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How Big Is An Octopus Brain

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One Strange Thing Is That An Octopus Doesnt Know Where Its Arm Is Unless It Can See It

Why the octopus brain is so extraordinary – Cláudio L. Guerra

The arm is sending signals about taste and texture but no details about location and orientation. In our bodies we have an ability called proprioception that lets us know where our arms are even if they are out of sight. We can scratch our backs with precision because we know where our hand is relative to our back.

Another interesting question about having eight arms covered with suckers how do they keep all those arms from sticking to each other and getting all tied up in knots? Especially when they dont know exactly where their arms are. Turns out that octopus skin secretes a chemical to keep the suckers from sticking to it. Sounds essential for avoiding a tangled mess!

Alien Intelligence: The Extraordinary Minds Of Octopuses And Other Cephalopods

After a startling encounter with a cuttlefish, Australian philosopher Peter Godfrey-Smith set out to explore the mysterious lives of cephalopods. He was left asking: why do such smart creatures live such a short time?

Inches above the seafloor of Sydneys Cabbage Tree Bay, with the proximity made possible by several millimetres of neoprene and a scuba diving tank, Im just about eyeball to eyeball with this creature: an Australian giant cuttlefish.

Even allowing for the magnifying effects of the mask snug across my nose, it must be about 60cm long, and the peculiarities that abound in the cephalopod family, that includes octopuses and squid, are the more striking writ so large.

Its body shaped around an internal surfboard-like shell, tailing off into a fistful of tentacles has the shifting colour of velvet in light, and its W-shaped pupils lend it a stern expression. I dont think Im imagining some recognition on its part. The question is, of what?

It was an encounter like this one at exactly the same place, actually, to the foot that first prompted Peter Godfrey-Smith to think about these most other of minds. An Australian academic philosopher, hed recently been appointed a professor at Harvard.

Charming anecdotes like this abound in Godfrey-Smiths book, particularly about captive octopuses frustrating scientists attempts at observation.

The Neurosecretory System: An Analog To The Hypothalamus

Neurosecretion is pivotal for orchestrating essential body functions and metabolism and is considered a common metazoan phenomenon . Neurosecretory cells are characterized by large dense core vesicles that are not produced locally , but in the cell soma and have to travel along an axon to reach their release site. In addition, neurosecretory centers are usually clustered in specific areas.

In vertebrates, the hypothalamus is located at the rostro-ventral region of the forebrain and among cellular-types are a set of neurosecretory cells . The evolutionary origins of neurosecretory cells can probably be traced to a common bilaterian ancestor or pre-bilaterian animal such as a cnidarian .

The neurosecretory centers of molluscan nervous systems tend to be distributed in the cerebral ganglia . Alternatively the cells tend to be organized into distinct clusters in the preoral regions associated with the esophagus, or the stomatogastric nervous systems . In cephalopods, neurosecretory cells are mainly found in the buccal , sub-pedunculate , and in part of dorsal basal lobes again in the supra-esophageal mass . Surrounding the brain there are several other potential neurosecretory regions such as those present in the sub-buccal and sub-pedunculate areas and in the optic gland, and the neurovenous tissue of the vena cava .

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This Means That Each Individual Octopus Must Discover And Learn Everything That It Needs To Know To Survive On Its Own

Imagine that! No parents around to tell the youngsters how to behave. For some human teens this might seem like a dream come true! But for a species as a whole, it results in major limitations. Not being able to pass on the wisdom gained by previous generations means a whole lot of learning gets repeated and rediscovered by each succeeding generation.

How Well Developed Is Octopus Vision

Cephalove: A View of the Octopus Brain.

When you look at any of the 300 or so octopus species, you will notice that three physical characteristics are held in common by all of them. They have eight arms, one large head, and two large eyes.

A closer examination of the eye of an octopus reveals that it is a very complex structure. An even deeper study of how the eye is integrated into the neurology of the octopus unveils how much more impressive octopus vision is.

Succinctly stated, octopus vision is very advanced.

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If you were an octopus, would you view the world from eight different points of view? Nine?

The answer may depend on how many brains an octopus has, or, to say it another way, whether the robust bunches of neurons in its coiling, writhing, incredibly handy arms bestow on each of them something akin to a brain. Is an octopus a creature ruled by a single consciousness centered in its large brain, or, by dint of its nerve-infused legs, a collaborative, cooperative, but distributed mind?

The idea of a distributed mind among animals is not new, according to Peter Godfrey-Smith, who focuses his efforts on the philosophy of science. Experiments indicate that when a bird learns a skill using only a single eye, and is later tested while being forced to use the other eye, the learning does not transfer well.

This suggests that animal minds lack the cohesiveness that humans have, said Godfrey-Smith, a philosophy professor at Harvard. It may have something to do with consciousness. Maybe it acts as a unifying tool.

Godfrey-Smith has been swimming with octopuses for years, diving in and around Sydney Harbour during summer breaks in his native Australia. It is only recently, however, that he noticed that supremely camouflaged octopuses were pretty common there.

For years, I was swimming and diving in this area of Sydney Harbour. I had an idea they were there, but didnt know what to look for, Godfrey-Smith said.

Cephalopod Brains: An Overview Of Current Knowledge To Facilitate Comparison With Vertebrates

  • 1Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Naples, Italy
  • 2Division of Biomedical Sciences, St. Georges University of London, London, United Kingdom

Cephalopod and vertebrate neural-systems are often highlighted as a traditional example of convergent evolution. Their large brains, relative to body size, and complexity of sensory-motor systems and behavioral repertoires offer opportunities for comparative analysis. Despite various attempts, questions on how cephalopod brains evolved and to what extent it is possible to identify a vertebrate-equivalence, assuming it exists, remain unanswered. Here, we summarize recent molecular, anatomical and developmental data to explore certain features in the neural organization of cephalopods and vertebrates to investigate to what extent an evolutionary convergence is likely. Furthermore, and based on whole body and brain axes as defined in early-stage embryos using the expression patterns of homeodomain-containing transcription factors and axonal tractography, we describe a critical analysis of cephalopod neural systems showing similarities to the cerebral cortex, thalamus, basal ganglia, midbrain, cerebellum, hypothalamus, brain stem, and spinal cord of vertebrates. Our overall aim is to promote and facilitate further, hypothesis-driven, studies of cephalopod neural systems evolution.

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How Many Brains Does An Octopus Have

An octopus has one brain. It is located in its head. However, unlike other creatures, not all of its neurons are located in its brain.

What? Look at it this way, imagine that the stuff that provides you with your brain processing power, instead of being solely in your head, were to be distributed throughout your arms and legs. That is the case with the octopus.

An octopus has approximately 500 million neurons. Of those, 30 to 40 percent reside in its formal brain located in its head. The remaining neurons are distributed throughout the animals eight arms.

The schematic structure for this distribution of neurons throughout the octopus is what gives rise to popular, although erroneous, myths that an octopus has multiple brains. You may read comments about an octopus having nine or ten brains. While they do not have multiple brains, the truth about the neural network of an octopus is still quite amazing.

The neurons that are in the arms link up to a denser cluster of neurons that is located at the base of each arm. These clusters are known as ganglia. Having eight arms, this means that an octopus has eight ganglia.

Each ganglia is connected to the formal brain of the octopus and are subordinate to it but also operate in an autonomous fashion. Each ganglia can receive sensory input from the arms and process it in a remote way without having to route it first to the main brain.

Fun Facts About Giant Pacific Octopuses

Octopus Steals Crab from Fisherman | Super Smart Animals | BBC Earth

1. Giant Pacific octopuses can grow to 29.5 feet wide from the tip of one arm to the tip of another and 44 pounds .

2. Giant Pacific octopuses can change color in one-tenth of a second.

3. Giant Pacific octopuses can be found more than 330 feet underwater.

4. Female giant Pacific octopuses never leave their eggs during the brooding process and die shortly after from self-cannibalization.1

5. Female giant Pacific octopuses lay 18,000 to 74,000 eggs that are the size of a grain of white rice.

6. Giant Pacific octopuses have short lifespans of only 2 to 3 years on average.

7. Giant Pacific octopuses have 2,140 to 2,240 suction cups on their arms, giving them a powerful grip and sense of taste and smell.2

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Signs That Octopuses Can See Color

More recent studies indicate that octopuses may very well be able to see in color.

This would explain why octopuses exhibit color detection abilities both in the wild and in captivity. It also explains why their skin color-changing capability is sometimes used to warn other octopuses who are getting too close or during mating to attract a mate.

After all, while the ability to change skin color solely to hide from predators can be rationalized as an adaptation that developed independently of vision, using color to scare off or attract your own kind would not make sense if you could not see color.

What Color Is An Octopus Blood

The color of an octopuss blood is blue. They have blue blood because these animals have adapted to cold waters that have low oxygen levels. Thus, octopuses make use of hemocyanin, a copper-rich protein that is more efficient at transporting oxygen molecules in cold areas with low-oxygen conditions.

In comparison with hemoglobin, hemocyanin transports oxygen better in cold conditions with low oxygen levels than hemoglobin. Instead of being carried within blood cells, the hemocyanin is dissolved in the plasma. This gives the blood a bluish color, thus, the reason why the blood of octopuses is blue. The blood is blue because hemocyanin that carries oxygen around the octopuss body, contains copper instead of iron as humans have in their hemoglobin.

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The Reverberating Circuitry Model

The similarity in connectivity between the cephalopod superior frontal-vertical lobe system and the vertebrate hippocampal formation, based on matrices and reverberating feedback network structure , is the basis of this model.

Cephalopod learning capacity is not localized in certain layers or grandmother cells but is distributed within a highly redundant series of matrices with recurrent circuits. Young emphasized the similarity with the hippocampal complex but avoided any clear statement about its relationship to the cerebral cortex . Indeed, the existence of long term potentiation in the cephalopod vertical lobe maybe the basis of long term memory as it is considered in the hippocampus of vertebrates with minor molecular differences . However, the higher matrix system of cephalopods is also comparable to that of the mammalian cerebral cortex which also forms distinct cellular and matrix units .

The Associative Learning Model

15 Interesting Facts about the Octopus You Need to Know ...

As reviewed by , Young and coworkers were able to provide an associative learning model of the octopus brain based on the existence of a series of matrices that allow computation and that were considered analogous to the limbic lobe of higher vertebrates . In the octopus learning system, the small interstitial neurons and their synapses play an important role in learning by means of their sensitizing effects on reward and punishment signals coming from outside. This model explains the short fluctuations in memory recall and long-term cumulative changes via Hebbs synaptic law, that frequent stimulation of certain synapses strengthen their signals and connectivity . The associative learning of O. vulgaris has been also a model in cybernetics , and appears surprisingly similar to a more recent one, suggested for the learning system of insects , particularly of the honeybee . In the insects, the model posits on the assumption that sensory odor signals are spatio-temporally represented by synaptic sets of small intrinsic interneurons in the neuropil of the mushroom body. The reward- or punishment-conditioned stimulus of these Kenyon cells strengthens synapses with their outputs.

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Do Octopuses Have Brains

The ocean is home to an incredible collection of marine life including a fantastic group of animals called cephalopods. The class cephalopoda includes animals like the nautilus, squids, cuttlefish and octopuses. These creatures are almost alien-like, which tends to prompt a lot of questions including do octopuses have brains?.

The word cephalopoda is a greek word that translates to head-feet. This is used to describe the way that their tentacles or feet are connected to their head. I guess you could say octopuses are always thinking on their feet!

An Octopus Is As Smart As A Dog

While the brain of an octopus have quite a few things in common with humans, they are the most similar to dogs. In addition to being as smart, if not smarter than a dog, they also display all those inquisitive, friendly behaviors reminiscent of dogs.

For scientists who study animal behavior, intelligence is not about acing a calculus test or taking a car apart and putting it back together. Intelligence comprises sophisticated cognitive skills that help an animal thrive. That may include the ability to come up with solutions to the problem of finding food, for example, or a knack for planning for some challenge in the future. Intelligent animals dont rely on fixed responses to survive they can invent new behaviors on the fly.

New York Times

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Animal Behavior Associated With Octopuses

Most octopus species are solitary when they are not mating. However, a few of them are known to occur in high densities. Also, with frequent interactions, mate defending, signaling, and eviction of individuals from dens. This is probably due to the abundant food supplies as well as limited den sites. The octopus species- the pacific striped octopus has been explained to be particularly social. They live in groups that are made up of up to 40 octopuses.

An octopus hides in dens. These are usually crevices in rocky outcrops or other hard structures. However, some octopus species burrow into mud or sand. Octopuses may not be territorial but they like to remain in a home range. In search of food, they may leave the area and navigate back to the den. They comfortably do this without having to retrace their outward route. They are not migratory.

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Cognition and behaviour

What is unique about the octopus brain? Invertebrates usually have simple nervous systems. They range from the elementary neuron network of cnidarians to the most centralised neuron ganglions of worms, which probably evolved under the same pressure of the bilateral body plan and the resulting forward movement. However, these neuron networks/ganglions are not considered proper brains in biology. Cephalopods, on the contrary, are known for their large and highly centralised brain with functionally specialised parts. Yet, octopus brains lack any of the major anatomical features of vertebrate brains, having evolved from a typical snail-like ancestor. Thanks to their independent evolution from humans, octopuses brains could be an ideal model for inferring common rules governing complex brain function, or any novel neurological workarounds cephalopods have developed.


The octopuss brain is unexpectedly complex for an invertebrate. Surprisingly though, most of its neurons are not in the brain, but in their arms. In the common octopus, of the about 500 million total nerve cells, 300 million of them can be found in the arms. The arms can independently explore the surrounding environment, change colour and shape, and sense light changes. Moreover, octopuses tissues and nerves are able to regenerate completely in a few days, making them an ideal model for nerve regeneration studies.

Cephalopod genetics

Cephalopod aquaculture

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Thinking On Their Feet

Let’s look more closely now at how the nervous system behind these behaviors evolved. The history of large brains has, very roughly, the shape of a letter Y. At the branching center of the Y is the last common ancestor of vertebrates and molluskssome 600 million years ago. That ancestor was probably a flattened, wormlike creature with a simple nervous system. It may have had simple eyes. Its neurons may have been partly bunched together at its front, but there would not have been much of a brain there.

From that stage the evolution of nervous systems proceeds independently in many lines, including two that led to large brains of different design. On our lineage, the chordate design emerges, with a cord of nerves down the middle of the animal’s back and a brain at one end. This design is seen in fish, reptiles, birds and mammals.


On the other side, the cephalopods’ side, a different body plan evolved and a different kind of nervous system. Invertebrates’ neurons are often collected into many ganglia, little knots that are spread through the body and connected to one another. The ganglia can be arranged in pairs, linked by connectors that run along the body and across it, like lines of latitude and longitude. This is sometimes called a ladderlike nervous system.

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