A new study reveals that a species of fish living on coral reefs can pass on traits to their offspring that make them more resistant to a 3-degree increase in water temperature and this happens within a single generation. Could this ability help the species survive better and adapt to warming ocean waters due to global climate change?
According to most cases, evolution is a very slow process, with its effects only noticeable after many generations.
Millions of years were required, for example, for a common ancestor of chimpanzees and humans living in African forests to evolve into a modern human.
In recent years the role of faster genetic mechanisms allowing adaptation to environmental changes such as climate change has become clearer.
A new study recently published shows that a species of fish living on coral reefs can pass on traits to their offspring that make them more resistant to a 3-degree increase in water temperature within just one generation. This ability could help the species survive better in the near future as ocean waters warm due to climate change.
Adapting Within Two Generations
The study, conducted by a group of researchers from various countries and recently published in the journal Nature Climate Change, focused on a common reef fish from the damselfish family living in the western Pacific Ocean (scientific name Acanthochromis polyacanthus).
In the experiment, researchers raised three generations of fish in laboratory conditions.
The first generation, the “grandparents,” grew entirely at the current ocean temperature.
The second generation, the “parents,” was divided into three groups and raised at different temperatures: one at the current ocean temperature, one 1.5 degrees Celsius higher, and one 3 degrees higher than current temperatures.
In the third generation, the “grandchildren,” all groups were raised at 3 degrees above the current ocean temperature, simulating the heat conditions the fish may face due to climate change.
At the end of the experiment, researchers examined gene expression in the fish from the three groups which genes were activated and translated into RNA and proteins, and which remained inactive.
They found that fish whose parents grew in warmer water survived well in water 3 degrees hotter than current temperatures.
Fish whose parents experienced a gradual temperature increase of 1.5 degrees showed the best adaptation to heat conditions.
Rapid Genetic Changes
The trait that parent fish pass on to their offspring, allowing them to survive heat well, is the ability to use oxygen more efficiently.
This ability is impaired in reef fish when water temperature rises a few degrees above the average summer temperature because warm water contains less dissolved oxygen and increases the fish’s metabolic rate.
This can affect essential functions such as growth, reproduction and social behavior.
Offspring of fish raised in warmer water had optimal oxygen consumption and avoided such damages.
The study also reveals the genetic mechanism enabling this rapid change.
This involves a relatively new field in genetics called “epigenetics,” which studies changes in gene expression due to environmental influences and lifestyle factors like diet, stress, and temperature, without altering the DNA sequence itself.
A key epigenetic mechanism is methylation a process in which a methyl group is added to a DNA region, causing the expression of certain genes to stop.
The study found differences in methylation patterns in the genome between fish groups.
Thus, the parents passed on to their offspring within one generation the ability to survive better in warmer waters.
However, although epigenetics allows fish to adapt to temperature changes, their survival still depends on their environment the coral reef habitat which itself is much less resilient to climate change.
Coral reefs worldwide have been severely affected in recent years by climate change impacts, including warming seas and ocean acidification, threatening the survival of many reef fish species.
Nature Cannot Adapt Fast Enough
Another risk from warmer water is increased disease.
Extreme heat can weaken animals, making them more susceptible to infections.
Even if the animal is not weakened, warmer water facilitates bacterial growth.
Bacteria reproduce faster and survive more easily in warmer conditions.
This is similar to the spread of diseases in humans in tropical regions compared to colder regions. Coral reefs show this clearly: a slight temperature increase causes more disease outbreaks.
Despite the impressive adaptation abilities observed in these fish, nature usually adapts much more slowly.
If climate changes occurred gradually, most fish could adapt.
The problem is that changes happen quickly and sharply, leaving nature unable to respond fast enough, and species have no time to adapt.