Abstract
DOI: 10.15414/afz.2014.17.04.130–135 Received 4. September 2014 ǀ Accepted 2. October 2014 ǀ Available online 24. November 2014 Individual phenotype is a result of an interacting genotype and environment with the most sensitive periods occurring within the late embryonic and early postnatal development. In this time, most of the signals come from the mother and such influences are termed maternal effects. In our review, we focus on hormone-mediated maternal effects in birds because the avian embryo develops without interactions with neuroendocrine milieu of the mother and the egg yolk contains biologically active substances including hormones. Thus, it is expected that the mother can adjust phenotypic development of her progeny to actual environmental conditions through differential deposition of hormones in the egg. The adaptive value of such hormone mediated maternal effects can have significant consequences for poultry performance but is still generally neglected. In the first part of our review, we summarise the data from wild living birds and urge the need to study maternal egg hormones also in poultry species. In the second part of this review, we present our experimental approach that is based on two genetic lines of Japanese quail divergently selected for yolk testosterone concentrations. We estimated relatively high heritability of yolk testosterone concentrations and proved that natural selection can shape hormone-mediated maternal effects. Our selected lines provided us with a unique model to explore mechanisms of maternal hormone transfer into the egg and epigenetic effects of maternal hormones on offspring. We expect that this approach will provide relevant data in the field of trans-generational maternal effects with potential application for poultry breeding and welfare. Keywords : maternal effects, hormones, androgens, genetic lines
Highlights
Individual phenotype is a result of interactions between genotype and environment
We focus on Japanese quail, which has been effectively used as a model species for genetic
Our original bidirectional selection for egg T content in Japanese quail provided us with a unique model to explore mechanisms of maternal hormone transfer into the egg and epigenetic effects of maternal hormones on offspring
Summary
Individual phenotype is a result of interactions between genotype and environment. These two factors interact with each other during the embryonic and postembryonic ontogeny. Maternal effects may be considered as adaptive tools by which the mother ‘programs’ her offspring to environmental conditions they will face after hatching (Mousseau and Fox, 1998) This phenomenon is generally known for a long time, only over the last two decades an active research of mechanisms, by which maternal phenotype modifies gene expression of the generation has started. A growing attention is dedicated to hormone mediated maternal effects that possess a potential to permanently organize offspring’s phenotype (Groothuis et al, 2005b) This mechanism is important from both, evolutionary perspective, as a rapid adaptation to unpredictable environmental conditions, as well as from the perspective of negative consequences of these adaptations for development of offspring and possible wrong programming. This field of research is becoming even more important with respect to problems of environmental contamination by endocrine disruptors, compounds that besides their direct negative effects can exert indirect effects via a modification of epigenetic adaptive mechanisms (Ottinger et al, 2008)
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