Scientists Discover How Fish Embryos Control Their Hatching Timing

Israeli researchers identify a transient brain structure and hormone mechanism that enables fish embryos to determine the optimal moment to hatch.

Researchers from Hebrew University and the Volcani Institute uncovered how fish embryos actively control their hatching through a newly identified neural circuit.
The process involves a transient brain structure that releases thyrotropin-releasing hormone (TRH), triggering enzymes to dissolve the egg wall at the right time.
This mechanism, observed in zebrafish and medaka, highlights an ancient evolutionary process shared across species that diverged over 200 million years ago.
The discovery sheds light on how embryos balance environmental conditions with survival risks to time their hatching optimally.
The findings open new avenues for studying hatching mechanisms in other species and understanding how climate change might affect this critical life-stage transition.