Scientists have known that an octopus is an intelligent animal with a complex nervous system like most cephalopods. But now researchers show that microRNAs play a significant role in the development of octopus brains just like in humans.
Previous studies have revealed that cephalopods and humans once shared a common ancestor, which is a worm-like animal with minimal intelligence and simple eyespots. But it went on to evolve into different groups of organisms: vertebrates and invertebrates. The former represents primates and mammals and developed large complex brains with diverse cognitive abilities, while the latter did not but with the exception of cephalopods.
MicroRNAs Responsible for Complex Brains of Octopuses
Researchers led by the Max Delbrück Center and Dartmouth College in the United States discussed in the paper, titled "MicroRNAs Are Deeply Linked to the Emergence of the Complex Octopus Brain" published in Science Advances, explain that an octopus has a massively expanded repertoire of microRNAs in their neural tissue that reflects similar developments in vertebrates.
Professor Nikolaus Rajewsky exclaimed that this might be what connects octopuses and humans. He explained that this finding most likely means that the microRNA plays a fundamental role in the development of complex brains in both cephalopods and vertebrates, SciTechDaily reported.
Rajewsky said that he once read a genetic analysis on octopuses that points to a lot of RNA editing that may occur in them. That means octopuses make extensive use of the enzymes that recode their RNA, which inspired Rajewsky to think that these cephalopods could have other RNA tricks too aside from being good at editing.
He collaborated with other colleagues and received samples of 18 different tissue types from dead octopuses. Their findings revealed surprising secrets that a lot of RNA editing is indeed happening. Most interestingly, the discovery was found in a well-known group of microRNAs, in which a total of 12 were found.
These genes were preserved even during evolution, which means they are functionally important. Rajewsky has been studying microRNA for two decades now and knows that these genes encode small pieces of RNA that bind to mRNA and influence protein production.
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Third-Largest Expansion of MicroRNA Families
Octopuses are unique animals among invertebrates from an evolutionary perspective as they have both a central and peripheral nervous system that can act independently, per News Medical Life Sciences. For example, their tentacles remain sensitive to touch and can still move even if they lose one of them.
The reason behind this could be due to their complex brains. In many instances, these cephalopods have demonstrated their intelligence as well as curiosity, and ability to remember things. They can recognize people and like some of them more than others. Scientists also believe that octopuses dream since they change their colors when they sleep.
Dr. Grygoriy Zolotarov, the lead author of the study, said that the discovery of microRNAs in octopuses is considered to be the third-largest expansion of microRNA families in the animal kingdom, especially outside of vertebrates. In comparison to mollusks who also share a similar ancestor, only have five new microRNA families but octopuses acquired 90.
Rajewsky said that looking at octopuses is very different from looking at a fish. He claims that the eyes of an octopus exude a sense of intelligence that cannot be seen in the eyes of a fish but is similarly complex to a camera or human eyes.
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