Physiological, morphological and behavioural effects of selecting zebra finches for divergent levels of corticosterone

The effects of environmental stress on the physiology and behaviour of higher vertebrates has become an important avenue of research in recent years. Evidence from recent studies has suggested that the avian stress-related hormone corticosterone (CORT) may play a role in immunocompetence and sexual selection. We tested whether CORT is immunosuppressive by studying humoral and cell-mediated immune responses in populations of captive zebra finches selected for divergent peak levels of CORT. We also investigated whether selection for peak CORT has an effect on the quality of several sexually selected regions of the male zebra finch; in addition we compared morphometric parameters and the dominance ranking in males from the different selection lines. We also tested whether different components of the immune system compete for limited resources. We found that selection for divergent levels of peak CORT had little effect on humoral immunity, male sexual signal quality or dominance ranking. However, contrary to expectations, we did find a positive relationship between CORT titre and cell-mediated immunity, as well as a greater cell-mediated response in the birds selected for high CORT titre than those selected for low CORT titre. Consistent with predictions, significant negative relationships were found between both testosterone and CORT titre on humoral immunity. Birds from the low CORT lines were significantly larger in terms of skeletal size than those from the high CORT lines. Overall, our results suggest that the cell-mediated immune response is associated with a reduction in the humoral response, but only in males, and that there is no simple relationship between peak CORT levels and immune function.

Maternal stress to partner quality is linked to adaptive offspring sex ratio adjustment

Female birds have been shown to have a remarkable degree of control over the sex ratio of the offspring they produce. However, it remains poorly understood how these skews are achieved. Female condition, and consequent variation in circulating hormones, provides a plausible mechanistic link between offspring sex biases and the environmental and social stresses commonly invoked to explain adaptive sex allocation, such as diet, territory quality, and body condition. However, although experimental studies have shown that female perception of male phenotype alone can lead to sex ratio biases, it is unknown how partner quality influences female physiological state. Using a controlled within-female experimental design where female Gouldian finches (Erythrura gouldiae) bred with both high- and low-quality males, we found that partner quality directly affects female hormonal status and subsequent fitness. When constrained to breeding with low-quality males, females had highly elevated stress responses (corticosterone levels) and produced adaptive male-biased sex ratios, whereas when they bred with high-quality males, females had low corticosterone levels and produced an equal offspring sex ratio. There was no effect of other maternal hormones (e.g., testosterone) or body condition on offspring sex ratios. Female physiological condition during egg production, and variation in circulating hormones in particular, may provide a general mechanistic route for strategic sex allocation in birds.

Atmospheric quality and distribution of heavy metals in Argentina employing Tillandsia capillaris as a biomonitor.

The atmospheric quality and distribution of heavy metals were evaluated throughout a wide region of Argentina. In addition, the biomonitor performance of Tillandsia capillaris Ruiz & Pav. f. capillaris was studied in relation to the accumulation of heavy metals and to its physiologic response to air pollutants. A sampling area of 50,000 km2 was selected in the central region of the Argentine Republic. This area was subdivided into grids of 25 x 25 km. Pools of T. capillaris, where present, were collected at each intersection point. From each pool three sub-samples were analyzed independently. Furthermore, five replicates were collected at 20% of the points in order to analyze the variability within the site. The content of Co, Cu, Fe, Ni, Mn, Pb and Zn was determined by Atomic Absorption Spectrometry. Chemical-physiological parameters were also determined to detect symptoms of foliar damage. Chlorophylls, phaeophytins, hydroperoxy conjugated dienes, malondialdehyde and sulfur were quantified in T. capillaris. Some of these parameters were used to calculate a foliar damage index. Data sets were evaluated by one-way ANOVA, correlation analysis, principal component analysis and mapping. Geographical distribution patterns were obtained for the different metals reflecting the contribution of natural and anthropogenic emission sources. According to our results it can be inferred that Fe, Mn and Co probably originated in the soil. For Pb, the highest values were found in the mountainous area, which can be attributed to the presence of Pb in the granitic rocks. Ni showed mainly an anthropogenic origin, with higher values found in places next to industrial centers. For Zn the highest values were in areas of agricultural development. The same was observed for Cu, whose presence could be related to the employment of pesticides. The foliar damage index distribution map showed that the central and southeastern zones were the ones where the major damage in the bioindicator was found. The central zone coincides with the city of Córdoba whereas the southeastern area is strictly agricultural, so the high values found there could be related to the use of pesticides.

Flying, fasting, and feeding in birds during migration: a nutritional and physiological ecology perspective

Unlike exercising mammals, migratory birds fuel very high intensity exercise (e.g., flight) with fatty acids delivered from the adipose tissue to the working muscles by the circulatory system. Given the primary importance of fatty acids for fueling intense exercise, we discuss the likely limiting steps in lipid transport and oxidation for exercising birds and the ecological factors that affect the quality and quantity of fat stored in wild birds. Most stored lipids in migratory birds are comprised of three fatty acids (16:0, 18:1 and 18:2) even though migratory birds have diverse food habits. Diet selection and selective metabolism of lipids play important roles in determining the fatty acid composition of birds which, in turn, affects energetic performance during intense exercise. As such, migratory birds offer an intriguing model for studying the implications of lipid metabolism and obesity on exercise performance. We conclude with a discussion of the energetic costs of migratory flight and stopover in birds, and its implications for bird migration strategies.

Understanding quality of life in medicine : a new approach

This article introduces the subjective side of quality of life as it has evolved within the discipline of psychology. Subjective well-being is also of special interest within medicine due to its links to pathology and the fact that it is managed by a homeostatic system. This form of management offers an explanation for the unusual properties of subjective well-being, including its normal positivity, stability, and nonlinear relationship to objective variables, such as physical health. Central to understanding is the proposition that subjective well-being mainly consists of a specific form of trait mood. This homeostatically protected mood has a genetic set point and it is the experience of this set-point mood that homeostasis is defending. The resources required to maintain normal homeostatic control are described. If these resources are inadequate to protect the experience of set-point mood, mood positivity falls, and there is a high probability of depression. In this article, the process of homeostasis is shown to assist understanding of intervention effectiveness within both psychology and medicine. This concerns matters of resilience, the nonlinear relationship between levels of subjective well-being, and the strength of challenging agents, and the important understanding that interventions designed to raise subjective well-being are critically dependent on its level at baseline. Key teaching points: • The physiological process of homeostasis has a parallel in psychology in the homeostatic management of subjective well-being. • Subjective well-being is a more globally informative construct than health-related quality of life. • How people feel about themselves and their lives cannot be simply predicted through measures of health. • When subjective well-being homeostasis is defeated, there is a high probability of depression.

Quantifying the physical demands of a musical performance and their effects on performance quality

This study investigated the effects of fatigue on performance quality induced by a prolonged musical performance. Ten participants prepared 10 min of repertoire for their chosen wind instrument that they played three times consecutively. Prior to the performance and within short breaks between performances, researchers collected heart rate, respiratory rate, blood pressure, blood lactate concentration, rating of perceived exertion (RPE), and rating of anxiety. All performances were audio recorded and later analysed for performance errors. Reliability in assessing performance errors was assessed by typical error of measure (TEM) of 15 repeat performances. Results indicate all markers of physical stress significantly increased by a moderate to large amount (4.6 to 62.2%; d = 0.50 to 1.54) once the performance began, while heart rate, respirations, and RPE continued to rise by a small to large amount (4.9 to 23.5%; d = 0.28 to 0.93) with each performance. Observed changes in performance between performances were well in excess of the TEM of 7.4%. There was a significant small (21%, d = 0.43) decrease in errors after the first performance; after the second performance, there was a significant large increase (70.4%, d = 1.14). The initial increase in physiological stress with corresponding decrease in errors after the first performance likely indicates "warming up," while the continued increase in markers of physical stress with dramatic decrement in performance quality likely indicates fatigue. Musicians may consider the relevance of physical fitness to maintaining performance quality over the duration of a performance.

Associations between parent-child relationship quality and obesogenic risk in adolescence: a systematic review of recent literature.

Adolescence is a period of significant cognitive, social and physiological change, presenting unique risk factors for weight gain. Childhood obesity research has traditionally focused on the influence of parent-level factors on children's eating and weight status. Increasingly, emphasis is turning towards the reciprocal nature of the parent-child relationship and its influence on health behaviour. A systematic literature review was conducted to investigate the relationship between parent-child relationship quality (defined as the felt emotional bond between parent and child) and obesogenic risk (weight status, eating attitudes and behaviours, level of physical activity and sedentary behaviour) in adolescence; 26 papers were included in the review. The results neither support nor challenge an association between parent-child relationship quality and weight, with study design flaws and limited measurement of the parent-child relationship precluding robust conclusions. The review does however suggests that several aspects of the parent-child relationship are important in understanding eating attitudes and behaviours, including the felt emotional bond between the parent and child, the child's perception of how much the parent cares for them and the mother's sensitivity towards the child. The need for further longitudinal research into the association between parent-child relationship quality and obesity risk across this developmental period is discussed.

Why fly the extra mile? Using stress biomarkers to assess wintering habitat quality in migratory shorebirds

Migratory birds make decisions about how far to travel based on cost-benefit trade-offs. However, in many cases the net effect of these trade-offs is unclear. We sought to address this question by measuring feather corticosterone (CORTf), leucocyte profile, avian malaria parasite prevalence and estimating fueling rates in three spatially segregated wintering populations of the migratory shorebird ruddy turnstone Arenaria interpres during their stay in the winter habitat. These birds fly from the high-Arctic breeding ground to Australia, but differ in that some decide to end their migration early (Broome, Western Australia), whereas others travel further to either South Australia or Tasmania. We hypothesized that the extra costs in birds migrating greater distances and overwintering in colder climates would be offset by benefits when reaching their destination. This would be evidenced by lower stress biomarkers in populations that travel further, owing to the expected benefits of greater resources and improved vitality. We show that avian malaria prevalence and physiological stress levels were lower in birds flying to South Australia and Tasmania than those overwintering in Broome. Furthermore, our modeling predicts that birds in the southernmost locations enjoy higher fueling rates. Our data are consistent with the interpretation that birds occupying more costly wintering locations in terms of higher migratory flight and thermoregulatory costs are compensated by better feeding conditions and lower blood parasite infections, which facilitates timely and speedy migration back to the breeding ground. These data contribute to our understanding of cost-benefit trade-offs in the decision making underlying migratory behaviour.