How can colorblind squids disguise themselves in different colors? Researchers have switched to advanced technology to expose a surprisingly complex brain.
There is more to squids — which belong to the family of cephalopods, including octopi and cuttlefish— than they meet the eye.
In addition, they can count, solve problems, identify patterns, and communicate via a variety of signals.
While colorblind, they can also change colors instantly, using various colors on their upper and lower bodies to blend into different backgrounds and attract potential mates.
Scholars have attracted strong interest in this complex practice over the years.
Now researchers at the University of Queensland in Brisbane, Australia, have turned to advanced technology to complete the squid’s first brain map based on MRI in 50 years.
The findings of their research now appear in the iScience journal.
“Despite intense interest and study on the complex behavioral and cognitive capacities of cephalopods, the large-scale complex cephalopod nervous systems, in particular, are an’ elephant in the room’ when it comes to knowledge gaps, with most of the work on their neuroarchitecture and function dating back more than 50 years ago,” Wen-Sung Chung said.
Chung, of the Queensland Brain Institute, and his team were particularly interested in these creatures ‘ neural ability to change color not only for camouflage but also for communication.
What they discovered was a more complex brain than the one of a rat or mouse. Their complexity was actually similar to that of a dog’s brain.
Complexity and camouflage
“These animals are vision-dominant predators, and nearly all coastal species are masters of complex coloring and camouflage based on direct chromatophore cell regulation throughout the skin,” Chung said.
“One very well-known case is about their visual communication during mating. Males can display a’ skin-powered’ alphabet and have physical fights to compete for the mate.”
“Squid will say his favorite lady’ I love you’ but they can use a different way. So it certainly isn’t an’ impulse reflection’ but a very complex system of thought in their brain.
The research team focused on the reef squid Sepioteuthis lessoniana, setting out to map the neural connections which drive these complex brains.
Instead of using classic histology — which looks section by section at the microscopic anatomy of the tissue and makes “very little and slow progress” on such large and numerically complex brains — Chung and team turned to MRI.
“For the vertebrate model animals, sophisticated molecular methods and imaging techniques have been developed in large measure. We essentially adapted the mouse brain research ideas and techniques with a lot of adjustments to make the first high-resistance squid brain imaging work,” Chung said.
Squids have more complex brains than rats
Some cephalopods have more than 500 million neurons, they found. The resourceful rat is 200 million in comparison, and the ordinary mollusk is 20,000 of it.
This amount also exceeds that of rats and mice, and is more comparable to what the brain of a dog contains.
“This the first time modern technology has been used to explore the brain of this amazing animal, and we proposed 145 new connections and pathways, more than 60% of which are linked to vision and motor systems.”
– Wen-Sung Chung
“We can see that many neural circuits are devoted to camouflage and visual communication, giving the squid a remarkable ability to evade predators, hunt, and interact directly with complex color changes.”
The first mesoscale brain map took some 4 years for Chung and team to come up with.
“It’s like we finally got an early stage Google map which helps us to navigate the complex brain lobes of these soft bodied creatures with a solid background of information.”
The study also showed that cephalopod nervous systems had evolved similarly to vertebrating central nervous systems in some respects, independently. This supports current theories of converging evolution.
“This was the first step towards providing a map of structural connections in a squid brain,” Chung said. “This may help scientists investigate certain different brain lobes or regions to analyze how these relatively smart, but ancient mollusks, animals evolve into these abilities.
” I concentrate on their vision-related skills, such as why and how they can do colorblind camouflage, and how they can see the polarization signals, which are invisible to most aquatic creatures, for my own personal interest.
In the future, Chung and colleagues are looking at a comparison of brain architecture among cephalopods— including vampire squid, solitary octopus, paired-bond octopus, cuttlefish, and a few unusual deep-sea squids— to see if their brains have evolved differently by environment.
We also seek to understand how the signal processing takes place in this complex brain.
“While the field of soft robotics is increasingly interested in using octopus body plans as biological engineering blueprints— for example, their limbs and polarization vision — we are hoping new findings will lead to a new animal model,” Chung explained.
He concluded that this groundbreaking model “combines various sensory and neural access mechanisms into bio-inspired applications such as soft bodied robotic design and a new generation of artificial intelligence algorithm design”
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