Seasonal variation in body mass and fat of Zebra Finches in south-eastern Australia

Rozman, Jan; Runciman, David; Zann, Richard

doi:10.1071/mu02003

Cited by 20 publications

(12 citation statements)

References 34 publications

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“…This could explain the larger size-corrected body masses of BSO females but not the lack of a similar effect in males. However, female birds increase in body mass by 7%-30% before reproduction (review in Lind et al 2010), and wild zebra finch females show a greater amplitude in annual body mass change than males (Rozman et al 2003). Moreover, egg-laying capacity in female zebra finches mostly relies on protein stores in pectoral muscles, which lose muscle mass during reproduction (Houston et al 1995b).…”

Section: Discussionmentioning

confidence: 99%

The Level of an Intracellular Antioxidant during Development Determines the Adult Phenotype in a Bird Species: A Potential Organizer Role for Glutathione

Romero-Haro

Alonso‐Álvarez

2015

The American Naturalist

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Online enhancement: appendix. Dryad data: http://dx.doi.org/10.5061/dryad.1rd58.abstract: Life-history traits are often involved in trade-offs whose outcome would depend on the availability of resources but also on the state of specific molecular signals. Early conditions can influence trade-offs and program the phenotype throughout the lifetime, with oxidative stress likely involved in many taxa. Here we address the potential regulatory role of a single intracellular antioxidant in lifehistory trade-offs. Blood glutathione levels were reduced in a large sample of birds (zebra finch Taeniopygia guttata) during development using the synthesis inhibitor buthionine sulfoximine (BSO). Results revealed several modifications in the adult phenotype. BSO-treated nestlings showed lower glutathione and plasma antioxidant levels. In adulthood, BSO birds endured greater oxidative damage in erythrocytes but stronger expression of a sexual signal. Moreover, adult BSO females also showed weaker resistance to oxidative stress but were heavier and showed better body condition. Results suggest that low glutathione values during growth favor the investment in traits that should improve fitness returns, probably in the form of early reproduction. Higher oxidative stress in adulthood may be endured if this cost is paid later in life. Either the presence of specific signaling mechanisms or the indirect effect of increased oxidative stress can explain our findings.

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Section: Discussionmentioning

confidence: 99%

The Level of an Intracellular Antioxidant during Development Determines the Adult Phenotype in a Bird Species: A Potential Organizer Role for Glutathione

Romero-Haro

Alonso‐Álvarez

2015

The American Naturalist

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“…During drought conditions or during periods of low food availability, zebra fi nches are thought to travel over large areas [Serventy, 1971;Zann and Straw, 1984;Rozman et al, 2003]. The ability to reduce testis volume without compromising sperm production may be part of a suite of physiological responses to drought that help to reduce body mass and redirect energy reserves during irruptive movements, although this remains to be tested.…”

Section: Functional and Behavioral Consequencesmentioning

confidence: 99%

Tonic Activation of Brain GnRH Immunoreactivity despite Reduction of Peripheral Reproductive Parameters in Opportunistically Breeding Zebra Finches

2006

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Opportunistically breeding species offer the unique opportunity to understand mechanisms in reproductive physiology that allow for extreme flexibility in the regulation of reproduction. We studied a well-known opportunistic breeder, the zebra finch (Taeniopygia guttata) to test the hypothesis that the reproductive axis of opportunists is in a constant state of ‘near-readiness’. In wild zebra finches, reproduction is highly correlated with rainfall, and in the laboratory, water availability and humidity are the strongest cues to affect reproductive activation. We therefore subjected individuals to water restriction for eleven weeks followed by a two week period of ad libitum access to water. The control group had water freely available for the entire experiment. We measured the state of activation of the hypothalamo-pituitary gonad (HPG) axis at three levels: in the hypothalamus by measuring immunoreactive (ir) cGnRH-I and cGnRH-II; in the anterior pituitary gland by measuring plasma luteinizing hormone (LH); and in the gonads by measuring gonadal volume and function. We found that water restriction caused a reduction in circulating LH concentrations and that testis volume was more likely to decrease in water restricted than in control birds. Subsequent short-term return to ad libitum water availability caused LH to return to baseline in water restricted birds. These changes occurred without significant changes in ir-cGnRH-I, ir-cGnRH-II, or in testis function. These data suggest that in these opportunistic breeders, an inhibition of parts of the reproductive axis is not necessarily correlated with full inactivation of reproductive potential. GnRH-ir cells in the hypothalamus appear to remain active and able to respond to subsequent stimulation.

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“…The relationship between energy and physiology is exemplified by the numerous energy storage mechanisms found in vertebrates (Arrington et al, 2006;Naya et al, 2008;Smith and McWilliams, 2010). Fat reserves, in the form of triglycerides, enable organisms to maintain the metabolic demands of self-maintenance and activity associated with periods of food scarcity (Rogers and Reed, 2003;Rozman et al, 2003). Prolonged periods of food scarcity can lead to loss of body mass due to the depletion of fat (breakdown to free glycerol) and protein (breakdown to amino acids) reserves for fueling gluconeogenesis (Fery et al, 1996;Wingfield, 2003).…”

Section: Introductionmentioning

confidence: 99%

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird

Fokidis

Roziers

Sparr

et al. 2012

Journal of Experimental Biology

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SUMMARYEnvironments often vary with regard to their temporal resource availability, but little is understood concerning how resource predictability impacts animals. The adaptive regulation hypothesis suggests that organisms act to conserve their current energetic state during periods of diminished food access and recuperate their energetic reserves (fat and muscle) during periods of greater food availability. In contrast, the chronic stress hypothesis suggests that variation in access to food can induce a prolonged stress response, resulting in maladaptive usage of energy reserves and increased behavioral activity. To distinguish between these hypotheses we compared the behavioral, hormonal and metabolic responses of captive curve-billed thrashers, Toxostoma curvirostre, fed varying amounts each day (variable group) with those of birds fed a constant amount every day (constant feeding group). Birds of both groups consumed, on average, a similar total amount of food during the course of the study, but birds in the variable feeding group lost mass and increased their circulating initial levels of the stress hormone corticosterone, showed evidence for increased secretion of a hypothalamic stress peptide, vasotocin, used greater amounts of fat and protein energy reserves, and were more behaviorally active than birds in the constant feeding group. Overall, these findings support the chronic stress hypothesis and suggest that birds such as thrashers may be particularly susceptible to the perception of unpredictable variation in food supplies independent of actual energetic constraints.Key words: chronic stress, food variability, predictability, curve-billed thrasher, corticosterone, energy reserve, vasotocin, fault bar, gluconeogenesis, lipid, protein, glucose. al., 1992;Lohmus et al., 2006) and can promote locomotor activity in captivity (Lynn et al., 2003;Fokidis et al., 2011a). These behavioral changes can also alter the energy balance. By responding to changes of the current energetic state, the HPA axis plays an important role in mediating transitions from regular 'life history' activities to vital 'emergency' functioning.In environments, such as those subjected to frequent inclement weather and where food availability can rapidly vary temporally, the relationship between maintenance of energy reserves and the stress of 'unpredictable' foraging has been considered in a risk foraging framework (Bednekoff and Houston, 1994). This framework suggests that periods of variable food intake due to variation in food abundance or interruptions in foraging due to increased 'risk' (such as predation or inclement weather) prompt individuals to regulate their body mass and energy usage (Bednekoff and Krebs, 1995;Witter et al., 1995; Cuthill et al., 2000). In birds and mammals, temporal variability in food availability is associated with fattening (Bednekoff and Krebs, 1995), an increase in daily torpor (Munn et al., 2010), increased or stabilized body mass (Witter et al., 1995; Cuthill et al., 2000) and less behavioral act...

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Seasonal variation in body mass and fat of Zebra Finches in south-eastern Australia

Cited by 20 publications

References 34 publications

The Level of an Intracellular Antioxidant during Development Determines the Adult Phenotype in a Bird Species: A Potential Organizer Role for Glutathione

The Level of an Intracellular Antioxidant during Development Determines the Adult Phenotype in a Bird Species: A Potential Organizer Role for Glutathione

Tonic Activation of Brain GnRH Immunoreactivity despite Reduction of Peripheral Reproductive Parameters in Opportunistically Breeding Zebra Finches

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird

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