What Are the Similarities Between Octopus and Human Brains?

Intelligent animals with sophisticated neurological systems include cephalopods, which also include squid, cuttlefish, and octopuses. The Max Delbrück Center’s Nikolaus Rajewsky and colleagues have recently published evidence in Science Advances suggesting their evolution is linked to a substantial expansion of their microRNA repertoire.

A primordial wormlike animal with low intelligence and simple eyespots is the last common ancestor of humans and cephalopods if we go back far enough in evolutionary history. Later, the animal kingdom can be roughly classified into two categories: vertebrates and invertebrates.

While invertebrates did not progress to having complex brains capable of a wide range of mental operations, vertebrates like primates and other mammals did. Except for those with a head (cephalopods). Scientists have pondered for a long time the question of why these mollusks, of all animals, were able to evolve such a sophisticated neurological system.

Now, an international group spearheaded by scientists from the United States’ Max Delbrück Center and Dartmouth College has proposed an explanation. They write in Science Advances about how octopuses, like vertebrates, have evolved to have a vastly augmented repertoire of microRNAs (miRNAs) in their neural tissue.

Professor Nikolaus Rajewsky, the paper’s senior author and director of the Systems Biology of Gene Regulatory Elements Lab at the Berlin Institute for Medical Systems Biology of the Max Delbrück Center (MDC-BIMSB), explains, “So this is what connects us to the octopus.” He says the discovery suggests miRNAs are crucial to the formation of sophisticated brains.

In 2019, Rajewsky perused an article regarding octopus genetic research. Researchers found that cephalopods use RNA editing enzymes frequently, suggesting that these animals frequently recode their RNA.

This led Rajewsky to speculate that octopuses might be capable of “additional RNA tricks up their sleeve in addition to editing.” The maritime research station Stazione Zoologica Anton Dohrn in Naples began working with him, and they provided him with samples of 18 different types of tissue from previously-deceased octopuses.

Somewhat unexpectedly, the investigations showed that “there was actually a lot of RNA editing going on, but not in places that we believe to be of interest,” as Rajewsky put it. Most intriguing was the rapid increase in the number of microRNAs, a previously recognized class of RNA genes.

Fourty-two new miRNA families were identified, almost entirely within the brain and other neural tissues. The team concluded that these genes must have served some useful purpose for cephalopods throughout evolution.

Rajewsky has spent over 20 years studying microRNAs. These genes encode short segments of RNA that bind to messenger RNA and regulate protein synthesis without being translated into messenger RNA. The conservation of these binding sites throughout cephalopod evolution is further evidence of the functional value of these new miRNAs.

What Are the Similarities Between Octopus and Human Brains
What Are the Similarities Between Octopus and Human Brains

New MicroRNA Families

Lead author Gregory Zolotarov, MD, a Ukrainian scientist who interned in Rajewsky’s group at MDC-BIMSB while completing medical school in Prague, and afterward, claims that this growth of microRNA families is the largest outside of vertebrates.

To put this into perspective, since their common ancestor, octopuses, and oysters diverged, the former has developed 90 new families of microRNAs, while the latter has developed only five. Further, as Zolotarov points out, oysters do not have a stellar reputation for brainpower.

Years ago, on a late-night visit to the Monterey Bay Aquarium in California, Rajewsky first became interested in octopuses. I came across this monster resting on the aquarium’s floor, and we stared at each other for what seemed like several minutes. “It’s not very scientific, but their eyes definitely convey a sense of intelligence,” he adds of octopuses, contrasting them with fish. Octopuses’ “camera” eyes are as sophisticated as our own.

There is nothing else quite like an octopus when looking at evolution among invertebrates. They have a fully functional, autonomous central neural system in addition to a peripheral nervous system. Even after being amputated, an octopus’s tentacle will still respond to touch and be able to move.

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Perhaps the fact that octopuses use their arms very consciously, as instruments to open shells, explains why they are the only cephalopods to have evolved such advanced cognitive abilities. Additional to being exceedingly interested and having good memories, octopuses also display other characteristics of intelligence. Not only that, but they are able to distinguish between different persons and develop preferences.

Scientists have discovered that as they sleep, their skin color and structure alter, leading them to believe that they dream.

What Are the Similarities Between Octopus and Human Brains
What Are the Similarities Between Octopus and Human Brains

Alien-Like Creatures

If you want to meet an alien, you should go scuba diving and make friends with an octopus, adds Rajewsky. Now, he wants to team up with other European octopus researchers to establish a network that would facilitate more communication and collaboration. While the octopus community of behavioral scientists is still very tiny, interest in the species is expanding, according to Rajewsky.

He finds it fascinating to examine a cognitive system that emerged separately from our own. However, this is not a simple task: “They lose interest quickly if you use food rewards for exams. And if my coworkers are to be believed, “Rajewsky argues.

Due to the fact that octopuses aren’t “standard model organisms,” as Zolotarov puts it, “our molecular-biological tools were very limited.” “Therefore, it is unclear at this time which cell types express the novel miRNAs.” For the next step, Rajewsky and his team hope to implement a technique created in their lab that will allow them to see individual cells in octopus tissue at the molecular level.

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Last Lines

Cephalopods like squid, cuttlefish, and octopuses are intelligent animals with complex nervous systems. Nikolaus Rajewsky of the Max Delbrück Center, along with his coworkers, has published evidence in Science Advances that suggests their evolution is connected to a significant increase in their microRNA repertoire.

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