(CN) — When it comes to survival, timing is everything — even for fish embryos. And according to researchers, these embryos aren’t just waiting around for the perfect moment to hatch. They’re actively deciding it.
In a study led by Matan Golan from the Hebrew University of Jerusalem and the Agricultural Research Organization-Volcani Institute scientists reveal that fish embryos use a neurohormone called Thyrotropin-Releasing Hormone (TRH) to control their hatching.
The research, published Thursday in Science, shows that the hormone triggers the release of enzymes that dissolve the egg wall, letting the embryo break free when conditions are just right.
This discovery sheds light on a previously unknown neural mechanism that determines a crucial life-stage transition. Researchers say it’s a breakthrough in understanding how embryos actively influence their survival, challenging the idea that they’re merely passive participants in their development.
Hatching is a high-stakes moment for any egg-laying species, the researchers say.
Emerging too soon can leave the hatchling unprepared for predators or environmental challenges, while waiting too long can be just as fatal. Golan’s team found that the key to perfect timing lies within the embryo itself, which uses its brain to send a signal for hatching when the time comes.
The Thyrotropin-Releasing Hormone travels through the bloodstream to a specialized gland, triggering the production of enzymes that dissolve the egg’s protective layer. This neural circuit for hatching forms just before the event and vanishes soon after. Without TRH, embryos are unable to release the enzymes, leading to death inside the egg.
According to researchers, these implications go beyond fish. They also revealed that long-sought mechanism in vertebrates, the largest group of animals on Earth.
As fish are the largest group of vertebrates on Earth, the researchers say their findings have significant evolutionary implications.
The research team plans to investigate whether similar processes occur in other species, which could further expand our understanding of how animals adapt to their environments.
By actively controlling their own hatching, fish embryos demonstrate a remarkable level of autonomy, showcasing the delicate balance between biology and environment.
As researchers continue to explore the role of neurohormones like TRH, this discovery opens the door to understanding how life-stage transitions are orchestrated across the animal kingdom.