Although it has long been known that octopuses are more intelligent than most invertebrates, a recent finding points to one possible explanation: a particular chemical similarity to the human brain.
A large number of 'jumping genes' or transposons, which have the ability to copy themselves or move across the genome, are present in both the human genome and the octopus genome. Even though not all of them are active, these transposons are thought of as the building blocks of evolution.
In a recent research, transposons from the LINE (Long Interspersed Nuclear Elements) family, which are also prevalent in the human brain, were located in the area of the octopus brain that controls cognitive functions.
"I literally jumped on the chair when, under the microscope, I saw a very strong signal of activity of this element in the vertical lobe, the structure of the brain which in the octopus is the seat of learning and cognitive abilities, just like the hippocampus in humans," says Giovanna Ponte, a scientist from the Italian Stazione Zoologica Anton Dohrn research facility.
Because LINE transposons are most active in the hippocampus, which is where learning processes are controlled, and recent research has shown how they are carefully regulated in the human brain, it is believed that they are connected to learning and memory.
The common octopus (Octopus vulgaris) and the Californian octopus (Octopus bimaculoides) both have these jumping genes in the same location in their brains, which leads scientists to believe they may have discovered a key factor contributing to the high intelligence displayed by these marine animals.
The study implies that there is more going on here and that there is a direct link to the complexity of the nervous system, including the brain. Transposons are known to employ molecular copy-and-paste and cut-and-paste methods.
"The discovery of an element of the LINE family, active in the brain of the two octopuses species, is very significant because it adds support to the idea that these elements have a specific function that goes beyond copy-and-paste," explains computational genomicist Remo Sanges of the Italian research center Scuola Internazionale Superiore di Studi Avanzati.
Additionally, the scientists believe that we may be witnessing an instance of convergent evolution, in which comparable features arise independently in species that are not even remotely related to one another yet serve to give the same adaptation—in this case, greater cognitive ability.
Scientists are still discovering neurological traits and evolutionary strategies that distinguish octopuses from other invertebrates and bring their brain activity and structure closer to that of mammals.
"The brain of the octopus is functionally analogous in many of its characteristics to that of mammals," according to Stazione Zoologica Anton Dohrn scientist Graziano Fiorito.
"For this reason, also, the identified LINE element represents a very interesting candidate to study to improve our knowledge on the evolution of intelligence."
The research has been published in BMC Biology.
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