Octopuses have found an incredible way to protect the more sensitive parts of their nervous systems from radically changing temperatures.
When conditions fluctuate, they can quickly recode key proteins in their nerve cells, ensuring key neurological activities remain functional even when temperatures drop dramatically.
How do you do that? Through the use of a rare superpower – the ability to spontaneously edit their RNA, an ability found in some species of octopus, octopus, and squid.
It’s an unusual strategy, but it appears to be effective, and scientists think it may be widespread throughout the cephalopod world.
“We generally assume that our genetic information is fixed, but the environment can influence how proteins are encoded, and in cephalopods this is happening to a large extent.” says marine biologist Joshua Rosenthal from the University of Chicago Marine Biological Laboratory, senior author of new research, published in cell.
“RNA recoding gives organisms the ability to express a diverse set of proteins when and where they want. In cephalopods, most of the recoding is for proteins that are really important to the functioning of the nervous system. So, of course, the question is, are they using this to “accustom themselves to changes in their physical environment?”
Our own genetic instructions for survival can change, but it tends to do so slowly, with cross-generational DNA adaptations. Variations in the genetic code determine the ultimate form and function of individual proteins that make up our bodies, including the systems and structural supports in our brain.
However, DNA does not directly make the proteins. These chemically encoded instructions stay in the nucleus of your cells and, via an intermediary molecule called messenger RNA (or mRNA), deliver templates that travel from the nucleus to the surrounding goo, where they feed tiny protein-building machines.
For most organisms this is fairly easy; As soon as the template is issued, no further changes are made to the RNA. With cephalopods, however, things are a little different.
In 2015, scientists found this out Squid, squid and octopus can optimize the RNA after leaving the coreEditing on the fly, allowing for rapid physiological response to… what?
some scientists I thought this might be why cephalopods are so weird and fascinating cleverbut the reason for this is unknown to us and has puzzled scientists.
Adjust to transient environmental changes seemed a plausible explanation. Marine organisms are exposed to different temperatures and octopuses do not have the ability for active thermoregulation. RNA editing would offer the opportunity to keep changing depending on circumstances, without the long-term implementation and relative permanence of DNA editing.
A team of researchers led by marine biologist Matthew Birk of the Marine Biological Laboratory and Saint Francis University put this assumption to the test.
Their subjects were California two-spotted octopuses (Octopus bimaculoides), whose entire genome was first sequenced in 2005, making it a useful animal for understanding genetic changes.
The researchers acclimated these octopuses to warm water at 22 degrees Celsius (71.6 Fahrenheit) or much cooler water at 13 degrees Celsius (55.4 Fahrenheit) and then compared their genetic information to the database genome. They specifically examined over 60,000 known editing pages and found astonishing results.
“Temperature-sensitive machining occurred at about a third of our sites — at over 20,000 individual locations. So it doesn’t happen here or there; it is a global phenomenon.” says the physicist Eli Eisenberg from Tel Aviv University, co-senior author of the article.
“Yet this doesn’t happen equally: Proteins that are altered tend to be neuronal proteins, and almost all sites that are temperature sensitive are altered more in the cold.”
So the change appeared to be a response to acclimatization to cold rather than warm water and affected neuronal proteins that are particularly sensitive to cold temperatures. And testing of structural proteins critical to the functioning of the octopus’ nervous system – kinesin and synaptotagmin – revealed that the changes induced would have implications for their function.
It was possible that what the team observed was the result of a lab visit, so they caught wild California two-spot octopuses and Verrill’s two-spot octopuses (Octopus bimaculatus) in summer and winter and also checked their genomes. These octopuses displayed similar patterns of RNA editing, suggesting they optimized their function for the current temperature conditions.
The team also tested how quickly the changes occur. You adjusted the temperature in an octopus’ aquarium from 14 degrees Celsius to 24 degrees Celsius or vice versa, increasing or decreasing the temperature in 0.5 degree increments over a period of 20 hours. They tested the level of RNA editing in each octopus just before the temperature change began, just after, and four days later.
It happens very fastthe researchers found.
“We had no real idea of how quickly that could happen: whether it would take weeks or hours,” Birk explains. “We were able to see significant changes in less than a day, and within four days they reached the new steady-state levels that you get at one month.”
These results suggest that at least one function of cephalopod RNA editing is rapid response to conditions that might otherwise be dangerous to the animals. There are also other environmental variables that might trigger a reaction. These include lack of oxygen, pollution and changing social conditions.
The researchers suspect that RNA editing is a fairly common strategy in octopuses and squid to stay alive as their environment changes, and plan to study the way it’s deployed in more detail.
The research was published in cell.
