Avian egg odour encodes information on embryo sex, fertility and development.

Ben Webster,Thomas W Pike,William Hayes,Nicola Saino

doi:10.1371/journal.pone.0116345

Abstract

Avian chemical communication is a rapidly emerging field, but has been hampered by a critical lack of information on volatile chemicals that communicate ecologically relevant information (semiochemicals). A possible, but as yet unexplored, function of olfaction and chemical communication in birds is in parent-embryo and embryo-embryo communication. Communication between parents and developing embryos may act to mediate parental behaviour, while communication between embryos can control the synchronicity of hatching. Embryonic vocalisations and vibrations have been implicated as a means of communication during the later stages of development but in the early stages, before embryos are capable of independent movement and vocalisation, this is not possible. Here we show that volatiles emitted from developing eggs of Japanese quail (Coturnix japonica) convey information on egg fertility, along with the sex and developmental status of the embryo. Specifically, egg volatiles changed over the course of incubation, differed between fertile and infertile eggs, and were predictive of embryo sex as early as day 1 of incubation. Egg odours therefore have the potential to facilitate parent-embryo and embryo-embryo interactions by allowing the assessment of key measures of embryonic development long before this is possible through other modalities. It also opens up the intriguing possibility that parents may be able to glean further relevant information from egg volatiles, such as the health, viability and heritage of embryos. By determining information conveyed by egg-derived volatiles, we hope to stimulate further investigation into the ecological role of egg odours.

Highlights

The eggs of many species of fish and insects emit volatile compounds that act, incidentally, as cues to predators and parasites as to their location [1,2,3,4]
We look at odours produced by Japanese quail eggs during incubation, and test whether egg volatiles reflect egg fertility, embryonic development, and embryo sex; information which is potentially valuable in both parent-embryo and embryo-embryo communication
We make two specific predictions: (1) there will be an interaction between fertility and developmental stage, with egg volatile composition initially not differing between fertile and infertile eggs, but diverging later in development; and (2) there will be an interaction between embryo sex and developmental stage, with no sex differences during the early stages of incubation, but differences between eggs containing male and female embryos emerging during later stages

Summary

Introduction

The eggs of many species of fish and insects emit volatile compounds that act, incidentally, as cues to predators and parasites as to their location [1,2,3,4]. One possible role for egg odours may be as a component of parent-embryo and embryo-embryo interactions It is well-established that embryo-parent communication occurs late on during incubation, when the embryo first begins to vocalise within the shell [12]. We look at odours produced by Japanese quail eggs during incubation, and test whether egg volatiles reflect egg fertility, embryonic development, and embryo sex; information which is potentially valuable in both parent-embryo and embryo-embryo communication. We make two specific predictions: (1) there will be an interaction between fertility and developmental stage, with egg volatile composition initially not differing between fertile and infertile eggs, but diverging later in development; and (2) there will be an interaction between embryo sex and developmental stage, with no sex differences during the early stages of incubation, but differences between eggs containing male and female embryos emerging during later stages

Materials and Methods

Findings

Discussion