H, Nowack J, Dausmann KH. Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.779381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Rapid environmental changes are challenging for endothermic species because they have direct and immediate impacts on their physiology by affecting microclimate and fundamental resource availability. Physiological flexibility can compensate for certain ecological perturbations, but our basic understanding of how species function in a given habitat and the extent of their adaptive scope is limited. Here we studied the effect of acute, experimental microclimate change on the thermal physiology of two populations of the widespread Malagasy bat, Macronycteris commersoni. Populations of this species are found roosting under contrasting conditions, i.e., in a constant hot and humid cave or below foliage unprotected from fluctuations in ambient conditions. We exposed free-ranging individuals of each population to the respective opposite condition and thus to novel microclimate within an ecologically realistic scope while measuring metabolic rate and skin temperature. Cave bats in forest setting had a limited capacity to maintain euthermia to the point that two individuals became hypothermic when ambient temperature dropped below their commonly experienced cave temperature. Forest bats on the other hand, had difficulties to dissipate heat in the humid cave set-up. The response to heat, however, was surprisingly uniform and all bats entered torpor combined with hyperthermia at temperatures exceeding their thermoneutral zone. Thus, while we observed potential for flexible compensation of heat through “hot” torpor, both populations showed patterns suggestive of limited potential to cope with acute microclimate changes deviating from their typically occupied roosts. Our study emphasizes that intraspecific variation among populations could be misleading when assessing species’ adaptive scopes, as variation may arise from genetic adaptation, developmental plasticity or phenotypic flexibility, all of which allow for compensatory responses at differing time scales. Disentangling these mechanisms and identifying the basis of variation is vital to make accurate predictions of species’ chances for persisting in ever rapidly changing habitats and climates.
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Vietri Rudan M, Watt FM. Mammalian Epidermis: A Compendium of Lipid Functionality. Front Physiol 2022; 12:804824. [PMID: 35095565 PMCID: PMC8791442 DOI: 10.3389/fphys.2021.804824] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/13/2021] [Indexed: 11/13/2022] Open
Abstract
Mammalian epidermis is a striking example of the role of lipids in tissue biology. In this stratified epithelium, highly specialized structures are formed that leverage the hydrophobic properties of lipids to form an impermeable barrier and protect the humid internal environment of the body from the dry outside. This is achieved through tightly regulated lipid synthesis that generates the molecular species unique to the tissue. Beyond their fundamental structural role, lipids are involved in the active protection of the body from external insults. Lipid species present on the surface of the body possess antimicrobial activity and directly contribute to shaping the commensal microbiota. Lipids belonging to a variety of classes are also involved in the signaling events that modulate the immune responses to environmental stress as well as differentiation of the epidermal keratinocytes themselves. Recently, high-resolution methods are beginning to provide evidence for the involvement of newly identified specific lipid molecules in the regulation of epidermal homeostasis. In this review we give an overview of the wide range of biological functions of mammalian epidermal lipids.
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4
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Paces B, Waringer BM, Domer A, Burns D, Zvik Y, Wojciechowski MS, Shochat E, Sapir N, Maggini I. Evaporative Water Loss and Stopover Behavior in Three Passerine Bird Species During Autumn Migration. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.704676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Migratory birds are often not specifically adapted to arid conditions, yet several species travel across deserts during their journeys, and often have more or less short stopovers there. We investigated whether differences in thermoregulatory mechanisms, specifically evaporative cooling, explain the different behavior of three passerine species while stopping over in the Negev desert, Israel. We measured cutaneous water loss (CWL) under ambient conditions and the temperature of panting onset in an experimental setup. In addition, we performed behavioral observations of birds at a stopover site where we manipulated water availability. Blackcaps had slightly higher CWL at relatively low temperatures than Willow Warblers and Lesser Whitethroats. When considered relative to total body mass, however, Willow Warblers had the highest CWL of the three species. Blackcaps started panting at lower ambient temperature than the other two species. Taken together, these results suggest that Willow Warblers are the most efficient in cooling their body, possibly with the cost of needing to regain water by actively foraging during their staging. Lesser Whitethroats had a similar pattern, which was reflected in their slightly higher levels of activity and drinking behavior when water was available. However, in general the behavior of migratory species was not affected by the availability of water, and they were observed drinking rather rarely. Our results indicate that differences in thermoregulatory mechanisms might be at the basis of the evolution of different stopover strategies of migratory birds while crossing arid areas such as deserts.
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5
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Hlubeň M, Kratochvíl L, Gvoždík L, Starostová Z. Ontogeny, phylogeny and mechanisms of adaptive changes in evaporative water loss in geckos. J Evol Biol 2021; 34:1290-1301. [PMID: 34131979 DOI: 10.1111/jeb.13891] [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: 03/30/2021] [Revised: 05/23/2021] [Accepted: 06/01/2021] [Indexed: 11/28/2022]
Abstract
Body size dependence of metabolic rate, body surface and scale morphology complicate disentangling the contribution of these characteristics to adaptive changes in total evaporative water loss (TEWL) of reptiles. To separate adaptive changes from size-related dependence, we compared intra- and interspecific scaling of several candidate traits in eyelid geckos (Eublepharidae), a group exhibiting large variation in body size and TEWL. The intraspecific allometry of TEWL of a eublepharid species fits the geometric surface-mass relationship. However, evolutionary shifts to both higher and lower evaporation were strongly correlated with habitat aridity and cannot be explained by shifts in body size alone. The intraspecific allometry of standard metabolic rate is nearly the same as the interspecific allometry. Unlike for mammals and birds, this pattern rules out respiratory water loss as a driver of the adaptive changes in TEWL among eublepharids. Scale morphology was independent of TEWL variation as well, but the correlation between cutaneous water loss and TEWL suggests a crucial role of skin permeability in adaptation to habitat aridity. Our analyses demonstrate how powerful a comparison between intra- and interspecific allometries can be for detecting body size-dependent mechanisms of adaptive changes in ecophysiological traits correlated with body size.
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Affiliation(s)
- Martin Hlubeň
- Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Lukáš Kratochvíl
- Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Lumír Gvoždík
- Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic
| | - Zuzana Starostová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic
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6
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Riddell EA, Roback EY, Wells CE, Zamudio KR, Sears MW. Thermal cues drive plasticity of desiccation resistance in montane salamanders with implications for climate change. Nat Commun 2019; 10:4091. [PMID: 31501425 PMCID: PMC6733842 DOI: 10.1038/s41467-019-11990-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 08/06/2019] [Indexed: 01/21/2023] Open
Abstract
Organisms rely upon external cues to avoid detrimental conditions during environmental change. Rapid water loss, or desiccation, is a universal threat for terrestrial plants and animals, especially under climate change, but the cues that facilitate plastic responses to avoid desiccation are unclear. We integrate acclimation experiments with gene expression analyses to identify the cues that regulate resistance to water loss at the physiological and regulatory level in a montane salamander (Plethodon metcalfi). Here we show that temperature is an important cue for developing a desiccation-resistant phenotype and might act as a reliable cue for organisms across the globe. Gene expression analyses consistently identify regulation of stem cell differentiation and embryonic development of vasculature. The temperature-sensitive blood vessel development suggests that salamanders regulate water loss through the regression and regeneration of capillary beds in the skin, indicating that tissue regeneration may be used for physiological purposes beyond replacing lost limbs.
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Affiliation(s)
- Eric A Riddell
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA.
| | - Emma Y Roback
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA.,Biology Department, Grinnell College, 1116 Eighth Ave, Grinnell, IA, 50112, USA
| | - Christina E Wells
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA
| | - Kelly R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, E145 Corson Hall, Ithaca, NY, 14853, USA
| | - Michael W Sears
- Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC, 29631, USA
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7
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Champagne AM, Pigg VA, Allen HC, Williams JB. Presence and persistence of a highly ordered lipid phase state in the avian stratum corneum. J Exp Biol 2018; 221:jeb.176438. [DOI: 10.1242/jeb.176438] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 03/20/2018] [Indexed: 11/20/2022]
Abstract
To survive high temperatures in a terrestrial environment, animals must effectively balance evaporative heat loss and water conservation. In passerine birds, cutaneous water loss (CWL) is the primary avenue of water loss at thermoneutral temperatures, and increases slightly as ambient temperature increases, indicating a change in the permeability of the skin. In the stratum corneum (SC), the outermost layer of skin, lipids arranged in layers called lamellae serve as the primary barrier to CWL in birds. The permeability of these lamellae depends in large part on the ability of lipid molecules to pack closely together in an ordered orthorhombic phase state. However, as temperature increases, lipids of the SC become more disordered, and may pack in more permeable hexagonal or liquid crystalline phase states. In this study, we used Fourier transform infrared spectroscopy to monitor the phase state of lipids in the SC of house sparrows (Passer domesticus) at skin temperatures ranging from 25 to 50°C. As temperature increased, lipids became slightly more disordered, but remained predominantly in the orthorhombic phase, consistent with the small increase in CWL observed in house sparrows as ambient temperature increases. These results differ considerably from studies on mammalian SC, which find a predominantly hexagonal arrangement of lipids at temperatures above 37°C, and the increased order in avian SC may be explained by longer lipid chain length, scarcity of cholesterol, and the presence of cerebrosides. Our results lend further insight into the arrangement and packing of individual lipid molecules in avian SC.
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Affiliation(s)
- Alex M. Champagne
- Department of Biology, University of Southern Indiana, Science Center 1255 8600 University Blvd., Evansville, IN 47712, USA
| | - Victoria A. Pigg
- Department of Biology, University of Southern Indiana, Science Center 1255 8600 University Blvd., Evansville, IN 47712, USA
| | - Heather C. Allen
- Department of Chemistry and Biochemistry, The Ohio State University, 1102 Newman and Wolfrom Laboratory 100 W 18th Ave., Columbus, OH 43210, USA
- Department of Pathology, The Ohio State University, 129 Hamilton Hall 1645 Neil Ave., Columbus, OH 43210, USA
| | - Joseph B. Williams
- Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Aronoff Laboratory 318 W 12th Ave., Columbus, OH 43210, USA
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Dupoué A, Rutschmann A, Le Galliard JF, Miles DB, Clobert J, DeNardo DF, Brusch GA, Meylan S. Water availability and environmental temperature correlate with geographic variation in water balance in common lizards. Oecologia 2017; 185:561-571. [PMID: 29018996 DOI: 10.1007/s00442-017-3973-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 08/27/2017] [Indexed: 12/14/2022]
Abstract
Water conservation strategies are well documented in species living in water-limited environments, but physiological adaptations to water availability in temperate climate environments are still relatively overlooked. Yet, temperate species are facing more frequent and intense droughts as a result of climate change. Here, we examined variation in field hydration state (plasma osmolality) and standardized evaporative water loss rate (SEWL) of adult male and pregnant female common lizards (Zootoca vivipara) from 13 natural populations with contrasting air temperature, air humidity, and access to water. We found different patterns of geographic variation between sexes. Overall, males were more dehydrated (i.e. higher osmolality) than pregnant females, which likely comes from differences in field behaviour and water intake since the rate of SEWL was similar between sexes. Plasma osmolality and SEWL rate were positively correlated with environmental temperature in males, while plasma osmolality in pregnant females did not correlate with environmental conditions, reproductive stage or reproductive effort. The SEWL rate was significantly lower in populations without access to free standing water, suggesting that lizards can adapt or adjust physiology to cope with habitat dryness. Environmental humidity did not explain variation in water balance. We suggest that geographic variation in water balance physiology and behaviour should be taken account to better understand species range limits and sensitivity to climate change.
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Affiliation(s)
- Andréaz Dupoué
- CNRS UPMC, UMR 7618, iEES Paris, Université Pierre et Marie Curie, Tours 44-45, 4 Place Jussieu, 75005, Paris, France.
| | - Alexis Rutschmann
- Station d'Ecologie Théorique et Expérimentale du CNRS à Moulis, UMR 5321, 2 route du CNRS, 09200, Saint Girons, France
| | - Jean François Le Galliard
- CNRS UPMC, UMR 7618, iEES Paris, Université Pierre et Marie Curie, Tours 44-45, 4 Place Jussieu, 75005, Paris, France
- Département de biologie, Ecole normale supérieure, PSL Research University, CNRS, UMS 3194, Centre de recherche en écologie expérimentale et prédictive (CEREEP-Ecotron IleDeFrance), 78 rue du château, 77140, Saint-Pierre-lès-Nemours, France
| | - Donald B Miles
- Department of Biological Sciences, Ohio University, Athens, OH, 45701, USA
| | - Jean Clobert
- Station d'Ecologie Théorique et Expérimentale du CNRS à Moulis, UMR 5321, 2 route du CNRS, 09200, Saint Girons, France
| | - Dale F DeNardo
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287-4501, USA
| | - George A Brusch
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287-4501, USA
| | - Sandrine Meylan
- CNRS UPMC, UMR 7618, iEES Paris, Université Pierre et Marie Curie, Tours 44-45, 4 Place Jussieu, 75005, Paris, France
- ESPE de Paris, Université Sorbonne Paris IV, 10 rue Molitor, 75016, Paris, France
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9
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Adams EM, Champagne AM, Williams JB, Allen HC. Interfacial properties of avian stratum corneum monolayers investigated by Brewster angle microscopy and vibrational sum frequency generation. Chem Phys Lipids 2017; 208:1-9. [PMID: 28807615 DOI: 10.1016/j.chemphyslip.2017.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/04/2017] [Accepted: 08/06/2017] [Indexed: 10/19/2022]
Abstract
The outermost layer of skin, the stratum corneum (SC), contains a complex mixture of lipids, which controls the rate of cutaneous water loss (CWL) in reptiles, mammals, and birds. However, the molecular structure of SC lipids and how molecular configurations influence CWL is poorly understood. Here, the organization and structure of SC lipids extracted from birds were investigated by means of Langmuir films. Properties of lipids from the SC of arid and semi-arid adapted larks, known to have a low CWL, were compared with lipids extracted from the SC of mesic lark species with higher CWL to gain insight into how structure impacts CWL. Film properties were probed with surface pressure-area isotherms, Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG). Results indicate organization and ordering of SC lipids in the arid-adapted hoopoe lark was vastly different from all other species, forming a miscible, rigid monolayer, whereas monolayers from semi-arid and mesic species were immiscible and disordered. Probing of interfacial water structure reveals that film morphology determines organization of water molecules near the monolayer; monolayers with a porous morphology had an increased population of water molecules that are weakly hydrogen-bonded. In general, CWL appears related to the miscibility and ordering of lipid components within the SC, as well as the ability of these lipids to interact with water molecules. From a broader perspective, CWL in larks appears linked to both the SC lipid composition and the aridity of the species' environment.
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Affiliation(s)
- Ellen M Adams
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, 43210, United States
| | - Alex M Champagne
- Department of Biology, University of Southern Indiana, Evansville, IN, 47712, United States
| | - Joseph B Williams
- Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH, 43210, United States
| | - Heather C Allen
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH, 43210, United States.
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10
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Klüg-Baerwald BJ, Brigham RM. Hung out to dry? Intraspecific variation in water loss in a hibernating bat. Oecologia 2017; 183:977-985. [PMID: 28213638 DOI: 10.1007/s00442-017-3837-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 02/07/2017] [Indexed: 02/05/2023]
Abstract
Hibernation is a period of water deficit for some small mammals, and humidity strongly influences hibernation patterns. Dry conditions reduce length of torpor bouts, stimulate arousals, and decrease overwinter survival. To mitigate these effects, many small mammals hibernate in near saturated (100% RH) conditions. However, big brown bats (Eptesicus fuscus) hibernate in a wider variety of conditions and tolerate lower humidity than most other bats. To assess arid tolerance in this species, we compared torpid metabolic rates (TMR) and rates of total evaporative water loss (TEWL) between two populations of E. fuscus with differing winter ecologies: one that hibernates in humid karst caves and one that hibernates in relatively dry rock crevices. We used flow-through respirometry to measure TMR and TEWL of bats in humid and dry conditions. Torpid metabolic rates did not differ between populations or with humidity treatments. Rates of TEWL were similar between populations in humid conditions, but higher for cave-hibernating bats than crevice-hibernating bats in dry conditions. Our results suggest that E. fuscus hibernating in arid environments have mechanisms to decrease evaporative water loss that are not evident at more humid sites. Drought tolerance may facilitate the sedentary nature of the species, allowing them to tolerate more variable microclimates during hibernation and thus increasing the availability of overwintering habitat. The ability to survive arid conditions may also lessen the susceptibility of E. fuscus to diseases that affect water balance.
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Affiliation(s)
| | - R Mark Brigham
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK, Canada
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11
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Organization of lipids in avian stratum corneum: Changes with temperature and hydration. Chem Phys Lipids 2015; 195:47-57. [PMID: 26708071 DOI: 10.1016/j.chemphyslip.2015.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 11/11/2015] [Accepted: 12/08/2015] [Indexed: 11/23/2022]
Abstract
In response to increases in ambient temperature (Ta), many animals increase total evaporative water loss (TEWL) through their skin and respiratory passages to maintain a constant body temperature, a response that compromises water balance. In birds, cutaneous water loss (CWL) accounts for approximately 65% of TEWL at thermoneutral temperatures. Although the proportion of TEWL accounted for by CWL decreases to only 25% at high Ta, the magnitude of CWL still increases, suggesting changes in the barrier function of the skin. The stratum corneum (SC) is composed of flat, dead cells called corneocytes embedded in a matrix of lipids, many of which arrange in layers called lamellae. The classes of lipids that comprise these lamellae, and their attendant physical properties, determine the rate of CWL. We measured CWL at 25, 30, 35, and 40 °C in House Sparrows (Passer domesticus) caught in the winter and summer, and in sparrows acclimated to warm and cold lab environments. We then used Fourier transform infrared spectroscopy to measure lipid-lipid and lipid-water interactions in the SC under different conditions of temperature and hydration, and correlated these results with lipid classes in the SC. As CWL increased at higher temperatures, the amount of gauche defects in lipid alkyl chains increased, indicating that lipid disorder is partially responsible for higher CWL at high temperatures. However, variation in CWL between groups could not be explained by the amount of gauche defects, and this remaining variation may be attributed to greater amounts of cerebrosides in birds with low CWL, as the sugar moieties of cerebrosides lie outside lipid lamellae and form strong hydrogen bonds with water molecules.
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12
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Williams JB. The (Mostly) Good, the (Few) Bad, and the (Couple of) Ugly Chapters in Sturkie’s Avian PhysiologySturkie’s Avian Physiology. Edited by Colin G. Scanes. Waltham, MA: Academic Press, 2014. ISBN 978-0-124-07160-5. Physiol Biochem Zool 2015. [DOI: 10.1086/682700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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13
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Champagne AM, Allen HC, Williams JB. Lipid composition and molecular interactions change with depth in the avian stratum corneum to regulate cutaneous water loss. ACTA ACUST UNITED AC 2015; 218:3032-41. [PMID: 26447196 DOI: 10.1242/jeb.125310] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The outermost 10-20 µm of the epidermis, the stratum corneum (SC), consists of flat, dead cells embedded in a matrix of intercellular lipids. These lipids regulate cutaneous water loss (CWL), which accounts for over half of total water loss in birds. However, the mechanisms by which lipids are able to regulate CWL and how these mechanisms change with depth in the SC are poorly understood. We used attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to measure lipid-lipid and lipid-water interactions as a function of depth in the SC of house sparrows (Passer domesticus Linnaeus) in the winter and summer. We then compared these molecular interactions at each depth with lipid composition at the same depth. We found that in both groups, water content increased with depth in the SC, and likely contributed to greater numbers of gauche defects in lipids in deeper levels of the SC. In winter-caught birds, which had lower rates of CWL than summer-caught birds, water exhibited stronger hydrogen bonding in deeper layers of the SC, and these strong hydrogen bonds were associated with greater amounts of polar lipids such as ceramides and cerebrosides. Based on these data, we propose a model by which polar lipids in deep levels of the SC form strong hydrogen bonds with water molecules to increase the viscosity of water and slow the permeation of water through the SC.
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Affiliation(s)
- Alex M Champagne
- Department of Biology, University of Southern Indiana, Science Center 1255 8600 University Blvd, Evansville, IN 47712, USA
| | - Heather C Allen
- Department of Chemistry and Biochemistry, The Ohio State University, 1102 Newman and Wolfrom Laboratory, 100 W 18th Avenue, Columbus, OH 43210, USA Department of Pathology, The Ohio State University, 129 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA
| | - Joseph B Williams
- Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Aronoff Laboratory, 318 W 12th Avenue, Columbus, OH 43210, USA
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14
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Gerson AR, Smith EK, Smit B, McKechnie AE, Wolf BO. The impact of humidity on evaporative cooling in small desert birds exposed to high air temperatures. Physiol Biochem Zool 2014; 87:782-95. [PMID: 25461643 DOI: 10.1086/678956] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Environmental temperatures that exceed body temperature (Tb) force endothermic animals to rely solely on evaporative cooling to dissipate heat. However, evaporative heat dissipation can be drastically reduced by environmental humidity, imposing a thermoregulatory challenge. The goal of this study was to investigate the effects of humidity on the thermoregulation of desert birds and to compare the sensitivity of cutaneous and respiratory evaporation to reduced vapor density gradients. Rates of evaporative water loss, metabolic rate, and Tb were measured in birds exposed to humidities ranging from ∼2 to 30 g H2O m(-3) (0%-100% relative humidity at 30°C) at air temperatures between 44° and 56°C. In sociable weavers, a species that dissipates heat primarily through panting, rates of evaporative water loss were inhibited by as much as 36% by high humidity at 48°C, and these birds showed a high degree of hyperthermia. At lower temperatures (40°-44°C), evaporative water loss was largely unaffected by humidity in this species. In Namaqua doves, which primarily use cutaneous evaporation, increasing humidity reduced rates of evaporative water loss, but overall rates of water loss were lower than those observed in sociable weavers. Our data suggest that cutaneous evaporation is more efficient than panting, requiring less water to maintain Tb at a given temperature, but panting appears less sensitive to humidity over the air temperature range investigated here.
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Affiliation(s)
- Alexander R Gerson
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131; 2Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa; 3DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
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15
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Cooper CE, Withers PC. Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1042-8. [DOI: 10.1152/ajpregu.00051.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice ( Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals.
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Affiliation(s)
- Christine Elizabeth Cooper
- Department of Environment and Agriculture, Curtin University Perth, Western Australia; and Animal Biology, University of Western Australia, Crawley, Western Australia
| | - Philip Carew Withers
- Department of Environment and Agriculture, Curtin University Perth, Western Australia; and Animal Biology, University of Western Australia, Crawley, Western Australia
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Khan HA, Arif IA, Williams JB, Champagne AM, Shobrak M. Skin lipids from Saudi Arabian birds. Saudi J Biol Sci 2014; 21:173-7. [PMID: 24600311 PMCID: PMC3942862 DOI: 10.1016/j.sjbs.2013.09.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 09/10/2013] [Accepted: 09/15/2013] [Indexed: 02/05/2023] Open
Abstract
Skin lipids play an important role in the regulation of cutaneous water loss (CWL). Earlier studies have shown that Saudi desert birds exhibit a tendency of reduced CWL than birds from temperate environment due to adaptive changes in composition of their skin lipids. In this study, we used thin-layer chromatography (TLC) for separation and detection of non-polar and polar lipids from the skin of six bird species including sooty gull, brown booby, house sparrow, Arabian waxbill, sand partridge, and laughing dove. The lipids were separated and detected on Silica gel G coated TLC plates and quantified by using densitometric image analysis. Rf values of the non-polar lipids were as follows: cholesterol (0.29), free fatty acids (0.58), triacylglycerol (0.69), fatty acids methyl esters (0.84) and cholesterol ester (0.97). Rf values for the polar lipids were: cerebroside (0.42), ceramide (0.55) and cholesterol (0.73). The results showed the abundance of fatty acids methyl esters (47.75-60.46%) followed by triacylglycerol (12.69-24.14%). The remaining lipid compositions were as follows: cholesterol (4.09-13.18%), ceramide (2.18-13.27%), and cerebroside (2.53-12.81%). In conclusion, our findings showed that TLC is a simple and sensitive method for the separation and quantification of skin lipids. We also reported a new protocol for lipid extraction using the zirconia beads for efficient disruption of skin tissues. This study will help us better understand the role of skin lipids in adaptive physiology towards adverse climatic conditions.
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Affiliation(s)
- Haseeb A. Khan
- Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
- Corresponding author. Address: Department of Biochemistry College of Science, Bld 5 King Saud University P.O. Box 2455, Riyadh 11451, Saudi Arabia. Tel.: +966 11 4675859.
| | - Ibrahim A. Arif
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Joseph B. Williams
- Department of Evolution, Ecology and Organismal Biology, Aronoff Laboratory, Ohio State University, Columbus, USA
| | - Alex M. Champagne
- Department of Evolution, Ecology and Organismal Biology, Aronoff Laboratory, Ohio State University, Columbus, USA
| | - Mohammad Shobrak
- Department of Biology, College of Science, Taif University, Taif, Saudi Arabia
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