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Seasonal
decline in nestling cellular immunocompetence results from environmental
factors - an experimental study
Dubiec A., Cichoń M.
CAN J ZOOL
2005; 83(7): 920-925
Abstract:
In a seasonal environment immune function in bird nestlings measured by the
ability to mount an immune response, number of leukocytes or immunoglobulins
circulating in the blood, has been reported to decline with hatching date. Two
groups of factors are suspected to contribute to this decline: 1) seasonal
deterioration of environmental conditions, e.g. food availability or 2)
differences in individual quality between parents breeding early and late in
the season. To distinguish between these effects, an experimental
manipulation of hatching date in great tits (Parus major) was conducted. Whole
clutches were swapped between pairs of nests with a 6-day difference in
expected hatching date, while some nests remained non-manipulated,
constituting a control group. Nestling T-cell-mediated immune response to
phytohaemaglutinin was negatively related to hatching date both within
non-manipulated control broods and all broods pulled together. Experimental
change in hatching date produced changes in nestling immune response as
predicted from the seasonal trend observed in the control nests. This
indicates that the seasonal decline in nestling immune function may be driven
by date-dependent environmental conditions rather than differences in
parental quality. Male and female nestlings did not differ in the level of
immune response and the seasonal decline in immune response did not differ
between sexes.
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