Cell subissue: How did the brains of squid and octopuses come about

Cephalopods — including octopuses, cuttlefish and their cuttlefish cousins — are capable of performing some truly charismatic behaviors
.
They can quickly process information, change shapes, colors, and even textures to blend in with their surroundings
.
They also communicate, show signs of spatial learning, and use tools to solve problems
.
They are so smart that they can even get bored
.

It's no secret: cephalopods have the most complex brains
of all invertebrates on Earth.
However, this process remains a mystery
.
Basically, scientists have been wondering how cephalopods got their big brains in the first place? A lab at Harvard University has studied the visual systems of these mollusks — the focus of two-thirds of their central processing tissue — and believes they are close to
figuring it out.
The process, they say, looks very familiar
.

Researchers at the FAS Center for Systems Biology describe how they used a new real-time imaging technique to observe the production of neurons in embryos, in near real time
.
They were then able to track these cells
through the development of the retinal nervous system.
What they saw surprised them
.

The behavior of the neural stem cells they tracked was strikingly similar
to that of these cells during the development of the vertebrate nervous system.
This suggests that although vertebrates and cephalopods began to differentiate 500 million years ago, not only did they use similar mechanisms to make their large brains, but that this process and the way cells move, divide, and form may have fundamentally mapped out the blueprints
needed to develop such nervous systems.

"Our conclusion is surprising because much of what we know about vertebrate nervous system development has long been thought to be specific to this lineage," said
Kristen Koenig, a John Harvard Distinguished Fellow and senior author of the study.
"By looking at the fact that this process is very similar, it shows us that these two very large nervous systems that evolved independently used the same mechanism to structure them
.
" This suggests that the same mechanisms that animals use during development — these tools — may be important
for building large nervous systems.
”

The researchers focused on the retina of the squid, which is called Doryteuthis pealeii, which is more simply a long-fin squid.

This squid can grow up to a foot long and is abundant in
the northwestern Atlantic Ocean.
As embryos, they have big heads and big eyes and look very cute
.

The researchers used techniques similar
to those popular when studying model organisms such as fruit flies and zebrafish.
They invented special tools and used a cutting-edge microscope to take high-resolution images every ten minutes to observe the behavior
of individual cells for hours on end.
The researchers used fluorescent dyes to label the cells so they could map them and track them
.

This real-time imaging technique allowed the team to look at stem cells known as neural progenitor cells and how they are organized
.
These cells form a special structure called pseudolayered epithelium
.
Its main feature is that the cells are elongated so that they can be densely arranged
.
The researchers also saw the nuclei of these structures move
up and down before and after division.
They say this movement is important
to keep the organization organized and continue to grow.

This structure is ubiquitous
during the development of vertebrate brains and eyes.
Historically, this has been thought to be one of the
reasons why vertebrate nervous systems have been able to grow so large and complex.
Scientists have observed this type of neuroepithelial cell in other animals, but the squid tissue they observed in this example was unusually similar
to vertebrate tissue in size, tissue, and the way the nucleus moved.

The study was led
by research assistants in Koenig's lab Francesca R.
Napoli and Christina M.
Daly.

Next, the lab plans to observe how different types of cells emerge
in cephalopod brains.
Koenig wanted to determine whether they were expressed at different times, how they decided to become one neuron rather than another, and whether the behavior was similar
across species.

Koenig is excited
about potential discoveries in the future.

"One of the great takeaways from this kind of work is to study the value
of diversity in life," Koenig said.
"By studying this diversity, you can actually go back to the basic idea
of our own development and biomedical-related issues.
" You can really answer these questions
.
”