Researchers at the Max Delbrück Center for Molecular Medicine have proposed that the intricate human brain shares notable parallels with the nervous system of octopuses. The study, which appears in Science Advances, explores how neural complexity in these creatures mirrors the astonishing versatility seen in our own species and hints at deep evolutionary connections in cognitive biology.
Earlier work showed that octopuses can alter their RNA sequences rapidly when the environment shifts. This flexibility is often described with an analogy: DNA acts as a master cookbook, while RNA carries a separate sheet with the actual recipes. Modifying information on a separate page is far simpler than reprinting an entire volume, making quick adaptation feasible after environmental changes.
The new work argues that this RNA adaptability is linked to the repertoire of microRNAs, tiny molecules that bind to specific sites on RNA. In octopuses, such microRNAs can adjust the production activity of the proteins created by RNA, effectively tuning how much of a given substance is produced to meet changing needs.
Researchers analyzed 18 tissue samples from several cephalopods, including Octopus vulgaris, Octopus bimaculoides, and the squid Euprymna scolopes. The findings supported the idea that microRNA networks play a crucial role in the brain and nervous tissue of these animals, with 138 microRNA families identified and 42 of them being new milestones in cephalopod biology.
Alongside this expansion, octopuses demonstrated a remarkable level of microRNA diversity, ranking high among both invertebrates and vertebrates. The data show that their microRNA inventory matches the breadth seen in vertebrate species such as chickens and frogs, underscoring a surprising parallel in molecular complexity.
When compared to oysters, which share a distant ancestor with cephalopods, the picture becomes even more striking. Oysters have acquired only a handful of new microRNA families since diverging from that common ancestor, whereas octopuses have added a much larger set. This level of microRNA growth, with roughly ninety new families in octopuses, contrasts with humans, where the genome encodes about two thousand six hundred mature microRNAs.
The researchers contend that this surge in microRNA variety may be a key factor behind the sophisticated neural capabilities observed in cephalopods. The broader implication is that a rich microRNA landscape could support complex brain functions, contributing to cognitive traits that rival those seen in other highly intelligent animals.
In addition to these molecular insights, the study reinforces the idea that the cephalopod brain is not a single centralized organ but a distributed network. A squid, for instance, possesses a brain that approaches the complexity of a domestic dog, and octopuses have been observed to dream in some experiments, a phenomenon rarely confirmed in invertebrates. Unlike many other creatures, a substantial portion of their roughly 500 million neurons resides in their arms, enabling each arm to make autonomous decisions and continue to respond to stimuli even when separated from the main body. This distributed architecture helps explain how these animals can exhibit flexible and adaptive behavior across diverse environments. [Source: Science Advances; attribution to the involved research teams]