Approximately 600 million years ago, octopuses, cuttlefish, and squids - all of which are cephalopods - branched off from the lineage that would eventually lead to humans. The octopus’ lineage consists solely of invertebrates, including cephalopods and insects. While some insects, such as honeybees and ants, exhibit complex behaviors, their nervous systems are relatively small, with a maximum of one million neurons. However, cephalopods, particularly octopuses, are an exception to this rule, boasting approximately 500 million neurons, comparable to a dog’s brain, whereas human brains possess 16 billion neurons. Octopuses are unique creatures equipped with eight arms, each containing a mini-brain. They have a ring-shaped central brain, circulate blue blood, and are powered by three hearts. The smallest species, Octopuss arborescens, is about 2 inches long. The common octopus (Octopus vulgaris), found along the east coast of the U.S., grows up to about three feet long and the largest species, the reddish pink giant Pacific octopus (Enteroctopus dofleini), may grow to 18 feet in length.
The Earth, which is 4.5 billion years old, saw the emergence of
life in the form of bacteria about 4 billion years ago. Animals appeared much
later, almost a billion years ago. Octopuses and other cephalopods share a
common ancestor from the Jurassic age, around 201.4 to 145 million years ago.
This is when the two main cephalopod lineages diverged, one with eight arms
including octopuses and another with ten arms including cuttlefish and squids.
Prior to this divergence in the Jurassic age, the common ancestor had
camera-like eyes with lenses, like our own, as do modern day octopuses. This
suggests that two vastly different lineages developed large brains and similar
vision capabilities. Despite being on completely different evolutionary paths,
nature found two distinct ways to develop minds.
The skin of an octopus is akin to a 10-megapixel screen. Its
outer layer, the dermis, contains chromatophores that hold color, iridophores
that reflect certain light wavelengths, and leucophores that also reflect
light. Despite most cephalopods reportedly being colorblind, an octopus’s skin
can sense light and respond by changing its color. This discovery implies that
an octopus can “see” with its skin. If the skin’s light sensing is connected to
the brain, the animal’s visual skin sensitivity is also dependent on its eyes.
If not, each arm might have its own independent vision. Even if the entire body
can see, it appears to be in monochrome. However, a chromatophore might act as
a filter over a light-sensitive cell, allowing a monochrome sensor to detect
color if the organism has different colored light filters and knows which ones
are in use at any given moment. Ultimately, the central nervous system is
monochromatic, but to blend in with the background so amazingly, an octopus must
be seeing in color with its skin to be able to match colors so well.
An interesting story of light is seen in the light producing
symbiosis that has been extensively studied in the Hawaiian bobtail squid, and
its relationship with the bacterium Vibrio fischeri. The bobtail
has two light organs inside their mantle which houses the symbiotic luminescent
bacteria. An example of quorum sensing, an act I discuss at length in my
blogpost on Liquid Brains, where when enough of a common life form is present
to make a quorum; with liquid brains it was with honeybees and a quorum was
with getting enough, a quorum, of bees at a prospective new nest site before
that site was chosen and the entire hive would then migrate to the new site.
Within the bobtail squid, bacteria produce light by chemical reaction, but only
if enough bacteria are around to join in. The bacteria achieve this by
detecting the local concentration of an inducer molecule, which is made by the
bacteria and gives each individual a sense of how many potential light
producers are around. When the bacteria sense a quorum of themselves is around they
start producing light, and when enough light is being produced, the squid
housing the bacteria gains the benefit of camouflage. This is because the
bobtail squid hunts at night when moonlight would normally cast its shadow down
to predators below. Their internal glowing bacteria cancel out their shadow.
Camouflage is intrinsically linked to the process of visual
perception. While it typically centers on the visual capabilities of various
predators, in the case of octopuses, it also pertains to their own visual
skills and the decision-making process involved in selecting a camouflage
strategy. As such, the ability to modify camouflage requires the development of
a method to swiftly analyze a visual scene, identify its key features, and
apply an effective camouflage pattern. This represents an exceptional cognitive
process that involves high-level decision-making. As just discussed above some,
if not most, of the decision making is taking place at the skin level under
control of mini-brains. For instance, the Cyanea
octopus, found in the Pacific coral reefs, alters its appearance more than 150
times per hour while foraging for food daily. Each change is necessary as
octopuses are mobile and continuously move into different visual environments.
They can create patterns on their skin in as little as 200 milliseconds, which
is equivalent to the speed of a human eye blink. Octopuses can sometimes mimic
stones, algae, the ocean floor, and corals, for example. They can remarkably
change their overall body shape, coloration and skin texture to match
three-dimensional objects in the distant background.
In 2015, the first complete genomic sequence of an octopus was
unveiled, and it’s astonishingly almost as large as that of humans. It also
includes hundreds of genes specific to cephalopods. A significant number of
these octopus-specific genes are expressed in their nervous systems, such as in
their arm’s suckers, mini-brains, and central brain. This explains the diverse
and unique cognitive abilities of these remarkable creatures. Additionally,
octopuses engage in the highest level of RNA editing among all animal species,
surpassing even humans. RNA editing is a process where, after a gene is
expressed by copying its DNA template into RNA, a process known as
transcription, the resulting RNA version of the gene is then cut and
reconnected in various ways and locations. This process allows the animal to
create a wide array of novel proteins using these edited RNAs as a guide. This
is done through a process called translation, where RNA-encoded information is
converted into specific types of proteins using the genetic code. This gives
the octopus a significantly larger effective genome. These protein variations
in the octopus’s nervous system can change the behavior of a given neuron by
directly or indirectly altering its firing pattern. This provides the octopus
with a multitude of ways to manipulate and control various abilities, such as
its ability to see with its skin, adjust its camouflage accordingly, learn, and
even think spatially.
Octopuses and other cephalopods' nervous systems are organized
very differently from ours. Cephalopod literally translates to the brain on the
foot. Their arms have not only the capacity to sense touch, but also detect
chemicals as in smell or taste. Each sucker on an octopus' arm may have 10,000
neurons to handle taste and touch. Hunting and foraging makes good sense for
the exploratory curiosity side of the octopus psyche especially their
engagement with novel objects. There seems to be a kind of mental
surplus in the octopus. The capacity for several types of learning is also seen
in both our own and the vastly different octopus lineage. Learning by attending
to reward and punishment, by tracking what works and what does not work, seem
to be invented independently several times over the course of evolution. There
are also more subtle psychological similarities. Octopuses, like us, seem to
have a distinction between short-term and long-term memory. Octopuses can use
tools: Octopuses can manipulate objects in their environment to achieve their
goals. For instance, they can use rocks or shells to cover the entrances of
their dens, protecting them from predators. They can also use coconut shells as
portable shelters, carrying them around and hiding inside them when needed.
Some octopuses have even been observed using sponges to wipe off dirt from
their bodies.
Additionally, Octopuses can learn and remember the layout of
complex environments, such as mazes or novel aquariums. They can use visual
cues or landmarks to find their way around and locate food or shelter. In one
experiment, octopuses were able to guide one of their arms through a maze,
where the octopus’ arm and its hundreds of suckers could not feel or smell its
way to the food, but had to be guided to the food by the observation of the
limb and food via its camera eyes and the central brain, demonstrating that
they can control their limbs independently and conduct them centrally while at
the same time allow the limbs the freedom to explore on their own. I am tempted
to call the octopus as having a Glassy Brain, that is, it is mostly solid, a
large central nervous system, but at the same time having a liquid aspect, much
like glass, which is technically a liquid, with the freedom displayed by their
highly innervated and exploratory arms and suckers.
Octopuses can apply their knowledge and skills to novel
situations and challenges. They can figure out how to open jars, boxes, or
puzzles that contain food or other rewards. They can also learn from observation
or experience how to escape from traps, nets, or tanks. Some octopuses have
even been reported to display mischievous or playful behavior, such as
squirting water at humans, playing with items, such as a plastic pill bottle
that they repeatedly push into the stream of water circulating in their tank to
watch it get shot out across the surface of the water in their tank and then
retrieving it to start the process over again for ten times in a row in some
cases for no other reason than they find it amusing. Octopuses can distinguish
between different individuals, both of their own species and others. They can
also recognize human caretakers based on their faces or clothing. Some
octopuses have shown preferences or aversions toward certain humans, depending
on how they were treated by them. They can also display different personalities
and moods.
Perhaps the most impressive display of intelligence in octopuses
is their ability to mimic other animals. Not only can they alter their
appearance to blend with their surroundings, but they can also impersonate
other creatures. The mimic octopus (Thaumoctopus mimicus) is a virtuoso
in this regard, capable of imitating over 15 different species, such as highly poisonous
sea snakes, lionfish, flatfish, and jellyfish. This mimicry serves to deter
predators, lure prey, and confound competitors. Residing in the Indo-Pacific
region, the mimic octopus faces numerous predators and competitors.
Interestingly, the mimic octopus isn’t born with the ability to specifically
mimic; it acquires this skill through observation and experimentation. It can
also tailor its mimicry based on the situation and the observer. For instance,
it might impersonate a sea snake when faced with a damselfish, known to be
afraid of sea snakes, or a highly venomous lionfish when confronted with a
large predator, or even a poisonous flatfish when traversing open sand, where
it’s exposed to predators.
The mimic octopus naturally exhibits a light brown or beige
color and shows a preference for river mouths and estuaries over reefs, which
are typically favored by other octopus species for shelter and protection from
predators. This habitat preference of the mimic octopus is attributed to its
unique ability to mimic toxic animals, thereby reducing its risk of predation
in open areas. The mimic octopus not only uses its mimicry defensively against
predators, but also employs mimicry to approach cautious prey. For instance, it
can imitate a crab’s potential mate, only to then consume the unsuspecting prey.
The mimic octopus is not just intelligent, but also inventive and adaptable. It
can even merge different mimics to create unique forms, like a half-sea snake
and half-flatfish. This remarkable cognitive and behavioral complexity
challenges our comprehension of animal intelligence. Scientists theorize that
such behavior necessitates advanced cognitive abilities; it must comprehend how
other animals perceive it and how it can manipulate their expectations by
changing its appearance. Moreover, it must be capable of modifying its
imitation strategy based on context; all demonstrations of advanced cognitive
abilities. It has often been postulated that octopuses live a difficult life in
environments dominated by vertebrate predators and that these evolutionary
selective pressures crafted the highly intelligent, incredibly resourceful, and
quite successful octopus species seen alive today. “Given all the remarkable
capabilities that octopuses indeed have, I find it impossible that these
extraordinary creatures are not conscious.”
Further Reading:
Baker, Beth (2010). "Unusual Adaptations: Evolution of the
Mimic Octopus". BioScience. 60 (11): 962–962.
Peter Godfrey-Smith (2016). Other Minds: The Octopus,
the Sea, and the Deep Origins of Consciousness. Farrar, Straus and Giroux.
Roger Hanlon, Michael Vecchione, Louise Allcock: (2018) Octopus,
Squid & Cuttlefish: A Visual, Scientific Guide to the Oceans’ Most Advanced
Invertebrates. The University of Chicago Press.
Harmon, Katherine (2013). "Mimic Octopus Makes Home on
Great Barrier Reef". Scientific American.
"Mimic Octopuses". Marinebio.org. 2017.
John Roach (2001). "Newfound Octopus Impersonates Fish,
Snakes". National Geographic.