Validating a Noninvasive Technique for Monitoring Embryo Movement In Ovo

Avian embryos are a commonly used model system for developmental studies, but monitoring of physiological parameters such as heart rate (HR) and movement in ovo poses a challenge to researchers. These are also increasingly common research objectives for ecological and embryo behavior studies in oviparous species. We therefore explored the validity of a new digital egg-monitoring system for the noninvasive monitoring of these parameters. We tested the relationship between frequency-of-movement values gathered by digital monitoring and those gathered by the current standard method, which is comparatively invasive and requires egg windowing, and demonstrated that the digital monitoring method effectively distinguishes individual movements but cannot reliably monitor HR in actively motile embryos. We therefore provide recommendations for the appropriate use of this technique for avian physiologists. We also applied the digital monitoring method to reveal how frequency of movement varies throughout prenatal ontogeny in the chicken and showed that commonly used protocols in developmental studies can themselves alter motility; egg windowing and application of light modulate frequency of movement. Recent work has revealed the importance of embryo motility in regulating gene expression and cellular activity during developmental processes. Together with our data, this highlights the value of noninvasive monitoring methods and the importance of controlling for altered embryo motility/behavior in developmental studies.