1
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Ridenour M, Spicer LJ, Grindstaff JL. Insulin-like growth factor 1 and the hormonal mediation of sibling rivalry. Gen Comp Endocrinol 2023; 330:114163. [PMID: 36356644 DOI: 10.1016/j.ygcen.2022.114163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 10/27/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022]
Abstract
In altricial animals, young are completely dependent on parents for provisioning. The ability to outcompete siblings to receive parental provisioning has clear fitness benefits, and may be mediated by hormones that influence growth. We analyzed the effects of insulin-like growth factor 1 (IGF-1) on body size, growth, and sibling rivalry in eastern bluebirds (Sialia sialis). To determine whether IGF-1 is upregulated in response to the competitive environment, we manipulated brood sizes and examined the effect on IGF-1 levels, nestling body size, growth rate, and behavior. In a separate experiment, we injected nestlings with exogenous IGF-1 to study its impacts on body size, growth rate, and sibling competition. Brood size manipulation did not influence endogenous IGF-1 levels, but male nestlings with higher IGF-1 levels early in the nestling period tended to have greater mass gain than males with lower IGF-1 levels. Nestlings with higher IGF-1 levels also tended to be fed more frequently by parents. In the injection experiment, IGF-1 injected individuals tended to be heavier than vehicle injected young by the end of the nestling period, which suggests that IGF-1 can influence mass gain in bluebirds. IGF-1 has been proposed to be a mediator of life-history strategies and post-hatching behavior. Our results suggest that although bluebird nestlings do not adaptively elevate IGF-1 in response to the presence or number of siblings, IGF-1 may influence growth during the nestling period. These findings shed light on sibling competition, life history strategies, and the hormones that underlie them.
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Affiliation(s)
- Matthew Ridenour
- Oklahoma State University, 501 Life Sciences West, Stillwater, OK 74078, USA
| | - Leon J Spicer
- Oklahoma State University, 101 Animal Science Building, Stillwater, OK 74078, USA
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2
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Rödel HG, Jardim V, Rangassamy M, Jaravel L, Jacquet D, Monclús R, Féron C, Costantini D. Early life parameters and personality affect oxidative status during adulthood in an altricial rodent. Physiol Rep 2022; 10:e15427. [PMID: 36200138 PMCID: PMC9535260 DOI: 10.14814/phy2.15427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 07/26/2022] [Indexed: 06/16/2023] Open
Abstract
It is increasingly recognized that alterations of the cellular oxidative status might be an important cost underlying challenging early life conditions. For example, an increased litter size can impose challenges as the offspring will face increased competition for maternal resources. Within a litter, individuals with relatively higher starting mass typically show higher growth rates, which can lead to increased oxidative damage. We investigated the long-term consequences of these early life parameters on the oxidative status in mature mound-building mice (Mus spicilegus). Individual differences in the animals' exploration tendency were assessed by repeated open field and novel object tests. We predicted less exploratory phenotypes, which typically show a higher stress responsiveness, to be particularly susceptible to possible effects of these early life parameters on oxidative status. We quantified oxidative damage of DNA (8-hydroxy-2'-deoxyguanosine levels, 8-OHdG) and proteins (protein carbonyl content, PCC), and activities of the antioxidants catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in liver and skeletal muscle tissue. 8-OHdG levels were positively associated with CAT and SOD in both tissues, indicating that increased oxidative DNA damage was associated with an upregulation of antioxidant production. Hepatic DNA damage after maturity was increased in animals from larger litters. In less exploratory animals, DNA damage and the activity of CAT and SOD in the muscle were increased, but only in individuals with higher relative starting mass (measured on postnatal day 9). This interaction may be explained by the typically higher adrenocortical activity in less exploratory phenotypes and by the higher growth in relatively heavier pups, two factors known to increase oxidative stress. These findings contribute to enlightening the complex interplay between early life conditions, personality, and oxidative status.
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Affiliation(s)
- Heiko G. Rödel
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - Veridiana Jardim
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
- Laboratory of Ethology, Ecology and Evolution of Social Insects, Department of Experimental PsychologyUniversity of Sao PauloSão PauloBrazil
| | - Marylin Rangassamy
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - Ludivine Jaravel
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - Daphné Jacquet
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - Raquel Monclús
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - Christophe Féron
- Laboratoire d'Ethologie Expérimentale et Comparée UR 4443 (LEEC)Université Sorbonne Paris NordVilletaneuseFrance
| | - David Costantini
- Unité Physiologie Moléculaire et Adaptation (PhyMA)Muséum National d'Histoire Naturelle, CNRS, CP32ParisFrance
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3
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Obomsawin AP, Mastromonaco GF, Leonard ML. Chronic noise exposure has context-dependent effects on stress physiology in nestling Tree Swallows (Tachycineta bicolor). Gen Comp Endocrinol 2021; 311:113834. [PMID: 34181934 DOI: 10.1016/j.ygcen.2021.113834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 03/11/2021] [Accepted: 06/17/2021] [Indexed: 01/04/2023]
Abstract
Anthropogenic noise is increasing in intensity and scope, resulting in changes to acoustic landscapes and largely negative effects on a range of species. In birds, noise can mask acoustic signals used in a variety of communication systems, including parent-offspring communication. As a result, nestling birds raised in noise may have challenges soliciting food from parents and avoiding detection by predators. Given that passerine nestlings are confined to a nest and therefore cannot escape these challenges, noise may also act as a chronic stressor during their development. Here, we raised Tree Swallow (Tachycineta bicolor) nestlings with or without continuous, white noise to test whether noise exposure affected baseline and stress-induced plasma, integrated feather corticosterone levels, and immune function. Stress physiology and immune function may also vary with the competitive environment during development, so we also examined whether noise effects varied with brood size and nestling mass. We found that overall, exposure to noise did not alter nestling stress physiology or immune function. However, light nestlings raised in noise exhibited lower baseline plasma and integrated feather corticosterone than heavy nestlings, suggesting alternative physiological responses to anthropogenic stimuli. Furthermore, light nestlings in larger broods had reduced PHA-induced immune responses compared to heavy nestlings, and PHA-induced immune responses were associated with higher levels of baseline plasma and feather CORT. Overall, our findings suggest that noise can alter the stress physiology of developing birds; however, these effects may depend on developmental conditions and the presence of other environmental stressors, such as competition for resources. Our findings may help to explain why populations are not uniformly affected by noise.
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Affiliation(s)
- Anik P Obomsawin
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
| | | | - Marty L Leonard
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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4
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Scharf HM, Hauber ME, Mommer BC, Hoover JP, Schelsky WM. The effect of avian brood parasitism on physiological responses of host nestlings. Oecologia 2021; 195:861-872. [PMID: 33709254 DOI: 10.1007/s00442-021-04888-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 02/22/2021] [Indexed: 01/22/2023]
Abstract
Avian obligate brood parasites lay their eggs in the nests of other species that may provide care for the foreign offspring. Brood parasitism often imparts substantial fitness losses upon host nestlings when they are raised alongside the typically more competitive, larger, and older parasitic chick(s). Whereas fitness costs due to reduced host offspring survival in parasitized broods have been studied in detail, the physiological changes in host nestlings caused by parasitic nestmate(s) are less well known. We compared prothonotary warbler (Protonotaria citrea) nestlings, a host of the nest-sharing brown-headed cowbird (Molothrus ater), in experimentally parasitized vs. non-parasitized broods. Our aim was to determine whether cohabitation with brood parasitic young impacted host nestling baseline corticosterone plasma concentrations, immune responses, body condition, and mortality. Corticosterone levels and body condition of host nestlings were similar between nests with or without a cowbird nestmate, whereas host immune responses were lower and nestling mortality was greater in parasitized broods, irrespective of variation in brood size or total brood mass. We detected no trade-offs of baseline corticosterone levels with either immune responses or with body condition. These results suggest that this host species' nestlings experience some adverse fitness-relevant physiological effects in parasitized broods, but are also resilient in other aspects when coping with brood parasitism.
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Affiliation(s)
- Hannah M Scharf
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
| | - Mark E Hauber
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.,Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Brett C Mommer
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.,Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, USA
| | - Jeffrey P Hoover
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, IL, USA
| | - Wendy M Schelsky
- Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.,Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, IL, USA
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5
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Injaian AS, Taff CC, Pearson KL, Gin MMY, Patricelli GL, Vitousek MN. Effects of experimental chronic traffic noise exposure on adult and nestling corticosterone levels, and nestling body condition in a free-living bird. Horm Behav 2018; 106:19-27. [PMID: 30189211 DOI: 10.1016/j.yhbeh.2018.07.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/26/2018] [Accepted: 07/26/2018] [Indexed: 01/17/2023]
Abstract
Transportation noise affects urbanized, rural, and otherwise unaltered habitats. Given expanding transportation networks, alterations in the acoustic landscapes experienced by animals are likely to be pervasive and persistent (i.e. chronic). It is important to understand if chronic noise exposure alters behavior and physiology in free-living animals, as it may result in long-lasting impacts, such as reduced reproductive success. Here, we experimentally tested the effects of chronic traffic noise on baseline and stress-induced corticosterone (the primary avian glucocorticoid), parental feeding behavior, and fitness proxies in breeding tree swallows (Tachycineta bicolor). Our results show that chronic traffic noise is related to altered corticosterone in both adult female and nestling tree swallows, suggesting that noise may be a stressor in both groups. In adult females, our results suggest that traffic noise is related to a limited ability to respond to subsequent acute stressors (i.e. reduced stress-induced corticosterone levels after handling). Further, our results show no evidence of habituation to noise during the breeding season, as the negative relationship between traffic noise and adult female stress-induced corticosterone became stronger over time. In nestlings, we found a positive relationship between traffic noise exposure and baseline corticosterone. Finally, we found a negative relationship between traffic noise and nestling body condition, despite no detectable effects of noise on nestling provisioning (e.g. parental feeding rate, or insect bolus size/composition). These results highlight the potential long-term consequences of chronic noise exposure, as increased baseline corticosterone and reduced nestling body condition in noise-exposed areas may have negative, population-level consequences.
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Affiliation(s)
- Allison S Injaian
- Department of Ecology and Evolution, University of California, Davis, CA, USA.
| | - Conor C Taff
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - Kira L Pearson
- Department of Ecology and Evolution, University of California, Davis, CA, USA
| | - Michelle M Y Gin
- Department of Ecology and Evolution, University of California, Davis, CA, USA
| | - Gail L Patricelli
- Department of Ecology and Evolution, University of California, Davis, CA, USA
| | - Maren N Vitousek
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
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6
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Hardt BM, Ardia DR, Bashaw MJ, Rivers JW. Experimental brood enlargement differentially influences the magnitude of the corticosterone stress response in closely related, co‐occurring songbirds. Funct Ecol 2018. [DOI: 10.1111/1365-2435.13116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Braelei M. Hardt
- Department of Fisheries and WildlifeOregon State University Corvallis Oregon
| | - Daniel R. Ardia
- Department of BiologyFranklin & Marshall College Lancaster Pennsylvania
| | - Meredith J. Bashaw
- Department of PsychologyFranklin & Marshall College Lancaster Pennsylvania
| | - James W. Rivers
- Department of Forest Ecosystems and SocietyOregon State University Corvallis Oregon
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7
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Vitousek MN, Jenkins BR, Hubbard JK, Kaiser SA, Safran RJ. An experimental test of the effect of brood size on glucocorticoid responses, parental investment, and offspring phenotype. Gen Comp Endocrinol 2017; 247:97-106. [PMID: 28137535 DOI: 10.1016/j.ygcen.2017.01.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/20/2017] [Indexed: 02/02/2023]
Abstract
Because elevated glucocorticoid levels can impair reproduction, populations or species that engage in particularly valuable reproductive attempts may down-regulate the glucocorticoid stress response during reproduction (the brood value hypothesis). It is not clear, however, whether individuals rapidly modulate glucocorticoid responses based on shifting cues about the likelihood of reproductive success. By manipulating brood size to create broods that differed in potential value, we tested whether female barn swallows (Hirundo rustica) rapidly modulated the glucocorticoid stress response to promote investment in high-value broods, and whether nestling phenotype was influenced by treatment. Within-individual changes in female corticosterone, body mass, and measures of oxidative stress were unrelated to brood size treatment. Standard offspring provisioning rate did not differ across treatments; however, in the presence of a model predator, females raising enlarged broods maintained higher offspring feeding rates relative to control broods. Brood size did influence nestling phenotype. Nestlings from enlarged broods had lower body mass and higher baseline corticosterone than those from reduced broods. Finally, in adult females both baseline and stress-induced corticosterone were individually repeatable. Thus, while under moderately challenging environmental conditions brood size manipulations had context-dependent effects on parental investment, and influenced nestling phenotype, maternal glucocorticoid levels were not modulated based on brood value but were individually consistent features of phenotype during breeding.
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Affiliation(s)
- Maren N Vitousek
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA; Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA; Cornell Lab of Ornithology, Ithaca, NY 14850, USA.
| | - Brittany R Jenkins
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Joanna K Hubbard
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Sara A Kaiser
- Cornell Lab of Ornithology, Ithaca, NY 14850, USA; Center for Conservation Genomics, Smithsonian Institution, Washington, DC 20013, USA
| | - Rebecca J Safran
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
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8
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López-Arrabé J, Cantarero A, Pérez-Rodríguez L, Palma A, Moreno J. Oxidative Stress in Early Life: Associations with Sex, Rearing Conditions, and Parental Physiological Traits in Nestling Pied Flycatchers. Physiol Biochem Zool 2016; 89:83-92. [PMID: 27082719 DOI: 10.1086/685476] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Conditions experienced during juvenile development can affect the fitness of an organism. During early life, oxidative stress levels can be particularly high as a result of the increased metabolism and the relatively immature antioxidant system of the individual, and this may have medium- and long-term fitness consequences. Here we explore variation in levels of oxidative stress measured during early life in relation to sex, rearing conditions (hatching date and brood size), and parental condition and levels of oxidative markers in a wild population of the pied flycatcher (Ficedula hypoleuca) followed for 2 yr. A marker of total antioxidant status (TAS) in plasma and total levels of glutathione (GSH) in red blood cells, as well as a marker of oxidative damage in plasma lipids (malondialdehyde [MDA]), were assessed simultaneously. Our results show that nestling total GSH levels were associated with parental oxidative status, correlating negatively with maternal MDA and positively with total GSH levels of both parents, with a high estimated heritability. This suggests that parental physiology and genes could be determinants for endogenous components of the antioxidant system of the offspring. Moreover, we found that total GSH levels were higher in female than in male nestlings and that hatching date was positively associated with antioxidant defenses (higher TAS and total GSH levels). These results suggest that different components of oxidative balance are related to a variety of environmental and intrinsic--including parental--influencing factors. Future experimental studies must disentangle the relative contribution of each of these on nestling oxidative status and how the resulting oxidative stress at early phases shape adult phenotype and fitness.
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9
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Jenkins BR, Vitousek MN, Hubbard JK, Safran RJ. An experimental analysis of the heritability of variation in glucocorticoid concentrations in a wild avian population. Proc Biol Sci 2015; 281:rspb.2014.1302. [PMID: 25056627 DOI: 10.1098/rspb.2014.1302] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Glucocorticoid hormones (CORT) are predicted to promote adaptation to variable environments, yet little is known about the potential for CORT secretion patterns to respond to selection in free-living populations. We assessed the heritable variation underlying differences in hormonal phenotypes using a cross-foster experimental design with nestling North American barn swallows (Hirundo rustica erythrogaster). Using a bivariate animal model, we partitioned variance in baseline and stress-induced CORT concentrations into their additive genetic and rearing environment components and estimated their genetic correlation. Both baseline and stress-induced CORT were heritable with heritability of 0.152 and 0.343, respectively. We found that the variation in baseline CORT was best explained by rearing environment, whereas the variation in stress-induced CORT was contributed to by a combination of genetic and environmental factors. Further, we did not detect a genetic correlation between these two hormonal traits. Although rearing environment appears to play an important role in the secretion of both types of CORT, our results suggest that stress-induced CORT levels are underlain by greater additive genetic variance compared with baseline CORT levels. Accordingly, we infer that the glucocorticoid response to stress has a greater potential for evolutionary change in response to selection compared with baseline glucocorticoid secretion patterns.
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Affiliation(s)
- Brittany R Jenkins
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Ramaley N122, UCB 334, Boulder, CO 80309, USA
| | - Maren N Vitousek
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Ramaley N122, UCB 334, Boulder, CO 80309, USA
| | - Joanna K Hubbard
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Ramaley N122, UCB 334, Boulder, CO 80309, USA
| | - Rebecca J Safran
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Ramaley N122, UCB 334, Boulder, CO 80309, USA
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10
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Braasch A, Becker PH, Groothuis TGG. Response of testosterone and corticosterone plasma levels to the challenge of sibling competition: a study in common terns. Gen Comp Endocrinol 2014; 204:95-103. [PMID: 24859255 DOI: 10.1016/j.ygcen.2014.05.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 05/03/2014] [Accepted: 05/05/2014] [Indexed: 11/30/2022]
Abstract
The hormonal response to social challenges has been widely studied, however, most work focused on adult behavior in a reproductive context although developing animals also encounter important social challenges early in life. We studied the relationship between acute sibling competition and plasma corticosterone (CORT) and testosterone (T) in common tern (Sterna hirundo) chicks, a species whose young compete for access to food by scramble interactions. Blood samples were taken in nests with two and only one single chick both immediately after a feeding bout and in non-challenged controls. We found that T levels were lower in siblings challenged by a feeding bout as compared to controls, which may be explained by the fact that T suppresses begging behavior and is only elevated in response to territorial intrusion but not sibling competition in a related species. Singletons had, corrected for body condition, generally lower CORT levels than siblings suggesting that growing up with siblings creates a competitive environment in which high CORT levels are sustained irrespective of a social challenge. CORT levels were also negatively correlated with body condition and were higher in males than in females. The latter may be related to sex-specific food requirements and susceptibility to stress. Our results suggest a possible suppressive effect of acute sibling competition on T secretion, and a positive effect on CORT levels by longer term sibling competition. The degree to which these dynamics are related to begging or aggression, or both, needs further experimental work.
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Affiliation(s)
- Alexander Braasch
- Institute of Avian Research "Vogelwarte Helgoland", An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany.
| | - Peter H Becker
- Institute of Avian Research "Vogelwarte Helgoland", An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany
| | - Ton G G Groothuis
- Behavioural Biology, Centre for Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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11
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Lynn SE, Kern MD, Phillips MM. Neonatal handling alters the development of the adrenocortical response to stress in a wild songbird (eastern bluebird, Sialia sialis). Gen Comp Endocrinol 2013; 186:157-63. [PMID: 23524000 DOI: 10.1016/j.ygcen.2013.03.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 03/02/2013] [Accepted: 03/04/2013] [Indexed: 02/01/2023]
Abstract
Neonatal handling of captive vertebrates can shape the development of their hypothalamo-pituitary-adrenal (HPA) axis and alter their ability to respond to stressful stimuli later in life. However, the long-term effects of such handling on this endocrine axis in free-living species are not well understood. We investigated the effects of age and neonatal handling on corticosterone secretion in response to restraint in eastern bluebird (Sialia sialis) chicks. We found that unhandled ("naïve") and handled ("experienced") chicks exhibited no corticosterone response to handling early in development. Thereafter, naïve individuals exhibited the progressive development of a corticosterone response with age, and by day 12 post-hatch, the response resembled that of adult bluebirds. Experienced nestlings, which were handled every other day from the day of hatch, showed a similar pattern of HPA development until day 12 post-hatch, when their corticosterone response was significantly reduced compared to that of naïve nestlings. In contrast, chicks that were handled only once, when 10days old, did not show a reduced corticosterone response at 12days old. Taken together, our data suggest that a certain threshold of accumulated neonatal handling episodes is necessary to depress corticosterone secretion, and/or that the cumulative effects of several handling episodes only manifest themselves once the HPA axis is fully developed. Our findings, in concert with studies on two other wild species, indicate that routine handling of nestlings in the field can alter their responses to stress in a species-specific manner, potentially leading to important fitness consequences.
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Affiliation(s)
- Sharon E Lynn
- The College of Wooster, Department of Biology, 931 College Mall, Wooster, OH 44691, USA.
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