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Kiran K Soma - One of the best experts on this subject based on the ideXlab platform.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:Abstract In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD+, and this is a critical rate-limiting step. We predicted that brain 3β-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3β-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3β-HSD activity, when measured without exogenous NAD+, increased by ∼ 250 to 500% in telencephalic regions of challenged subjects. When brain 3β-HSD activity was measured with exogenous NAD+, these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD+ levels or increase 3β-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD(+), and this is a critical rate-limiting step. We predicted that brain 3beta-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3beta-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3beta-HSD activity, when measured without exogenous NAD(+), increased by approximately 250 to 500% in telencephalic regions of challenged subjects. When brain 3beta-HSD activity was measured with exogenous NAD(+), these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD(+) levels or increase 3beta-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.
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territorial aggression and hormones during the non Breeding Season in a tropical bird
2004Co-Authors: Michaela Hau, Steven T Stoddard, Kiran K SomaAbstract:The hormonal control of territorial aggression in male and female vertebrates outside the Breeding Season is still unresolved. Most vertebrates have regressed gonads when not Breeding and do not secrete high levels of sex steroids. However, recent studies implicate estrogens in the regulation of non-Breeding territoriality in some bird species. One possible source of steroids during the non-Breeding Season could be the adrenal glands that are known to produce sex steroid precursors such as dehydroepiandrosterone (DHEA). We studied tropical, year-round territorial spotted antbirds (Hylophylax n. naevioides) and asked (1). whether both males and females are aggressive in the non-Breeding Season and (2). whether DHEA is detectable in the plasma at that time. We conducted simulated territorial intrusions (STIs) with live decoys to male and female free-living spotted antbirds in central Panama. Non-Breeding males and females displayed robust aggressive responses to STIs, and responded more intensely to decoys of their own sex. In both sexes, plasma DHEA concentrations were detectable and higher than levels of testosterone (T) and 17beta-estradiol (E(2)). In males, plasma DHEA concentrations were positively correlated with STI duration. Next, we conducted STIs in captive non-Breeding birds. Captive males and females displayed robust aggressive behavior. Plasma DHEA concentrations were detectable in both sexes, whereas T was non-detectable (E(2) was not measured). Plasma DHEA concentrations of males were positively correlated with aggressive vocalizations and appeared to increase with longer STI durations. We conclude that male and female spotted antbirds can produce DHEA during the non-Breeding Season and DHEA may serve as a precursor of sex steroids for the regulation of year-round territorial behavior in both sexes.
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oestrogen regulates male aggression in the non Breeding Season
2000Co-Authors: Kiran K Soma, Anthony D Tramontin, John C WingfieldAbstract:Extensive research has focused on territorial aggression during the Breeding Season and the roles of circulating testosterone (T) and its conversion to 17β–oestradiol (E2) in the brain. However, many species also defend territories in the non–Breeding Season, when circulating T–levels are low. The endocrine control of non–Breeding territoriality is poorly understood. The male song sparrow of Washington State is highly territorial year–round, but plasma T is basal in the non–Breeding Season (autumn and winter). Castration has no effect on aggression in autumn, suggesting that autumnal territoriality is independent of gonadal hormones. However, non–gonadal sex steroids may regulate winter territoriality (e.g. oestrogen synthesis by brain aromatase). In this field experiment, we treated wild non–Breeding male song sparrows with a specific aromatase inhibitor (fadrozole, FAD) using micro–osmotic pumps. FAD greatly reduced several aggressive behaviours. The effects of FAD were reversed by E2 replacement. Treatment did not affect body condition or plasma corticosterone, suggesting that all subjects were healthy. These data indicate that E2 regulates male aggression in the non–Breeding Season and challenge the common belief that aggression in the non–Breeding Season is independent of sex steroids. More generally, these results raise fundamental questions about how sexual and/or aggressive behaviours are maintained in a variety of model vertebrate species despite low circulating levels of sex steroids or despite castration. Such nonclassical endocrine mechanisms may be common among vertebrates and play an important role in the regulation of behaviour.
D F Owen - One of the best experts on this subject based on the ideXlab platform.
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the food of the heron ardea cinerea in the Breeding Season
2008Co-Authors: D F OwenAbstract:Summary. 1 Food samples were collected from nestlings at three heronries by forcing them to regurgitate recent meals. 2 Young Herons are fed about 3–4 times in 24 hours when one parent is feeding and about twice as often when both are feeding. Feeding is most frequent just after dawn and in the evening. It is estimated that a brood of Herons receives on the average 230 pounds of food during the nestling period. 3 Herons select food between certain size limits, avoiding both very small and very large prey. 4 The proportion of each species of prey was different at different heronries, correlated with the available feeding grounds. There were also some differences between years. 5 The proportion of the various prey-species varied with the Season because some species changed their habits and were thus not always equally available to the Herons. At the peak of the Breeding Season food was more plentiful than either earlier or later. 6 Certain Herons tended to specialize on certain species of prey, apparently because they often returned to the same feeding area. 7 Many nestling Herons died of starvation and it is concluded that food is often short in the Breeding Season. The importance of asynchronous hatching is discussed. 8 The Breeding Season of the Heron appears to be timed so that the young are in the nest when the chief species of prey are most available.
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the Breeding Season and clutch size of the rook corvus frugilegus
2008Co-Authors: D F OwenAbstract:Summary. 1 Annual variations in the Breeding Season of the Rook near Oxford could be correlated with mean air temperatures in the period prior to egg-laying. 2 The most frequent clutch-size was four to five, and in five out of six years, broods starting as five raised on the average more young than broods starting as four, even though not one brood of five was completely successful. In the other year, broods starting as four and five raised on the average the same number of young per brood.
John C Wingfield - One of the best experts on this subject based on the ideXlab platform.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD(+), and this is a critical rate-limiting step. We predicted that brain 3beta-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3beta-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3beta-HSD activity, when measured without exogenous NAD(+), increased by approximately 250 to 500% in telencephalic regions of challenged subjects. When brain 3beta-HSD activity was measured with exogenous NAD(+), these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD(+) levels or increase 3beta-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:Abstract In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD+, and this is a critical rate-limiting step. We predicted that brain 3β-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3β-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3β-HSD activity, when measured without exogenous NAD+, increased by ∼ 250 to 500% in telencephalic regions of challenged subjects. When brain 3β-HSD activity was measured with exogenous NAD+, these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD+ levels or increase 3β-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.
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oestrogen regulates male aggression in the non Breeding Season
2000Co-Authors: Kiran K Soma, Anthony D Tramontin, John C WingfieldAbstract:Extensive research has focused on territorial aggression during the Breeding Season and the roles of circulating testosterone (T) and its conversion to 17β–oestradiol (E2) in the brain. However, many species also defend territories in the non–Breeding Season, when circulating T–levels are low. The endocrine control of non–Breeding territoriality is poorly understood. The male song sparrow of Washington State is highly territorial year–round, but plasma T is basal in the non–Breeding Season (autumn and winter). Castration has no effect on aggression in autumn, suggesting that autumnal territoriality is independent of gonadal hormones. However, non–gonadal sex steroids may regulate winter territoriality (e.g. oestrogen synthesis by brain aromatase). In this field experiment, we treated wild non–Breeding male song sparrows with a specific aromatase inhibitor (fadrozole, FAD) using micro–osmotic pumps. FAD greatly reduced several aggressive behaviours. The effects of FAD were reversed by E2 replacement. Treatment did not affect body condition or plasma corticosterone, suggesting that all subjects were healthy. These data indicate that E2 regulates male aggression in the non–Breeding Season and challenge the common belief that aggression in the non–Breeding Season is independent of sex steroids. More generally, these results raise fundamental questions about how sexual and/or aggressive behaviours are maintained in a variety of model vertebrate species despite low circulating levels of sex steroids or despite castration. Such nonclassical endocrine mechanisms may be common among vertebrates and play an important role in the regulation of behaviour.
Denoël Mathieu - One of the best experts on this subject based on the ideXlab platform.
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Movements of Alpine newts (Mesotriton alpestris) between small aquatic habitats (ruts) during the Breeding Season
2010Co-Authors: Kopecky Oldrich, Vojar Jiri, Denoël MathieuAbstract:Many species with complex life cycles, such as caudate amphibians, migrate from terrestrial to aquatic habitats for reproduction. However, movements between reproductive ponds within a Breeding Season have rarely been studied and are usually considered to be limited. Our aim was to determine whether this pattern occurs frequently in Alpine newts (Mesotriton alpestris) inhabiting complexes of small ruts on muddy forest tracks. We analysed capture-recapture data for individually marked newts as a function of locality, sex, body condition and hydroperiod throughout the Breeding Season. More than one third of the newts changed their ruts. Movements occurred more often towards ruts that did not dry during the Breeding Season. The body condition of males that changed ponds (but not that of females) was higher compared to that of resident newts in one of the studied populations. The relatively high frequency of movements between ruts can be seen as an adaptive strategy in unpredictable habitats which have a high probability of drying. The promiscuous pattern of newts also favours low site tenacity, because few sexual partners are available in each rut. Because of the broad occurrence of this kind of habitat, future studies should take into account these movements to better understand newt population dynamics and how to apply adequate conservation measures.Peer reviewe
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Movements of Alpine newts (Mesotriton alpestris) between small aquatic habitats (ruts) during the Breeding Season
2010Co-Authors: Kopecky Oldrich, Vojar Jiri, Denoël MathieuAbstract:peer reviewedaudience: researcher, professionalMany species with complex life cycles, such as caudate amphibians, migrate from terrestrial to aquatic habitats for reproduction. However, movements between reproductive ponds within a Breeding Season have rarely been studied and are usually considered to be limited. Our aim was to determine whether this pattern occurs frequently in Alpine newts (Mesotriton alpestris) inhabiting complexes of small ruts on muddy forest tracks. We analysed capture-recapture data for individually marked newts as a function of locality, sex, body condition and hydroperiod throughout the Breeding Season. More than one third of the newts changed their ruts. Movements occurred more often towards ruts that did not dry during the Breeding Season. The body condition of males that changed ponds (but not that of females) was higher compared to that of resident newts in one of the studied populations. The relatively high frequency of movements between ruts can be seen as an adaptive strategy in unpredictable habitats which have a high probability of drying. The promiscuous pattern of newts also favours low site tenacity, because few sexual partners are available in each rut. Because of the broad occurrence of this kind of habitat, future studies should take into account these movements to better understand newt population dynamics and how to apply adequate conservation measures
Devaleena S Pradhan - One of the best experts on this subject based on the ideXlab platform.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:Abstract In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD+, and this is a critical rate-limiting step. We predicted that brain 3β-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3β-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3β-HSD activity, when measured without exogenous NAD+, increased by ∼ 250 to 500% in telencephalic regions of challenged subjects. When brain 3β-HSD activity was measured with exogenous NAD+, these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD+ levels or increase 3β-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.
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aggressive interactions rapidly increase androgen synthesis in the brain during the non Breeding Season
2010Co-Authors: Devaleena S Pradhan, John C Wingfield, Amy E M Newman, Douglas W Wacker, Barney A Schlinger, Kiran K SomaAbstract:In male song sparrows (Melospiza melodia), territorial challenges during the Breeding Season can rapidly increase circulating levels of testosterone (T). During the non-Breeding Season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-Breeding Season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD(+), and this is a critical rate-limiting step. We predicted that brain 3beta-HSD activity varies Seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3beta-HSD activity was highest in the non-Breeding Season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-Breeding song sparrows. Brain 3beta-HSD activity, when measured without exogenous NAD(+), increased by approximately 250 to 500% in telencephalic regions of challenged subjects. When brain 3beta-HSD activity was measured with exogenous NAD(+), these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD(+) levels or increase 3beta-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-Breeding Season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-Breeding Season.