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Bidirectional selection for yolk testosterone content in Japanese quail

Posted on 25. February, 2014.

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The variability of hormone levels in avian eggs has often been accounted for by adaptive yolk hormone-mediated maternal effects by which the phenotype of the next generation can be adjusted to environmental conditions experienced by the mother. The environment, therefore, represents an important variable that can create variations in the relative amounts of yolk hormones.

Egg testosterone (T) concentrations have been shown to vary depending on a broad range of factors like social context, male quality, immunological challenge and food resources.
However, substantial inter-female differences in yolk androgen deposition have pointed to the fact that this diversity cannot be attributed only to the environment, but also must have a genetic component. Both direct and indirect evidence gathered in recent studies prove the presence of genetic background of maternal androgen transfer into the egg.

In Japanese quail, we experimentally demonstrated that 
yolk T concentrations responded to bidirectional selection resulting in high (HET) and low (LET) egg T lines.
Based on three generations, the estimated heritability of yolk T concentrations explained nearly half of the total phenotypic variance in the yolk T concentration. 

This finding has important consequences since the additive genetic variance of yolk androgens indicates the potential for natural selection to act and provides support for the validity of adaptive hypotheses. Moreover, maternally derived yolk androgens produce multiple effects on offspring phenotypes and in the terms of indirect genetic effects yolk androgens may significantly modify the evolutionary dynamics of these offspring traits.

Read the entire article in Avian Biology Research, Volume 7, Number 1, February 2014 , pp. 18-24
Photograph by Ingrid Taylar


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