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Lyons SA, McClelland GB. Commentary: Tracing the fate of metabolic substrates during changes in whole-body energy expenditure in mice. Comp Biochem Physiol B Biochem Mol Biol 2024; 274:111008. [PMID: 39059702 DOI: 10.1016/j.cbpb.2024.111008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 07/20/2024] [Accepted: 07/22/2024] [Indexed: 07/28/2024]
Abstract
For small mammals, such as mice, cannulation procedures can be quite challenging, limiting research associated with tracing isotopically labelled substrates at the whole-animal level. When cannulation in mice is possible, assessment of substrate use is further limited to when mice are either under anesthesia or are at rest, as there are no studies directly quantifying substrate use during exercise in mice. The use of isotopic tracer techniques has greatly advanced our knowledge in understanding how metabolic substrates (carbohydrates, amino acids, and fatty acids) contribute to whole-body metabolism. However, research regarding tissue-specific fuel use contributions to whole-body energy expenditure in mice at varying metabolic intensities (i.e., exercise) is lacking, despite the popularity of using mice in a variety of metabolic models. In this commentary, we briefly discuss the methodologies, advantages, and disadvantages of using radiolabelled, positron emission, and stable isotopes with a specific focus on fatty acids. We highlight recent mouse studies that have used creative experimental designs employing the use of isotopic tracer techniques and we briefly discuss how these methodologies can be further pursued to deepen our understanding of substrate use during exercise. Lastly, we show findings of a recent study we performed using a radiolabelled fatty acid tracer (14C-bromopalmitic acid) to determine fatty acid uptake in 16 muscles, two brown and two white adipose tissue depots during submaximal exercise in deer mice.
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Affiliation(s)
- Sulayman A Lyons
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada.
| | - Grant B McClelland
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada.
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2
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Husak JF, Lailvaux SP. Stable isotopes reveal sex- and context-dependent amino acid routing in green anole lizards (Anolis carolinensis). J Exp Biol 2024; 227:jeb248024. [PMID: 39155675 DOI: 10.1242/jeb.248024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Accepted: 08/07/2024] [Indexed: 08/20/2024]
Abstract
Allocation of acquired resources to phenotypic traits is affected by resource availability and current selective context. While differential investment in traits is well documented, the mechanisms driving investment at lower levels of biological organization, which are not directly related to fitness, remain poorly understood. We supplemented adult male and female Anolis carolinensis lizards with an isotopically labelled essential amino acid (13C-leucine) to track routing in four tissues (muscle, liver, gonads and spleen) under different combinations of resource availability (high- and low-calorie diets) and exercise training (sprint training and endurance capacity). We predicted sprint training should drive routing to muscle, and endurance training to liver and spleen, and that investment in gonads should be of lower priority in each of the cases of energetic stress. We found complex interactions between training regime, diet and tissue type in females, and between tissue type and training, and tissue type and diet in males, suggesting that males and females adjust their 13C-leucine routing strategies differently in response to similar environmental challenges. Importantly, our data show evidence of increased 13C-leucine routing in training contexts not to muscle as we expected, but to the spleen, which turns over blood cells, and to the liver, which supports metabolism under differing energetic scenarios. Our results reveal the context-specific nature of long-term trade-offs associated with increased chronic activity. They also illustrate the importance of considering the costs of locomotion in studies of life-history strategies.
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Affiliation(s)
- Jerry F Husak
- Department of Biology, University of St Thomas, St Paul, MN 55105, USA
| | - Simon P Lailvaux
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
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3
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McCue MD. CO 2 scrubbing, zero gases, Keeling plots, and a mathematical approach to ameliorate the deleterious effects of ambient CO 2 during 13 C breath testing in humans and animals. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9639. [PMID: 37817343 DOI: 10.1002/rcm.9639] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Revised: 07/17/2023] [Accepted: 08/26/2023] [Indexed: 10/12/2023]
Abstract
13 C breath testing is increasingly used in physiology and ecology research because of what it reveals about the different fuels that animals oxidize to meet their energetic demands. Here I review the practice of 13 C breath testing in humans and other animals and describe the impact that contamination by ambient/background CO2 in the air can have on the accuracy of 13 C breath measurements. I briefly discuss physical methods to avoid sample contamination as well as the Keeling plot approach that researchers have been using for the past two decades to estimate δ13 C from breath samples mixed with ambient CO2 . Unfortunately, Keeling plots are not suited for 13 C breath testing in common situations where (1) a subject's VCO2 is dynamic, (2) ambient [CO2 ] may change, (3) a subject is sensitive to hypercapnia, or (4) in any flow-through indirect calorimetry system. As such, I present a mathematical solution that addresses these issues by using information about the instantaneous [CO2 ] and the δ13 CO2 of ambient air as well as the diluted breath sample to back-calculate the δ13 CO2 in the CO2 exhaled by the animal. I validate this approach by titrating a sample of 13 C-enriched gas into an air stream and demonstrate its ability to provide accurate values across a wide range of breath and air mixtures. This approach allows researchers to instantaneously calculate the δ13 C of exhaled gas of humans or other animals in real time without having to scrub ambient CO2 or rely on estimated values.
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4
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Nutrient Utilization during Male Maturation and Protein Digestion in the Oriental Hornet. BIOLOGY 2022; 11:biology11020241. [PMID: 35205107 PMCID: PMC8869360 DOI: 10.3390/biology11020241] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 11/17/2022]
Abstract
Males of social Hymenoptera spend the first days following eclosion inside the nest before dispersing to find a young queen to mate with. During this period, they must acquire enough nutrients to enable their sexual maturation and store energy to sustain them through their nuptial journey. It was previously argued that adult hornets are unable to process dietary proteins and rely on the larvae to supply them with free amino acids and carbohydrates that they secrete via trophallaxis. Using isotopically enriched diets, we examined nutrient allocation and protein turnover in newly-emerged males of the Oriental hornet during their maturation period and tested the protein digestion capability in the presence and absence of larvae in both males and worker hornets. The results indicated that protein turnover in males occurs during the first days following eclosion, while carbohydrates are incorporated into body tissues at higher rates towards the end of the maturation period. Additionally, we found that males cannot digest protein and depend on larval secretions as a source of nutrition, while workers, in contrast to previous reports, can metabolize protein independently. Our findings demonstrate the contribution of adult male nutrition and larval secretions to colony fitness.
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Bodner L, Bouchebti S, Levin E. Allocation and metabolism of naturally occurring dietary amino acids in the Oriental hornet. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2021; 139:103675. [PMID: 34744018 DOI: 10.1016/j.ibmb.2021.103675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 10/12/2021] [Accepted: 10/26/2021] [Indexed: 06/13/2023]
Abstract
Oriental hornet (Vespa orientalis) foragers are strong, long-distance flyers exhibiting a high metabolic rate. Accordingly, they feed on carbohydrate-rich diets, such as floral nectar and larval secretions. These nutritional sources, in addition to carbohydrates, also contain free amino acids (AAs). Leucine, glycine, and proline are three common AAs in the diet of social wasps. Using diets enriched with carbon-specific (13C1) isotopically labeled leucine, glycine, and proline, and a cavity ring-down spectroscope (CRDS) stable carbon isotope analyzer, we examined the metabolism of these AAs, their allocation in the hornets' respiration during rest and activity, and their incorporation into the body tissues. In hornets that consumed 13C proline, we detected the heavy isotope only in the exhaled CO2, suggesting that proline was utilized solely as a metabolic fuel and was not incorporated into their body (i.e., as protein). Labeled carbons from glycine and leucine, in contrast, were found in all the examined tissues (i.e., muscles, brain, fat bodies, ovaries, and venom glands), and were also utilized as a metabolic fuel, but mostly during rest. Using AAs labeled with a specific stable carbon isotope, we demonstrate the compatibility between the hornet's metabolic requirements and AA use, in both the living organism as a whole and in its different body tissues.
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Affiliation(s)
- Levona Bodner
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Sofia Bouchebti
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
| | - Eran Levin
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
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Shpigler HY, Magory Cohen T, Ben-Shimol E, Ben-Betzalel R, Levin E. Juvenile hormone functions as a metabolic rate accelerator in bumble bees (Bombus terrestris). Horm Behav 2021; 136:105073. [PMID: 34634696 DOI: 10.1016/j.yhbeh.2021.105073] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 11/23/2022]
Abstract
Juvenile hormone (JH) is a modulator of many physiological transitions in insects, including molting, metamorphosis, diapause, and reproduction. These processes often include metabolic changes. Here we show that JH accelerates metabolic rate in bumble bees (Bombus terrestris). We reduced JH levels in worker bumble bees by removing their corpora allata (allatectomy) and elevated JH levels in queens through a topical application of JH-III. Natural and high JH levels increased the metabolic rate in both workers and queens and triggered an increased protein turnover rate. Following the treatments, JH also caused an increase in food consumption and a reduction in lipid levels and flight muscle mass of queens, and a reduction in lipids levels in workers. Furthermore, the topical application of a JH analog to queens prior to their diapause caused a decline in their survival of diapause. These findings support the hypothesis that JH acts as a metabolic rate accelerator, initiating a resource shift in bumble bees, and thereby reducing diapause survival in queens. Based on previous studies on JH we suggest that, additional to its behavioral or physiological effects, JH's function as an accelerator of metabolic processes is conserved across different life stages and insect species.
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Affiliation(s)
| | - Tali Magory Cohen
- School of Zoology, Faculty of Life Sciences, Tel-Aviv, Israel; Steinhardt Museum of Natural History, Tel Aviv University, Tel Aviv, Israel
| | | | | | - Eran Levin
- School of Zoology, Faculty of Life Sciences, Tel-Aviv, Israel.
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7
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Cooper-Mullin C, Carter WA, Amato RS, Podlesak D, McWilliams SR. Dietary vitamin E reaches the mitochondria in the flight muscle of zebra finches but only if they exercise. PLoS One 2021; 16:e0253264. [PMID: 34181660 PMCID: PMC8238215 DOI: 10.1371/journal.pone.0253264] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 06/01/2021] [Indexed: 01/10/2023] Open
Abstract
Whether dietary antioxidants are effective for alleviating oxidative costs associated with energy-demanding life events first requires they are successfully absorbed in the digestive tract and transported to sites associated with reactive species production (e.g. the mitochondria). Flying birds are under high energy and oxidative demands, and although birds commonly ingest dietary antioxidants in the wild, the bioavailability of these consumed antioxidants is poorly understood. We show for the first time that an ingested lipophilic antioxidant, α-tocopherol, reached the mitochondria in the flight muscles of a songbird but only if they regularly exercise (60 min of perch-to-perch flights two times in a day or 8.5 km day-1). Deuterated α-tocopherol was found in the blood of exercise-trained zebra finches within 6.5 hrs and in isolated mitochondria from pectoral muscle within 22.5 hrs, but never reached the mitochondria in caged sedentary control birds. This rapid pace (within a day) and extent of metabolic routing of a dietary antioxidant to muscle mitochondria means that daily consumption of such dietary sources can help to pay the inevitable oxidative costs of flight muscle metabolism, but only when combined with regular exercise.
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Affiliation(s)
- Clara Cooper-Mullin
- Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Wales A. Carter
- Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Ronald S. Amato
- Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - David Podlesak
- Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Scott R. McWilliams
- Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island, United States of America
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8
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Denommé M, Deakin JE, Morbey YE, Guglielmo CG. Using breath δ 13C analysis to determine the effects of dietary carbohydrate and protein on glucose and leucine oxidation at rest in the yellow-rumped warbler (Setophaga coronata). Comp Biochem Physiol A Mol Integr Physiol 2021; 256:110936. [PMID: 33713811 DOI: 10.1016/j.cbpa.2021.110936] [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: 01/15/2021] [Revised: 03/07/2021] [Accepted: 03/07/2021] [Indexed: 10/21/2022]
Abstract
Fat is the major fuel for migratory flight of birds, but protein is also catabolized. Flight range could be reduced if protein is used too quickly from muscles and organs, and it is important to understand factors that influence protein catabolism. Previous correlative studies suggested high protein diets may increase protein use in flight, although a wind tunnel study with yellow-rumped warblers (Setophaga coronata) did not support this relationship. We tested the hypothesis that diet composition affects nutrient oxidation in resting, fasted yellow-rumped warblers. For method development, we gavaged or subcutaneously injected warblers with 13C labelled glucose or leucine, and measured δ13C of breath CO2 in real time using infrared laser spectrometry. Regardless of route of administration, leucine had greater instantaneous and cumulative oxidation than glucose. Compared to subcutaneous injection, gavaged birds reached maximum oxidation rate faster for leucine and glucose, respectively, had a higher maximum oxidation rate, and reached final cumulative oxidation approximately faster for leucine or glucose, respectively, indicating immediate oxidation of the substrates by the digestive system. Warblers (N = 10 each) were fed isocaloric 60% carbohydrate or 60% protein diets for minimum 2 weeks, and subcutaneously injected with 13C labelled glucose or leucine. Diet composition had little effect on oxidation kinetics except that warblers fed high-carbohydrate reached final cumulative oxidation of leucine more quickly than those fed high-protein. The findings do not support the hypothesis that high protein diets increase the oxidation of protein during negative energy states in migratory birds, and provide methodology that could be applied to test it in flight.
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Affiliation(s)
- Melanie Denommé
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A5B7, Canada.
| | - Jessica E Deakin
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A5B7, Canada
| | - Yolanda E Morbey
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A5B7, Canada
| | - Christopher G Guglielmo
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A5B7, Canada
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9
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Anparasan L, Hobson KA. Tracing sources of carbon and hydrogen to stored lipids in migratory passerines using stable isotope (δ 13C, δ 2H) measurements. Oecologia 2021; 195:37-49. [PMID: 33389017 DOI: 10.1007/s00442-020-04827-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 12/09/2020] [Indexed: 11/29/2022]
Abstract
Using measurements of naturally occurring stable isotopes in feathers to determine avian origin and migratory patterns is well established. However, isotopically determining nutritional origins of lipids, a major migratory fuel, has not been attempted. This study explores isotopic links between diet and stored lipids in captive white-throated sparrows (Zonotrichia albicollis) by providing isotopically distinct mixtures of carbohydrates/oils and drinking water and assessing the δ13C and δ2H values of stored lipid, breath CO2 (δ13C) and breath water vapour (δ2H). Stored lipid δ13C and δ2H values correlated with the isotopic values found in dietary carbohydrates/oils and drinking water treatments, respectively, indicating a clear traceable transfer of environmental dietary isotopic signals into body lipids. Dietary oils and carbohydrates contributed 80-82% of carbon and 44-46% of hydrogen, respectively, to stored lipids. Drinking water contributed 18-28% of hydrogen to stored lipids. Isotopic relationships were quantifiable using linear calibration algorithms which provide the basis for the construction of tissue isoscapes for migratory passerines. Breath CO2 δ13C values and breath water vapour δ2H values for fed and fasted birds reflected dietary sources. Breath CO2 δ13C values were higher for fasted birds than for fed birds by an average of 4.5‰ while breath water vapour δ2H values were lower for fasted birds by an average of 48.9‰. These results indicate that lipids and metabolites from their subsequent breakdown for fuel isotopically reflect dietary sources but complicate interpretation of such data, especially for wild migrating birds. Applications and limitations of these findings to the creation of "liposcapes" are examined.
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Affiliation(s)
- Libesha Anparasan
- Department of Biology, University of Western Ontario, 1151 Richmond St, London, ON, N6A 3K7, Canada.
| | - Keith A Hobson
- Department of Biology, University of Western Ontario, 1151 Richmond St, London, ON, N6A 3K7, Canada.,Environment and Climate Change Canada, Saskatoon, SK, S7N 3H5, Canada
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McCue MD, Javal M, Clusella‐Trullas S, Le Roux JJ, Jackson MC, Ellis AG, Richardson DM, Valentine AJ, Terblanche JS. Using stable isotope analysis to answer fundamental questions in invasion ecology: Progress and prospects. Methods Ecol Evol 2019. [DOI: 10.1111/2041-210x.13327] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Marshall D. McCue
- Sable Systems International Las Vegas NV USA
- Department of Conservation Ecology and Entomology Centre for Invasion Biology Stellenbosch University Stellenbosch South Africa
| | - Marion Javal
- Department of Conservation Ecology and Entomology Centre for Invasion Biology Stellenbosch University Stellenbosch South Africa
| | - Susana Clusella‐Trullas
- Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
| | - Johannes J. Le Roux
- Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
- Department of Biological Sciences Macquarie University NSW Australia
| | - Michelle C. Jackson
- Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
- Department of Life Sciences Imperial College London Ascot UK
- Department of Zoology Oxford University Oxford UK
| | - Allan G. Ellis
- Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
| | - David M. Richardson
- Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
| | - Alex J. Valentine
- Department of Botany and Zoology Stellenbosch University Stellenbosch South Africa
| | - John S. Terblanche
- Department of Conservation Ecology and Entomology Centre for Invasion Biology Stellenbosch University Stellenbosch South Africa
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11
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Pettit TV, Pettit RJ, Durso AM, French SS. Investment of both essential fatty and amino acids to immunity varies depending on reproductive stage. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 331:552-561. [PMID: 31625280 DOI: 10.1002/jez.2324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 08/10/2019] [Accepted: 09/08/2019] [Indexed: 12/29/2022]
Abstract
Trade-offs among the key life-history traits of reproduction and immunity have been widely documented. However, the currency in use is not well-understood. We investigated how reproducing female side-blotched lizards, Uta stansburiana, allocate lipids versus proteins when given an immune challenge. We tested whether lizards would invest more in reproduction or immunity depending on reproductive stage. Females were given stable isotopes (15 N-leucine and 13 C-1-palmitic acid), maintained on a regular diet and given either a cutaneous biopsy or a sham biopsy (control). Stable isotopes were monitored and analyzed in feces and uric acid, skin biopsies, eggs, and toe clips. We found that lizards deposited both proteins and lipids into their healing wounds (immune-challenged), skin (control), and eggs (all) and that catabolism of proteins exceeded incorporation into tissue during wound-healing. Specifically, we found that healed biopsies of wounded animals had more leucine and palmitic acid than the nonregrown skin biopsies taken from unwounded control animals. Earlier in reproduction, lizards invested relatively more labeled proteins into healing their wound tissue, but not into unwounded skin of control animals. Thus, reproduction is sometimes favored over self-maintenance, but only in later reproductive stages. Finally, we documented positive relationships among the amount of palmitic acid deposited in the eggs, the amount of food eaten, and the amount of palmitic acid excreted, suggesting higher turnover rates of lipids in lizards investing highly in their eggs.
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Affiliation(s)
- Taylor V Pettit
- Department of Biology and the Ecology Center, Utah State University, Logan, Utah
| | - R John Pettit
- Department of Biology and the Ecology Center, Utah State University, Logan, Utah
| | - Andrew M Durso
- Department of Biology and the Ecology Center, Utah State University, Logan, Utah
| | - Susannah S French
- Department of Biology and the Ecology Center, Utah State University, Logan, Utah
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12
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The Importance of Isotopic Turnover for Understanding Key Aspects of Animal Ecology and Nutrition. DIVERSITY-BASEL 2019. [DOI: 10.3390/d11050084] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Stable isotope-based methods have proved to be immensely valuable for ecological studies ranging in focus from animal movements to species interactions and community structure. Nevertheless, the use of these methods is dependent on assumptions about the incorporation and turnover of isotopes within animal tissues, which are oftentimes not explicitly acknowledged and vetted. Thus, the purpose of this review is to provide an overview of the estimation of stable isotope turnover rates in animals, and to highlight the importance of these estimates for ecological studies in terrestrial, freshwater, and marine systems that may use a wide range of stable isotopes. Specifically, we discuss 1) the factors that contribute to variation in turnover among individuals and across species, which influences the use of stable isotopes for diet reconstructions, 2) the differences in turnover among tissues that underlie so-called ‘isotopic clocks’, which are used to estimate the timing of dietary shifts, and 3) the use of turnover rates to estimate nutritional requirements and reconstruct histories of nutritional stress from tissue isotope signatures. As we discuss these topics, we highlight recent works that have effectively used estimates of turnover to design and execute informative ecological studies. Our concluding remarks suggest several steps that will improve our understanding of isotopic turnover and support its integration into a wider range of ecological studies.
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13
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Ek C, Garbaras A, Yu Z, Oskarsson H, Wiklund AKE, Kumblad L, Gorokhova E. Increase in stable isotope ratios driven by metabolic alterations in amphipods exposed to the beta-blocker propranolol. PLoS One 2019; 14:e0211304. [PMID: 31095563 PMCID: PMC6522046 DOI: 10.1371/journal.pone.0211304] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 05/05/2019] [Indexed: 12/15/2022] Open
Abstract
Anthropogenic pressures, such as contaminant exposure, may affect stable isotope ratios in biota. These changes are driven by alterations in the nutrient allocation and metabolic pathways induced by specific stressors. In a controlled microcosm study with the amphipod Gammarus spp., we studied effects of the β-blocker propranolol on stable isotope signatures (δ15N and δ13C), elemental composition (%C and %N), and growth (protein content and body size) as well as biomarkers of oxidative status (antioxidant capacity, ORAC; lipid peroxidation, TBARS) and neurological activity (acetylcholinesterase, AChE). Based on the known effects of propranolol exposure on cellular functions, i.e., its mode of action (MOA), we expected to observe a lower scope for growth, accompanied by a decrease in protein deposition, oxidative processes and AChE inhibition, with a resulting increase in the isotopic signatures. The observed responses in growth, biochemical and elemental variables supported most of these predictions. In particular, an increase in %N was observed in the propranolol exposures, whereas both protein allocation and body size declined. Moreover, both ORAC and TBARS levels decreased with increasing propranolol concentration, with the decrease being more pronounced for TBARS, which indicates the prevalence of the antioxidative processes. These changes resulted in a significant increase of the δ15N and δ13C values in the propranolol-exposed animals compared to the control. These findings suggest that MOA of β-blockers may be used to predict sublethal effects in non-target species, including inhibited AChE activity, improved oxidative balance, and elevated stable isotope ratios. The latter also indicates that metabolism-driven responses to environmental contaminants can alter stable isotope signatures, which should be taken into account when interpreting trophic interactions in the food webs.
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Affiliation(s)
- Caroline Ek
- Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
| | - Andrius Garbaras
- Mass Spectrometry Laboratory, Center for Physical Science and Technology, Vilnius, Lithuania
| | - Zhenyang Yu
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, P. R. China
| | - Hanna Oskarsson
- Department of Ecology, Environment and Plant Science, Stockholm University, Svante Stockholm, Sweden
| | | | - Linda Kumblad
- Department of Ecology, Environment and Plant Science, Stockholm University, Svante Stockholm, Sweden
| | - Elena Gorokhova
- Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
- * E-mail:
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14
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Plasman M, McCue MD, Reynoso VH, Terblanche JS, Clusella-Trullas S. Environmental temperature alters the overall digestive energetics and differentially affects dietary protein and lipid use in a lizard. J Exp Biol 2019; 222:222/6/jeb194480. [DOI: 10.1242/jeb.194480] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/10/2019] [Indexed: 12/18/2022]
Abstract
ABSTRACT
Processing food (e.g. ingestion, digestion, assimilation) requires energy referred to as specific dynamic action (SDA) and is at least partially fuelled by oxidation of the nutrients (e.g. proteins and lipids) within the recently ingested meal. In ectotherms, environmental temperature can affect the magnitude and/or duration of the SDA, but is likely to also alter the mixture of nutrients that are oxidized to cover these costs. Here, we examined metabolic rate, gut passage time, assimilation efficiency and fuel use in the lizard Agama atra digesting cricket meals at three ecologically relevant temperatures (20, 25 and 32°C). Crickets were isotopically enriched with 13C-leucine or 13C-palmitic-acid tracers to distinguish between protein and lipid oxidation, respectively. Our results show that higher temperatures increased the magnitude of the SDA peak (by 318% between 32 and 20°C) and gut passage rate (63%), and decreased the duration of the SDA response (by 20% for males and 48% for females). Peak rate of dietary protein oxidation occurred sooner than peak lipid oxidation at all temperatures (70, 60 and 31 h earlier for 20, 25 and 32°C, respectively). Assimilation efficiency of proteins, but not lipids, was positively related to temperature. Interestingly, the SDA response exhibited a notable circadian rhythm. These results show that temperature has a pronounced effect on digestive energetics in A. atra, and that this effect differs between nutrient classes. Variation in environmental temperatures may thus alter the energy budget and nutrient reserves of these animals.
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Affiliation(s)
- Melissa Plasman
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch 7600, South Africa
| | | | - Víctor Hugo Reynoso
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch 7600, South Africa
- Instituto de Biología, Departamento de Zoología, Universidad Nacional Autónoma de México, Ciudad de México, 04510, Mexico
| | - John S. Terblanche
- Centre for Invasion Biology, Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch 7600, South Africa
| | - Susana Clusella-Trullas
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch 7600, South Africa
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15
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Carter WA, Cooper-Mullin C, McWilliams SR. Turnover of muscle lipids and response to exercise differ between neutral and polar fractions in a model songbird, the zebra finch. ACTA ACUST UNITED AC 2018; 221:jeb.168823. [PMID: 29444847 DOI: 10.1242/jeb.168823] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 02/01/2018] [Indexed: 01/12/2023]
Abstract
The turnover rates of tissues and their constituent molecules give us insights into animals' physiological demands and their functional flexibility over time. Thus far, most studies of this kind have focused on protein turnover, and few have considered lipid turnover despite an increasing appreciation of the functional diversity of this class of molecules. We measured the turnover rates of neutral and polar lipids from the pectoralis muscles of a model songbird, the zebra finch (Taeniopygia guttata, N=65), in a 256 day C3/C4 diet shift experiment, with tissue samples taken at 10 time points. We also manipulated the physiological state of a subset of these birds with a 10 week flight training regimen to test the effect of exercise on lipid turnover. We measured lipid δ13C values via isotope ratio mass spectrometry (IRMS) and estimated turnover in different fractions and treatment groups with non-linear mixed-effect regression. We found a significant difference between the mean retention times (τ) of neutral and polar lipids (t119=-2.22, P=0.028), with polar lipids (τ=11.80±1.28 days) having shorter retention times than neutral lipids (τ=19.47±3.22 days). When all birds were considered, we also found a significant decrease in the mean retention time of polar lipids in exercised birds relative to control birds (difference=-2.2±1.83 days, t56=-2.37, P=0.021), but not neutral lipids (difference=4.2± 7.41 days, t56=0.57, P=0.57). A larger, more variable neutral lipid pool and the exposure of polar lipids in mitochondrial membranes to oxidative damage and increased turnover provide mechanisms consistent with our results.
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Affiliation(s)
- Wales A Carter
- Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USA
| | - Clara Cooper-Mullin
- Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USA
| | - Scott R McWilliams
- Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USA
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16
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Durso AM, French SS. Stable isotope tracers reveal a trade‐off between reproduction and immunity in a reptile with competing needs. Funct Ecol 2017. [DOI: 10.1111/1365-2435.13002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrew M. Durso
- Department of Biology & The Ecology Center Utah State University Logan UT USA
| | - Susannah S. French
- Department of Biology & The Ecology Center Utah State University Logan UT USA
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17
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Levin E, McCue MD, Davidowitz G. Sex differences in the utilization of essential and non-essential amino acids in Lepidoptera. ACTA ACUST UNITED AC 2017; 220:2743-2747. [PMID: 28495867 DOI: 10.1242/jeb.154757] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 05/08/2017] [Indexed: 01/04/2023]
Abstract
The different reproductive strategies of males and females underlie differences in behavior that may also lead to differences in nutrient use between the two sexes. We studied sex differences in the utilization of two essential amino acids (EAAs) and one non-essential amino acid (NEAA) by the Carolina sphinx moth (Manduca sexta). On day one post-eclosion from the pupae, adult male moths oxidized greater amounts of larva-derived AAs than females, and more nectar-derived AAs after feeding. After 4 days of starvation, the opposite pattern was observed: adult females oxidized more larva-derived AAs than males. Adult males allocated comparatively small amounts of nectar-derived AAs to their first spermatophore, but this allocation increased substantially in the second and third spermatophores. Males allocated significantly more adult-derived AAs to their flight muscle than females. These outcomes indicate that adult male and female moths employ different strategies for allocation and oxidation of dietary AAs.
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Affiliation(s)
- Eran Levin
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
| | - Marshall D McCue
- Department of Biological Sciences, St Mary's University, San Antonio, TX 78228, USA
| | - Goggy Davidowitz
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
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18
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Heck MJ, Pehlivanovic M, Purcell JU, Hahn DA, Hatle JD. Life-extending Dietary Restriction Reduces Oxidative Damage of Proteins in Grasshoppers but Does Not Alter Allocation of Ingested Nitrogen to Somatic Tissues. J Gerontol A Biol Sci Med Sci 2017; 72:616-623. [PMID: 27307298 DOI: 10.1093/gerona/glw094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 05/04/2016] [Indexed: 11/13/2022] Open
Abstract
Dietary restriction (DR) extends life span and reduces reproduction in most animals. The disposable soma hypothesis suggests that this longevity is the result of reduced investment in reproduction and increased nutrient allocation to the soma, permitting an increase in cellular maintenance. To investigate the role of nutrient allocation upon life-extending DR, tissue-specific nitrogen allocation was tracked in grasshoppers (Romalea microptera) upon a full or restricted (60% of full) diet. In addition, carbonyl (oxidized protein) assays addressed tissue maintenance. To develop a labeled diet on which grasshoppers could thrive, hydroponically grown Romaine lettuce was enriched with 15N. This allowed quantification of nitrogen allocation upon a normal or restricted diet. There was a 50% decrease in reproductive investment upon DR. At the same time, relative allocation of 15N to the ovary did not change. Most important, relative allocation was similar between restricted and full diet grasshoppers for somatic tissues (ie, mandibular and femur muscle, dried hemolymph, gut, and fat body). Carbonyl assays of muscles, hemolymph, and gut revealed an overall reduction in protein oxidation upon DR. These data suggest that DR does not alter nutrient allocation but does reduce protein oxidation, an observation that is inconsistent with the basic predictions of the disposable soma hypothesis.
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Affiliation(s)
- Matthew J Heck
- Department of Biology, University of North Florida, Jacksonville
| | - Mirna Pehlivanovic
- Department of Biology, University of North Florida, Jacksonville
- Present address: Stony Brook University, New York
| | - Jennifer U Purcell
- Department of Biology, University of North Florida, Jacksonville
- Present address: Lake Erie College of Medicine, Florida, Pennsylvania
| | - Daniel A Hahn
- Department of Entomology, University of Florida, Gainesville
| | - John D Hatle
- Department of Biology, University of North Florida, Jacksonville
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McCue MD, Sandoval J, Beltran J, Gerson AR. Dehydration Causes Increased Reliance on Protein Oxidation in Mice: A Test of the Protein-for-Water Hypothesis in a Mammal. Physiol Biochem Zool 2017; 90:359-369. [DOI: 10.1086/690912] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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20
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McCue MD, Albach A, Salazar G. Previous Repeated Exposure to Food Limitation Enables Rats to Spare Lipid Stores during Prolonged Starvation. Physiol Biochem Zool 2017; 90:63-74. [PMID: 28051943 DOI: 10.1086/689323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The risk of food limitation and, ultimately, starvation dates back to the dawn of heterotrophy in animals, yet starvation remains a major factor in the regulation of modern animal populations. Researchers studying starvation more than a century ago suggested that animals subjected to sublethal periods of food limitation are somehow more tolerant of subsequent starvation events. This possibility has received little attention over the past decades, yet it is highly relevant to modern science for two reasons. First, animals in natural populations are likely to be exposed to bouts of food limitation once or more before they face prolonged starvation, during which the risk of mortality becomes imminent. Second, our current approach to studying starvation physiology in the laboratory focuses on nourished animals with no previous exposure to nutritional stress. We examined the relationship between previous exposure to food limitation and potentially adaptive physiological responses to starvation in adult rats and found several significant differences. On two occasions, rats were fasted until they lost 20% of their body mass maintained lower body temperatures, and had presumably lower energy requirements when subjected to prolonged starvation than their naive cohort that never experienced food limitation. These rats that were trained in starvation also had lower plasma glucose set -points and reduced their reliance on endogenous lipid oxidation. These findings underscore (1) the need for biologists to revisit the classic hypothesis that animals can become habituated to starvation, using a modern set of research tools; and (2) the need to design controlled experiments of starvation physiology that more closely resemble the dynamic nature of food availability.
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21
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Viegas I, Araújo PM, Rocha AD, Villegas A, Jones JG, Ramos JA, Masero JA, Alves JA. Metabolic plasticity for subcutaneous fat accumulation in a long distance migratory bird traced by 2H2O. J Exp Biol 2017; 220:1072-1078. [DOI: 10.1242/jeb.150490] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 12/30/2016] [Indexed: 11/20/2022]
Abstract
The migrant black-tailed godwit (Limosa limosa) traditionally used natural wetlands in the Iberian Peninsula preparing for migratory flights by feeding mainly in estuaries. In recent decades this species has become increasingly dependent on rice fields, thereby relying on a plant-based diet for fueling. Dietary fatty acids (FA) seem to be determinant to the composition of accumulated subcutaneous fat in migratory birds. It is still unclear whether metabolic plasticity allows for modification and/or synthesis of FA, contributing for a lipid profile that enables a successful migratory performance.
Deuterated water was administered to captive black-tailed godwits submitted to two diets (fly larvae vs. rice) and the incorporation of deuterium (2H) into subcutaneous triglycerides was analysed by NMR. A recently developed localized biopsy method for sampling subcutaneous fat was employed with ulterior successful release of all birds into the wild. The average chemical structure reflected mostly a mixture of saturated and monounsaturated 16- and 18-carbon FA, a profile frequently found in migrant birds. Significantly higher levels of polyunsaturated FA, as well as detectable levels of n-3 FA were observed in fly larvae-fed birds. Excess 2H-enrichments in FA revealed significantly higher rates of fractional de novo lipogenesis and FA desaturation capacity in rice-fed birds.
This novel and non-lethal tracer method revealed the capacity of this species to alter its lipid metabolism to compensate for a poorer dietary lipid contribution. Due to its versatility, adapting this method to other scenarios and/or other migratory species is considered feasible and cost-effective.
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Affiliation(s)
- Ivan Viegas
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
- CFE - Center for Functional Ecology, Department Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Pedro M. Araújo
- MARE – Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Afonso D. Rocha
- MARE – Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Auxiliadora Villegas
- Conservation Biology Research Group, Área de Zoología, Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain
| | - John G. Jones
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Jaime A. Ramos
- MARE – Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - José A. Masero
- Conservation Biology Research Group, Área de Zoología, Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain
| | - José A. Alves
- CESAM, Dep. Biologia, Universidade de Aveiro, Campus Universitário de Santiago, 3180-193 Aveiro, Portugal
- University of Iceland, South Iceland Research Centre, Fjölheimer, Bankavegur IS-800 Selfoss, Iceland
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22
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Kirschman LJ, McCue MD, Boyles JG, Warne RW. Exogenous stress hormones alter energetic and nutrient costs of development and metamorphosis. J Exp Biol 2017; 220:3391-3397. [DOI: 10.1242/jeb.164830] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 07/17/2017] [Indexed: 11/20/2022]
Abstract
Variation in environmental conditions during larval life stages can shape development during critical windows and have lasting effects on the adult organism. Changes in larval developmental rates in response to environmental conditions, for example, can trade-off with growth to determine body size and condition at metamorphosis, which can affect adult survival and fecundity. However, it is unclear how use of energy and nutrients shape trade-offs across life stage transitions because no studies have quantified these costs of larval development and metamorphosis. We used an experimental approach to manipulate physiological stress in larval amphibians, along with respirometry and 13C-breath testing to quantify the energetic and nutritional costs of development and metamorphosis. Central to larval developmental responses to environmental conditions is the hypothalamus pituitary-adrenal/interrenal (HPA/I) axis, which regulates development, as well as energy homeostasis and stress responses across many taxa. Given these pleiotropic effects of HPA/I activity, manipulation of the HPA/I may provide insight into costs of metamorphosis. We measured the energetic and nutritional costs across the entire larval period and metamorphosis in a larval amphibian exposed to exogenous glucocorticoid (GC) hormones- the primary hormone secreted by the HPA/I axis. We measured metabolic rates and dry mass across larval ontogeny, and quantified lipid stores and nutrient oxidation via 13C-breath testing during metamorphosis, under control and GC-exposed conditions. Changes in dry mass match metamorphic states previously reported in the literature, but dynamics of metabolism were influenced by the transition from aquatic to terrestrial respiration. GC-treated larvae had lower dry mass, fat stores, and higher oxygen consumption during stages where controls were conserving energy. GC-treated larvae also oxidized greater amounts of 13C-labelled protein stores. These results provide evidence for a proximate cause of the physiological trade-off between larval growth and development, and provide insight into the energetic and nutrient costs that shape fitness trade-offs across life stages.
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Affiliation(s)
- Lucas J. Kirschman
- Department of Zoology, Southern Illinois University, Carbondale, IL USA, 62901
| | - Marshall D. McCue
- Department of Biological Sciences, St. Mary's University, San Antonio, TX, 78228, USA
| | - Justin G. Boyles
- Cooperative Wildlife Research Laboratory, Department of Zoology, Southern Illinois University, Carbondale, IL USA, 62901
| | - Robin W. Warne
- Department of Zoology, Southern Illinois University, Carbondale, IL USA, 62901
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23
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Herrera M. LG, Osorio M. J. Tracking Nutrient Routing in Avian Consumers in a Subtropical Desert. Biotropica 2016. [DOI: 10.1111/btp.12274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- L. Gerardo Herrera M.
- Estación de Biología de Chamela; Instituto de Biología; Universidad Nacional Autónoma de México; Apartado Postal 21 San Patricio Jalisco 48980 Mexico
| | - Jazmín Osorio M.
- Departamento de Ecología y Recursos Naturales; Centro Universitario de la Costa Sur; Universidad de Guadalajara; Av. Independencia Nacional #151 Autlán Jalisco 48900 Mexico
- Facultad de Ciencias Biológicas y Agropecuarias; Autopista Colima-Manzanillo km 40 Crucero de Tecomán; Tecomán Colima 28100 Mexico
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24
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McCue MD, Welch KC. (13)C-Breath testing in animals: theory, applications, and future directions. J Comp Physiol B 2015; 186:265-85. [PMID: 26660654 DOI: 10.1007/s00360-015-0950-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 11/11/2015] [Accepted: 11/25/2015] [Indexed: 10/22/2022]
Abstract
The carbon isotope values in the exhaled breath of an animal mirror the carbon isotope values of the metabolic fuels being oxidized. The measurement of stable carbon isotopes in carbon dioxide is called (13)C-breath testing and offers a minimally invasive method to study substrate oxidation in vivo. (13)C-breath testing has been broadly used to study human exercise, nutrition, and pathologies since the 1970s. Owing to reduced use of radioactive isotopes and the increased convenience and affordability of (13)C-analyzers, the past decade has witnessed a sharp increase in the use of breath testing throughout comparative physiology--especially to answer questions about how and when animals oxidize particular nutrients. Here, we review the practical aspects of (13)C-breath testing and identify the strengths and weaknesses of different methodological approaches including the use of natural abundance versus artificially-enriched (13)C tracers. We critically compare the information that can be obtained using different experimental protocols such as diet-switching versus fuel-switching. We also discuss several factors that should be considered when designing breath testing experiments including extrinsic versus intrinsic (13)C-labelling and different approaches to model nutrient oxidation. We use case studies to highlight the myriad applications of (13)C-breath testing in basic and clinical human studies as well as comparative studies of fuel use, energetics, and carbon turnover in multiple vertebrate and invertebrate groups. Lastly, we call for increased and rigorous use of (13)C-breath testing to explore a variety of new research areas and potentially answer long standing questions related to thermobiology, locomotion, and nutrition.
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25
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McCue MD, Guzman RM, Passement CA, Davidowitz G. How and When Do Insects Rely on Endogenous Protein and Lipid Resources during Lethal Bouts of Starvation? A New Application for 13C-Breath testing. PLoS One 2015; 10:e0140053. [PMID: 26465334 PMCID: PMC4605643 DOI: 10.1371/journal.pone.0140053] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 09/21/2015] [Indexed: 01/16/2023] Open
Abstract
Most of our understanding about the physiology of fasting and starvation comes from studies of vertebrates; however, for ethical reasons, studies that monitor vertebrates through the lethal endpoint are scant. Insects are convenient models to characterize the comparative strategies used to cope with starvation because they have diverse life histories and have evolved under the omnipresent challenge of food limitation. Moreover, we can study the physiology of starvation through its natural endpoint. In this study we raised populations of five species of insects (adult grasshoppers, crickets, cockroaches, and larval beetles and moths) on diets labeled with either 13C-palmitic acid or 13C-leucine to isotopically enrich the lipids or the proteins in their bodies, respectively. The insects were allowed to become postabsorptive and then starved. We periodically measured the δ13C of the exhaled breath to characterize how each species adjusted their reliance on endogenous lipids and proteins as energy sources. We found that starving insects employ a wide range of strategies for regulating lipid and protein oxidation. All of the insects except for the beetle larvae were capable of sharply reducing reliance on protein oxidation; however, this protein sparing strategy was usually unsustainable during the entire starvation period. All insects increased their reliance on lipid oxidation, but while some species (grasshoppers, cockroaches, and beetle larvae) were still relying extensively on lipids at the time of death, other species (crickets and moth larvae) allowed rates of lipid oxidation to return to prestarvation levels. Although lipids and proteins are critical metabolic fuels for both vertebrates and insects, insects apparently exhibit a much wider range of strategies for rationing these limited resources during starvation.
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Affiliation(s)
- Marshall D. McCue
- St. Mary’s University, Department of Biological Sciences, San Antonio, Texas, United States of America
- * E-mail:
| | - R. Marena Guzman
- St. Mary’s University, Department of Biological Sciences, San Antonio, Texas, United States of America
| | - Celeste A. Passement
- St. Mary’s University, Department of Biological Sciences, San Antonio, Texas, United States of America
| | - Goggy Davidowitz
- University of Arizona, Department of Entomology, Tucson, Arizona, United States of America
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26
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McCue MD, Guzman RM, Passement CA. Digesting pythons quickly oxidize the proteins in their meals and save the lipids for later. ACTA ACUST UNITED AC 2015; 218:2089-96. [PMID: 25987734 DOI: 10.1242/jeb.118349] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 04/29/2015] [Indexed: 01/03/2023]
Abstract
Pythons digesting rodent meals exhibit up to 10-fold increases in their resting metabolic rate (RMR); this increase in RMR is termed specific dynamic action (SDA). Studies have shown that SDA is partially fueled by oxidizing dietary nutrients, yet it remains unclear whether the proteins and the lipids in their meals contribute equally to this energy demand. We raised two populations of mice on diets labeled with either [(13)C]leucine or [(13)C]palmitic acid to intrinsically enrich the proteins and lipids in their bodies, respectively. Ball pythons (Python regius) were fed whole mice (and pureed mice 3 weeks later), after which we measured their metabolic rates and the δ(13)C in the breath. The δ(13)C values in the whole bodies of the protein- and lipid-labeled mice were generally similar (i.e. 5.7±4.7‰ and 2.8±5.4‰, respectively) but the oxidative kinetics of these two macronutrient pools were quite different. We found that the snakes oxidized 5% of the protein and only 0.24% of the lipids in their meals within 14 days. Oxidation of the dietary proteins peaked 24 h after ingestion, at which point these proteins provided ∼90% of the metabolic requirement of the snakes, and by 14 days the oxidation of these proteins decreased to nearly zero. The oxidation of the dietary lipids peaked 1 day later, at which point these lipids supplied ∼25% of the energy demand. Fourteen days after ingestion, these lipids were still being oxidized and continued to account for ∼25% of the metabolic rate. Pureeing the mice reduced the cost of gastric digestion and decreased SDA by 24%. Pureeing also reduced the oxidation of dietary proteins by 43%, but it had no effect on the rates of dietary lipid oxidation. Collectively, these results demonstrate that pythons are able to effectively partition the two primary metabolic fuels in their meals. This approach of uniquely labeling the different components of the diet will allow researchers to examine new questions about how and when animals use the nutrients in their meals.
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Affiliation(s)
- Marshall D McCue
- Department of Biological Sciences, St Mary's University, San Antonio, TX 78228, USA
| | - R Marena Guzman
- Department of Biological Sciences, St Mary's University, San Antonio, TX 78228, USA
| | - Celeste A Passement
- Department of Biological Sciences, St Mary's University, San Antonio, TX 78228, USA
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Welch KC, Péronnet F, Hatch KA, Voigt CC, McCue MD. Carbon stable-isotope tracking in breath for comparative studies of fuel use. Ann N Y Acad Sci 2015; 1365:15-32. [PMID: 25817456 DOI: 10.1111/nyas.12737] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Almost half a century ago, researchers demonstrated that the ratio of stable carbon isotopes in exhaled breath of rats and humans could reveal the oxidation of labeled substrates in vivo, opening a new chapter in the study of fuel use, the fate of ingested substrates, and aerobic metabolism. Until recently, the combined use of respirometry and stable-isotope tracer techniques had not been broadly employed to study fuel use in other animal groups. In this review, we summarize the history of this approach in human and animal research and define best practices that maximize its utility. We also summarize several case studies that use stable-isotope measurements of breath to explore the limits of aerobic metabolism and substrate turnover among several species and various physiological states. We highlight the importance of a comparative approach in revealing the profound effects that phylogeny, ecology, and behavior can have in shaping aerobic metabolism and energetics as well as the fundamental biological principles that underlie fuel use and metabolic function across taxa. New analytical equipment and refinement of methodology make the combined use of respirometry and stable-isotope tracer techniques simpler to perform, less costly, and more field ready than ever before.
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Affiliation(s)
- Kenneth C Welch
- Department of Biology, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - François Péronnet
- Département de Kinésiologie, Université de Montréal, Montréal, Québec, Canada
| | - Kent A Hatch
- Department of Biology, Long Island University Post, Brookville, New York
| | - Christian C Voigt
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
| | - Marshall D McCue
- Department of Biological Sciences, St. Mary's University, San Antonio, Texas
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28
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McCue MD, Passement CA, Rodriguez M. The magnitude of the naturally occurring isotopic enrichment of 13C in exhaled CO2 is directly proportional to exercise intensity in humans. Comp Biochem Physiol A Mol Integr Physiol 2015; 179:164-71. [DOI: 10.1016/j.cbpa.2014.08.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/26/2014] [Accepted: 08/28/2014] [Indexed: 10/24/2022]
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29
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Coon CAC, Brace AJ, McWilliams SR, McCue MD, Martin LB. Introduced and Native Congeners Use Different Resource Allocation Strategies to Maintain Performance during Infection. Physiol Biochem Zool 2014; 87:559-67. [DOI: 10.1086/676310] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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30
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Targeted 13C enrichment of lipid and protein pools in the body reveals circadian changes in oxidative fuel mixture during prolonged fasting: A case study using Japanese quail. Comp Biochem Physiol A Mol Integr Physiol 2013; 166:546-54. [DOI: 10.1016/j.cbpa.2013.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 08/15/2013] [Accepted: 08/16/2013] [Indexed: 11/21/2022]
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31
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Chen CCW, Welch KC. Hummingbirds can fuel expensive hovering flight completely with either exogenous glucose or fructose. Funct Ecol 2013. [DOI: 10.1111/1365-2435.12202] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chris Chin Wah Chen
- Department of Biological Sciences University of Toronto Scarborough 1265 Military TrailToronto Ontario M1C 1A4 Canada
- Department of Cell & Systems Biology University of Toronto 25 Harbord StreetToronto Ontario M5S 3G5 Canada
| | - Kenneth Collins Welch
- Department of Biological Sciences University of Toronto Scarborough 1265 Military TrailToronto Ontario M1C 1A4 Canada
- Department of Cell & Systems Biology University of Toronto 25 Harbord StreetToronto Ontario M5S 3G5 Canada
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32
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Measurements of substrate oxidation using 13CO2-breath testing reveals shifts in fuel mix during starvation. J Comp Physiol B 2013; 183:1039-52. [DOI: 10.1007/s00360-013-0774-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 07/01/2013] [Accepted: 07/19/2013] [Indexed: 10/26/2022]
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Khalilieh A, McCue MD, Pinshow B. Physiological responses to food deprivation in the house sparrow, a species not adapted to prolonged fasting. Am J Physiol Regul Integr Comp Physiol 2012; 303:R551-61. [DOI: 10.1152/ajpregu.00076.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Many wild birds fast during reproduction, molting, migration, or because of limited food availability. Species that are adapted to fasting sequentially oxidize endogenous fuels in three discrete phases. We hypothesized that species not adapted to long fasts have truncated, but otherwise similar, phases of fasting, sequential changes in fuel oxidization, and similar changes in blood metabolites to fasting-adapted species. We tested salient predictions in house sparrows ( Passer domesticus biblicus), a subspecies that is unable to tolerate more than ∼32 h of fasting. Our main hypothesis was that fasting sparrows sequentially oxidize substrates in the order carbohydrates, lipids, and protein. We dosed 24 house sparrows with [13C]glucose, palmitic acid, or glycine and measured 13CO2 in their breath while they fasted for 24 h. To ascertain whether blood metabolite levels reflect fasting-induced changes in metabolic fuels, we also measured glucose, triacylglycerides, and β-hydroxybutyrate in the birds' blood. The results of both breath 13CO2 and plasma metabolite analyses did not support our hypothesis; i.e., that sparrows have the same metabolic responses characteristic of fasting-adapted species, but on a shorter time scale. Contrary to our main prediction, we found that recently assimilated 13C-tracers were oxidized continuously in different patterns with no definite peaks corresponding to the three phases of fasting and also that changes in plasma metabolite levels accurately tracked the changes found by breath analysis. Notably, the rate of recently assimilated [13C]glycine oxidization was significantly higher ( P < 0.001) than that of the other metabolic tracers at all postdosing intervals. We conclude that the inability of house sparrows to fast for longer than 32 h is likely related to their inability to accrue large lipid stores, separately oxidize different fuels, and/or spare protein during fasting.
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Affiliation(s)
- Anton Khalilieh
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel; and
| | - Marshall D. McCue
- Department of Biological Sciences, St. Mary's University, San Antonio, Texas
| | - Berry Pinshow
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel; and
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Muñoz-Garcia A, Aamidor SE, McCue MD, McWilliams SR, Pinshow B. Allocation of endogenous and dietary protein in the reconstitution of the gastrointestinal tract in migratory blackcaps at stopover sites. ACTA ACUST UNITED AC 2012; 215:1069-75. [PMID: 22399651 DOI: 10.1242/jeb.062547] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During migratory flight, the mass of the gastrointestinal tract (GIT) and its associated organs in small birds decreases in size by as much as 40%, compared with the preflight condition because of the catabolism of protein. At stopover sites, birds need 2-3 days to rebuild their GIT so that they can restore body mass and fat reserves to continue migration. The source of protein used to rebuild the GIT may be exogenous (from food ingested) or endogenous (reallocated from other organs) or both. Because the relative contribution of these sources to rebuild the GIT of migratory birds is not yet known, we mimicked in-flight fasting and then re-feeding in two groups of blackcaps (Sylvia atricapilla), a Palearctic migratory passerine. The birds were fed a diet containing either 3% or 20% protein to simulate different refueling scenarios. During re-feeding, birds received known doses of (15)N-(l)-leucine before we measured the isotope concentrations in GIT and associated digestive organs and in locomotory muscles. We then quantified the extent to which blackcaps rebuilt their GIT with endogenous and/or dietary protein while refeeding after a fast. Our results indicate that blackcaps fed the low-protein diet incorporated less exogenous nitrogen into their tissues than birds fed the 20% protein diet. They also allocated relatively more exogenous protein to the GIT than to pectoral muscle than those birds re-fed with the high-protein diet. However, this compensation was not sufficient for birds eating the low-protein diet to rebuild their intestine at the same rate as the birds re-fed the high-protein diet. We concluded that blackcaps must choose stopover sites at which they can maximize protein intake to minimize the time it takes to rebuild their GIT and, thus, resume migration as soon as possible.
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Affiliation(s)
- Agustí Muñoz-Garcia
- Mitrani Department of Desert Ecology, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel.
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Murray IW, Wolf BO. Tissue carbon incorporation rates and diet-to-tissue discrimination in ectotherms: tortoises are really slow. Physiol Biochem Zool 2012; 85:96-105. [PMID: 22237293 DOI: 10.1086/663867] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Abstract Understanding carbon incorporation rates and diet-to-tissue discrimination (Δ(13)C(tissue-diet)) in animals is necessary to interpret stable isotope data collected from animals in the field. Our current understanding of the carbon dynamics in terrestrial ectotherms such as snakes, lizards, and turtles is poorly developed. Here we use a diet switch experiment to estimate carbon incorporation rates and diet-to-tissue discrimination factors in growing desert tortoises (Gopherus agassizii). Average carbon retention times for red blood cells (RBCs) and plasma were 126.7 ± 40.3 and 32.9 ± 14.5 days, respectively. Tissue carbon incorporation rates were affected by both growth and metabolism, with growth accounting for 50% of the carbon turnover in RBCs and 13% of carbon turnover in plasma. At equilibrium, scute keratin (0.8 ± 0.1) and plasma (1.0 ± 0.2) showed enriched discrimination values (Δ(13)C) compared to the test diet, but RBC Δ(13)C values were indistinguishable from diet (0.2 ± 0.3). We also found that new keratin continued to contribute significant material to previously grown keratin rings on the tortoise's shell. Changes in the δ(13)C of previously laid down growth rings indicated that the old rings closest to the region of new growth received about 73% of the carbon from the current diet; these data suggest that the interpretation of dietary history using growth rings must recognize that each ring may represent the weighted average of the diet over several seasons. These results continue to highlight the importance of laboratory experiments in interpreting isotopic data derived from field studies.
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Affiliation(s)
- Ian W Murray
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131
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McCue MD, Smith A, McKinney R, Rewald B, Pinshow B, McWilliams SR. A Mass Balance Approach to Identify and Compare Differential Routing of 13C-Labeled Carbohydrates, Lipids, and Proteins In Vivo. Physiol Biochem Zool 2011; 84:506-13. [DOI: 10.1086/661638] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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