Response to acute stress in the Harlequin Duck (<i>Histrionicus histrionicus</i>) during the breeding season and moult: relationships to gender, condition, and life-history stage

121

144

SUMMARYEarly developmental experiences, such as incubation conditions, can have important consequences for post-hatching fitness in birds. Although the effects of incubation temperature on phenotype of avian hatchlings are poorly understood, recent research suggests that subtle changes in incubation conditions can influence hatchling characteristics, including body size and condition. We designed an experiment to explore the effects of incubation temperature on hatching success, survival to 9 days post hatch, growth and the hypothalamo-pituitary-adrenal (HPA) axis in wood ducks (Aix sponsa). Wood duck eggs were collected from nest boxes and experimentally incubated at three temperatures (35.0, 35.9 and 37.0°C), each falling within the range of temperatures of naturally incubated wood duck nests. Survival and growth were monitored in ducklings fed ad libitum for 9 days post hatch. In addition, baseline and stress-induced plasma corticosterone concentrations were measured in 2 and 9 day old ducklings. Hatching success and survival to 9 days was greatest in ducks incubated at the intermediate temperature. Ducklings incubated at 35.9°C and 37.0°C had 43% higher growth rates than ducklings incubated at 35.0°C. In addition, ducklings incubated at 35.0°C had higher baseline (17-50%) and stress-induced (32-84%) corticosterone concentrations than ducklings incubated at 35.9°C and 37.0°C at 2 and 9 days post hatch. We also found a significant negative correlation between body size and plasma corticosterone concentrations (baseline and stress-induced) in 9 day old ducklings. To our knowledge, this is the first study to demonstrate that thermal conditions experienced during embryonic development can influence the HPA axis of young birds. Our results illustrate that subtle changes (<1.0°C) in the incubation environment can have important consequences for physiological traits important to fitness.

Section: Discussionmentioning

confidence: 58%

Slight differences in incubation temperature affect early growth and stress endocrinology of wood duck (Aix sponsa) ducklings

DuRant

Hepp

Moore

et al. 2010

121

144

“…Increased CORT levels have also been found to be negatively related to body condition (Schwabl, 1995;Hood et al, 1998;Kitaysky et al, 2001;Sockman and Schwabl, 2001;Perfito et al, 2002;Breuner and Hahn, 2003;Pereyra and Wingfield, 2003;Love et al, 2005;Perez-Rodriguez et al, 2006;Roberts et al, 2007a). However, some studies have found no relationship between either CORT (Lormee et al, 2003;Lynn et al, 2003) or T (Buttemer and Astheimer, 2000;AlonsoAlvarez et al, 2002) and body condition.…”

Section: Introductionmentioning

confidence: 99%

The effects of testosterone on immune function in quail selected for divergent plasma corticosterone response

Roberts

Buchanan

Evans

et al. 2009

SUMMARYThe immunocompetence handicap hypothesis (ICHH) suggests that the male sex hormone testosterone has a dual effect; it controls the development and expression of male sexually selected signals, and it suppresses the immune system. Therefore only high quality males are able to fully express secondary sexual traits because only they can tolerate the immunosuppressive qualities of testosterone. A modified version of the ICHH suggests that testosterone causes immunosuppression indirectly by increasing the stress hormone corticosterone (CORT). Lines of Japanese quail (Coturnix japonica) selected for divergent responses in levels of plasma CORT were used to test these hypotheses. Within each CORT response line (as well as in a control stock) we manipulated levels of testosterone in castrated quail by treatment with zero (sham), low or high testosterone implants, before testing the birdsʼ humoral immunity and phytohaemagglutinin (PHA)-induced immune response, as well as body condition. The PHA-induced response was not significantly affected by CORT selected line, testosterone treatment or their interaction. There was, however, a significant effect of CORT line on humoral immunity in that the control birds exhibited the greatest antibody production, but there was no significant effect of testosterone manipulation on humoral immunity. The males in the sham implant treatment group had significantly greater mass than the males in the high testosterone group, suggesting a negative effect of high testosterone on general body condition. We discuss these results in the context of current hypotheses in the field of sexual selection.

“…There is some evidence to suggest that high levels of CORT may have a negative effect on body condition in birds (Schwabl, 1995;Hood et al, 1998;Kitaysky et al, 2001;Sockman and Schwabl, 2001;Perfito et al, 2002;Breuner and Hahn, 2003;Pereyra and Wingfield, 2003), and this may affect the quality of male sexual signals. This negative relationship between sexual signal quality and CORT level has been found previously (see Saino et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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

Roberts

Buchanan

Hasselquist

et al. 2007

SUMMARY 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.