Tom Kleindienst/Marine Biological Laboratory
Octopuses are curious and smart. They can solve mazes and puzzles, use tools, and are masters of disguise. These complex abilities are backed up by their highly developed and gigantic brains.
Now, in the journal cellResearchers report that octopuses are able to modify genetic information to quickly re-sculpt those brains when faced with changes in their environment.
These findings shed new light on the amazing adaptability of these shape-shifting creatures and may help scientists design treatments for problematic mutations in our bodies.
Octopuses are among the most intelligent invertebrates on the planet, with well-developed brains and complex nervous systems. In other animals, these large brains usually need to be treated with care.
Just think of your fragile brain. It’s covered in a skull, flooded with oxygen, and set to operate at a relatively constant body temperature. “We expend a ton of energy maintaining a constant temperature,” he says. Josh Rosenthal, a neurobiologist at the Marine Biology Laboratory in Woods Hole, Massachusetts. “And a lot more of it so our nervous system can function more efficiently.”
Too hot (with a high fever) or too cold (with a hypothermia) and our brains fade and start to fail – that’s several degrees off normal. So our bodies keep everything at a constant temperature.
Octopuses do not have this luxury. Their brains require just as much protection as ours, but they’re in squishy bodies that swim in water whose temperature can fluctuate about 20 degrees.
“It’s difficult to maintain a complex nervous system in the face of changing temperatures,” says Rosenthal. This presents challenges.
Rapid genetic modification
Octopuses have overcome this challenge with a unique trick hidden inside their cells. It has to do with a molecule called RNA, which is used to help translate DNA into the proteins that make up our bodies. To use an analogy, let’s say you want to make a loaf of bread and you walk into a library full of cookbooks.
Says “This is the same cookbook, it’s already out of print and I can’t change the book” Matthew Burke, a biologist at Saint Francis University. “But what I can do is make a copy, take it home to my kitchen,” and bake the bread there.
Here, cookbooks are DNA, which is hard coded and unchanging, bread is the protein your body wants to make, and RNA is a copy of a recipe that explains how to do it. RNA tends not to change all that much. It’s just a messenger.
But what if you’re missing an ingredient — like butter?
“If those are the guidelines you have, you’re kind of overwhelmed,” says Rosenthal. “But if you know the oil is going to work well — if you can tweak that recipe and put that in, that gives you flexibility.”
In the brains of most animals — from fish to birds to bees to humans — only a small percentage of RNA is edited. But within the brains of octopuses and their relatives, this occurs on a large scale, affecting more than 60%.
The researchers wondered if something in these animals’ environment might be causing all this tweaking, such as temperature. Burke decided to conduct an experiment with the help of a California two-spotted octopus, which, when scanned, is the size of a soccer ball.
“They look a lot like your typical octopus,” Burke says, “although they have a couple of iridescent blue spots to try and scare a predator away.” He says they are mischievous and good at camouflaging. Its coastal habitat in southern California and northern Mexico oscillates between warm summers and cold winters.
In the lab, Burke placed half of his octopuses in cold water and the other half in warm water. After a few weeks, he collected RNA from their brains.
“We found that there were over 20,000 different sites on different different proteins that were modified,” Burke says, with more tweaking for cooler conditions.
In response to changing temperatures, the octopuses reshaped their brains, presumably to keep their brains functioning properly. The same was true in the wild, where Burke would collect individuals in summer and winter by flushing them out of their underwater dens with an infusion of vinegar.
Octopuses can make these adjustments in less than a day. Compare that to DNA, which takes generations to change. RNA provides a more flexible alternative.
Modifying RNAs—modifying the temporary transcripts of recipes—cause changes in the proteins they tell the cell to make. For octopuses, there is no single favorite type of protein. Instead, there are multiple versions of several proteins in the animal brain, each fitting a different scenario.
“This study shows for the first time that in the same organism, under different conditions, different proteins of the same gene are expressed,” Eli Eisenberg, a physicist at Tel Aviv University. “And they have a different functional behavior that is presumably appropriate to the outside temperature.”
The inner life of an octopus
It is still not clear how these changes might affect the octopus in its daily life.
“What would be great to see in the future are the kinds of behaviors that are affected by these different types of changes — their reaction speed and their ability to camouflage,” he says. Robin Crooka neuroscientist at San Francisco State University who was not involved in the research.
Since octopuses do more liberation at lower temperatures, Crook also notes that the strategy may not help them in the face of a changing climate and warming oceans. Although these octopuses can function across a range of temperatures, she says it may not be “a viable escape mechanism from environmental change as a result of human activity.”
Although octopuses live different lives than we do, their unique brains may one day be useful to us.
“We’re trying to figure out how to capture this ability to use in treatments,” Burke explains, “such as reducing pain or fixing harmful mutations that cause disease.”
He says that octopuses have a lot to teach us.
“It’s so cool and interesting, not just from the outside, that we can all see,” Burke says. “But also from the inside.”
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