Octopus brain diversity study reveals


Day octopus (Octopus cyanea)

Source: National Marine Sanctuaries, via Wikimedia Commons. Public domain.

In a new study, researchers at the University of Queensland used advanced magnetic resonance imaging (MRI) scans to visualize the brains of several species of octopus. The conclusions, published in Current biology, shed new light on the brains of octopus and reveal a previously unknown neuroanatomical diversity.

Exceptional octopuses

Our current knowledge of octopus brain anatomy and associated behavior is primarily based on studies of one species, the nocturnal European octopus. Common octopus. But octopus species vary widely in their ecological niches, habitats and behaviors. Some species live in visually complex and crowded coral reefs, while others inhabit deeper waters, which are relatively featureless and more empty. Some species are active during the day, while others are nocturnal. And among the octopuses, there are some species that are masters of camouflage and some that have demonstrated complex cognitive abilities.

Yet how these different ecologies and behaviors are reflected in the octopus’ central nervous system was largely unknown. Researchers used high-resolution MRIs to create detailed, three-dimensional, digital images of octopus brains and show how brain development is linked to animal lifestyles and environments.

Totti, via Wikimedia Commons.  Distributed under CC BY-SA 4.0 license.

Blue-striped octopus (Hapalochlaena fasciata)

Source: Totti, via Wikimedia Commons. Distributed under CC BY-SA 4.0 license.

Lead author Wen-Sung Chung and colleagues chose four species to study, including a deep-sea octopus (Vampyroteuthis infernalis, the vampire squid), a solitary nocturnal species (Hap alochlaena fasciata, the octopus with blue lines) and two inhabitants of different reefs active during the day (Abdopus capricornicus and Cyan octopus, the octopus of the day).

Chung says these last two species of diurnal octopus are interesting for several reasons. In addition to being active during the day and possessing excellent camouflage, they regularly interact with other animals.

“We know that most octopuses are solitary and rarely interact with others outside of mating season,” says Chung. “But these octopuses often interact with others of the same species as well as with animals of different species.”

The octopus of the day, Cyan octopus, for example, has been documented to hunt in conjunction with reef fish and can even communicate with fish using distinctive gestures.

Brain complexity and lifestyle

Overall, Chung and his colleagues found that the enlargement, division and folding of the visual and learning lobes of the octopus brain are associated with their habits and habitats.

For example, the vampire squid, Vampyroteuthis infernalis, lives in the deep sea and has a slow pace of life with limited behavioral interactions. It also has a less complex and smoother brain than species that inhabit shallower waters and more complex environments. These reef-living diurnal octopuses have more complex brain structures with more folds.

Monterey Bay Aquarium Research Institute (MBARI), via Wikimedia Commons.  Distributed under CC BY-SA 4.0 license.

Vampire squid (Vampyroteuthis infernalis)

Source: Monterey Bay Aquarium Research Institute (MBARI), via Wikimedia Commons. Distributed under CC BY-SA 4.0 license.

“This brain folding was speculated in octopuses because more complex brains with more folds can increase the ability to support advanced cognition or learning,” Chung explains. Folding increases the area and volume of the brain, and in vertebrates, more brain folds are an indicator of increased size, complexity, and information processing capacity.

Additionally, Chung and his colleagues found that in reef octopuses, their vertical brain lobe (which plays a role in learning and memory) is made up of seven subdivisions. Previous studies of the solitary and the nocturnal Common octopus showed that it only had five subdivisions. Chung says these species may have more brain subdivisions and folds in order to support their behavioral complexity.

Secrets of cephalopods

These findings are intriguing but raise more questions for Chung. One of these is why octopuses invest so much energy in developing their brains when they only live for about a year.

Totti, via Wikimedia Commons.  Distributed under CC BY-SA 4.0 license.

Day octopus (Octopus cyanea)

Source: Totti, via Wikimedia Commons. Distributed under CC BY-SA 4.0 license.

Another mystery is that they are color blind, but they do incredible feats of camouflage. Chung says their ability to see polarized light could be a factor. His team has developed a polarization vision camera, allowing them to see what the octopus sees, and an ongoing project is studying how octopuses use different properties of light, including polarization, in their camouflage.

“They are iconic marine animals, but we know very little about them,” says Chung. “I hope our study can spark more interest in these unique animals and stimulate more research into their brains and behavior. There is a lot we can learn from cephalopods.


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