Overview

Scientists have found that some animals react to the external world while they’re still just embryos in a phenomenon called acoustic developmental programming. They do this by listening to the sound cues from their parents, siblings, and environments, which guide their embryonic development.

What is acoustic developmental programming?

According to a new study published in the journal Cell Press, scientists have discovered that the embryos of many different animal species rely on sound signals during development. This phenomenon is called “acoustic developmental programming,” and while the embryos don’t consciously know that they are receiving these acoustic signals, that doesn’t stop their bodies from responding to the sounds.

“Acoustic developmental programming occurs when a sound informs embryos about the environment they’ll encounter postnatally and changes their development to better suit this environment,” lead author of the new study, Mylene Mariette of Deakin University, explained in a press statement.

“We have found evidence of this happening in birds, where parental calls can warn embryos about heatwaves or predators. Before that, there was also evidence that cricket nymphs use male songs to predict the level of competition for mates.”

Acoustic developmental programming is common in many species

What’s most fascinating about the new study is how the acoustic developmental programming phenomenon seems to be rather widespread among species. And it’s not just about immediate threats. It can also help prepare offspring for longer-term environmental conditions.

“The functions are really diverse,” said Mariette. “Embryos in lots of species use sound, but the way they use it varies a lot, and that’s why we think this is probably a lot more common than we know. For example, across all animal groups that lay eggs, such as insects, frogs, reptiles, and birds, embryos use sound or vibration to know when the best time is to hatch.

This suggests that acoustic developmental programming is “likely to happen in many animal species and for a whole range of conditions. But, until recently, scientists did not know it was happening,” Mariette added.

How does it work?

So far, it’s not exactly clear how acoustic developmental programming works, but Mariette and her team identified some likely mechanisms.

When crickets are nymphs (the stage between egg and adult), females will develop faster if they hear males’ reproductive “songs” so that they can make the most of the opportunity to mate. On the other hand, when male nymphs hear those songs, they interpret them as more sexual competition. Thus, they will slow down development and invest more resources into reproduction.

“In crickets, when developing nymphs hear many sexy songs, females develop quickly to make the most of the opportunity, whereas males delay metamorphosis to grow bigger and invest more in reproduction,” Mariette explained. “In zebra finches, embryos exposed to parental heat calls grow less to reduce the physiological damage of heat exposure, which then allows them to produce more babies at adulthood.”

Embryos, however, can’t decide to change their development. “It just happens”

According to the research team, acoustic signals directly impact the behaviors and physiology of embryos, “without any conscious processing.”

“This is why, for example, music triggers spontaneous emotions of sadness or happiness, without us having to remember which movie that soundtrack came from. Or in fact without us even noticing our reaction to the music,” Mariette explained. “It seems to occur on its own because there are direct connections in the brain between the auditory pathway and the areas that control emotion, reflex learning, and hormone production. So the higher cortical areas don’t need to decode the information.”

Mariette added that sounds and vibrations experienced early in life could trigger the same spontaneous reactions in embryos. In fact, they can have long-lasting effects because this is the time when the embryo’s brain is developing and consolidating connections.

The bottom line?

Sound and vibrations have a much more profound impact on embryo development than previously thought. Thus, this study suggests it’s very vital that we preserve natural soundscapes that may play crucial roles in animal adaptation, particularly in fast-changing environments.