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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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Wang Z, Nie Y, Yu S, Chen L, Zhang L, Zhu W, Zhou Z, Diao J. Consolidation of temperature-dependent toxicity and thermoregulatory behavior into risk assessments of insecticides under thermal scenarios: A prospective study on Eremias argus. ENVIRONMENT INTERNATIONAL 2023; 172:107742. [PMID: 36669286 DOI: 10.1016/j.envint.2023.107742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/10/2022] [Accepted: 01/06/2023] [Indexed: 06/17/2023]
Abstract
In this study, the temperature-dependent chemical toxicity of three insecticides and the resulting thermoregulatory (TR) behavior of the lizard Eremias argus have been consolidated into the current risk assessment framework. According to acute dermal toxicity assays, an increase of ambient temperature from 15 °C to 35 °C decreased the acute dermal toxicity of beta-cyfluthrin (BC) but increased the toxicity of chlorpyrifos (CPF). The toxicity of avermectin (AVM) did not show significant temperature-dependent responses. Based on thermal preference trials, lizards changed their body temperature via TR behavior to adaptively reduce toxicity under sub-lethal doses, which can be understood as a "self-rescue" behavior attenuating lethal effects. However, the risk quotient indicated that the effectiveness of this "self-rescue" behavior is limited. Metabolomics analysis showed that six different metabolites (i.e., creatine, glutamate, succinate, N-acetylaspartate, acetylcholine, and lactate) contributed to TR behavior changes. Biochemical assays and insecticide residue results demonstrated that the temperature-dependent toxicity of BC, CPF, and AVM affected lizards in the three aspects of biotransformation, oxidative stress, and neurometabolic interference. This work clarifies the ecotoxicological impacts of representative insecticides on reptiles from toxicological understanding to risk relevance. This knowledge may improve ecological predictions of agrochemical applications in the context of global climate change.
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Affiliation(s)
- Zikang Wang
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Yufan Nie
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Simin Yu
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Li Chen
- Human Nutrition Program, Department of Human Sciences, The Ohio State University, Columbus, OH 43210, USA
| | - Luyao Zhang
- School of Food and Biological Engineering, Shaanxi University of Science and Technology, Xi'an 710021, China
| | - Wentao Zhu
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Zhiqiang Zhou
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Jinling Diao
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China.
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Gregorovicova M, Bartos M, Jensen B, Janacek J, Minne B, Moravec J, Sedmera D. Anguimorpha as a model group for studying the comparative heart morphology among Lepidosauria: Evolutionary window on the ventricular septation. Ecol Evol 2022; 12:e9476. [PMID: 36381397 PMCID: PMC9643144 DOI: 10.1002/ece3.9476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 11/11/2022] Open
Abstract
The group Anguimorpha represents one of the most unified squamate clades in terms of body plan, ecomorphology, ecophysiology and evolution. On the other hand, the anguimorphs vary between different habitats and ecological niches. Therefore, we focused on the group Anguimorpha to test a possible correlation between heart morphology and ecological niche with respect to phylogenetic position in Squamata with Sphenodon, Salvator, and Pogona as the outgroups. The chosen lepidosaurian species were investigated by microCT. Generally, all lepidosaurs had two well‐developed atria with complete interatrial septum and one ventricle divided by ventricular septa to three different areas. The ventricles of all lepidosaurians had a compact layer and abundant trabeculae. The compact layer and trabeculae were developed in accordance with particular ecological niche of the species, the trabeculae in nocturnal animals with low metabolism, such as Sphenodon, Heloderma or Lanthanotus were more massive. On the other hand athletic animals, such as varanids or Salvator, had ventricle compartmentalization divided by three incomplete septa. A difference between varanids and Salvator was found in compact layer thickness: thicker in monitor lizards and possibly linked to their mammalian‐like high blood pressure, and the level of ventricular septation. In summary: heart morphology varied among clades in connection with the ecological niche of particular species and it reflects the phylogenetic position in model clade Anguimorpha. In the absence of fossil evidence, this is the closest approach how to understand heart evolution and septation in clade with different cardiac compartmentalization levels.
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Affiliation(s)
- Martina Gregorovicova
- First Faculty of Medicine, Institute of Anatomy Charles University Prague Czech Republic
| | - Martin Bartos
- First Faculty of Medicine, Institute of Anatomy Charles University Prague Czech Republic
- First Faculty of Medicine Institute of Dental Medicine, Charles University Prague Czech Republic
| | - Bjarke Jensen
- Department of Medical Biology, Amsterdam Cardiovascular Sciences University of Amsterdam Amsterdam The Netherlands
| | - Jiri Janacek
- Laboratory of Biomathematics, Institute of Physiology Czech Academy of Sciences Prague Czech Republic
| | - Bryan Minne
- Amphibian Evolution Lab Free University of Brussels Brussels Belgium
| | | | - David Sedmera
- First Faculty of Medicine, Institute of Anatomy Charles University Prague Czech Republic
- Laboratory of Developmental Cardiology, Institute of Physiology Czech Academy of Sciences Prague Czech Republic
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Arfuso F, Cerutti RD, Scaglione MC, Sciabarrasi A, Giannetto C, Piccione G. Evaluation of locomotor activity in female Chelonoidis chilensis (Testudinidae, Gray 1870) in response to artificial photoperiod and temperature treatments. AMPHIBIA-REPTILIA 2022. [DOI: 10.1163/15685381-bja10096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Abstract
Turtles as many other reptiles are capable of orientating their bodies toward the sun. This conduct requires the presence of an internal biological chronometer in the organism that regulates this behavior. Thus, a description of the internal clock in these reptiles is of interest. The assessment of locomotor activity can be considered a reliable indicator of biological clock function. This study aimed to investigate the effect of different artificial photoperiod and ambient temperature schedules on total locomotor activity of female Chelonoidis chilensis and its rhythmicity. Six C. chilensis specimens were exposed to different artificial photoperiods and temperature regimes each fixed for seven days. It was observed that the activity period during the different experimental schedules was close to the 24 hours indicating a daily rhythmicity. Moreover, all tortoises showed a similar total locomotor activity pattern displaying the most of motion during light phase. Under the condition of constant light tortoises exhibited a self-sustaining rhythm not entrained to light and temperature zeitgebers, thus, suggesting its possible endogenous periodicity. Though this study deepens the knowledge on the rhythmic system of C. chilensis, further investigations are needed to achieve a more detailed understanding of tortoise biological clock.
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Affiliation(s)
- Francesca Arfuso
- Department of Veterinary Sciences, University of Messina, Polo University Annunziata, 98168 Messina, Italy
| | - Raúl D. Cerutti
- Department of Veterinary Sciences, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Maria C. Scaglione
- Department of Veterinary Sciences, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Antonio Sciabarrasi
- Department of Veterinary Sciences, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Claudia Giannetto
- Department of Veterinary Sciences, University of Messina, Polo University Annunziata, 98168 Messina, Italy
| | - Giuseppe Piccione
- Department of Veterinary Sciences, University of Messina, Polo University Annunziata, 98168 Messina, Italy
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Boukens BJD, Joyce W, Kristensen DL, Hooijkaas I, Jongejan A, Wang T, Jensen B. Catecholamines are key modulators of ventricular repolarization patterns in the ball python (Python regius). J Gen Physiol 2022; 154:212914. [PMID: 34910097 PMCID: PMC8679508 DOI: 10.1085/jgp.202012761] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/28/2021] [Accepted: 11/19/2021] [Indexed: 12/13/2022] Open
Abstract
Ectothermic vertebrates experience daily changes in body temperature, and anecdotal observations suggest these changes affect ventricular repolarization such that the T-wave in the ECG changes polarity. Mammals, in contrast, can maintain stable body temperatures, and their ventricular repolarization is strongly modulated by changes in heart rate and by sympathetic nervous system activity. The aim of this study was to assess the role of body temperature, heart rate, and circulating catecholamines on local repolarization gradients in the ectothermic ball python (Python regius). We recorded body-surface electrocardiograms and performed open-chest high-resolution epicardial mapping while increasing body temperature in five pythons, in all of which there was a change in T-wave polarity. However, the vector of repolarization differed between individuals, and only a subset of leads revealed T-wave polarity change. RNA sequencing revealed regional differences related to adrenergic signaling. In one denervated and Ringer's solution-perfused heart, heating and elevated heart rates did not induce change in T-wave polarity, whereas noradrenaline did. Accordingly, electrocardiograms in eight awake pythons receiving intra-arterial infusion of the β-adrenergic receptor agonists adrenaline and isoproterenol revealed T-wave inversion in most individuals. Conversely, blocking the β-adrenergic receptors using propranolol prevented T-wave change during heating. Our findings indicate that changes in ventricular repolarization in ball pythons are caused by increased tone of the sympathetic nervous system, not by changes in temperature. Therefore, ventricular repolarization in both pythons and mammals is modulated by evolutionary conserved mechanisms involving catecholaminergic stimulation.
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Affiliation(s)
- Bastiaan J D Boukens
- University of Amsterdam, Amsterdam UMC, Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
| | - William Joyce
- Department of Biology, Zoophysiology, Aarhus University, Aarhus, Denmark
| | | | - Ingeborg Hooijkaas
- University of Amsterdam, Amsterdam UMC, Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
| | - Aldo Jongejan
- University of Amsterdam, Amsterdam UMC, Department of Epidemiology & Data Science, Amsterdam, The Netherlands
| | - Tobias Wang
- Department of Biology, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - Bjarke Jensen
- University of Amsterdam, Amsterdam UMC, Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
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Rocha GC, Castro SA, Taylor EW, Tavares D, Leite CAC. A Decerebrate Preparation of the Rattlesnake, Crotalus durissus, Provides an Experimental Model for Study of Autonomic Modulation of the Cardiovascular System in Reptiles. Physiol Biochem Zool 2021; 94:269-285. [PMID: 34142933 DOI: 10.1086/714973] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractThe South American rattlesnake, Crotalus durissus, has been successfully used as an experimental model to study control of the cardiovascular system in squamate reptiles. Recent technical advances, including equipment miniaturization, have lessened the impact of instrumentation on in vivo recordings, and an increased range of anesthetic drugs has improved recording conditions for in situ preparations. Nevertheless, any animal-based experimental approach has to manage limitations regarding the avoidance of pain and stress the stability of the preparation and duration of experiments and the potentially overriding effects of anesthesia. To address such aspects, we tested a new experimental preparation, the decerebrate rattlesnake, in a study of the autonomic control of cardiovascular responses following the removal of general anesthesia. The preparation exhibited complex cardiovascular adjustments to deal with acute increases in venous return (caused by tail lifting), to compensate for blood flow reduction in the cephalic region (caused by head lifting), for body temperature control (triggered by an external heating source), and in response to stimulation of chemoreceptors (triggered by intravenous injection of NaCN). The decerebrate preparation retained extensive functional integrity of autonomic centers, and it was suitable for monitoring diverse cardiac and vascular variables. Furthermore, reanesthetizing the preparation markedly blunted cardiovascular performance. Isoflurane limited the maintenance of recovered cardiovascular variables in the prepared animal and reduced or abolished the observed cardiovascular reflexes. This preparation enables the recording of multiple concomitant cardiovascular variables for the study of mechanistic questions regarding the central integration of autonomic reflex responses in the absence of anesthesia.
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7
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Falcón W, Baxter RP, Furrer S, Bauert M, Hatt J, Schaepman‐Strub G, Ozgul A, Bunbury N, Clauss M, Hansen DM. Patterns of activity and body temperature of Aldabra giant tortoises in relation to environmental temperature. Ecol Evol 2018; 8:2108-2121. [PMID: 29468029 PMCID: PMC5817133 DOI: 10.1002/ece3.3766] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 10/19/2017] [Accepted: 12/06/2017] [Indexed: 11/25/2022] Open
Abstract
We studied the temperature relations of wild and zoo Aldabra giant tortoises (Aldabrachelys gigantea) focusing on (1) the relationship between environmental temperature and tortoise activity patterns (n = 8 wild individuals) and (2) on tortoise body temperature fluctuations, including how their core and external body temperatures vary in relation to different environmental temperature ranges (seasons; n = 4 wild and n = 5 zoo individuals). In addition, we surveyed the literature to review the effect of body mass on core body temperature range in relation to environmental temperature in the Testudinidae. Diurnal activity of tortoises was bimodally distributed and influenced by environmental temperature and season. The mean air temperature at which activity is maximized was 27.9°C, with a range of 25.8-31.7°C. Furthermore, air temperature explained changes in the core body temperature better than did mass, and only during the coldest trial, did tortoises with higher mass show more stable temperatures. Our results, together with the overall Testudinidae overview, suggest that, once variation in environmental temperature has been taken into account, there is little effect of mass on the temperature stability of tortoises. Moreover, the presence of thermal inertia in an individual tortoise depends on the environmental temperatures, and we found no evidence for inertial homeothermy. Finally, patterns of core and external body temperatures in comparison with environmental temperatures suggest that Aldabra giant tortoises act as mixed conformer-regulators. Our study provides a baseline to manage the thermal environment of wild and rewilded populations of an important island ecosystem engineer species in an era of climate change.
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Affiliation(s)
- Wilfredo Falcón
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
| | - Rich P. Baxter
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
| | | | | | - Jean‐Michel Hatt
- Clinic for Zoo Animals, Exotic Pets and WildlifeVetsuisse FacultyUniversity of ZurichZurichSwitzerland
| | - Gabriela Schaepman‐Strub
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
| | - Arpat Ozgul
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
| | - Nancy Bunbury
- Seychelles Islands FoundationPO Box 853, MaheSeychelles
| | - Marcus Clauss
- Clinic for Zoo Animals, Exotic Pets and WildlifeVetsuisse FacultyUniversity of ZurichZurichSwitzerland
| | - Dennis M. Hansen
- Department of Evolutionary Biology and Environmental StudiesUniversity of ZurichZurichSwitzerland
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8
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Cooper CE. Endocrinology of osmoregulation and thermoregulation of Australian desert tetrapods: A historical perspective. Gen Comp Endocrinol 2017; 244:186-200. [PMID: 26449158 DOI: 10.1016/j.ygcen.2015.10.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/30/2015] [Accepted: 10/03/2015] [Indexed: 10/22/2022]
Abstract
Many Australian tetrapods inhabit desert environments characterised by low productivity, unpredictable rainfall, high temperatures and high incident solar radiation. Maintaining a homeostatic milieu intérieur by osmoregulation and thermoregulation are two physiological challenges faced by tetrapods in deserts, and the endocrine system plays an important role in regulating these processes. There is a considerable body of work examining the osmoregulatory role of antidiuretic hormones for Australian amphibians, reptiles and mammals, with particular contributions concerning their role and function for wild, free-living animals in arid environments. The osmoregulatory role of the natriuretic peptide system has received some attention, while the role of adrenal corticosteroids has been more thoroughly investigated for reptiles and marsupials. The endocrinology of thermoregulation has not received similar attention. Reptiles are best-studied, with research examining the influence of arginine vasotocin and melatonin on body temperature, the role of prostaglandins in heart rate hysteresis and the effect of melanocyte-stimulating hormone on skin reflectivity. Australian mammals have been under-utilised in studies examining the regulation, development and evolution of endothermy, and there is little information concerning the endocrinology of thermoregulation for desert species. There is a paucity of data concerning the endocrinology of osmoregulation and thermoregulation for Australian desert birds. Studies of Australian desert fauna have made substantial contributions to endocrinology, but there is considerable scope for further research. A co-ordinated approach to examine arid-habitat adaptations of the endocrine system in an environmental and evolutionary context would be of particular value.
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Affiliation(s)
- Christine Elizabeth Cooper
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia 6847, Australia; School of Animal Biology, University of Western Australia, Crawley, Western Australia 6009, Australia.
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9
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Kolomeyets NL, Roshchevskaya IM. The electrical resistivity of a segment of the tail, lungs, liver, and intercostal muscles of the grass snake during in vivo cooling. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916050110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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10
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Smith KR, Cadena V, Endler JA, Porter WP, Kearney MR, Stuart-Fox D. Colour change on different body regions provides thermal and signalling advantages in bearded dragon lizards. Proc Biol Sci 2016; 283:20160626. [PMCID: PMC4920320 DOI: 10.1098/rspb.2016.0626] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/13/2016] [Indexed: 11/23/2023] Open
Abstract
Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300–700 nm) and near-infrared (NIR; 700–2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards (Pogona vitticeps ) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.
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Affiliation(s)
- Kathleen R. Smith
- School of Biosciences, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Viviana Cadena
- School of Biosciences, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - John A. Endler
- School of Life and Environmental Sciences, Deakin University, Waurn Ponds 3220, Victoria, Australia
| | - Warren P. Porter
- Department of Zoology, The University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael R. Kearney
- School of Biosciences, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Devi Stuart-Fox
- School of Biosciences, The University of Melbourne, Parkville 3010, Victoria, Australia
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Sanders CE, Tattersall GJ, Reichert M, Andrade DV, Abe AS, Milsom WK. Daily and annual cycles in thermoregulatory behaviour and cardio-respiratory physiology of black and white tegu lizards. J Comp Physiol B 2015; 185:905-15. [PMID: 26266400 DOI: 10.1007/s00360-015-0928-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 07/08/2015] [Accepted: 07/31/2015] [Indexed: 11/25/2022]
Abstract
This study was designed to determine the manner in which metabolism is suppressed during dormancy in black and white tegu lizards (Tupinambis merianae). To this end, heart rate (fH), respiration rate (fR), and deep body temperature (Tb) were continuously monitored in outdoor enclosures by radio-telemetry for nine months. There was a continuous decline in nighttime breathing and heart rate, at constant Tb, throughout the late summer and fall suggestive of an active metabolic suppression that developed progressively at night preceding the entrance into dormancy. During the day, however, the tegus still emerged to bask. In May, when the tegus made a behavioural commitment to dormancy, Tb (day and night) fell to match burrow temperature, accompanied by a further reduction in fH and fR. Tegus, under the conditions of this study, did arouse periodically during dormancy. There was a complex interplay between changes in fH and Tb associated with the direct effects of temperature and the indirect effects of thermoregulation, activity, and changes in metabolism. This interplay gave rise to a daily hysteresis in the fH/Tb relationship reflective of the physiological changes associated with warming and cooling as preferred Tb alternated between daytime and nighttime levels. The shape of the hysteresis curve varied with season along with changes in metabolic state and daytime and nighttime body temperature preferences.
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Affiliation(s)
- Colin E Sanders
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
| | - Glenn J Tattersall
- Department of Biological Sciences, Brock University, St. Catharines, ON, Canada
| | - Michelle Reichert
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
| | - Denis V Andrade
- Depto de Zoologia, Instituto Nacional de Ciência e Tecnologia em Fisiologia Comparada, Univ Estadual Paulista, Rio Claro, SP, 13506-900, Brazil
| | - Augusto S Abe
- Depto de Zoologia, Instituto Nacional de Ciência e Tecnologia em Fisiologia Comparada, Univ Estadual Paulista, Rio Claro, SP, 13506-900, Brazil
| | - William K Milsom
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada.
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Tattersall GJ, Sinclair BJ, Withers PC, Fields PA, Seebacher F, Cooper CE, Maloney SK. Coping with Thermal Challenges: Physiological Adaptations to Environmental Temperatures. Compr Physiol 2012; 2:2151-202. [DOI: 10.1002/cphy.c110055] [Citation(s) in RCA: 184] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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13
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Hagensen MK, Abe AS, Wang T. Baroreflex control of heart rate in the broad-nosed caiman Caiman latirostris is temperature dependent. Comp Biochem Physiol A Mol Integr Physiol 2010; 156:458-62. [DOI: 10.1016/j.cbpa.2010.03.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 03/23/2010] [Accepted: 03/27/2010] [Indexed: 10/19/2022]
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14
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Cadena V, Tattersall G. The Effect of Thermal Quality on the Thermoregulatory Behavior of the Bearded DragonPogona vitticeps: Influences of Methodological Assessment. Physiol Biochem Zool 2009; 82:203-17. [DOI: 10.1086/597483] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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15
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McKenzie DJ, Campbell HA, Taylor EW, Micheli M, Rantin FT, Abe AS. The autonomic control and functional significance of the changes in heart rate associated with air breathing in the jeju,Hoplerythrinus unitaeniatus. J Exp Biol 2007; 210:4224-32. [DOI: 10.1242/jeb.009266] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe jeju is a teleost fish with bimodal respiration that utilizes a modified swim bladder as an air-breathing organ (ABO). Like all air-breathing fish studied to date, jeju exhibit pronounced changes in heart rate(fH) during air-breathing events, and it is believed that these may facilitate oxygen uptake (MO2) from the ABO. The current study employed power spectral analysis (PSA) of fH patterns, coupled with instantaneous respirometry, to investigate the autonomic control of these phenomena and their functional significance for the efficacy of air breathing. The jeju obtained less than 5%of total MO2(MtO2) from air breathing in normoxia at 26°C, and PSA of beat-to-beat variability in fHrevealed a pattern similar to that of unimodal water-breathing fish. In deep aquatic hypoxia (water PO2=1 kPa) the jeju increased the frequency of air breathing (fAB) tenfold and maintained MtO2 unchanged from normoxia. This was associated with a significant increase in heart rate variability (HRV),each air breath (AB) being preceded by a brief bradycardia and then followed by a brief tachycardia. These fH changes are qualitatively similar to those associated with breathing in unimodal air-breathing vertebrates. Within 20 heartbeats after the AB, however, a beat-to-beat variability in fH typical of water-breathing fish was re-established. Pharmacological blockade revealed that both adrenergic and cholinergic tone increased simultaneously prior to each AB, and then decreased after it. However, modulation of inhibitory cholinergic tone was responsible for the major proportion of HRV, including the precise beat-to-beat modulation of fH around each AB. Pharmacological blockade of all variations in fH associated with air breathing in deep hypoxia did not, however, have a significant effect upon fAB or the regulation of MtO2. Thus, the functional significance of the profound HRV during air breathing remains a mystery.
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Affiliation(s)
- D. J. McKenzie
- Institut des Sciences de l'Evolution de Montpellier, UMR 5554 CNRS-Université Montpellier II, Station Méditerranéenne de l'Environnement Littoral, 1 quai de la Daurade, 34200 Sète,France
| | - H. A. Campbell
- School of Integrative Biology, University of Queensland, Brisbane, QL 4072, Australia
| | - E. W. Taylor
- School of Biosciences, University of Birmingham, Birmingham, B15 2TT,UK
| | - M. Micheli
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - F. T. Rantin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - A. S. Abe
- Departamento de Zoologia, Centro de Aquicultura, UNESP, Rio Claro,São Paulo, Brazil
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16
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Seebacher F, Franklin CE. Redistribution of blood within the body is important for thermoregulation in an ectothermic vertebrate (Crocodylus porosus). J Comp Physiol B 2007; 177:841-8. [PMID: 17639414 DOI: 10.1007/s00360-007-0181-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 06/18/2007] [Accepted: 06/19/2007] [Indexed: 10/23/2022]
Abstract
Changes in blood flow are a principal mechanism of thermoregulation in vertebrates. Changes in heart rate will alter blood flow, although multiple demands for limited cardiac output may compromise effective thermoregulation. We tested the hypothesis that regional differences in blood flow during heating and cooling can occur independently from changes in heart rate. We measured heart rate and blood pressure concurrently with blood flow in the crocodile, Crocodylus porosus. We measured changes in blood flow by laser Doppler flowmetry, and by injecting coloured microspheres. All measurements were made under different heat loads, with and without blocking cholinergic and beta-adrenergic receptors (autonomic blockade). Heart rates were significantly faster during heating than cooling in the control animals, but not when autonomic receptors were blocked. There were no significant differences in blood flow distribution between the control and autonomic blockade treatments. In both treatments, blood flow was directed to the dorsal skin and muscle and away from the tail and duodenum during heating. When the heat source was switched off, there was a redistribution of blood from the dorsal surface to the duodenum. Blood flow to the leg skin and muscle, and to the liver did not change significantly with thermal state. Blood pressure was significantly higher during the autonomic blockade than during the control. Thermal time constants of heating and cooling were unaffected by the blockade of autonomic receptors. We concluded that animals partially compensated for a lack of differential heart rates during heating and cooling by redistributing blood within the body, and by increasing blood pressure to increase flow. Hence, measures of heart rate alone are insufficient to assess physiological thermoregulation in reptiles.
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Affiliation(s)
- Frank Seebacher
- School of Biological Sciences A08, The University of Sydney, NSW 2006, Sydney, Australia.
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17
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Bicego KC, Barros RCH, Branco LGS. Physiology of temperature regulation: comparative aspects. Comp Biochem Physiol A Mol Integr Physiol 2006; 147:616-639. [PMID: 16950637 DOI: 10.1016/j.cbpa.2006.06.032] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 05/28/2006] [Accepted: 06/16/2006] [Indexed: 10/24/2022]
Abstract
Few environmental factors have a larger influence on animal energetics than temperature, a fact that makes thermoregulation a very important process for survival. In general, endothermic species, i.e., mammals and birds, maintain a constant body temperature (Tb) in fluctuating environmental temperatures using autonomic and behavioural mechanisms. Most of the knowledge on thermoregulatory physiology has emerged from studies using mammalian species, particularly rats. However, studies with all vertebrate groups are essential for a more complete understanding of the mechanisms involved in the regulation of Tb. Ectothermic vertebrates-fish, amphibians and reptiles-thermoregulate essentially by behavioural mechanisms. With few exceptions, both endotherms and ectotherms develop fever (a regulated increase in Tb) in response to exogenous pyrogens, and regulated hypothermia (anapyrexia) in response to hypoxia. This review focuses on the mechanisms, particularly neuromediators and regions in the central nervous system, involved in thermoregulation in vertebrates, in conditions of euthermia, fever and anapyrexia.
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Affiliation(s)
- Kênia C Bicego
- Department of Animal Physiology and Morfology, College of Agricultural and Veterinarian Sciences, Sao Paulo State University, Jaboticabal, São Paulo, Brazil.
| | - Renata C H Barros
- Department of General and Specialized Nursing, Nursing School of Ribeirão Preto, University of São Paulo, 14040-904, Ribeirão Preto, São Paulo, Brazil
| | - Luiz G S Branco
- Department of Morphology, Estomatology and Physiology, Dental School of Ribeirão Preto, University of São Paulo, 14040-904, Ribeirão Preto, São Paulo, Brazil
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18
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Liu C, Li R, Liu Z, Yin S, Wang Z. The role of prostaglandins and the hypothalamus in thermoregulation in the lizard, Phrynocephalus przewalskii (Agamidae). J Comp Physiol B 2005; 176:321-8. [PMID: 16333626 DOI: 10.1007/s00360-005-0054-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 10/24/2005] [Accepted: 11/01/2005] [Indexed: 10/25/2022]
Abstract
Typically, small lizards rely heavily on behavioral thermoregulation rather than physiological mechanisms to control their rates of warming and cooling. We tested the hypothesis that prostaglandins participate in mediating the cardiovascular response to heating and cooling and temperature regulating neurons in the hypothalamus of the small lizard Phrynocephalus przewalskii. In vivo and in vitro treatments, heart rates (HRs) were all found to be higher during heating than during cooling, hysteresis was distinct below 30 and 26 degrees Celsius, respectively. In vivo, as administration of COX inhibitor, there were no differences in HR between heating and cooling at any body temperature and administration of agonist prostaglandins only produced a significant effect on HR below 25 degrees Celsius. Single-unit activity was recorded extracellularly in vitro with microelectrodes, found the firing rate of the continuous unit increased 23% when the temperature of the artificial cerebrospinal fluid dropped from 30-20 degrees Celsius. We conclude that prostaglandins appear to play only a limited role in modulating heart activity in Phrynocephalus przewalskii and suggest that cold-sensitive neurons in the preoptic and anterior hypothalamus (PO/AH) are involved in thermoregulatory control during heating or cooling.
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Affiliation(s)
- Chongbin Liu
- School of Life Sciences, Lanzhou University, Lanzhou, 730000, Gansu, People's Republic of China
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19
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Tattersall GJ, Gerlach RM. Hypoxia progressively lowers thermal gaping thresholds in bearded dragons,Pogona vitticeps. J Exp Biol 2005; 208:3321-30. [PMID: 16109893 DOI: 10.1242/jeb.01773] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYMost animals, including reptiles, lower body temperature(Tb) under hypoxic conditions. Numerous physiological and behavioural traits significant to the regulation of Tb are altered by hypoxia in ways that suggest an orchestrated adjustment of Tb at a new and lower regulated level. We examined this matter in bearded dragons, Pogona vitticeps, a species of reptile that naturally exhibits open mouth gaping at high temperatures, presumably in order to promote evaporation and thus prevent or avoid further increases in Tb. The threshold for the onset of gaping (assessed as the temperature at which lizards spent 50% of their time gaping) was reduced from 36.9°C in normoxia to 35.5°C at 10% and 34.3°C at 6%O2. The overall magnitude or degree of gaping, measured qualitatively, was more pronounced at lower temperatures in hypoxia. Females consistently had lower gaping threshold temperatures than did males, and this difference was retained throughout exposure to hypoxia. In addition to gaping,evaporative water loss from the cloaca may also play a significant role in temperature regulation, since the ambient temperature at which cloacal discharge occurred was also reduced significantly in hypoxia. The results reported herein strongly support the view that hypoxia reduces temperature set-point in lizards and that such changes are coordinated by specific behavioural thermoeffectors that modulate evaporative water loss and thus facilitate a high potential for controlling or modifying Tb.
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Affiliation(s)
- Glenn J Tattersall
- Department of Biological Sciences, Brock University, St Catharines, Ontario, L2S 3A1, Canada.
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20
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Clark TD, Butler PJ, Frappell PB. Digestive state influences the heart rate hysteresis and rates of heat exchange in the varanid lizard Varanus rosenbergi. ACTA ACUST UNITED AC 2005; 208:2269-76. [PMID: 15939769 DOI: 10.1242/jeb.01657] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To maximize the period where body temperature (Tb) exceeds ambient temperature (Ta), many reptiles have been reported to regulate heart rate (fH) and peripheral blood flow so that the rate of heat gain in a warming environment occurs more rapidly than the rate of heat loss in a cooling environment. It may be hypothesized that the rate of cooling, particularly at relatively cool Tbs, would be further reduced during postprandial periods when specific dynamic action (SDA) increases endogenous heat production (i.e. the heat increment of feeding). Furthermore, it may also be hypothesized that the increased perfusion of the gastrointestinal organs that occurs during digestion may limit peripheral blood flow and thus compromise the rate of heating. Finally, if the changes in fh are solely for the purpose of thermoregulation, there should be no associated changes in energy demand and, consequently, no hysteresis in the rate of oxygen consumption (V(O2)). To test these hypotheses, seven individual Varanus rosenbergi were heated and cooled between 19 degrees C and 35 degrees C following at least 8 days fasting and then approximately 25 h after consumption of a meal (mean 10% of fasted body mass). For a given Tb between the range of 19-35 degrees C, fh of fasting lizards was higher during heating than during cooling. Postprandial lizards also displayed a hysteresis in fh, although the magnitude was reduced in comparison with that of fasting lizards as a result of a higher fh during cooling in postprandial animals. Both for fasting and postprandial lizards, there was no hysteresis in V(O2) at any Tb throughout the range although, as a result of SDA, postprandial animals displayed a significantly higher V(O2) than fasting animals both during heating and during cooling at Tbs above 24 degrees C. The values of fh during heating at a given Tb were the same for fasting and postprandial animals, which, in combination with a slower rate of heating in postprandial animals, suggests that a prioritization of blood flow to the gastrointestinal organs during digestion is occurring at the expense of higher rates of heating. Additionally, postprandial lizards took longer to cool at Tbs below 23 degrees C, suggesting that the endogenous heat produced during digestion temporarily enhances thermoregulatory ability at lower temperatures, which would presumably assist V. rosenbergi during cooler periods in the natural environment by augmenting temperature-dependent physiological processes.
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Affiliation(s)
- T D Clark
- Adaptational and Evolutionary Respiratory Physiology Laboratory, Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia.
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21
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Seebacher F, Franklin CE. Physiological mechanisms of thermoregulation in reptiles: a review. J Comp Physiol B 2005; 175:533-41. [PMID: 16047177 DOI: 10.1007/s00360-005-0007-1] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 04/29/2005] [Accepted: 05/20/2005] [Indexed: 10/25/2022]
Abstract
The thermal dependence of biochemical reaction rates means that many animals regulate their body temperature so that fluctuations in body temperature are small compared to environmental temperature fluctuations. Thermoregulation is a complex process that involves sensing of the environment, and subsequent processing of the environmental information. We suggest that the physiological mechanisms that facilitate thermoregulation transcend phylogenetic boundaries. Reptiles are primarily used as model organisms for ecological and evolutionary research and, unlike in mammals, the physiological basis of many aspects in thermoregulation remains obscure. Here, we review recent research on regulation of body temperature, thermoreception, body temperature set-points, and cardiovascular control of heating and cooling in reptiles. The aim of this review is to place physiological thermoregulation of reptiles in a wider phylogenetic context. Future research on reptilian thermoregulation should focus on the pathways that connect peripheral sensing to central processing which will ultimately lead to the thermoregulatory response.
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Affiliation(s)
- Frank Seebacher
- Integrative Physiology, School of Biological Sciences A08, University of Sydney, NSW, Australia.
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22
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Seebacher F, Franklin CE, Read M. Diving behaviour of a reptile (Crocodylus johnstoni) in the wild: interactions with heart rate and body temperature. Physiol Biochem Zool 2005; 78:1-8. [PMID: 15702457 DOI: 10.1086/425192] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/16/2004] [Indexed: 11/03/2022]
Abstract
The differences in physical properties of air and water pose unique behavioural and physiological demands on semiaquatic animals. The aim of this study was to describe the diving behaviour of the freshwater crocodile Crocodylus johnstoni in the wild and to assess the relationships between diving, body temperature, and heart rate. Time-depth recorders, temperature-sensitive radio transmitters, and heart rate transmitters were deployed on each of six C. johnstoni (4.0-26.5 kg), and data were obtained from five animals. Crocodiles showed the greatest diving activity in the morning (0600-1200 hours) and were least active at night, remaining at the water surface. Surprisingly, activity pattern was asynchronous with thermoregulation, and activity was correlated to light rather than to body temperature. Nonetheless, crocodiles thermoregulated and showed a typical heart rate hysteresis pattern (heart rate during heating greater than heart rate during cooling) in response to heating and cooling. Additionally, dive length decreased with increasing body temperature. Maximum diving length was 119.6 min, but the greatest proportion of diving time was spent on relatively short (<45 min) and shallow (<0.4 m) dives. A bradycardia was observed during diving, although heart rate during submergence was only 12% lower than when animals were at the surface.
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Affiliation(s)
- Frank Seebacher
- School of Biological Sciences A08, University of Sydney, Sydney, New South Wales 2006, Australia.
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23
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24
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Goudkamp JE, Seebacher F, Ahern M, Franklin CE. Physiological thermoregulation in a crustacean? Heart rate hysteresis in the freshwater crayfish Cherax destructor. Comp Biochem Physiol A Mol Integr Physiol 2004; 138:399-403. [PMID: 15313496 DOI: 10.1016/j.cbpb.2004.06.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Revised: 06/02/2004] [Accepted: 06/03/2004] [Indexed: 11/18/2022]
Abstract
Differential heart rates during heating and cooling (heart rate hysteresis) are an important thermoregulatory mechanism in ectothermic reptiles. We speculate that heart rate hysteresis has evolved alongside vascularisation, and to determine whether this phenomenon occurs in a lineage with vascularised circulatory systems that is phylogenetically distant from reptiles, we measured the response of heart rate to convective heat transfer in the Australian freshwater crayfish, Cherax destructor. Heart rate during convective heating (from 20 to 30 degrees C) was significantly faster than during cooling for any given body temperature. Heart rate declined rapidly immediately following the removal of the heat source, despite only negligible losses in body temperature. This heart rate 'hysteresis' is similar to the pattern reported in many reptiles and, by varying peripheral blood flow, it is presumed to confer thermoregulatory benefits particularly given the thermal sensitivity of many physiological rate functions in crustaceans.
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25
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Galli G, Taylor EW, Wang T. The cardiovascular responses of the freshwater turtleTrachemys scriptato warming and cooling. J Exp Biol 2004; 207:1471-8. [PMID: 15037641 DOI: 10.1242/jeb.00912] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYSeven freshwater turtles Trachemys scripta were instrumented with flow probes and cannulated for blood pressure measurements. The turtles were warmed from 24 to 34°C, and cooled down to 24°C, with and without atropine. Animals exhibited a hysteresis of heart rate and blood flow to both the pulmonary and systemic circulations, which was not cholinergically mediated. Blood pressure remained constant during both warming and cooling,while systemic resistance decreased during heating and increased during cooling, indicating a barostatic response. There was a large right-to-left(R–L) shunt during warming and cooling in untreated animals, which remained relatively constant. Atropinisation resulted in a large L–R shunt, which decreased during warming and increased during cooling. Nevertheless, heating rates were the same in untreated and atropinised animals, and cooling rates were significantly longer in atropinised animals,indicating that shunt patterns contribute little to heat exchange.
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Affiliation(s)
- Gina Galli
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark.
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26
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Zaar M, Larsen E, Wang T. Hysteresis of heart rate and heat exchange of fasting and postprandial savannah monitor lizards (Varanus exanthematicus). Comp Biochem Physiol A Mol Integr Physiol 2004; 137:675-82. [PMID: 15123175 DOI: 10.1016/j.cbpb.2004.01.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Revised: 01/23/2004] [Accepted: 01/28/2004] [Indexed: 11/29/2022]
Abstract
Reptiles are ectothermic, but regulate body temperatures (T(b)) by behavioural and physiological means. Body temperature has profound effects on virtually all physiological functions. It is well known that heating occurs faster than cooling, which seems to correlate with changes in cutaneous perfusion. Increased cutaneous perfusion, and hence elevated cardiac output, during heating is reflected in an increased heart rate (f(H)), and f(H), at a given T(b), is normally higher during heating compared to cooling ('hysteresis of heart rate'). Digestion is associated with an increased metabolic rate. This is associated with an elevated f(H) and many species of reptiles also exhibited a behavioural selection of higher T(b) during digestion. Here, we examine whether digestion affects the rate of heating and cooling as well as the hysteresis of heart rate in savannah monitor lizards (Varanus exanthematicus). Fasting lizards were studied after 5 days of food deprivation while digesting lizards were studied approximately 24 h after ingesting dead mice that equalled 10% of their body mass. Heart rate was measured while T(b) increased from 28 to 38 degrees C under a heat lamp and while T(b) decreased during a subsequent cooling phase. The lizards exhibited hysteresis of heart rate, and heating occurred faster than cooling. Feeding led to an increased f(H) (approximately 20 min(-1) irrespective of T(b)), but did not affect the rate of temperature change during heating or cooling. Therefore, it is likely that the increased blood flows during digestion are distributed exclusively to visceral organs and that the thermal conductance remains unaffected by the elevated metabolic rate during digestion.
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Affiliation(s)
- Morten Zaar
- Department of Zoophysiology, Institute of Biology, Aarhus University, Building 131, Universitetsparken, 8000 Aarhus C, Denmark
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27
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Franklin CE, Seebacher F. The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus. J Exp Biol 2003; 206:1143-51. [PMID: 12604574 DOI: 10.1242/jeb.00222] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23 degrees C and (3) heated via convective transfer by increasing water temperature from 23 degrees C to 35 degrees C. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23 degrees C. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (<0.5 degrees C) resulted in Q(10) values greater than 4000, calling into question the usefulness of this measure on heart rate during the initial stages of heating and cooling. In the later phases of heating and cooling, heart rate changed with body temperature, with Q(10) values of 2-3. The magnitude of the heart rate response differed between treatments, with radiant heating during submergence eliciting the smallest response. The heart rate of C. porosus outside of the 'rapid response' periods was found to be a function of the heat load experienced at the animal surface, as well as on the mode of heat transfer. Heart rate increased or decreased rapidly when C. porosus experienced large positive (above 25 W) or negative (below -15 W) heat loads, respectively, in all treatments. For heat loads between -15 W and 20 W, the increase in heart rate was smaller for the 'unnatural' heating by convection in water compared with either treatment using radiant heating. Our data indicate that changes in heart rate constitute a thermoregulatory mechanism that is modulated in response to the thermal environment occupied by the animal, but that heart rate during heating and cooling is, in part, controlled independently of body temperature.
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Affiliation(s)
- Craig E Franklin
- Department of Zoology and Entomology, University of Queensland, St Lucia, Qld 4072, Australia
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28
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Seebacher F, Guderley H, Elsey RM, Trosclair PL. Seasonal acclimatisation of muscle metabolic enzymes in a reptile (Alligator mississippiensis). J Exp Biol 2003; 206:1193-200. [PMID: 12604579 DOI: 10.1242/jeb.00223] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Reptiles living in heterogeneous thermal environments are often thought to show behavioural thermoregulation or to become inactive when environmental conditions prevent the achievement of preferred body temperatures. By contrast, thermally homogeneous environments preclude behavioural thermoregulation, and ectotherms inhabiting these environments (particularly fish in which branchial respiration requires body temperature to follow water temperature) modify their biochemical capacities in response to long-term seasonal temperature fluctuations. Reptiles may also be active at seasonally varying body temperatures and could, therefore, gain selective advantages from regulating biochemical capacities. Hence, we tested the hypothesis that a reptile (the American alligator Alligator mississippiensis) that experiences pronounced seasonal fluctuations in body temperature will show seasonal acclimatisation in the activity of its metabolic enzymes. We measured body temperatures of alligators in the wild in winter and summer (N=7 alligators in each season), and we collected muscle samples from wild alligators (N=31 in each season) for analysis of metabolic enzyme activity (lactate dehydrogenase, citrate synthase and cytochrome c oxidase). There were significant differences in mean daily body temperatures between winter (15.66+/-0.43 degrees C; mean +/- S.E.M.) and summer (29.34+/-0.21 degrees C), and daily body temperatures fluctuated significantly more in winter compared with summer. Alligators compensated for lower winter temperatures by increasing enzyme activities, and the activities of cytochrome c oxidase and lactate dehydrogenase were significantly greater in winter compared with summer at all assay temperatures. The activity of citrate synthase was significantly greater in the winter samples at the winter body temperature (15 degrees C) but not at the summer body temperature (30 degrees C). The thermal sensitivity (Q(10)) of mitochondrial enzymes decreased significantly in winter compared with in summer. The activity of mitochondrial enzymes was significantly greater in males than in females, but there were no differences between sexes for lactate dehydrogenase activity. The differences between sexes could be the result of the sex-specific seasonal demands for locomotor performance. Our data indicate that biochemical acclimatisation is important in thermoregulation of reptiles and that it is not sufficient to base conclusions about their thermoregulatory ability entirely on behavioural patterns.
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Affiliation(s)
- Frank Seebacher
- School of Biological Sciences A08, University of Sydney, New South Wales 2006, Australia.
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