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Merchant HN, Thirkell JE, Portugal SJ. No evidence for a signal in mammalian basal metabolic rate associated with a fossorial lifestyle. Sci Rep 2024; 14:11297. [PMID: 38760353 PMCID: PMC11101413 DOI: 10.1038/s41598-024-61595-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 05/07/2024] [Indexed: 05/19/2024] Open
Abstract
A vast array of challenging environments are inhabited by mammals, such as living in confined spaces where oxygen levels are likely to be low. Species can exhibit adaptations in basal metabolic rate (BMR) to exploit such unique niches. In this study we use 801 species to determine the relationship between BMR and burrow use in mammals. We included pre-existing data for mammalian BMR and 16 life history traits. Overall, mammalian BMR is dictated primarily by environmental ambient temperature. There were no significant differences in BMR of terrestrial, semi-fossorial and fossorial mammals, suggesting that species occupying a subterranean niche do not exhibit baseline metabolic costs on account of their burrowing lifestyle. Fossorial mammals likely show instantaneous metabolic responses to low oxygen in tunnels, rather than exhibit adaptive long-term responses in their BMR.
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Affiliation(s)
- Hana N Merchant
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.
| | - Jack E Thirkell
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Steven J Portugal
- Department of Biological Sciences, School of Life and Environmental Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
- Department of Biology, University of Oxford, OX1 3SZ, Oxford, United Kingdom
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2
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Smorkatcheva AV, Bushuev AV. Reproduction, postnatal development and resting metabolic rate of a poorly studied subterranean rodent, the long-clawed vole (Prometheomys schaposchnikowi). Mamm Biol 2022. [DOI: 10.1007/s42991-022-00302-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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3
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Cutrera AP, Luna F, Zenuto RR. Acute-Phase Immune Response Involves Fever, Sickness Behavior, and an Elevated Metabolic Rate in the Subterranean Rodent Ctenomys talarum. Physiol Biochem Zool 2022; 95:183-199. [PMID: 35148257 DOI: 10.1086/718409] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
AbstractThe acute-phase response (APR) is an induced innate response and may involve pronounced physiological and behavioral changes. One of the most common assays to study the APR involves the use of a lypopolysaccharide (LPS) from the cell wall of gram-negative bacteria. In this study, we determined the energetic costs of the APR in the subterranean rodent Ctenomys talarum, as well as the effects of the exposure to LPS on body temperature, body mass loss, and behavior in this species. Furthermore, we monitored levels of circulating endotoxin after LPS exposure. Our results suggest that in C. talarum, the APR is energetically costly, resulting in a 14% increase in metabolic rate. Animals exposed to LPS experienced a short-term thermal response, weight loss, and changes in their behavior that included more time spent resting and with their eyes totally or partially closed. However, the magnitude of the effects of LPS exposure varied between sexes and among animals. Also, there was a clear peak in circulating endotoxin levels in plasma 3 h postinjection (hpi) and a significant decrease of these levels 24 hpi, but peak endotoxin concentration values recorded were highly variable among animals. In light of these results, ecological determinants of immune function variation in tuco-tucos are discussed considering the roles of pace of life, habitat, and degree of pathogen exposure in these subterranean rodents.
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4
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Rosario Carotenuto A, Guarracino F, Šumbera R, Fraldi M. Burrowing below ground: interaction between soil mechanics and evolution of subterranean mammals. J R Soc Interface 2020; 17:20190521. [PMID: 31910769 DOI: 10.1098/rsif.2019.0521] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The evolution of species is governed by complex phenomena in which biological and environmental features may interact dynamically. Subterranean mammals dig tunnels whose diameter minimizes energetic costs during excavations and display anatomical adaptations in order to burrow structurally stable tunnels according to specific features of the soil. These animals weight from less than 50 g up to 1-2 kg, and dig tunnels with diameters from 3 to 15 cm. The use of allometric laws has enabled these data to be correlated. However, since tunnels need to be stable with respect to the geomechanical characteristics of the resident soils, a mathematical treatment linking the admissible dimensions of tunnels to the environment here suggests a mechanically grounded correlation between the body mass of subterranean mammals and the maximum dimensions of tunnels. Remarkably, such theoretical findings reflect very well the empirical allometric relationship and contribute to explain the wide differences observed in body sizes of subterranean mammals. In this respect, a far from ancillary role of environmental mechanics on the morphological evolution of subterranean mammals can be hypothesized.
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Affiliation(s)
- Angelo Rosario Carotenuto
- Department of Structures for Engineering and Architecture, University of Napoli Federico II, Napoli, Italy
| | - Federico Guarracino
- Department of Structures for Engineering and Architecture, University of Napoli Federico II, Napoli, Italy
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Massimiliano Fraldi
- Department of Structures for Engineering and Architecture, University of Napoli Federico II, Napoli, Italy
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5
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Baldo MB, Antenucci CD. Diet effect on osmoregulation in the subterranean rodent Ctenomys talarum. Comp Biochem Physiol A Mol Integr Physiol 2019; 235:148-158. [PMID: 31176767 DOI: 10.1016/j.cbpa.2019.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 04/25/2019] [Accepted: 06/02/2019] [Indexed: 11/19/2022]
Abstract
Water conservation requires osmoregulatory skills, sometimes limited by the environment and/or physiological and behavioral characteristics acquired along the evolutionary history of the species. Fossoriality had probably emerged as a survival mechanism to face increasing aridity, as suggested for Ctenomys, a genus that radiated to different environments. Ctenomys talarum (tuco-tuco) is an herbivorous subterranean rodent that lives in coastal grasslands inside humid burrows that reduce evaporation. However, their osmoregulatory mechanisms may be challenged by atmospheric variations when foraging aboveground and by the annual variability in dietary water and salt content. Then, it is of great interest to identify how much of this flexibility of C .talarum is attributed to physiological regulation. We analyzed the effect of water and salt content of diet on urinary, plasmatic, fecal and respiratory parameters. Tuco-tucos were not able to maintain their body weight under the offered monodiet, especially under the low hydrated diet, which explains its generalist and opportunistic foraging behavior. C. talarum mainly obtained water through food, whereas water metabolic production was negligible. Evaporative water loss did not vary between diets, but individuals under water restriction showed decreased fecal water loss and urine volume, high urine concentration but stable plasmatic osmolality and ionic concentration values. Under salt stress, urinary parameters remained relatively stable and high plasmatic osmolality was detected. Despite C. talarum produced more diluted urine than rodents from xeric environments, it is able to concentrate it 4 times above than the required at field even under the lowest water availability. This may be a characteristic associated with the evolutionary history of the species, which evolved in an arid context.
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Affiliation(s)
- María Belén Baldo
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC)-CONICET, Universidad Nacional de Mar del Plata, Argentina.
| | - C Daniel Antenucci
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC)-CONICET, Universidad Nacional de Mar del Plata, Argentina
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6
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Thermogenic capacity in subterranean Ctenomys: Species-specific role of thermogenic mechanisms. J Therm Biol 2019; 80:164-171. [PMID: 30784482 DOI: 10.1016/j.jtherbio.2019.01.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/28/2019] [Accepted: 01/28/2019] [Indexed: 11/24/2022]
Abstract
One way to understand ecological patterns of species is to determine their physiological diversity on a large geographic and/or temporal scales, in a context of hierarchical biodiversity framework. In particular, macrophysiological studies analyze how environmental factors affect the physiology and therefore the distribution of species. Subterranean species are an excellent model for evaluating the large-scale effects of ambient temperature (Ta) conditions on thermal physiology and distribution, due to their extensive use of burrows that provide a relatively thermal stable environment. Species belonging to the genus Ctenomys are all subterranean and endemic of South America. Cold induced maximum metabolic rate (MMR), basal metabolic rate (BMR) and non shivering thermogenesis (NST) were analyzed, as well as the expression of uncoupled proteins (UCP) in brown adipose tissue (BAT). Biogeographical variables appear to have no effect MMR experimentally induced by cold condition within Ctenomys. Also, mechanisms of heat production are species-specific, varying from a combination of ST and NST to a complete use of shivering mechanisms. This pattern is correlated at tissue level, since species that use only ST show a smaller interscapular BAT patch, not detectable presence of UCP1 and low COX activity. Thus, other factors, including body mass, that constrain cold induced MMR could affect thermogenic variability among Ctenomys. In the evolutionary timescale, if low O2 levels of burrows impose a ceiling in cold induced MMR, and ST is enhanced due to species-specific life history traits, such as digging effort, then the observed differences among Ctenomys species might be explained.
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Merlo J, Cutrera AP, Zenuto RR. Assessment of Trade-Offs between Simultaneous Immune Challenges in a Slow-Living Subterranean Rodent. Physiol Biochem Zool 2019; 92:92-105. [PMID: 30601103 DOI: 10.1086/701320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The coexistence of two or more infectious agents in the same host is common in nature. Given this, the study of trade-offs within the immune system itself is key to understanding how immune defenses act in wild species in their natural environment. Here we assessed the possible trade-off between an inflammatory response (induced by phytohemagglutinin [PHA]; involving innate and adaptive responses in the study species) and an antibody response (induced by sheep red blood cells [SRBC]; adaptive response) in a slow-living subterranean rodent, the Talas tuco-tuco (Ctenomys talarum Thomas, 1898). According to life-history theory, slow-living species should rely more heavily on adaptive immunity, which develops more slowly than an innate response but is beneficial against repeated infections. Individual physiological condition (estimated by measuring levels of infection and immune, nutritional, and stress parameters) was analyzed during immune challenges. Contrary to what was expected, we found that the magnitude and energetic costs of both immune responses were similar when stimulated alone or simultaneously. Variation in natural antibodies, neutrophils, basophils, total leukocytes, and the ratio of neutrophils to lymphocytes in relation to the different treatments was also detected. In particular, natural antibodies were negatively affected by the induction of both immune challenges simultaneously and an increase of neutrophil counts was detected in all animals with the exception of those challenged with SRBC, while the pattern of variation of basophils, total leukocytes, and ratio of neutrophils to lymphocytes was not clearly associated with any triggered immune response. In general, our results suggest the absence of an energetic or resource-based trade-off between the immune responses triggered by PHA and SRBC in C. talarum.
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Bacigalupe LD, Gaitán‐Espitia JD, Barria AM, Gonzalez‐Mendez A, Ruiz‐Aravena M, Trinder M, Sinervo B. Natural selection on plasticity of thermal traits in a highly seasonal environment. Evol Appl 2018; 11:2004-2013. [PMID: 30459844 PMCID: PMC6231472 DOI: 10.1111/eva.12702] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/22/2018] [Accepted: 08/24/2018] [Indexed: 01/10/2023] Open
Abstract
For ectothermic species with broad geographical distributions, latitudinal/altitudinal variation in environmental temperatures (averages and extremes) is expected to shape the evolution of physiological tolerances and the acclimation capacity (i.e., degree of phenotypic plasticity) of natural populations. This can create geographical gradients of selection in which environments with greater thermal variability (e.g., seasonality) tend to favor individuals that maximize performance across a broader range of temperatures compared to more stable environments. Although thermal acclimation capacity plays a fundamental role in this context, it is unknown whether natural selection targets this trait in natural populations. Additionally, understanding whether and how selection acts on thermal physiological plasticity is also highly relevant to climate change and biological conservation. Here, we addressed such an important gap in our knowledge in the northernmost population of the four-eyed frog, Pleurodema thaul. We measured plastic responses of critical thermal limits for activity, behavioral thermal preference, and thermal sensitivity of metabolism to acclimation at 10 and 20°C. We monitored survival during three separate recapture efforts and used mark-recapture integrated into an information-theoretic approach to evaluate the relationship between survivals as a function of the plasticity of thermal traits. Overall, we found no evidence that thermal acclimation in this population is being targeted by directional selection, although there might be signals of selection on individual traits. According to the most supported models, survival increased in individuals with higher tolerance to cold when cold-acclimated, probably because daily low extremes are frequent during the cooler periods of the year. Furthermore, survival increased with body size. However, in both cases, the directional selection estimates were nonsignificant, and the constraints of our experimental design prevented us from evaluating more complex models (i.e., nonlinear selection).
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Affiliation(s)
- Leonardo D. Bacigalupe
- Facultad de Ciencias, Instituto de Ciencias Ambientales y EvolutivasUniversidad Austral de ChileValdiviaChile
| | - Juan D. Gaitán‐Espitia
- The Swire Institute of Marine Science and School of Biological SciencesThe University of Hong KongHong KongChina
- CSIRO Oceans and AtmosphereHobartTasmaniaAustralia
| | - Aura M. Barria
- Facultad de Ciencias, Instituto de Ciencias Ambientales y EvolutivasUniversidad Austral de ChileValdiviaChile
| | - Avia Gonzalez‐Mendez
- Departamento de Ecología and Center of Applied Ecology and Sustainability (CAPES), Facultad de Ciencias BiológicasPontificia Universidad Católica de ChileSantiagoChile
| | - Manuel Ruiz‐Aravena
- School of Natural Sciences, College of Sciences and EngineeringUniversity of TasmaniaHobartTasmaniaAustralia
| | | | - Barry Sinervo
- Department of Ecology and Evolutionary BiologyUniversity of CaliforniaSanta CruzCalifornia
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Tachinardi P, Valentinuzzi VS, Oda GA, Buck CL. The Interplay of Energy Balance and Daily Timing of Activity in a Subterranean Rodent: A Laboratory and Field Approach. Physiol Biochem Zool 2017; 90:546-552. [PMID: 28665185 DOI: 10.1086/693003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The tuco-tuco (Ctenomys aff. knighti) is among the rodent species known to be nocturnal under standard laboratory conditions and diurnal under natural conditions. The circadian thermoenergetics (CTE) hypothesis postulates that switches in activity timing are a response to energetic challenges; daytime activity reduces thermoregulatory costs by consolidating activity to the warmest part of the day. Studying wild animals under both captive and natural conditions can increase understanding of how temporal activity patterns are shaped by the environment and could serve as a test of the CTE hypothesis. We estimated the effects of activity timing on energy expenditure for the tuco-tuco by combining laboratory measurements of metabolic rate with environmental temperature records in both winter and summer. We showed that, in winter, there would be considerable energy savings if activity is allocated at least partially during daylight, lending support to the CTE hypothesis. In summer, the impact of activity timing on energy expenditure is small, suggesting that during this season other factors, such as predation risk, water balance, and social interaction, may have more important roles than energetics in the determination of activity time.
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10
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Genoud M, Isler K, Martin RD. Comparative analyses of basal rate of metabolism in mammals: data selection does matter. Biol Rev Camb Philos Soc 2017; 93:404-438. [PMID: 28752629 DOI: 10.1111/brv.12350] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 05/29/2017] [Accepted: 06/05/2017] [Indexed: 12/21/2022]
Abstract
Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non-reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a 'subsampling procedure' was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less-reliable estimates of BMR were generally about 12-20% larger than more-reliable ones. Larger effects were found with more-limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more-limited, order-level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non-linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes.
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Affiliation(s)
- Michel Genoud
- Department of Ecology and Evolution, University of Lausanne, CH-1015, Lausanne, Switzerland.,Division of Conservation Biology, Institute of Ecology and Evolution, Department of Biology, University of Bern, CH-3012, Bern, Switzerland
| | - Karin Isler
- Department of Anthropology, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
| | - Robert D Martin
- Integrative Research Center, The Field Museum, Chicago, IL, 60605-2496, U.S.A.,Institute of Evolutionary Medicine, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
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11
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Luna F, Naya H, Naya DE. Understanding evolutionary variation in basal metabolic rate: An analysis in subterranean rodents. Comp Biochem Physiol A Mol Integr Physiol 2017; 206:87-94. [PMID: 28179141 DOI: 10.1016/j.cbpa.2017.02.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/09/2016] [Accepted: 02/02/2017] [Indexed: 11/26/2022]
Abstract
Understanding how evolutionary variation in energetic metabolism arises is central to several theories in animal biology. Basal metabolic rate (BMR) -i.e., the minimum rate of energy necessary to maintain thermal homeostasis in endotherms- is a highly informative measure to increase our understanding, because it is determined under highly standardized conditions. In this study we evaluate the relationship between taxa- and mass-independent (residual) BMR and ten environmental factors for 34 subterranean rodent species. Both conventional and phylogenetically informed analyses indicate that ambient temperature is the major determinant of residual BMR, with both variables inversely correlated. By contrast, other environmental factors that have been shown to affect residual BMR in endotherms, such as habitat productivity and rainfall, were not significant predictors of residual BMR in this group of species. Then, the results for subterranean rodents appear to support a central prediction of the obligatory heat model (OHM), which is a mechanistic model aimed to explain the evolution of residual BMR. Specifically, OHM proposes that during the colonization of colder environments, individuals with greater masses of metabolically expensive tissues (and thus with greater BMR) are favored by natural selection due to the link between greater masses of metabolically expensive tissues and physiological capacities. This way, natural selection should establishes a negative correlation between ambient temperature and both internal organ size and residual BMR.
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Affiliation(s)
- Facundo Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
| | - Hugo Naya
- Unidad de Bioinformática, Institut Pasteur de Montevideo, Montevideo 11400, Uruguay
| | - Daniel E Naya
- Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Montevideo 11400, Uruguay.
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Baldo MB, Luna F, Antenucci CD. Does acclimation to contrasting atmospheric humidities affect evaporative water loss in the South American subterranean rodentCtenomys talarum? J Mammal 2016. [DOI: 10.1093/jmammal/gyw104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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13
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Castellanos-Frías E, García-Perea R, Gisbert J, Bozinovic F, Virgós E. Intraspecific variation in the energetics of the Cabrera vole. Comp Biochem Physiol A Mol Integr Physiol 2015; 190:32-8. [DOI: 10.1016/j.cbpa.2015.08.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 08/17/2015] [Accepted: 08/19/2015] [Indexed: 11/26/2022]
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14
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Tachinardi P, Tøien Ø, Valentinuzzi VS, Buck CL, Oda GA. Nocturnal to Diurnal Switches with Spontaneous Suppression of Wheel-Running Behavior in a Subterranean Rodent. PLoS One 2015; 10:e0140500. [PMID: 26460828 PMCID: PMC4603895 DOI: 10.1371/journal.pone.0140500] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 09/25/2015] [Indexed: 01/15/2023] Open
Abstract
Several rodent species that are diurnal in the field become nocturnal in the lab. It has been suggested that the use of running-wheels in the lab might contribute to this timing switch. This proposition is based on studies that indicate feed-back of vigorous wheel-running on the period and phase of circadian clocks that time daily activity rhythms. Tuco-tucos (Ctenomys aff. knighti) are subterranean rodents that are diurnal in the field but are robustly nocturnal in laboratory, with or without access to running wheels. We assessed their energy metabolism by continuously and simultaneously monitoring rates of oxygen consumption, body temperature, general motor and wheel running activity for several days in the presence and absence of wheels. Surprisingly, some individuals spontaneously suppressed running-wheel activity and switched to diurnality in the respirometry chamber, whereas the remaining animals continued to be nocturnal even after wheel removal. This is the first report of timing switches that occur with spontaneous wheel-running suppression and which are not replicated by removal of the wheel.
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Affiliation(s)
| | - Øivind Tøien
- Institute of Arctic Biology, University of Alaska, Fairbanks, United States of America
| | - Veronica S. Valentinuzzi
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica (CRILAR), La Rioja, Argentina
| | - C. Loren Buck
- Department of Biological Sciences, University of Alaska, Anchorage, United States of America
| | - Gisele A. Oda
- Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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15
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Baldo MB, Antenucci CD, Luna F. Effect of ambient temperature on evaporative water loss in the subterranean rodent Ctenomys talarum. J Therm Biol 2015; 53:113-8. [DOI: 10.1016/j.jtherbio.2015.09.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 09/14/2015] [Accepted: 09/15/2015] [Indexed: 11/25/2022]
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16
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Vassallo AI, Becerra F, Echeverría AI, Casinos A. Ontogenetic integration between force production and force reception: a case study inCtenomys(Rodentia: Caviomorpha). ACTA ZOOL-STOCKHOLM 2015. [DOI: 10.1111/azo.12119] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Aldo I. Vassallo
- Departamento de Biología; Facultad de Ciencias Exactas y Naturales; Instituto de investigaciones Marinas y Costeras; Universidad Nacional de Mar del Plata - CONICET; Dean Funes 3250 Mar del Plata 7600 Argentina
| | - Federico Becerra
- Departamento de Biología; Facultad de Ciencias Exactas y Naturales; Instituto de investigaciones Marinas y Costeras; Universidad Nacional de Mar del Plata - CONICET; Dean Funes 3250 Mar del Plata 7600 Argentina
| | - Alejandra I. Echeverría
- Departamento de Biología; Facultad de Ciencias Exactas y Naturales; Instituto de investigaciones Marinas y Costeras; Universidad Nacional de Mar del Plata - CONICET; Dean Funes 3250 Mar del Plata 7600 Argentina
| | - Adriá Casinos
- Departamento de Biología Animal; Facultat de Biología; Universitat de Barcelona; Avinguda Diagonal 643 Barcelona Spain
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17
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Merlo JL, Cutrera AP, Luna F, Zenuto RR. PHA-induced inflammation is not energetically costly in the subterranean rodent Ctenomys talarum (tuco-tucos). Comp Biochem Physiol A Mol Integr Physiol 2014; 175:90-5. [PMID: 24905647 DOI: 10.1016/j.cbpa.2014.05.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 05/28/2014] [Accepted: 05/28/2014] [Indexed: 11/30/2022]
Abstract
Immune activity has been proposed to be associated with substantial costs, due to trade-offs with other functions or activities that share common resources and contribute to an animal's fitness. However, direct estimates of the cost of mounting an immune response are few and have been performed mainly in birds. Thus, further work is needed to clarify the relative costs of different components of the immune system and the role of environmental and life-history traits in modulating the costs of resistance. Within the components of immunity, inflammation is considered to be associated with a larger energetic expenditure. Here, we evaluated the energetic cost of the inflammatory response to phytohemagglutinin (PHA) in a wild population of a subterranean rodent, Ctenomys talarum, and the trade-offs between immune activity and reproduction. C. talarum develops an inflammatory response to PHA, but contrary to our predictions, this response was not associated with an increase in oxygen consumption regardless of reproductive status or sex. Our study shows that an immune challenge may not always result in a detectable energetic cost. We discuss the possibility that other currencies could be underlying the cost, such as micro-or macronutrients requirements, autoimmunity or oxidative stress.
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Affiliation(s)
- Julieta L Merlo
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET-Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina; Laboratorio de Ecofisiología, CIC-Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina.
| | - Ana P Cutrera
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET-Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina
| | - Facundo Luna
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET-Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina
| | - Roxana R Zenuto
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET-Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina
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Cutrera AP, Luna F, Merlo JL, Baldo MB, Zenuto RR. Assessing the energetic costs and trade-offs of a PHA-induced inflammation in the subterranean rodent Ctenomys talarum: immune response in growing tuco-tucos. Comp Biochem Physiol A Mol Integr Physiol 2014; 174:23-8. [PMID: 24726606 DOI: 10.1016/j.cbpa.2014.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 04/01/2014] [Accepted: 04/01/2014] [Indexed: 10/25/2022]
Abstract
A traditional approach used to assess whether immune defense is costly is to explore the existence of trade-offs between immunity and other functions; however, quantitative studies of the energetic costs associated with the activation of the immune system are scarce. We assessed the magnitude of a PHA-triggered immune response and the associated energetic costs in 60-day old Ctenomys talarum. We expected that the magnitude of the macroscopic inflammatory response to PHA is lower in young tuco-tucos compared with that of adults, given the allocation of substantial energy to growth, and that the magnitude of the inflammation is lower in male pups compared to females, due to the higher investment in growth of the larger sex. Concomitantly, we expected that the pups challenged with PHA show an increase in oxygen consumption compared to control animals and that a positive association exists between magnitude of the PHA-induced inflammation and oxygen consumption. Contrary to what was expected, young tuco-tucos mounted a higher inflammatory response compared with adults and there were no differences in the magnitude of this response between sexes. The inflammatory response induced by a PHA injection did not represent a significant energetic cost for young tuco-tucos. There were no differences in oxygen consumption between PHA-injected and control animals, and tuco-tucos that mounted a higher inflammatory response to PHA did not show higher oxygen consumption. Energy expenditure, however, is not the only physiological cost involved in trade-offs between immune response and various functions of the organism, and other currencies are discussed.
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Affiliation(s)
- Ana Paula Cutrera
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET Universidad Nacional de Mar del Plata, CC 1245 Mar del Plata, Argentina.
| | - Facundo Luna
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET Universidad Nacional de Mar del Plata, CC 1245 Mar del Plata, Argentina
| | - Julieta L Merlo
- Laboratorio de Ecofisiología, CIC - Universidad Nacional de Mar del Plata, CC 1245 Mar del Plata, Argentina
| | - María Belén Baldo
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET Universidad Nacional de Mar del Plata, CC 1245 Mar del Plata, Argentina
| | - Roxana R Zenuto
- Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, CONICET Universidad Nacional de Mar del Plata, CC 1245 Mar del Plata, Argentina
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Baldo MB, Luna F, Schleich CE, Antenucci CD. Thermoregulatory development and behavior of Ctenomys talarum pups during brief repeated postnatal isolation. Comp Biochem Physiol A Mol Integr Physiol 2014; 173C:35-41. [PMID: 24667557 DOI: 10.1016/j.cbpa.2014.03.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 03/05/2014] [Accepted: 03/16/2014] [Indexed: 01/14/2023]
Abstract
In altricial mammals, the role of the mother and siblings throughout pup's early ontogeny is critical to determine "normal" development in neonates. It has been reported that variations in parental investment during pups' development affect thermoregulatory capacity, growth patterns, brain development and behavior during lifetime, such as spatial learning and memory in adults. Ctenomys talarum (tuco-tuco) is a solitary subterranean rodent, who inhabits complex burrows and exhibits developed spatial orientation abilities. Tuco-tuco's pups display an altricial development, spending more than 80% of the time in contact with the mother. Throughout weaning period, pups display active exploratory behavior and improvements in their spatial capabilities. Then, we determined the effect of repeated brief postnatal isolations on the acquisition of physiological thermoregulation and the development of spatial learning capabilities in tuco-tuco's pups. As it occurs in wild animals, daily brief isolations (30min) did not affect the acquisition of adult's body temperature nor resting metabolic rate's development pattern. Moreover, behavioral response and adult spatial abilities of isolated pups were similar to that observed in non-isolated ones. Then, during periods of mother's absence, minor physiological and behavioral adjustments, such as shivering and postural changes, are required to keep C. talarum pups within allostasis.
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Affiliation(s)
- María Belén Baldo
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
| | - Facundo Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
| | - Cristian E Schleich
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
| | - C Daniel Antenucci
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
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Becerra F, Echeverría AI, Casinos A, Vassallo AI. Another one bites the dust: Bite force and ecology in three caviomorph rodents (Rodentia, Hystricognathi). ACTA ACUST UNITED AC 2014; 321:220-32. [DOI: 10.1002/jez.1853] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 12/18/2013] [Accepted: 01/06/2014] [Indexed: 11/05/2022]
Affiliation(s)
- Federico Becerra
- Departamento de Biología-Instituto de Investigaciones Marinas y Costeras (IIMyC); Universidad Nacional de Mar del Plata (UNMdP)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Mar del Plata Buenos Aires Argentina
| | - Alejandra Isabel Echeverría
- Departamento de Biología-Instituto de Investigaciones Marinas y Costeras (IIMyC); Universidad Nacional de Mar del Plata (UNMdP)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Mar del Plata Buenos Aires Argentina
| | - Adrià Casinos
- Departament de Biologia Animal; Universitat de Barcelona (UB); Barcelona Spain
| | - Aldo Iván Vassallo
- Departamento de Biología-Instituto de Investigaciones Marinas y Costeras (IIMyC); Universidad Nacional de Mar del Plata (UNMdP)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Mar del Plata Buenos Aires Argentina
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Tachinardi P, Bicudo JEW, Oda GA, Valentinuzzi VS. Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco. PLoS One 2014; 9:e85674. [PMID: 24454916 PMCID: PMC3893220 DOI: 10.1371/journal.pone.0085674] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 12/05/2013] [Indexed: 11/19/2022] Open
Abstract
The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions. The underground environment also poses energetic challenges (e.g. high-energy demands of digging, hypoxia, high humidity, low food availability) that have motivated thermoregulation studies in several subterranean rodent species. By using chronobiological protocols, the present work aims to contribute towards these studies by exploring day-night variations of thermoregulatory functions in tuco-tucos, starting with body temperature and its temporal relationship to locomotor activity. Animals showed daily, 24 h body temperature rhythms that persisted even in constant darkness and temperature, synchronizing to a daily light/dark cycle, with highest values occurring during darkness hours. The range of oscillation of body temperature was slightly lower than those reported for similar-sized and dark-active rodents. Most rhythmic parameters, such as period and phase, did not change upon removal of the running wheel. Body temperature and locomotor activity rhythms were robustly associated in time. The former persisted even after removal of the acute effects of intense activity on body temperature by a statistical method. Finally, regression gradients between body temperature and activity were higher in the beginning of the night, suggesting day-night variation in thermal conductance and heat production. Consideration of these day-night variations in thermoregulatory processes is beneficial for further studies on thermoregulation and energetics of subterranean rodents.
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Affiliation(s)
- Patricia Tachinardi
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - José Eduardo Wilken Bicudo
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Gisele Akemi Oda
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Verónica Sandra Valentinuzzi
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR-CONICET). Entre Ríos y Mendoza s/n, Anillaco, La Rioja, Argentina
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Luna F, Roca P, Oliver J, Antenucci CD. Maximal thermogenic capacity and non-shivering thermogenesis in the South American subterranean rodent Ctenomys talarum. J Comp Physiol B 2012; 182:971-83. [PMID: 22614630 DOI: 10.1007/s00360-012-0675-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 04/23/2012] [Accepted: 04/30/2012] [Indexed: 10/28/2022]
Abstract
Subterranean rodents inhabit closed tunnel systems that are hypoxic and hypercapnic and buffer aboveground ambient temperature. In contrast to other strictly subterranean rodents, Ctenomys talarum exhibits activity on the surface during foraging and dispersion and hence, is exposed also to the aboveground environment. In this context, this species is a valuable model to explore how the interplay between underground and aboveground use affects the relationship among basal metabolic rate (BMR), cold-induced maximum metabolic rate (MMR), shivering (ST), and non-shivering thermogenesis (NST). In this work, we provide the first evidence of the presence of NST, including the expression of uncoupling proteins in brown adipose tissue (BAT), and shivering thermogenesis in Ctenomys talarum, a species belonging to the most numerous subterranean genus, endemic to South America. Our results show no differences in BMR, cold-induced MMR, and NST between cold- (15 °C) and warm- (25 °C) acclimated individuals. Furthermore, thermal acclimation had no effect on the expression of mitochondrial uncoupling protein 1 (UCP1) in BAT. Only cytochrome c oxidase (COX) content and activity increased during cold acclimation. When interscapular BAT was removed, NST decreased more than 30%, whereas cold-induced MMR remained unchanged. All together, these data suggest that cold-induced MMR reaches a maximum in warm-acclimated individuals and so a probable ceiling in NST and UCP1 expression in BAT. Possible thermogenic mechanisms explaining the increase in the oxidative capacity, mediated by COX in BAT of cold-acclimated individuals and the role of ST in subterranean life habits are proposed.
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Affiliation(s)
- Facundo Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento, Instituto de Investigaciones Marinas y Costeras (IIMyC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
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White CR. Allometric estimation of metabolic rates in animals. Comp Biochem Physiol A Mol Integr Physiol 2011; 158:346-57. [DOI: 10.1016/j.cbpa.2010.10.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 10/01/2010] [Accepted: 10/01/2010] [Indexed: 10/19/2022]
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Energetics in Liolaemini lizards: implications of a small body size and ecological conservatism. J Comp Physiol B 2010; 181:373-82. [DOI: 10.1007/s00360-010-0524-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2010] [Revised: 09/12/2010] [Accepted: 09/16/2010] [Indexed: 11/26/2022]
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Cutrera AP, Zenuto RR, Luna F, Antenucci CD. Mounting a specific immune response increases energy expenditure of the subterranean rodent Ctenomys talarum (tuco-tuco): implications for intraspecific and interspecific variation in immunological traits. J Exp Biol 2010; 213:715-24. [DOI: 10.1242/jeb.037887] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
It was recently hypothesised that specific induced defences, which require substantial time and resources and are mostly beneficial against repeated infections, are more likely to be favoured in ‘slow-living-pace’ species. Therefore, understanding how different types of immune defences might vary with life history requires knowledge of the costs and benefits of defence components. Studies that have explored the energetic costs of immunity in vertebrates have done so with a focus primarily on birds and less so on mammals, particularly surface-dwelling rodents. In this study, we evaluated whether an experimental induction of the immune system with a non-pathogenic antigen elevates the energetic expenditure of a subterranean rodent: Ctenomys talarum (tuco-tucos). In both seasons studied, a significant increase in oxygen consumption was verified in immune-challenged tuco-tucos injected with sheep red blood cells (SRBC) compared with control animals. The increase in oxygen consumption 10 days after the exposure to SRBC was lower for female tuco-tucos monitored in the breeding season compared with females in the non-breeding season. Interestingly, antibody titres of female tuco-tucos did not decrease during the breeding season. Our results add new insight into the role of other factors such as basal metabolic rate or degree of parasite exposure besides ‘pace of life’ in modulating the interspecific immunological variation observed in natural populations of mammals.
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Affiliation(s)
- A. P. Cutrera
- Laboratorio de Ecofisiología, Departamento de Biología—Universidad Nacional de Mar del Plata, C. C. 1245, Mar del Plata, Argentina
| | - R. R. Zenuto
- Laboratorio de Ecofisiología, Departamento de Biología—Universidad Nacional de Mar del Plata, C. C. 1245, Mar del Plata, Argentina
| | - F. Luna
- Laboratorio de Ecofisiología, Departamento de Biología—Universidad Nacional de Mar del Plata, C. C. 1245, Mar del Plata, Argentina
| | - C. D. Antenucci
- Laboratorio de Ecofisiología, Departamento de Biología—Universidad Nacional de Mar del Plata, C. C. 1245, Mar del Plata, Argentina
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Zelová J, Šumbera R, Okrouhlík J, Burda H. Cost of digging is determined by intrinsic factors rather than by substrate quality in two subterranean rodent species. Physiol Behav 2010; 99:54-8. [DOI: 10.1016/j.physbeh.2009.10.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 10/06/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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Effect of diet quality and soil hardness on metabolic rate in the subterranean rodent Ctenomys talarum. Comp Biochem Physiol A Mol Integr Physiol 2009; 154:298-307. [PMID: 19497381 DOI: 10.1016/j.cbpa.2009.05.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 05/22/2009] [Accepted: 05/26/2009] [Indexed: 11/23/2022]
Abstract
The present work is aimed to establish, in Ctenomys talarum, the physiological and behavioral adjustments undergone by individuals when they are allowed to dig burrows in soils with different hardness and fed with diets of different quality. For each soil-diet combination, we estimated: resting metabolic rate (RMR), body temperature (T(b)), body mass, digestibility, food consumption rate, transit time, reingestion rate, feces production and time devoted to feeding, resting, locomotor activity and coprophagy. Soil type and diet quality affected RMR, but response to soil hardness was verified later. Animals fed with high quality (HQ) diet showed similar body temperature irrespective of soil condition, while animals fed with low quality (LQ) diet showed lower T(b) under soft soil (SS). Individuals fed with LQ diet showed lower RMR and both, lower digestibility and high transit time of food than those fed with HQ diet. Moreover, increments in feeding and defecation rates were observed in the former group. Number of reingested feces did not differ between animals fed with diets of different quality. However, when incidence of reingestion was considered, animals fed with HQ diet showed higher values of feces ingestion. Either feeding, resting and activity patterns were arrhythmic. However, for animals fed with LQ diet a tendency to rhythmic coprophagy was observed and it could be considered as a way to optimize feeding. This study shows that RMR is limited by digestive efficiency which is influenced by diet quality, but also thermal stress may limit the conversion of assimilated energy into work and heat.
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