It took a valiant effort to map out the optic lobes of the brains of octopuses, cell by cell. This revealed a system with striking similarities and significant differences to ours.
These parallels are especially interesting as they reveal the coincidental nature, if not accidental, of convergent evolutionary processes.
Humans and octopuses derived from a common ancestor approximately 500 million years ago. However, our vision systems have evolved in uncanny ways to solve similar problems. For example, vertebrates are independent of octopuses in terms of their morphologies, lifestyles and environments. However, they both developed a pupil as well as a lens that directs light onto a retina.
Soft-bodied cephalopods – squids, octopuses, and cuttlefish – have the largest brains of any invertebrate, with two-thirds of their central processing tissue reserved just for sight.
These ocean creatures are able to see well in darkness, as you would expect. The skin of an Octopus It contains the same pigment proteins that its eyes, which allows the dermis to “see” its surroundings and camouflage accordingly.
Researchers from the University of Oregon have completed the first comprehensive mapping of the octopus’ visual system. This required the analysis of more than 26,000 cells collected during dissections of two juveniles. California two-spotsOctopus bimaculoides) Octopuses.
The brains of these young octopuses appeared to be fully functional, but they were still in the process of growing. Nearly a third of neurons in the visual lobes appeared to be still developing.
When researchers sequenced the cephalopod cells they found four main populations, each releasing a different chemical signal – some released dopamine, some released acetylcholine, some released glutamine, and others signaled with both dopamine and glutamine.
These neurotransmitters can also be found in vertebrate brains like ours. However, there were smaller clusters of neurons in the cephalopod’s brain that produced unique chemicals.
For example, it was discovered that octopamine is produced by cells in the optic lobe. This neurotransmitter is closely related to noradrenaline, which is a hormone found in our bodies.
It is still unknown what octopamine does to octopuses. This mystery will take more research. It is however known that it is active in the brains and nervous system of fruit flies, as well as in other invertebrates, for functions related to getting their bodies and nervous system ready for action.
Future efforts could benefit from this new octopus brainmap. Researchers discovered several genes and signaling molecules unique to octopuses that could help influence neural development.
These factors could be removed or muffled in further studies to determine their role in the brain of cephalopods.
The authors state that the atlas they present provides a roadmap to such studies and, more generally, a path towards unlocking the functional, development, and evolutionary logic in the cephalopod visual systems. Send an email.
The octopus’ visual system is similar to that of vertebrates. However, it is not structured in the same manner as ours. Fundamentally, the cephalopod brain has a different organization and a variety of cell types.
“At the obvious level, the neurons don’t map onto each other – they’re using different neurotransmitters,” explainsCris Niell is a biologist from the University of Oregon.
“But they might be doing the same types of computations but in a different manner.”
One of the most fundamental questions is how the cephalopod’s visual system develops. The brains of octopuses take years to develop. But how can information from their retina be used to direct this growth?
Photoreceptors in vertebrates don’t directly connect to the brain. They instead relay messages to other neurons. Cephalopods have photoreceptors that connect directly to the optic lobes of the brain.
Future research will be needed to understand how these messages influence the development and integration of mature visual systems.
Niell and his collaborators are continuing their work on the remaining third of an octopus’ brain.
The study was published by Current Biology.
