I recall one summer clearly when I was in italy: an unexpected spike in temperature tested the balance of my tank. A few colonies of Acropora indicated stress, but upon restoration of the best conditions, the same corals recovered at an astonishing rate. What intrigued me most, though, was finding that these corals, after recovering from this stress, appeared to respond better to subsequent small changes, like short spikes in salinity or lighting.
Initially, it seemed to be mere coincidence owing to personal hardiness or minuscule differences in location. But the question remained: does some sort of “memory” of earlier experience indeed persist in these creatures so far away from us?
The solution to this question came to me while studying the principle of epigenetics. Briefly speaking, the term of epigenetics includes all those chemical modifications that “inform” genes how and when to be activated and deactivated, but keep the DNA unchanged.
For corals, this means that exposure to stress—such as heat or acidification can leave a sort of “mark” on the genes. This mark regulates their response to future stress and, surprisingly, can even be passed on to their offspring, boosting the species’ adaptability.
In recent decades, studies have cataloged this process in increasing detail. Work like Dixon et al. (2014) has demonstrated how certain stocks of Acropora, following repeated exposure to heat stress, come to tolerate higher temperature better. This isn’t because of mere mutation, but because of changes at an epigenetic level, changes that pass to offspring.
Other work, such as that of Putnam et al. (2016), has confirmed that even ocean acidification can induce epigenetic changes in corals that increase their resilience.
This “epigenetic memory” enables corals not only to respond better to stress, but also to pass on this ability to future generations, supporting the survival of the entire colony.
What most struck me from this finding was the aspect that what happened from my own aquarium was anything but coincidence.
Witnessing firsthand how corals can “learn” from bad experiences compelled me further to read up, discuss with fellow aquarists, and delve into the scientific papers themselves. Now, I realize that what at first appeared to be happenstance is really the work of intricate, elaborate natural processes enabling corals to adapt and persevere even under fast changing environments. Wonder and Responsibility Knowing that corals possess this extraordinary capacity for adaptation honed over millions of years of evolution has taught me to look at them with even greater respect.
Epigenetics is part of the explanation of how they are resilient, both naturally and at our aquariums. As an enthusiast, I remain an observer and recorder of these phenomena, aware that one small detail may provide new directions for investigation and awe. As, even at the aquarium, nature tends to surprise us.
Summary of Putnam et al. (2016) Study
Summary of Dixon et al. (2014) Study
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