For fish, the timing of their birth can be a matter of life or death.
Scientists were already aware that fish have the ability to choose their own birthday - the day and time they hatch - but did not know how they did it. But now they do.
Researchers have discovered that fish trigger the hatching process via a brain signal called the thyrotropin-releasing hormone, or TRH, which travels to a hatching gland that disintegrates the egg wall. As a result, the young fish can emerge.
The key to the novel finding was the uncovering of this hidden neural circuit in zebrafish, which indicates that the fish are essentially in control of their destiny from the embryo. And yet, this short-lived circuit determines a fish’s fate at an early age. “This groundbreaking discovery uncovers a previously unknown neural mechanism that governs a critical life-stage transition, showing that embryos are not passive but instead actively make life-or-death decisions,” say the Hebrew University of Jerusalem researchers.
This process determines the outcome of “one of the most critical events for oviparous species [which produce eggs that hatch outside the mother’s body],” the study reads. “The decision to hatch is often carefully timed to coincide with favorable conditions that will improve survival through early life stages.”
The research was published in the journal Science.