Environmental effects shape the maternal transfer of carotenoids and vitamin E to the yolk

Abstract

Introduction: Maternal effects occur when the phenotype of the offspring is influenced by the phenotype of the mother, which in turn depends on her heritable state as well as on influences from the current and past environmental conditions. All of these pathways may, therefore, form significant sources of variation in maternal effects. Here, we focused on the maternal transfer of carotenoids and vitamin E to the egg yolk, using canaries as a model species. Maternal yolk carotenoids and vitamin E are known to generate significant phenotypic variation in offspring, representing examples of maternal effects. We studied the intra-individual consistency in deposition patterns across two years and the mother-daughter resemblance across two generations in order to estimate the level of heritable variation. The effects of the current environmental conditions were studied via a food supplementation experiment, while the consequences of past environmental conditions were estimated on the basis of the early growth trajectories.

Results: There was a significant effect of the current environmental conditions on the yolk carotenoid and vitamin E deposition, but this effect varied between antioxidant components. The deposition of yolk carotenoids and vitamin E were linked to the process of yolk formation. Past environmental conditions did not contribute to the variation in yolk carotenoid and vitamin E levels nor did we find significant heritable variation.

Conclusions: The transfer of carotenoids or vitamin E may be an example where current environmental variation is largely passed from the mother to the offspring, despite the numerous intermediate physiological steps that are involved. Differences in the effect of the environmental conditions as experienced by the mother during laying may be due to differences in availability as well as physiological processes such as competitive exclusion or selective absorption.

Figure 1

Mother-daughter resemblance. Comparison of the alpha-tocopherol (a), gamma-tocopherol (b) and carotenoid (c) concentrations in the egg yolk of mothers and daughters. In neither case was the mother-daughter resemblance statistically significant.

Figure 2

Environmental effects acting during egg laying (food manipulation experiment). Females on a high quality diet (HQ) deposited significantly more alpha-tocopherol in their yolk compared to females that received a low quality diet (LQ) (a), but there were no significant differences in the gamma-tocopherol concentrations (b). The egg yolk of females on a HQ diet contained significantly less carotenoids compared to the egg yolk of females on a LQ diet (c).

Figure 3

Long-lasting consequences of past environmental effects that acted during the early developmental period. Relationship between the asymptotic body mass (indicator of the early developmental conditions) and the concentrations of alpha-tocopherol (a), gamma-tocopherol (b) and carotenoids (c) in the yolk of their eggs laid as adult. In neither case was the relationship statistically significant.