Avian Egg Odour Encodes Information on Embryo Sex, Fertility and Development

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.

鸟类化学通讯是快速兴起的研究领域，但因缺乏对传递生态学相关信息的挥发性化学物质（semiochemicals，信息化学物）的系统性认知，其发展长期受到制约。嗅觉与化学通讯在鸟类中或许存在一项尚未被发掘的功能：介导亲代-胚胎以及胚胎-胚胎间的信息交流。亲代与发育中胚胎的通讯可调控亲代行为，而胚胎间的通讯则能够调控孵化同步性。在发育后期，胚胎的发声与振动已被证实可作为通讯媒介，但在发育早期，胚胎尚不具备独立运动与发声能力，此类通讯方式便无从实现。本研究证实，日本鹌鹑（Coturnix japonica）发育中卵所释放的挥发性物质，可传递卵的受精状态、胚胎性别与发育状况的相关信息。具体而言，卵挥发性物质的组成会随孵化进程动态变化，在受精卵与未受精卵间存在显著差异，且早在孵化第1天即可预测胚胎性别。因此，卵气味有望通过让相关个体在其他感知模态可行之前，便可评估胚胎发育的关键指标，从而促进亲代-胚胎与胚胎间的交互。这同时也开启了一项颇具吸引力的研究可能：亲代或许能够从卵挥发性物质中获取更多相关信息，例如胚胎的健康水平、存活能力与遗传背景。本研究通过解析卵源性挥发性物质所传递的信息，以期推动学界对卵气味生态学功能的进一步探索。