Mangrove forests are not the most stable places for fish to live.  The temperature can change a lot from day to day and from season to season.  Fish that live there have to be tough.  They have to be able to adapt to these changes quickly.  One way they do this is through something called plasticity.  Plasticity is like a superpower that lets them change their traits to fit new conditions.  This is especially important when it comes to temperature.  Scientists wanted to see how temperature changes affect the genes of a special kind of fish called the mangrove rivulus.  This fish is unique because it can reproduce on its own and it can handle a wide range of temperatures.

To start, the scientists improved the map of the fish's genes.  This map is like a treasure map that shows where all the important genetic information is.  Then, they looked at how the genes of the fish embryos changed when they were exposed to different temperatures.  They found that both the temperature and the stage of development affected which genes were turned on or off.  Early on, the embryos didn't show many differences in their genes, no matter the temperature.  This suggests that they are pretty resistant to small, random changes in temperature early in life.

But things changed after a certain point in development.  Embryos that were exposed to cold temperatures showed less variation in their genes than those that were exposed to warm temperatures.  This could mean that the fish are somehow "locking in" their response to the cold, making it more consistent.  When they looked closer, they found that certain groups of genes were more active in the cold.  These genes are involved in things like fixing DNA, building tiny structures inside cells, and moving gases around.  On the other hand, genes related to brain development, cell communication, and cell sticking together were less active in the cold.  These changes in gene activity could have big effects on how the fish grow and develop in response to temperature changes.

So, what does all this mean?  Well, it shows that temperature can have a big impact on how fish develop, even before they are born.  It also shows that fish have ways to adapt to these changes, making them more likely to survive and thrive in their ever-changing homes.  But it also raises questions.  How do these changes affect the fish in the long run?  And how might climate change affect these processes?  These are important questions to consider as we think about the future of our planet and the creatures that call it home.

How Heat and Cold Shape Fish Babies' Genes

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