Sounds Shape the Embryonic Development, Study Suggests

On a typical hot day, Mylene Mariette, a behavioural ecologist at the Deakin University in Australia, had her eyes fixed at a parent of a Zebra Finch, a common Australian passerine, as it incubated its babies. The bird was screeching at quite a high pitch so Mariette decided to record it. Curious to understand its impact on embryos, Mariette then repeatedly played the recorded calls to the eggs that were incubated in her laboratory condition.

Reporting on 27th May, in the journal ‘Trends in Ecology and Evolution', Mariette and her team concluded that an embryo keeps an ear out to the worldly noise as it twirls inside the mother's womb (or incubating egg) adjusting its growth in the process. They had clear results to back up this conclusion. Embryos exposed to the high-pitched heat calls grew less in the heat after hatching than the unexposed ones. What's more, Mariette was even surprised when she found that sound affects development across lots of animal groups.

A Zebra Finch incubating its eggs (Courtesy: Mariette)

“It is quite amazing how sound alone has such an impact on embryos,” she said. The paper convincingly documented the influence of sound for embryos across wide animal groups and urges the scientific community to recognize the phenomena. Researchers suspect that the smaller body size among the finch hatchlings reduced the damage from heat exposure, which increased their breeding success. But it’s not something that embryos decide consciously, Mariette says. “It just happens.”

Frog embryos in eggs (Courtesy: K Warkentin)

Not only in birds but in humans as well, a mother’s voice and her heartbeat influence an unborn child's brain development and its ability in sensing sound. Red-eyed tree frog embryos can perceive the vibrations of approaching predators to hatch early and escape predation. Hundreds of insect nymphs hatch simultaneously by detecting sounds and vibrations of their siblings. Some water snake hatch early by detecting the heartbeats of siblings resulting in compromised swimming ability. Female cricket nymphs develop quickly when they hear “sexy songs” while males listening to the same songs delay the hatching process in a mere hope to get bigger and better.

A Crocodile Hatchling (Courtesy: Mathevon) 

All in all, the bottom line comes to this: Sounds have an important role in shaping the growth and development across animals from an embryonic stage. But further research may only reveal how exactly do they do it.