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The evolution of cephalopods is even stranger than we thought!

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A surprising study suggests that cephalopods evolve differently from almost every other organism on the planet. Octopuses, squid and cuttlefish can in fact regularly modify their RNA sequences (ribonucleic acid) in order to adapt to their environments. 

Over the course of the past sixty years, squid and octopuses have literally invaded the seas and oceans and their population has been exponentially increasing. Cephalopods are in fact able to adapt faster than other marine animals to the harmful changes that the ocean is constantly undergoing, such as global warming, pollution of the marine environment and the depletion of water resources. But how do they do it? A study recently led by biologist Joshua Rosenthal, from a US marine biology laboratory, suggests that octopuses as well as certain species of squid and cuttlefish regularly modify their RNA sequences (ribonucleic acid) in order to adapt to their environment.

In multicellular animals, these changes usually occur via genetic mutation in the DNA. In order to simplify this process, imagine a kitchen. The DNA is the recipe and the RNA is the chef following the recipe in each cell, and ensuring there is enough protein produced to look after the organism. Except that the RNA is not content to blindly follow instructions. From time to time, it improvises, adding or changing certain ingredients. We call this RNA editing, which is in fact post-transcriptional modification of the RNA, which changes the existing coding sequence of the DNA.

When such a process takes place, it can change the way in which the proteins function, allowing the organism to refine its genetic information, without undergoing genetic mutations. But the majority of organisms do not use this method, as it can lead to more problems than solutions. Thus, the majority of organisms, like us, don’t take the risk. But it appears that cephalopods have decided otherwise: “With cephalopods, it’s not the exception, it’s the rule. A rule which means that the majority of proteins are in the process of modification”, explains the co-author of the study Eli Eisenberg, biophysicist in the University of Tel Aviv, Israel.

In 2015, researchers discovered that in fact squid edit over 60% of the RNA in their nervous system. These modifications essentially modify the physiology of the brain, without a doubt in order to adapt to diverse temperature conditions in the ocean. More surprising still, this new study suggests that at least two species of octopus and one species of cuttlefish do exactly the same thing. The researchers are now asking whether RNA editing could contribute to these animals’ remarkable intelligence.

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