KU Leuven researchers expose some surprising similarities with animals that are 600 million years of evolution removed from us.
Although octopuses have been wandering a different evolutionary path for around 600 million years, the formation of their brain cells shows some surprising similarities with that of humans. This is shown in research from developmental biologists at KU Leuven. These similarities prove that this method of brain development - whereby brain cells only migrate to the parts of the brain where they will carry out their function after they form - is necessary in order to be able to form complex brain structures.
Particular to the development of our brain cells is that it does not take place in the location where they will carry out their function. Brain cells develop from brain stem cells, which form a thin layer around the cerebral cavities. When brain stem cells grow into functional brain cells, they then need to make a journey to their final place in the brain. "This unusual phenomenon is visible in the brains of vertebrates such as humans, but we had no idea whether this migration process was important for complex brain formation in general," says Eve Seuntjens, Professor of Developmental Biology at KU Leuven. "In order to answer that question, you need to search for an animal with an equally complex brain that is as far removed from us in evolutionary terms as possible. Only when there are similarities between animals with a completely different evolutionary starting point does that suggest that this method of brain development is not a coincidence."
Octopuses as a model for human brains
The eight-armed octopuses turned out to be the answer to this question. They have a complex brain structure, which they make good use of to boot. Octopuses are able to play, to dream, to use objects and even to plan ahead. These invertebrates have a completely different evolutionary starting point, which nonetheless has somehow led to behaviour that we as humans recognise.
"We built an ideal environment for octopus eggs to develop in at the lab. Because the eggs are transparent, we were easily able to monitor every phase of the development. To our great surprise, brain cells in octopuses display the same migratory behaviour as human brain cells. This proves that the migration of brain cells is fundamental to the formation of complex brains," says post-doctoral researcher Astrid Deryckere. "In the next phase, we will try to find out how you get from this ingenious structure to actual brain activity and how this then leads on to certain behaviours," adds Professor Seuntjens.