Life history shapes variation in egg composition in the blue tit Cyanistes caeruleus

TL;DR

This study investigates how maternal investment influences egg composition in blue tits, revealing that egg biochemical profiles vary with laying order and female age, affecting embryonic development.

Contribution

It provides the first detailed proteomic analysis of blue tit eggs and links maternal effects to specific biochemical variations in egg composition.

Findings

Egg composition varies with laying order and female age.

Proteomic profiles are mainly driven by laying order.

Maternal effects involve passive and active mechanisms.

Abstract

Maternal investment directly shapes early developmental conditions and therefore has longterm fitness consequences for the offspring. In oviparous species prenatal maternal investment is fixed at the time of laying. To ensure the best survival chances for most of their offspring, females must equip their eggs with the resources required to perform well under various circumstances, yet the actual mechanisms remain unknown. Here we describe the blue tit egg albumen and yolk proteomes and evaluate their potential to mediate maternal effects. We show that variation in egg composition (proteins, lipids, carotenoids) primarily depends on laying order and female age. Egg proteomic profiles are mainly driven by laying order, and investment in the egg proteome is functionally biased among eggs. Our results suggest that maternal effects on egg composition result from both passive and active (partly compensatory) mechanisms, and that variation in egg composition creates diverse biochemical environments for embryonic development.