1
|
Smiley KO, Lipshutz SE, Kimmitt AA, DeVries MS, Cain KE, George EM, Covino KM. Beyond a biased binary: A perspective on the misconceptions, challenges, and implications of studying females in avian behavioral endocrinology. Front Physiol 2022; 13:970603. [PMID: 36213250 PMCID: PMC9532843 DOI: 10.3389/fphys.2022.970603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/18/2022] [Indexed: 12/04/2022] Open
Abstract
For decades, avian endocrinology has been informed by male perspectives and male-focused research, leaving significant gaps in our understanding of female birds. Male birds have been favored as research subjects because their reproductive behaviors are considered more conspicuous and their reproductive physiology is presumably less complex than female birds. However, female birds should not be ignored, as female reproductive behavior and physiology are essential for the propagation of all avian species. Endocrine research in female birds has made much progress in the last 20 years, but a substantial disparity in knowledge between male and female endocrinology persists. In this perspective piece, we provide examples of why ornithology has neglected female endocrinology, and we propose considerations for field and laboratory techniques to facilitate future studies. We highlight recent advances that showcase the importance of female avian endocrinology, and we challenge historic applications of an oversimplified, male-biased lens. We further provide examples of species for which avian behavior differs from the stereotypically described behaviors of male and female birds, warning investigators of the pitfalls in approaching endocrinology with a binary bias. We hope this piece will inspire investigators to engage in more comprehensive studies with female birds, to close the knowledge gap between the sexes, and to look beyond the binary when drawing conclusions about what is ‘male’ versus ‘female’ biology.
Collapse
Affiliation(s)
- Kristina O. Smiley
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
- Center for Neuroendocrine Studies and Department of Psychological and Brain Sciences, University of Massachusetts-Amherst, Amherst, MA, United States
- *Correspondence: Kristina O. Smiley,
| | - Sara E. Lipshutz
- Biology Department, Loyola University Chicago, Chicago, IL, United States
| | - Abigail A. Kimmitt
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, United States
| | - M. Susan DeVries
- Department of Biological Sciences, University of Wisconsin-Whitewater, Whitewater, WI, United States
| | - Kristal E. Cain
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Elizabeth M. George
- Biology Department, Texas A&M University, College Station, TX, United States
| | - Kristen. M. Covino
- Biology Department, Loyola Marymount University, Los Angeles, CA, United States
| |
Collapse
|
2
|
Tao CY, Harley JZ, Spencer SL, Cohen RE. Characterizing seasonal transitions: Breeding-like morphology and behavior during the late non-breeding season in green anole lizards. Horm Behav 2022; 139:105106. [PMID: 34995849 DOI: 10.1016/j.yhbeh.2021.105106] [Citation(s) in RCA: 3] [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: 07/17/2021] [Revised: 12/03/2021] [Accepted: 12/22/2021] [Indexed: 11/19/2022]
Abstract
Seasonally breeding animals, such as green anole lizards (Anolis carolinensis), allow for the examination of the control of reproduction during different reproductive states. During the breeding season, the gonads are large and reproductively active. Following the breeding season, gonads regress and become less active, and the lizards enter a refractory period where breeding is inhibited. After this stage, a post-refractory period occurs during which the lizards are still in a non-breeding state, but environmental changes can trigger the onset of breeding. However, it is unclear what causes these changes in reproductive state and we hypothesized that this may be due to alterations in gonadotropin-releasing hormone (GnRH) signaling. The present study aimed to identify morphological and behavioral differences in GnRH- and saline-injected refractory and post-refractory male anoles when housed under the same non-breeding environmental conditions. We found that post-refractory anoles had increased testicular weight, recrudescence, sperm presence, and reproductive behavior, with no impact of GnRH injection. Renal sex segment size and steroidogenic acute regulatory protein (StAR) mRNA levels did not differ among groups, indicating that testosterone levels likely had not increased in post-refractory lizards. Post-refractory anoles in this study were beginning to transition towards a breeding state without exposure to changing environmental conditions, and GnRH was not necessary for these changes. These data reveal a complex interaction between the activation of breeding, changing environmental conditions, and the underlying physiology regulating reproduction in seasonally breeding lizards. Future studies are needed to further elucidate the mechanisms that regulate this relationship.
Collapse
Affiliation(s)
- Cai Y Tao
- Department of Biological Sciences, Minnesota State University, Mankato, Mankato, MN 56001-6062, USA
| | - Jada Z Harley
- Department of Biological Sciences, Minnesota State University, Mankato, Mankato, MN 56001-6062, USA
| | - Savannah L Spencer
- Department of Biological Sciences, Minnesota State University, Mankato, Mankato, MN 56001-6062, USA
| | - Rachel E Cohen
- Department of Biological Sciences, Minnesota State University, Mankato, Mankato, MN 56001-6062, USA.
| |
Collapse
|
3
|
Loveland JL, Giraldo-Deck LM, Lank DB, Goymann W, Gahr M, Küpper C. Functional differences in the hypothalamic-pituitary-gonadal axis are associated with alternative reproductive tactics based on an inversion polymorphism. Horm Behav 2021; 127:104877. [PMID: 33186586 DOI: 10.1016/j.yhbeh.2020.104877] [Citation(s) in RCA: 6] [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: 07/20/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 01/01/2023]
Abstract
The evolution of social behavior depends on genetic changes, yet, how genomic variation manifests itself in behavioral diversity is still largely unresolved. Chromosomal inversions can play a pivotal role in producing distinct behavioral phenotypes, in particular, when inversion genes are functionally associated with hormone synthesis and signaling. Male ruffs exhibit alternative reproductive tactics (ARTs) with an autosomal inversion determining two alternative morphs with clear behavioral and hormonal differences from the ancestral morph. We investigated hormonal and transcriptomic differences in the pituitary and gonads. Using a GnRH challenge, we found that the ability to synthesize testosterone in inversion carriers is severely constrained, whereas the synthesis of androstenedione, a testosterone precursor, is not. Inversion morphs were able to produce a transient increase in androstenedione following the GnRH injection, supporting the view that pituitary sensitivity to GnRH is comparable to that of the ancestral morph. We then performed gene expression analyses in a second set of untreated birds and found no evidence of alterations to pituitary sensitivity, gonadotropin production or gonad sensitivity to luteinizing hormone or follicle-stimulating hormone across morphs. Inversion morphs also showed reduced progesterone receptor expression in the pituitary. Strikingly, in the gonads, inversion morphs over-expressed STAR, a gene that is located outside of the inversion and responsible for providing the cholesterol substrate required for the synthesis of sex hormones. In conclusion, our results suggest that the gonads determine morph-specific differences in hormonal regulation.
Collapse
MESH Headings
- Androstenedione/metabolism
- Animals
- Charadriiformes/genetics
- Charadriiformes/physiology
- Follicle Stimulating Hormone, beta Subunit/genetics
- Follicle Stimulating Hormone, beta Subunit/metabolism
- Gene Expression/drug effects
- Gonadal Steroid Hormones/biosynthesis
- Gonadotropin-Releasing Hormone/pharmacology
- Gonads/drug effects
- Gonads/metabolism
- Gonads/physiology
- Hypothalamo-Hypophyseal System/drug effects
- Hypothalamo-Hypophyseal System/metabolism
- Hypothalamo-Hypophyseal System/physiology
- Male
- Pituitary Gland/drug effects
- Pituitary Gland/metabolism
- Polymorphism, Genetic
- Receptors, FSH/genetics
- Receptors, FSH/metabolism
- Receptors, LH/genetics
- Receptors, LH/metabolism
- Receptors, LHRH/genetics
- Receptors, LHRH/metabolism
- Reproduction/drug effects
- Reproduction/genetics
- Sequence Inversion
- Sexual Behavior, Animal/drug effects
- Sexual Behavior, Animal/physiology
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Testosterone/metabolism
Collapse
Affiliation(s)
- J L Loveland
- Behavioural Genetics and Evolutionary Ecology Research Group, Max Planck Institute for Ornithology, Seewiesen, Germany.
| | - L M Giraldo-Deck
- Behavioural Genetics and Evolutionary Ecology Research Group, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - D B Lank
- Department of Biological Sciences, Simon Fraser University, Burnaby, Canada
| | - W Goymann
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - M Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - C Küpper
- Behavioural Genetics and Evolutionary Ecology Research Group, Max Planck Institute for Ornithology, Seewiesen, Germany
| |
Collapse
|
4
|
Kimmitt AA, Webb AL, Greives TJ, Ketterson ED. Migrant and resident female songbirds differ in gonadal response to upstream stimulation during seasonal sympatry. Gen Comp Endocrinol 2020; 293:113469. [PMID: 32220572 DOI: 10.1016/j.ygcen.2020.113469] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 03/15/2020] [Accepted: 03/22/2020] [Indexed: 02/06/2023]
Abstract
Timing of seasonal reproduction is driven by environmental cues acting on the hypothalamic-pituitary-gonadal (HPG) axis. Groups of individuals, or populations, of the same species can exhibit different phenology despite facing similar environmental cues or living in the same habitat (i.e., seasonal sympatry). The mechanisms giving rise to population-level differences in reproductive timing are not fully understood, particularly for females. We studied the dark-eyed junco, a songbird with migratory and sedentary (i.e., resident) populations that live in overlapping distributions during winter. In early spring, residents initiate breeding and associated behaviors, including territory establishment and formation of pair bonds, while migrants prepare to depart for their breeding grounds. We tested whether migrant and resident hormonal response to upstream hormonal stimulation differed during this time period. We collected blood from free-living females in early spring, and challenged them with repeated gonadotropin-releasing hormone (GnRH) injections to measure testosterone (T) response. We predicted that if migrants are less sensitive to upstream stimulation than residents, then they would exhibit lower response to the repeated GnRH challenges in migrants. We found that migrant and resident females both responded to an initial challenge by elevating T, but residents responded more robustly, indicating that the ovary plays a role in population-level differences in reproductive timing. We also found that migrants and residents attenuated their response to repeated challenges, and did not differ from one another in final T levels. We speculate that the explanation for the generally reduced T response after repeated GnRH injections need not be the same for migrants and residents, but possible explanations include suppression of upstream stimulation owing to negative feedback after the initial injection oraromatization of T to estradiol between sampling time points. We suggest that future studies experimentally explore how the ovarian response to upstream stimulation changes during the transition to reproduction.
Collapse
Affiliation(s)
- Abigail A Kimmitt
- Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47405, USA.
| | - Ashlee L Webb
- Department of Biological Sciences, Boise State University, 1910 University Drive, Boise, ID 83725, USA
| | - Timothy J Greives
- Department of Biological Sciences and Environmental and Conservation Sciences Program, North Dakota State University, 1340 Bolley Drive, Fargo, ND 58102, USA
| | - Ellen D Ketterson
- Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47405, USA; Environmental Resilience Institute, Indiana University, 717 E. Eighth St., Bloomington, IN 47408, USA
| |
Collapse
|
5
|
Wingfield JC, Goymann W, Jalabert C, Soma KK. Reprint of "Concepts derived from the Challenge Hypothesis". Horm Behav 2020; 123:104802. [PMID: 32540136 DOI: 10.1016/j.yhbeh.2020.104802] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/28/2019] [Accepted: 06/28/2019] [Indexed: 12/19/2022]
Abstract
The Challenge Hypothesis was developed to explain why and how regulatory mechanisms underlying patterns of testosterone secretion vary so much across species and populations as well as among and within individuals. The hypothesis has been tested many times over the past 30years in all vertebrate groups as well as some invertebrates. Some experimental tests supported the hypothesis but many did not. However, the emerging concepts and methods extend and widen the Challenge Hypothesis to potentially all endocrine systems, and not only control of secretion, but also transport mechanisms and how target cells are able to adjust their responsiveness to circulating levels of hormones independently of other tissues. The latter concept may be particularly important in explaining how tissues respond differently to the same hormone concentration. Responsiveness of the hypothalamo-pituitary-gonad (HPG) axis to environmental and social cues regulating reproductive functions may all be driven by gonadotropin-releasing hormone (GnRH) or gonadotropin-inhibiting hormone (GnIH), but the question remains as to how different contexts and social interactions result in stimulation of GnRH or GnIH release. These concepts, although suspected for many decades, continue to be explored as integral components of environmental endocrinology and underlie fundamental mechanisms by which animals, including ourselves, cope with a changing environment. Emerging mass spectrometry techniques will have a tremendous impact enabling measurement of multiple steroids in specific brain regions. Such data will provide greater spatial resolution for studying how social challenges impact multiple steroids within the brain. Potentially the Challenge Hypothesis will continue to stimulate new ways to explore hormone-behavior interactions and generate future hypotheses.
Collapse
Affiliation(s)
- John C Wingfield
- Department of Neurobiology, Physiology and Behavior, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Wolfgang Goymann
- Department of Behavioral Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Cecilia Jalabert
- Department of Zoology, University of British Columbia, Vancouver, Canada; Djavad Mofawaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada
| | - Kiran K Soma
- Department of Zoology, University of British Columbia, Vancouver, Canada; Djavad Mofawaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; Department of Psychology, University of British Columbia, Vancouver, Canada
| |
Collapse
|
6
|
Martin RJ, Kruger MC, MacDougall-Shackleton SA, Sherry DF. Black-capped chickadees (Poecile atricapillus) use temperature as a cue for reproductive timing. Gen Comp Endocrinol 2020; 287:113348. [PMID: 31786139 DOI: 10.1016/j.ygcen.2019.113348] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 11/26/2019] [Accepted: 11/27/2019] [Indexed: 11/29/2022]
Abstract
Reliable environmental cues, such as photoperiod, act as initial predictive cues that allow birds to time reproduction to match peak food abundance for their offspring. More variable local cues, like temperature, may, however, provide more precise information about the timing of food abundance. Non-migratory birds, in particular, should be sensitive to temperature cues and use them to modulate their reproductive timing. We conducted two experiments to examine the effect of temperature on reproductive condition (gonad size and circulating androgen levels) in non-migratory black-capped chickadees (Poecile atricapillus). First, we exposed groups of birds in outdoor aviaries to three different over-winter temperature treatments and assessed gonad size in the spring. Second, we manipulated temperature in environmental chambers under photostimulatory and non-photostimulatory photoperiodic conditions and assessed gonad size and circulating testosterone levels. Temperature had no independent effect on gonad size or testosterone levels, but when photostimulated birds exposed to warmer conditions became reproductively ready earlier than birds experiencing cooler conditions. We conclude that temperature acts as a supplementary cue that modulates the photoperiod-driven timing of reproduction.
Collapse
Affiliation(s)
- R Jeffrey Martin
- Department of Biology, University of Western Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, Canada.
| | - M Charlotte Kruger
- Department of Biology, University of Western Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, Canada
| | - Scott A MacDougall-Shackleton
- Department of Biology, University of Western Ontario, Canada; Department of Psychology, University of Western Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, Canada
| | - David F Sherry
- Department of Biology, University of Western Ontario, Canada; Department of Psychology, University of Western Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, Canada
| |
Collapse
|
7
|
Wingfield JC, Goymann W, Jalabert C, Soma KK. Concepts derived from the Challenge Hypothesis. Horm Behav 2019; 115:104550. [PMID: 31265826 DOI: 10.1016/j.yhbeh.2019.06.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/28/2019] [Accepted: 06/28/2019] [Indexed: 12/25/2022]
Abstract
The Challenge Hypothesis was developed to explain why and how regulatory mechanisms underlying patterns of testosterone secretion vary so much across species and populations as well as among and within individuals. The hypothesis has been tested many times over the past 30years in all vertebrate groups as well as some invertebrates. Some experimental tests supported the hypothesis but many did not. However, the emerging concepts and methods extend and widen the Challenge Hypothesis to potentially all endocrine systems, and not only control of secretion, but also transport mechanisms and how target cells are able to adjust their responsiveness to circulating levels of hormones independently of other tissues. The latter concept may be particularly important in explaining how tissues respond differently to the same hormone concentration. Responsiveness of the hypothalamo-pituitary-gonad (HPG) axis to environmental and social cues regulating reproductive functions may all be driven by gonadotropin-releasing hormone (GnRH) or gonadotropin-inhibiting hormone (GnIH), but the question remains as to how different contexts and social interactions result in stimulation of GnRH or GnIH release. These concepts, although suspected for many decades, continue to be explored as integral components of environmental endocrinology and underlie fundamental mechanisms by which animals, including ourselves, cope with a changing environment. Emerging mass spectrometry techniques will have a tremendous impact enabling measurement of multiple steroids in specific brain regions. Such data will provide greater spatial resolution for studying how social challenges impact multiple steroids within the brain. Potentially the Challenge Hypothesis will continue to stimulate new ways to explore hormone-behavior interactions and generate future hypotheses.
Collapse
Affiliation(s)
- John C Wingfield
- Department of Neurobiology, Physiology and Behavior, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Wolfgang Goymann
- Department of Behavioral Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Cecilia Jalabert
- Department of Zoology, University of British Columbia, Vancouver, Canada; Djavad Mofawaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada
| | - Kiran K Soma
- Department of Zoology, University of British Columbia, Vancouver, Canada; Djavad Mofawaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; Department of Psychology, University of British Columbia, Vancouver, Canada
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Funghi C, Trigo S, Gomes ACR, Soares MC, Cardoso GC. Release from ecological constraint erases sex difference in social ornamentation. Behav Ecol Sociobiol 2018. [DOI: 10.1007/s00265-018-2486-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
11
|
Covino KM, Jawor JM, Morris SR, Moore FR. Sex-specific hypothalamic-pituitary-gonadal axis sensitivity in migrating songbirds. Horm Behav 2018; 97:112-120. [PMID: 29128250 DOI: 10.1016/j.yhbeh.2017.11.003] [Citation(s) in RCA: 13] [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: 01/30/2017] [Revised: 10/13/2017] [Accepted: 11/03/2017] [Indexed: 01/21/2023]
Abstract
In seasonally migratory species, the overlap between the migratory and breeding life history stages is a balance between the physiological and behavioral requirements of each stage. Previous studies investigating the degree to which songbirds prepare for breeding during spring migration have focused on either circulating hormone levels or direct measures of gonadal recrudescence. In this study, we evaluated the phenology of breeding preparation in a long-distance migratory songbird, the Swainson's Thrush (Catharus ustulatus), by assessing hypothalamic-pituitary-gonadal (HPG) axis sensitivity with gonadotropin-releasing hormone (GnRH) bioassays throughout the migratory period. During spring migration both males and females had a significant response to GnRH injections as reflected in elevated testosterone levels. The magnitude of response to GnRH injections, Rpotential, in females stayed consistent throughout spring migration; however, Rpotential in males increased as the migratory season progressed. It is clear that at least some degree of endocrinological breeding development occurs either before or during spring migration in both sexes, however the phenology appears to be sex specific. In males this breeding development continues at a relatively steady pace throughout the migratory period while in females, relatively little endocrine breeding development occurs during migration. These sex-specific differences in the phenology of the endocrine breeding development warrant future investigations for both male and female songbirds. Moreover, research focused on how physiological breeding development is balanced with the expression of migratory traits in long-distance songbird migrants is needed.
Collapse
Affiliation(s)
- Kristen M Covino
- Biology Department, Canisius College, 2001 Main St., Buffalo, NY 14208, USA; Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS 39406, USA; Shoals Marine Laboratory, 102 Chase Ocean Engineering Lab, 24 Colovos Rd, Durham, NH 03824, USA.
| | - Jodie M Jawor
- Biology Department, Canisius College, 2001 Main St., Buffalo, NY 14208, USA
| | - Sara R Morris
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS 39406, USA; Shoals Marine Laboratory, 102 Chase Ocean Engineering Lab, 24 Colovos Rd, Durham, NH 03824, USA
| | - Frank R Moore
- Biology Department, Canisius College, 2001 Main St., Buffalo, NY 14208, USA
| |
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Wright S, Fokidis HB. Sources of variation in plasma corticosterone and dehydroepiandrosterone in the male northern cardinal (Cardinalis cardinalis): II. Effects of urbanization, food supplementation and social stress. Gen Comp Endocrinol 2016; 235:201-209. [PMID: 27255367 DOI: 10.1016/j.ygcen.2016.05.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 02/06/2023]
Abstract
Perturbations in an organism's environment can induce significant shifts in hormone secretory patterns. In this context, the glucocorticoid (GC) steroids secreted by the adrenal cortex have received much attention from ecologists and behaviorists due to their role in the vertebrate stress response. Adrenal GCs, such as corticosterone (CORT), are highly responsive to instability in environmental and social conditions. However, little is understood about how adrenal dehydroepiandrosterone (DHEA) is influenced by changing conditions. We conducted field experiments to determine how circulating CORT and DHEA vary during restraint stress in the male northern cardinals (Cardinalis cardinalis). Specifically, we examined how four different changes in the physical (urbanization and food availability) and social (territorial conflict, distress of a mate) environment affect CORT and DHEA levels. The majority of cardinals responded to restraint stress by increasing and decreasing CORT and DHEA, respectively, however this depended on sampling context. Cardinals sampled from urban habitats had both lower initial and restraint stress CORT concentrations, but a comparable DHEA pattern to those sampled from a forest. Supplementing food to territorial males did not alter circulating initial DHEA or CORT concentrations nor did it change the response to restraint stress when compared to unsupplemented controls. Exposing cardinals to varying durations of song playback, which mimics a territorial intrusion, did not affect CORT levels, but did attenuate the DHEA response to restraint stress. Examining a larger dataset of males captured before, after or at the same time as their female mate, allowed us to address how the stress of a captured mate affected the male's CORT and DHEA response. Males showed elevated initial and restraint CORT and DHEA when their female mate was captured first. Taken together, these data demonstrate that both CORT and DHEA secretion patterns depends on environmental, and particularly current social conditions.
Collapse
Affiliation(s)
- Sarah Wright
- Department of Biology, Rollins College, Winter Park, FL 37289, USA
| | - H Bobby Fokidis
- Department of Biology, Rollins College, Winter Park, FL 37289, USA.
| |
Collapse
|
15
|
Fokidis HB. Sources of variation in plasma corticosterone and dehydroepiandrosterone in the male northern cardinal (Cardinalis cardinalis): I. Seasonal patterns and effects of stress and adrenocorticotropic hormone. Gen Comp Endocrinol 2016; 235:192-200. [PMID: 27255363 DOI: 10.1016/j.ygcen.2016.05.024] [Citation(s) in RCA: 7] [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: 08/04/2015] [Revised: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 11/16/2022]
Abstract
The secretion of steroids from the adrenal gland is a classic endocrine response to perturbations that can affect homeostasis. During an acute stress response, glucocorticoids (GC), such as corticosterone (CORT), prepare the metabolic physiology and cognitive abilities of an animal in a manner that promotes survival during changing conditions. Although GC functions during stress are well established, much less is understood concerning how adrenal androgens, namely dehydroepiandrosterone (DHEA) are influenced by stress. I conducted three field studies (one experimental and two descriptive) aimed at identifying how both CORT and DHEA secretion in free-living male northern cardinals (Cardinalis cardinalis), vary during acute stress; across different circulations (brachial vs. jugular); in response to ACTH challenge; and during the annual cycle. As predicted, restraint stress increased plasma CORT, but unexpectedly DHEA levels decreased, but the latter effect was only seen for blood sampled from the jugular vein, and not the brachial. The difference in DHEA between circulations may result from increased neural uptake of DHEA during stress. Injection with exogenous adrenocorticotropic hormone (ACTH) increased CORT concentrations, but failed to alter DHEA levels, thus suggesting ACTH is not a direct regulator of DHEA. Monthly field sampling revealed distinct seasonal patterns to both initial and restraint stress CORT and DHEA levels with distinct differences in the steroid milieu between breeding and non-breeding seasons. These data suggest that the CORT response to stress remains relatively consistent, but DHEA secretion is largely independent of the response by CORT. Although CORT functions have been well-studied in wild animals, little research exists for the role of DHEA and their variable relationship sets the stage for future experimental research addressing steroid stress responses.
Collapse
Affiliation(s)
- H Bobby Fokidis
- Department of Biology, Rollins College, Winter Park, FL 37289, USA.
| |
Collapse
|
16
|
Davies S, Gao S, Valle S, Bittner S, Hutton P, Meddle SL, Deviche P. Negative energy balance in a male songbird, the Abert's towhee, constrains the testicular endocrine response to luteinizing hormone stimulation. ACTA ACUST UNITED AC 2016; 218:2685-93. [PMID: 26333925 PMCID: PMC4582157 DOI: 10.1242/jeb.123042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Energy deficiency can suppress reproductive function in vertebrates. As the orchestrator of reproductive function, endocrine activity of the hypothalamo-pituitary-gonadal (HPG) axis is potentially an important mechanism mediating such effects. Previous experiments in wild-caught birds found inconsistent relationships between energy deficiency and seasonal reproductive function, but these experiments focused on baseline HPG axis activity and none have investigated the responsiveness of this axis to endocrine stimulation. Here, we present data from an experiment in Abert's towhees, Melozone aberti, using gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) challenges to investigate whether energy deficiency modulates the plasma testosterone responsiveness of the HPG axis. Wild-caught birds were either ad libitum fed or energetically constrained via chronic food restriction during photoinduced reproductive development. Energy deficiency did not significantly affect the development of reproductive morphology, the baseline endocrine activity of the HPG axis, or the plasma testosterone response to GnRH challenge. Energy deficiency did, however, decrease the plasma testosterone responsiveness to LH challenge. Collectively, these observations suggest that energy deficiency has direct gonadal effects consisting of a decreased responsiveness to LH stimulation. Our study, therefore, reveals a mechanism by which energy deficiency modulates reproductive function in wild birds in the absence of detectable effects on baseline HPG axis activity.
Collapse
Affiliation(s)
- Scott Davies
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Sisi Gao
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Shelley Valle
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Stephanie Bittner
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Pierce Hutton
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Simone L Meddle
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
| | - Pierre Deviche
- School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| |
Collapse
|
17
|
Covino KM, Morris SR, Moore FR. Patterns of testosterone in three Nearctic-Neotropical migratory songbirds during spring passage. Gen Comp Endocrinol 2015; 224:186-93. [PMID: 26315385 DOI: 10.1016/j.ygcen.2015.08.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/11/2015] [Accepted: 08/22/2015] [Indexed: 11/19/2022]
Abstract
Preparation for breeding may overlap extensively with vernal migration in long-distance migratory songbirds. Testosterone plays a central role in mediating this transition into breeding condition by facilitating changes to physiology and behavior. While changes in testosterone levels are well studied in captive migrants, these changes are less well known in free-living birds. We examined testosterone levels in free-living Nearctic-Neotropical migrants of three species during their vernal migration. Testosterone levels increased during the migratory period in males of all three species but significantly so in only two. Testosterone levels in females remained the same throughout their migration. Our results support the extensive overlap between vernal migration and breeding preparation in male songbirds. The pattern of testosterone changes during vernal migration is far from clear in females.
Collapse
Affiliation(s)
- Kristen M Covino
- Department of Biological Sciences, University of Southern Mississippi, 118 College Drive Box 5018, Hattiesburg, MS 39406, USA; Shoals Marine Laboratory, 102 Chase Ocean Engineering Lab, 24 Colovos Rd, Durham, NH 03824, USA.
| | - Sara R Morris
- Shoals Marine Laboratory, 102 Chase Ocean Engineering Lab, 24 Colovos Rd, Durham, NH 03824, USA; Biology Department, Canisius College, 2001 Main St., Buffalo, NY 14208, USA
| | - Frank R Moore
- Department of Biological Sciences, University of Southern Mississippi, 118 College Drive Box 5018, Hattiesburg, MS 39406, USA
| |
Collapse
|
18
|
DeVries MS, Winters CP, Jawor JM. Testosterone might not be necessary to support female aggression in incubating northern cardinals. Anim Behav 2015. [DOI: 10.1016/j.anbehav.2015.06.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
19
|
Goymann W, Villavicencio CP, Apfelbeck B. Does a short-term increase in testosterone affect the intensity or persistence of territorial aggression? - An approach using an individual's hormonal reactive scope to study hormonal effects on behavior. Physiol Behav 2015; 149:310-6. [PMID: 26122036 DOI: 10.1016/j.physbeh.2015.06.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 06/18/2015] [Accepted: 06/20/2015] [Indexed: 11/24/2022]
Abstract
In this study, we describe an approach based on an individual's hormonal reactive scope to study short-term effects of hormones on behavior. The control of territorial aggression has been traditionally linked to testosterone. Males of some vertebrate species show an increase in testosterone during territorial interactions and implantation studies suggest that such an increase in testosterone enhances the intensity and persistence of aggression. Here, we tested whether a short-term maximum release of testosterone - based on an individual's hormonal reactive scope - affects the intensity or persistence of territorial aggression in male black redstarts, a bird species in which testosterone does not increase during territorial encounters. An injection with gonadotropin-releasing-hormone (GnRH) induced a physiological peak in plasma testosterone that was specific for each individual (=individual reactive scope). However, such short-term surges in an individual's testosterone concentration did not affect the intensity or persistence of aggression. In conclusion, this study demonstrated (1) that a species that naturally does not increase testosterone during male-male encounters would not benefit from such an increase in terms of being more aggressive, (2) that behavioral studies using GnRH-injections represent a promising approach to study species differences in androgen responsiveness, and (3) that injections of releasing or tropic hormones in general may be a suitable approach to study short-term influences of hormones on behavior. These injections effectively mimic the potential short-term changes in hormones that can occur in the real life of individuals and enable us to study the effects of hormonal changes on behavior or other traits within an ecological and evolutionary framework.
Collapse
Affiliation(s)
- Wolfgang Goymann
- Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Eberhard-Gwinner-Straße 6a, D-82319 Seewiesen, Germany.
| | - Camila P Villavicencio
- Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Eberhard-Gwinner-Straße 6a, D-82319 Seewiesen, Germany
| | - Beate Apfelbeck
- Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Eberhard-Gwinner-Straße 6a, D-82319 Seewiesen, Germany; Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| |
Collapse
|
20
|
Rosvall KA, Bergeon Burns CM, Hahn TP, Ketterson ED. Sources of variation in HPG axis reactivity and individually consistent elevation of sex steroids in a female songbird. Gen Comp Endocrinol 2013; 194:230-9. [PMID: 24090613 PMCID: PMC3852689 DOI: 10.1016/j.ygcen.2013.09.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 09/03/2013] [Accepted: 09/16/2013] [Indexed: 11/16/2022]
Abstract
Understanding sources of individual differences in steroid hormone production has important implications for the evolution of reproductive and social behaviors. In females in particular, little is known about the mechanistic sources of these individual differences, despite established linkages between sex steroids and a variety of fitness-related traits. Using captive female dark-eyed juncos (Junco hyemalis) from two subspecies, we asked how variation in different components of the hypothalamo-pituitary-gonadal (HPG) axis related to variation in testosterone production among females, and we compared females to males in multiple components of the HPG axis. We demonstrated consistent individual differences in testosterone elevation in response to challenges with luteinizing hormone (LH) and gonadotropin-releasing hormone (GnRH). These hormone challenges led to more LH production but less testosterone production in females than males, and the sexes differed in some but not all measures of sensitivity to hormones along the HPG axis. Similar to findings in males, variation in testosterone production among females was not related to variation in LH production, gonadal LH-receptor mRNA abundance, or hypothalamic abundance of androgen receptor mRNA or aromatase mRNA. Rather, the primary source of individual variation in circulating steroids appears to the gonad, a conclusion further supported by positive correlations between testosterone and estradiol production. Unlike males, females did not differ by subspecies in any of the endocrine parameters that we assessed, suggesting some degree of independent evolution between the two sexes. Our results highlight the sources of physiological variation that may underlie the evolution of hormone-mediated phenotypes in females.
Collapse
|
21
|
Stevenson TJ, Bernard DJ, McCarthy MM, Ball GF. Photoperiod-dependent regulation of gonadotropin-releasing hormone 1 messenger ribonucleic acid levels in the songbird brain. Gen Comp Endocrinol 2013; 190:81-7. [PMID: 23660447 PMCID: PMC3742601 DOI: 10.1016/j.ygcen.2013.04.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 04/15/2013] [Accepted: 04/16/2013] [Indexed: 12/19/2022]
Abstract
Annual changes in day length induce marked changes in reproductive function in temperate zone vertebrates. In many avian species, in contrast to other seasonally breeding animals, plasticity in hypothalamic gonadotropin-releasing hormone - 1 (GnRH1) expression rather than (or in addition to) release governs changes in pituitary-gonadal activity. Investigations of the cellular and molecular mechanisms that govern GnRH1 plasticity were previously hindered by a collective inability of scientists in the field to characterize the gnrh1 cDNA in songbirds. We finally overcame this roadblock after data from the zebra finch (Taeniopygia guttata) genome project enabled us to rapidly clone the gnrh1 cDNA from hypothalamic RNA of zebra finches and European starlings (Sturnus vulgaris). Here, we review the original data that identified GnRH1 protein plasticity in the songbird brain and discuss earlier failed attempts to clone gnrh1 in these animals. Then, we present recent efforts, including our own, that successfully characterized gnrh1 in zebra finch and starling, and demonstrated dynamic regulation of gnrh1 mRNA expression, particularly in sub-populations of preoptic area neurons, in the latter. Overall, this paper highlights GnRH1 plasticity in the avian brain, and weaves into the narrative the previously untold story of the challenges to sequencing gnrh1 in songbirds.
Collapse
Affiliation(s)
- Tyler J Stevenson
- Institute for Mind and Biology, University of Chicago, Chicago, IL, USA.
| | | | | | | |
Collapse
|
22
|
Natural variation in circulating testosterone does not predict nestling provisioning rates in the northern cardinal, Cardinalis cardinalis. Anim Behav 2013. [DOI: 10.1016/j.anbehav.2013.02.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
23
|
DeVries MS, Winters CP, Jawor JM. Testosterone elevation and response to gonadotropin-releasing hormone challenge by male northern cardinals (Cardinalis cardinalis) following aggressive behavior. Horm Behav 2012; 62:99-105. [PMID: 22613708 DOI: 10.1016/j.yhbeh.2012.05.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 05/03/2012] [Accepted: 05/11/2012] [Indexed: 11/15/2022]
Abstract
There is much discrepancy about the relationship between testosterone (T) and male aggressive behavior. For example, in birds, males of many species significantly elevate T levels during inter-male conflict. However, this is not universal, and in species where males typically do not elevate T during aggressive interactions, concentrations of the hormone are often assumed to be circulating at maximum levels. We examined if male northern cardinals (Cardinalis cardinalis) significantly elevated T during simulated territorial intrusions (STIs). We also examined if individuals had the capacity to further elevate T levels in response to gonadotropin-releasing hormone (GnRH) injections immediately after an aggressive encounter. Our results indicate that male cardinals do not significantly elevate T levels in response to STIs, but have the physiological capacity to significantly elevate T in response to GnRH injections following aggressive interactions. This implies that T levels of individuals captured during STIs were not at maximum concentrations. However, additional findings in this study also suggest the possibility that prolonged social instability could elicit significant elevations in T in males of this species, warranting further investigation.
Collapse
Affiliation(s)
- M Susan DeVries
- Department of Biological Sciences, The University of Southern Mississippi, 118 College Drive # 5018, Hattiesburg, MS 39406, USA.
| | | | | |
Collapse
|