1
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Caro SP, Cornil CA, van Oers K, Visser ME. Personality and gonadal development as sources of individual variation in response to GnRH challenge in female great tits. Proc Biol Sci 2020; 286:20190142. [PMID: 31039718 DOI: 10.1098/rspb.2019.0142] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Seasonal timing of reproduction is a key life-history trait, but we know little about the mechanisms underlying individual variation in female endocrine profiles associated with reproduction. In birds, 17β-oestradiol is a key reproductive hormone that links brain neuroendocrine mechanisms, involved in information processing and decision-making, to downstream mechanisms in the liver, where egg-yolk is produced. Here, we test, using a simulated induction of the reproductive system through a Gonadotropin-Releasing Hormone (GnRH) challenge, whether the ovary of pre-breeding female great tits responds to brain stimulation by increasing oestradiol. We also assess how this response is modified by individual-specific traits like age, ovarian follicle size, and personality, using females from lines artificially selected for divergent levels of exploratory behaviour. We show that a GnRH injection leads to a rapid increase in circulating concentrations of oestradiol, but responses varied among individuals. Females with more developed ovarian follicles showed stronger responses and females from lines selected for fast exploratory behaviour showed stronger increases compared to females from the slow line, indicating a heritable component. This study shows that the response of the ovary to reproductive stimulation from the brain greatly varies among individuals and that this variation can be attributed to several commonly measured individual traits, which sheds light on the mechanisms shaping heritable endocrine phenotypes.
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Affiliation(s)
- Samuel P Caro
- 1 Netherlands Institute of Ecology (NIOO-KNAW) , Wageningen , The Netherlands.,2 Centre d'Ecologie Fonctionnelle et Evolutive (CEFE-CNRS), Unité Mixte de Recherche CNRS 5175 , Montpellier , France
| | | | - Kees van Oers
- 1 Netherlands Institute of Ecology (NIOO-KNAW) , Wageningen , The Netherlands
| | - Marcel E Visser
- 1 Netherlands Institute of Ecology (NIOO-KNAW) , Wageningen , The Netherlands
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2
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Lipshutz SE, George EM, Bentz AB, Rosvall KA. Evaluating testosterone as a phenotypic integrator: From tissues to individuals to species. Mol Cell Endocrinol 2019; 496:110531. [PMID: 31376416 PMCID: PMC6731036 DOI: 10.1016/j.mce.2019.110531] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 06/14/2019] [Accepted: 07/30/2019] [Indexed: 12/19/2022]
Abstract
Hormones have the potential to bring about rapid phenotypic change; however, they are highly conserved over millions of years of evolution. Here, we examine the evolution of hormone-mediated phenotypes, and the extent to which regulation is achieved via independence or integration of the many components of endocrine systems. We focus on the sex steroid testosterone (T), its cognate receptor (androgen receptor) and related endocrine components. We pose predictions about the mechanisms underlying phenotypic integration, including coordinated sensitivity to T within and among tissues and along the HPG axis. We then assess these predictions with case studies from wild birds, asking whether gene expression related to androgenic signaling naturally co-varies among individuals in ways that would promote phenotypic integration. Finally, we review how mechanisms of integration and independence vary over developmental or evolutionary time, and we find limited support for integration.
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Affiliation(s)
- S E Lipshutz
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
| | - E M George
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - A B Bentz
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - K A Rosvall
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
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3
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Schuppe ER, Fuxjager MJ. Phenotypic variation reveals sites of evolutionary constraint in the androgenic signaling pathway. Horm Behav 2019; 115:104538. [PMID: 31211944 DOI: 10.1016/j.yhbeh.2019.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 05/19/2019] [Accepted: 06/10/2019] [Indexed: 01/05/2023]
Abstract
Steroid hormone systems play an important role in shaping the evolution of vertebrate sexual traits, but several aspects of this relationship remain unclear. For example, we currently know little about how steroid signaling complexes are adapted to accommodate the emergence of behavior in response to sexual selection. We use downy woodpeckers (Dryobates pubescens) to evaluate how the machinery underlying androgen action can evolve to accommodate this bird's main territorial signal, the drum. We focus specifically on modifications to androgenic mechanisms in the primary neck muscle that actuates the hammering movements underlying this signal. Of the signaling components we examine, we find that levels of circulating testosterone (T) and androgen receptor (AR) expression are consistently increased in a way that likely enhances androgenic regulation of drumming. By contrast, the expression of nuclear receptor co-factors-the 'molecular rheostats' of steroid action-show no such relationship in our analyses. If anything, co-factors are expressed in directions that would presumably hinder androgenic regulation of the drum. These findings therefore collectively point to T levels and AR as the more evolutionarily labile components of the androgenic system, in that they are likely more apt to change over time to support sexual selection for territorial signaling in woodpeckers. Yet the signaling elements that fine-tune AR's functional effects on the genome-namely the receptor's transcriptional co-factors-do not change in such a manner, and thus may be under tighter evolutionary constraint.
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Affiliation(s)
- Eric R Schuppe
- Department of Biology, Wake Forest University, 455 Vine Street, Winston-Salem, NC 27101, United States of America
| | - Matthew J Fuxjager
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, United States of America.
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4
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Kimmitt AA, Hardman JW, Stricker CA, Ketterson ED. Migratory strategy explains differences in timing of female reproductive development in seasonally sympatric songbirds. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13386] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | - Jack W. Hardman
- Department of Biology Indiana University Bloomington Indiana
| | | | - Ellen D. Ketterson
- Department of Biology Indiana University Bloomington Indiana
- Environmental Resilience Institute Indiana University Bloomington Indiana
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5
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Graham JL, Needham KB, Bertucci EM, Pearson AA, Bauer CM, Greives TJ. Onset of Daily Activity in a Female Songbird Is Related to Peak-Induced Estradiol Levels. Integr Comp Biol 2019; 59:1059-1067. [DOI: 10.1093/icb/icz112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Research in captive birds and mammals has demonstrated that circadian (i.e., daily) behavioral rhythms are altered in response to increases in sex-steroid hormones. Recently, we and others have demonstrated a high degree of individual repeatability in peak (gonadotropin-releasing hormone [GnRH]-induced sex) steroid levels, and we have found that these GnRH-induced levels are highly correlated with their daily (night-time) endogenous peak. Whether or not individual variation in organization and activity of the reproductive endocrine axis is related to daily timing in wild animals is not well known. To begin to explore these possible links, we tested the hypothesis that maximal levels of the sex steroid hormone estradiol (E2) and onset of daily activity are related in a female songbird, the dark-eyed junco (Junco hyemalis). We found that females with higher levels of GnRH-induced E2 departed from their nest in the morning significantly earlier than females with lower stimulated levels. We did not observe a relationship between testosterone and this measure of onset of activity. Our findings suggest an interaction between an individual’s reproductive endocrine axis and the circadian system and variation observed in an individuals’ daily activity onset. We suggest future studies examine the relationship between maximal sex-steroid hormones and timing of daily activity onset.
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Affiliation(s)
- Jessica L Graham
- Ecologie Comportementale, Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Centre National De La Recherche Scientifique (CNRS), 1919 Route de Mende, 34293 Montpellier 5, France
- Department of Biological Sciences, North Dakota State University, 201 Stevens Hall, 1340 Bolley Drive, Fargo, ND 58108-6050, USA
| | - Katie B Needham
- Department of Biological Sciences, North Dakota State University, 201 Stevens Hall, 1340 Bolley Drive, Fargo, ND 58108-6050, USA
| | - Emily M Bertucci
- School of Ecology, University of Georgia, 140 E Green Street, Athens, GA 30602-2202, USA
| | - Alexis A Pearson
- Department of Biological Sciences, North Dakota State University, 201 Stevens Hall, 1340 Bolley Drive, Fargo, ND 58108-6050, USA
| | - Carolyn M Bauer
- Department of Biology, Adelphi University, 1 South Ave, Garden City, NY 11530, USA
| | - Timothy J Greives
- Department of Biological Sciences, North Dakota State University, 201 Stevens Hall, 1340 Bolley Drive, Fargo, ND 58108-6050, USA
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6
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Needham KB, Bergeon Burns C, Graham JL, Bauer CM, Kittilson JD, Ketterson ED, Hahn T, Greives TJ. Changes in processes downstream of the hypothalamus are associated with seasonal follicle development in a songbird, the dark-eyed junco (Junco hyemalis). Gen Comp Endocrinol 2019; 270:103-112. [PMID: 30339809 DOI: 10.1016/j.ygcen.2018.10.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 10/04/2018] [Accepted: 10/15/2018] [Indexed: 02/07/2023]
Abstract
Mechanisms related to seasonal reproductive timing in vertebrates have received far more study in males than in females, despite the fact that female timing decisions dictate when rearing of offspring will occur. Production and release of gonadotropin-releasing hormone (GnRH) by the hypothalamus stimulates the pituitary to secrete gonadotropins, initiating the beginning stages of gonadal recrudescence and production of the sex steroids, testosterone and estradiol, which are necessary to prime the liver for secretion of yolk precursors in breeding female birds. While stimulation by the hypothalamus can occur during the pre-breeding period, egg development itself is likely regulated downstream of the hypothalamus. We used GnRH challenges to examine variation in breeding-stage-specific patterns of pituitary and ovarian responsiveness in free-living female dark-eyed juncos (Junco hyemalis) and also examined the ovary and liver for variation in mRNA expression of candidate genes. Baseline LH levels increased during the transition from pre-breeding to egg-development, however no significant difference was observed in post-GnRH injection levels for LH or sex steroids (testosterone and estradiol). Interestingly, a stage by time-point interaction was observed, with post-GnRH LH levels increasing over baseline during the pre-breeding stage, but not during the egg-development stage. We observed a decrease in liver mRNA expression of estradiol receptor-alpha, and glucocorticoid and mineralocorticoid receptors and a decrease in glucocorticoid receptor expression levels in the ovary. A decline in FSH receptor expression across stages was also observed in the ovary. Combined, our data suggest seasonal variation in female's sensitivity to signals of HPG activity and energetic or stress signals. These data provide additional insight into the physiological mechanisms regulating onset of clutch initiation.
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Affiliation(s)
- Katie B Needham
- Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Environmental and Conservation Sciences Program, North Dakota State University, Fargo, ND, USA
| | | | - Jessica L Graham
- Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Environmental and Conservation Sciences Program, North Dakota State University, Fargo, ND, USA
| | - Carolyn M Bauer
- Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Department of Biology, Adelphi University, Garden City, NY, USA
| | - Jeffrey D Kittilson
- Department of Biological Sciences, North Dakota State University, Fargo, ND, USA
| | | | - Thomas Hahn
- College of Biological Sciences, UC Davis, Davis, CA, USA
| | - Timothy J Greives
- Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Environmental and Conservation Sciences Program, North Dakota State University, Fargo, ND, USA
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7
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Bentz AB, Dossey EK, Rosvall KA. Tissue-specific gene regulation corresponds with seasonal plasticity in female testosterone. Gen Comp Endocrinol 2019; 270:26-34. [PMID: 30291863 DOI: 10.1016/j.ygcen.2018.10.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 09/25/2018] [Accepted: 10/01/2018] [Indexed: 01/01/2023]
Abstract
Testosterone (T) is a sex steroid hormone that often varies seasonally and mediates trade-offs between territorial aggression and parental care. Prior work has provided key insights into the 'top-down' hypothalamic control of this seasonal plasticity in T, yet mechanisms acting outside of the brain may also influence circulating T levels. We hypothesized that peripheral mechanisms may be especially critical for females, because peripheral regulation may mitigate the costs of systemically elevated T. Here, we begin to test this hypothesis using a seasonal comparative approach, measuring gene expression in peripheral tissues in tree swallows (Tachycineta bicolor), a songbird with intense female-female competition and T-mediated aggression. We focused on the gonad and liver for their role in T production and metabolism, respectively, and we contrasted females captured during territory establishment versus incubation. During territory establishment, when T levels are highest, we found elevated gene expression of the hepatic steroid metabolizing enzyme CYP2C19 along with several ovarian steroidogenic enzymes, including the androgenic 5α-reductase. Despite these seasonal changes in gene expression along the steroidogenic pathway, we did not observe seasonal changes in sensitivity to upstream signals, measured as ovarian mRNA abundance of luteinizing hormone receptor. Together, these data suggest that differential regulation of steroidogenic gene expression in the ovary is a potentially major contributor to seasonal changes in T levels in females. Furthermore, these data provide a unique and organismal glimpse into tissue-specific gene regulation and its potential role in hormonal plasticity in females.
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Affiliation(s)
- Alexandra B Bentz
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Emma K Dossey
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Kimberly A Rosvall
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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8
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George EM, Rosvall KA. Testosterone production and social environment vary with breeding stage in a competitive female songbird. Horm Behav 2018; 103:28-35. [PMID: 29807035 DOI: 10.1016/j.yhbeh.2018.05.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 04/02/2018] [Accepted: 05/22/2018] [Indexed: 12/16/2022]
Abstract
In many vertebrates, males increase circulating testosterone (T) levels in response to seasonal and social changes in competition. Females are also capable of producing and responding to T, but the full extent to which they can elevate T across life history stages remains unclear. Here we investigated T production during various breeding stages in female tree swallows (Tachycineta bicolor), which face intense competition for nesting sites. We performed GnRH and saline injections and compared changes in T levels 30 min before and after injection. We found that GnRH-injected females showed the greatest increases in T during territory establishment and pre-laying stages, whereas saline controls dramatically decreased T production during this time. We also observed elevated rates of conspecific aggression during these early stages of breeding. During incubation and provisioning, however, T levels and T production capabilities declined. Given that high T can disrupt maternal care, an inability to elevate T levels in later breeding stages may be adaptive. Our results highlight the importance of saline controls for contextualizing T production capabilities, and they also suggest that social modulation of T is a potential mechanism by which females may respond to competition, but only during the period of time when competition is most intense. These findings have broad implications for understanding how females can respond to their social environment and how selection may have shaped these hormone-behavior interactions.
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Affiliation(s)
- Elizabeth M George
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA.
| | - Kimberly A Rosvall
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA
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9
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Berzins LL, Shrimpton JM, Dawson RD. Experimentally altering pre-breeding sex steroids reduces extra-pair paternity in female tree swallows. Ethology 2018. [DOI: 10.1111/eth.12745] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lisha L. Berzins
- Ecosystem Science and Management Program; University of Northern British Columbia; Prince George BC Canada
| | - J. Mark Shrimpton
- Ecosystem Science and Management Program; University of Northern British Columbia; Prince George BC Canada
| | - Russell D. Dawson
- Ecosystem Science and Management Program; University of Northern British Columbia; Prince George BC Canada
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10
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Okuliarova M, Meddle SL, Zeman M. Egg deposition of maternal testosterone is primarily controlled by the preovulatory peak of luteinizing hormone in Japanese quail. Gen Comp Endocrinol 2018; 256:23-29. [PMID: 28495270 PMCID: PMC5771469 DOI: 10.1016/j.ygcen.2017.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/27/2017] [Accepted: 05/06/2017] [Indexed: 01/13/2023]
Abstract
Differential transfer of maternal testosterone (T) into egg yolk provides a means of adjusting an offspring's phenotype to ambient environmental conditions. While the environmental and genetic driven variability in yolk T levels is widely described, the underlying mechanisms are poorly understood. Here, we investigated whether neuroendocrine mechanisms controlling ovulatory processes are associated with the regulation of yolk T deposition. Circulatory profiles of luteinizing hormone (LH), T and estradiol levels were analysed during the last 7h before ovulation in Japanese quail selected for contrasting yolk T concentrations. Moreover, the pituitary responsiveness to a single challenge with gonadotropin releasing hormone (GnRH) was evaluated. High egg T (HET) birds displayed higher concentrations of LH at 3.5h before ovulation than low egg T (LET) birds while no differences were found around the time of expected ovulation. The pre-ovulatory profile of T and estradiol levels did not differ between LET and HET females but pre-ovulatory plasma T positively correlated with LH concentrations at 6.5h and 3.5h before ovulation. The LH response to GnRH did not differ between LET and HET females. Our results demonstrate that the pre-ovulatory LH surge can determine the amount of T transferred into the egg yolk. This link between yolk T deposition and the ovulatory cycle driven variation of reproductive hormones may explain balance between the effects of circulating T on female's reproductive physiology and yolk T on offspring phenotype.
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Affiliation(s)
- Monika Okuliarova
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic.
| | - Simone L Meddle
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, UK
| | - Michal Zeman
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic; Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovak Republic
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11
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Lindsay WR, Barron DG, Webster MS, Schwabl H. Testosterone activates sexual dimorphism including male-typical carotenoid but not melanin plumage pigmentation in a female bird. ACTA ACUST UNITED AC 2017; 219:3091-3099. [PMID: 27707865 DOI: 10.1242/jeb.135384] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 07/26/2016] [Indexed: 01/01/2023]
Abstract
In males it is frequently testosterone (T) that activates the expression of sexually selected morphological and behavioral displays, but the role of T in regulating similar traits in females is less clear. Here, we combine correlational data with results from T and gonadotropin-releasing hormone (GnRH) manipulations in both sexes to assess the role of T in mediating sexually dimorphic coloration and morphology in the red-backed fairy-wren (Malurus melanocephalus). We show that: (1) natural variation in female expression of ornamental traits (darkened bills and red back feathers) is positively associated with age and circulating androgen titres, (2) females have the capacity to express most male-typical traits in response to exogenous T, including carotenoid-pigmented body plumage, shorter feathers, darkened bill and enlarged cloacal protuberance, but (3) appear constrained in production of male-typical melanin-pigmented plumage, and (4) low androgen levels during the pre-nuptial molt, probably because of low ovarian capacity for steroid production (or luteinizing hormone sensitivity), prevent females from developing male-like ornamentation. Thus, females appear to retain molecular mechanisms for hormonally regulated male-typical ornamentation, although these are rarely activated because of insufficient production of the hormonal signal.
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Affiliation(s)
- Willow R Lindsay
- Department of Biological and Environmental Sciences, Göteborg University, Box 463, Göteborg 405 30, Sweden School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA
| | - Douglas G Barron
- School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA Department of Biological Sciences, Arkansas Tech University, Russellville, AR 72801, USA
| | - Michael S Webster
- Department of Neurobiology and Behavior and Cornell Laboratory for Ornithology, Cornell University, Ithaca, NY 14850, USA
| | - Hubert Schwabl
- School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA
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12
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Ho JM, Bergeon Burns CM, Rendon NM, Rosvall KA, Bradshaw HB, Ketterson ED, Demas GE. Lipid signaling and fat storage in the dark-eyed junco. Gen Comp Endocrinol 2017; 247:166-173. [PMID: 28161439 PMCID: PMC5410188 DOI: 10.1016/j.ygcen.2017.01.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 12/13/2016] [Accepted: 01/28/2017] [Indexed: 12/11/2022]
Abstract
Seasonal hyperphagia and fattening promote survivorship in migratory and wintering birds, but reduced adiposity may be more advantageous during the breeding season. Factors such as photoperiod, temperature, and food predictability are known environmental determinants of fat storage, but the underlying neuroendocrine mechanisms are less clear. Endocannabinoids and other lipid signaling molecules regulate multiple aspects of energy balance including appetite and lipid metabolism. However, these functions have been established primarily in mammals; thus the role of lipid signals in avian fat storage remains largely undefined. Here we examined relationships between endocannabinoid signaling and individual variation in fat storage in captive white-winged juncos (Junco hyemalis aikeni) following a transition to long-day photoperiods. We report that levels of the endocannabinoid 2-arachidonoylglycerol (2-AG), but not anandamide (AEA), in furcular and abdominal fat depots correlate negatively with fat mass. Hindbrain mRNA expression of CB1 endocannabinoid receptors also correlates negatively with levels of fat, demonstrating that fatter animals experience less central and peripheral endocannabinoid signaling when in breeding condition. Concentrations of the anorexigenic lipid, oleoylethanolamide (OEA), also inversely relate to adiposity. These findings demonstrate unique and significant relationships between adiposity and lipid signaling molecules in the brain and periphery, thereby suggesting a potential role for lipid signals in mediating adaptive levels of fat storage.
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Affiliation(s)
- Jacqueline M Ho
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Christine M Bergeon Burns
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Nikki M Rendon
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Kimberly A Rosvall
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Heather B Bradshaw
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA; Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | - Ellen D Ketterson
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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13
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Ambardar M, Grindstaff JL. Pre-GnRH and GnRH-induced testosterone levels do not vary across behavioral contexts: A role for individual variation. Gen Comp Endocrinol 2017; 246:51-62. [PMID: 28322761 DOI: 10.1016/j.ygcen.2017.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/23/2017] [Accepted: 03/15/2017] [Indexed: 10/19/2022]
Abstract
Hormones can facilitate the expression of behavior, but relatively few studies have considered individual variation and repeatability in hormone-behavior relationships. Repeated measures of hormones are valuable because repeatability in hormone levels might be a mechanism that drives repeatability in behavior ("personality"). Testosterone is predicted to promote territorial aggression and suppress parental behaviors. In our population of eastern bluebirds (Sialia sialis), parental care and nest defense aggression toward a heterospecific are repeatable. We tested the hypothesis that repeatability of testosterone levels within individuals underlies repeatable behaviors observed in our population. We measured nestling provisioning and aggressive nest defense against a heterospecific. After behavioral observations we captured either the male or female bluebird, and determined initial testosterone levels and maximum capacity of the gonads to secrete testosterone by injecting gonadotropin-releasing hormone (GnRH). We found among-individual variation in initial testosterone levels for males and females. Individual males were repeatable in both initial and GnRH-induced testosterone levels across behavioral contexts, while individual females were repeatable in GnRH-induced testosterone levels. However, testosterone levels were not significantly related to parental or nest defense behaviors, suggesting that repeatable testosterone levels may not drive repeatable parental and heterospecific nest defense behaviors in this population. The absence of a relationship between testosterone and parental and heterospecific nest defense behaviors might be due to among-individual variation in testosterone levels. Considering the sources of variation in testosterone levels may reveal why some populations exhibit high individual variation in hormone levels.
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Affiliation(s)
- Medhavi Ambardar
- Department of Integrative Biology, 501 Life Science West, Oklahoma State University, Stillwater, OK 74078, USA.
| | - Jennifer L Grindstaff
- Department of Integrative Biology, 501 Life Science West, Oklahoma State University, Stillwater, OK 74078, USA.
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14
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Sangenstedt S, Jaljuli I, Sachser N, Kaiser S. Stress responsiveness and anxiety-like behavior: The early social environment differentially shapes stability over time in a small rodent. Horm Behav 2017; 90:90-97. [PMID: 28263764 DOI: 10.1016/j.yhbeh.2017.02.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 02/09/2017] [Accepted: 02/13/2017] [Indexed: 01/01/2023]
Abstract
The early social environment can profoundly affect behavioral and physiological phenotypes. We investigated how male wild cavy offspring, whose mothers had either lived in a stable (SE) or an unstable social environment (UE) during pregnancy and lactation, differed in their anxiety-like behavior and stress responsiveness. At two different time points in life, we tested the offspring's anxiety-like behavior in a dark-light test and their endocrine reaction to challenge in a cortisol reactivity test. Furthermore, we analyzed whether individual traits remained stable over time. There was no effect of the early social environment on anxiety-like behavior and stress responsiveness. However, at an individual level, anxiety-like behavior was stable over time in UE- but not in SE-sons. Stress responsiveness, in turn, was rather inconsistent in UE-sons and temporally stable in SE-sons. Conclusively, we showed for the first time that the early social environment differentially shapes the stability of behavioral and endocrine traits. At first glance, these results may be surprising, but they can be explained by the different functions anxiety-like behavior and stress responsiveness have.
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Affiliation(s)
- Susanne Sangenstedt
- Department of Behavioural Biology, University of Münster, Münster, Germany; Münster Graduate School of Evolution, University of Münster, Münster, Germany.
| | - Iman Jaljuli
- Department of Statistics and Operations Research, School of Mathematical Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Norbert Sachser
- Department of Behavioural Biology, University of Münster, Münster, Germany; Münster Graduate School of Evolution, University of Münster, Münster, Germany.
| | - Sylvia Kaiser
- Department of Behavioural Biology, University of Münster, Münster, Germany; Münster Graduate School of Evolution, University of Münster, Münster, Germany.
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15
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Ronald KL, Zeng R, White DJ, Fernández-Juricic E, Lucas JR. What makes a multimodal signal attractive? A preference function approach. Behav Ecol 2017. [DOI: 10.1093/beheco/arx015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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16
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Greives TJ, Fudickar AM, Atwell JW, Meddle SL, Ketterson ED. Early spring sex differences in luteinizing hormone response to gonadotropin releasing hormone in co-occurring resident and migrant dark-eyed juncos (Junco hyemalis). Gen Comp Endocrinol 2016; 236:17-23. [PMID: 27374492 PMCID: PMC5036536 DOI: 10.1016/j.ygcen.2016.06.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 06/27/2016] [Accepted: 06/28/2016] [Indexed: 01/09/2023]
Abstract
To optimally time reproduction, animals must coordinate changes in the hypothalamo-pituitary-gonadal (HPG) axis. The extent of intra-species variation in seasonal timing of reproductive function is considerable, both within and among populations. Dark-eyed junco (Junco hyemalis) populations are known to differ in their reproductive timing response to cues experienced in the same habitat in late winter/early spring. Specifically in juncos cohabitating on shared wintering grounds, residents initiate breeding and reproductive activity but migrants delay reproductive development and prepare to migrate before breeding. Here, we test the hypothesis that the pituitary gland acts as a 'control point' to modulate differential HPG axis activity across populations. We sampled free-living resident and migrant juncos on their shared over-wintering grounds in March, thus all individuals were experiencing the same environmental cues, including photoperiod. We predicted that during this critical time of transition, residents would more readily respond to repeated gonadotropin releasing hormone (GnRH) stimulation with increases in luteinizing hormone (LH), in contrast to migrants, which should delay full reproductive activity. Our data indicate that migrant females, while still on the overwintering grounds, have a reduced LH response to repeated GnRH injections compared to resident females. Male migrant and resident birds did not differ in their responsiveness to repeated GnRH. Our results suggest a sex difference in the costs of mistimed activation of the HPG axis, with female migrants being less responsive than residents females and males to repeated stimulation. Further, our data implicate a key role for the pituitary in regulating appropriate reproductive timing responses.
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Affiliation(s)
- Timothy J Greives
- Department of Biological Sciences and Environmental and Conservation Sciences Program, North Dakota State University, Fargo, ND, United States.
| | - Adam M Fudickar
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
| | - Jonathan W Atwell
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
| | - Simone L Meddle
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Midlothian, EH25 9RG Scotland, UK
| | - Ellen D Ketterson
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
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17
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Rosvall KA, Bergeon Burns CM, Jayaratna SP, Ketterson ED. Divergence along the gonadal steroidogenic pathway: Implications for hormone-mediated phenotypic evolution. Horm Behav 2016; 84:1-8. [PMID: 27206546 PMCID: PMC4996689 DOI: 10.1016/j.yhbeh.2016.05.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/18/2016] [Accepted: 05/16/2016] [Indexed: 11/19/2022]
Abstract
Across a range of taxa, hormones regulate suites of traits that influence survival and reproductive success; however, the mechanisms by which hormone-mediated traits evolve are still unclear. We hypothesized that phenotypic divergence might follow from differential regulation of genes encoding key steps in hormone biosynthesis and thus the rate of hormone production. We tested this hypothesis in relation to the steroid hormone testosterone by comparing two subspecies of junco (Junco hyemalis) in the wild and in captivity. These subspecies have diverged over the last 10-15kyears in multiple testosterone-mediated traits, including aggression, ornamentation, and body size. We show that variation in gonadal gene expression along the steroid biosynthetic pathway predicts phenotypic divergence within and among subspecies, and that the more androgenized subspecies exhibits a more prolonged time-course of elevated testosterone following exogenous stimulation. Our results point to specific genes that fulfill key conditions for phenotypic evolution because they vary functionally in their expression among individuals and between populations, and they map onto population variation in phenotype in a common garden. Our findings therefore build an important bridge between hormones, genes, and phenotypic evolution.
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Affiliation(s)
- Kimberly A Rosvall
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA.
| | - Christine M Bergeon Burns
- Center for the Integrative Study of Animal Behavior, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA
| | - Sonya P Jayaratna
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA
| | - Ellen D Ketterson
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, 1001 E. Third Street, Bloomington, IN 47405, USA
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18
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Rosvall KA, Bergeon Burns CM, Jayaratna SP, Dossey EK, Ketterson ED. Gonads and the evolution of hormonal phenotypes. Integr Comp Biol 2016; 56:225-34. [PMID: 27252189 DOI: 10.1093/icb/icw050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hormones are dynamic signaling molecules that influence gene activity and phenotype, and they are thus thought to play a central role in phenotypic evolution. In vertebrates, many fitness-related traits are mediated by the hormone testosterone (T), but the mechanisms by which T levels evolve are unclear. Here, we summarize a series of studies that advance our understanding of these mechanisms by comparing males from two subspecies of dark-eyed junco (Junco hyemalis) that differ in aggression, body size, and ornamentation. We first review our research demonstrating population differences in the time-course of T production, as well as findings that point to the gonad as a major source of this variation. In a common garden, the subspecies do not differ in pituitary output of luteinizing hormone, but males from the more androgenized subspecies have greater gonadal gene expression for specific steroidogenic enzymes, and they may be less sensitive to feedback along the hypothalamo-pituitary-gonadal (HPG) axis. Furthermore, we present new data from a common garden study demonstrating that the populations do not differ in gonadal sensitivity to gonadotropin-inhibitory hormone (i.e., GnIH receptor mRNA abundance), but the more androgenized subspecies expresses less gonadal mRNA for glucocorticoid receptor and mineralocorticoid receptor, suggesting altered cross-talk between the hypothalamo-pituitary-gonadal and -adrenal axes as another mechanism by which these subspecies have diverged in T production. These findings highlight the diversity of mechanisms that may generate functional variation in T and influence hormone-mediated phenotypic evolution.
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Affiliation(s)
- Kimberly A Rosvall
- *Department of Biology Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405 USA
| | | | | | | | - Ellen D Ketterson
- *Department of Biology Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405 USA
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19
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Zinzow-Kramer WM, Horton BM, Maney DL. Evaluation of reference genes for quantitative real-time PCR in the brain, pituitary, and gonads of songbirds. Horm Behav 2014; 66:267-75. [PMID: 24780145 PMCID: PMC4131286 DOI: 10.1016/j.yhbeh.2014.04.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 04/01/2014] [Accepted: 04/20/2014] [Indexed: 01/18/2023]
Abstract
Quantitative real-time PCR (qPCR) is becoming a popular tool for the quantification of gene expression in the brain and endocrine tissues of songbirds. Accurate analysis of qPCR data relies on the selection of appropriate reference genes for normalization, yet few papers on songbirds contain evidence of reference gene validation. Here, we evaluated the expression of ten potential reference genes (18S, ACTB, GAPDH, HMBS, HPRT, PPIA, RPL4, RPL32, TFRC, and UBC) in brain, pituitary, ovary, and testis in two species of songbirds: zebra finch and white-throated sparrow. We used two algorithms, geNorm and NormFinder, to assess the stability of these reference genes in our samples. We found that the suitability of some of the most popular reference genes for target gene normalization in mammals, such as 18S, depended highly on tissue type. Thus, they are not the best choices for brain and gonad in these songbirds. In contrast, we identified alternative genes, such as HPRT, RPL4 and PPIA, that were highly stable in brain, pituitary, and gonad in these species. Our results suggest that the validation of reference genes in mammals does not necessarily extrapolate to other taxonomic groups. For researchers wishing to identify and evaluate suitable reference genes for qPCR in songbirds, our results should serve as a starting point and should help increase the power and utility of songbird models in behavioral neuroendocrinology.
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Affiliation(s)
| | - Brent M Horton
- Department of Psychology, Emory University, Atlanta, GA, USA
| | - Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA, USA
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20
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Rosvall KA. Proximate perspectives on the evolution of female aggression: good for the gander, good for the goose? Philos Trans R Soc Lond B Biol Sci 2013; 368:20130083. [PMID: 24167313 PMCID: PMC3826212 DOI: 10.1098/rstb.2013.0083] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Female-female aggression often functions in competition over reproductive or social benefits, but the proximate mechanisms of this apparently adaptive behaviour are not well understood. The sex steroid hormone testosterone (T) and its metabolites are well-established mediators of male-male aggression, and several lines of evidence suggest that T-mediated mechanisms may apply to females as well. However, a key question is whether mechanisms of female aggression primarily reflect correlated evolutionary responses to selection acting on males, or whether direct selection acting on females has made modifications to these mechanisms that are adaptive in light of female life history. Here, I examine the degree to which female aggression is mediated at the level of T production, target tissue sensitivity to T, or downstream genomic responses in order to test the hypothesis that selection favours mechanisms that facilitate female aggression while minimizing the costs of systemically elevated T. I draw heavily from avian systems, including the dark-eyed junco (Junco hyemalis), as well as other organisms in which these mechanisms have been well studied from an evolutionary/ecological perspective in both sexes. Findings reveal that the sexes share many behavioural and hormonal mechanisms, though several patterns also suggest sex-specific adaptation. I argue that greater attention to multiple levels of analysis-from hormone to receptor to gene network, including analyses of individual variation that represents the raw material of evolutionary change-will be a fruitful path for understanding mechanisms of behavioural regulation and intersexual coevolution.
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Affiliation(s)
- Kimberly A. Rosvall
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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