A mimic octopus (Thaumoctopus mimicus) pretending to be a venomous banded sole
(Credit: Alex Mustard/naturepl.com)
Master of disguise
The evolutionary arms race
has led animals to develop many devious ways to fool each other.
are grass snakes that play dead to avoid being eaten, male fish that
pretend to be female to boost their reproductive prospects, and birds
that feign broken wings to lure predators away from vulnerable
Yet of all of nature's charlatans, the mimic octopus must be a leading contender for the title of "master of disguise"
octopuses can change the colour and texture of their skin to give
predators the slip.
The mimic is the only octopus that has been observed
impersonating other animals.
It can change its shape, movement and
behaviour to impersonate at least 15 different species.
When travelling across sand, it can flatten its arms against its body and undulate like a venomous banded sole
When moving through open water, it mimics a lionfish
, which is also venomous.
Another trick is to put six of its arms into a hole and use the remaining two to look like a banded sea krait
, a type of sea snake that is, of course, venomous.
A common octopus (Octopus vulgaris)
(Credit: Claudio Contreras/naturepl.com)
A problem solved
Octopuses can use trial and error to find the best way to get what they want.
In work published in 2007, Mather and Anderson observed giant Pacific octopuses trying to get at the meat in different types of shellfish
They simply broke open fragile mussels, pulled apart stronger Manila
clams, and used their tongue-like radulas to drill into very strong
When given a choice of the three, the octopuses
favoured the mussels, presumably because they required less effort to
get a meal.
The researchers then tried to confuse their subjects
by wiring Manila clams shut. However, the octopuses simply switched
Mather concluded that they could learn based on non-visual
"It told us that octopuses are problem-solvers," she
"They have different strategies to achieve the same ends, and they
will use whichever is easiest first."
A California two-spot octopus (Octopus bimaculoides)
(Credit: Visuals Unlimited/naturepl.com)
Mazes for molluscs
During fieldwork in
Bermuda, Mather observed octopuses returning to their dens after hunting
trips without retracing their outgoing routes.
They also visited
different parts of their ranges one after another on subsequent hunts
In a study published in 1991, she concluded that octopuses have complex memory abilities
They can remember the values of known food locations, and information about places they have recently visited.
animals use landmarks to help them navigate, they have to be understand
the landmarks' relevance within their contexts.
This ability, known as
conditional discrimination, has traditionally been seen as a form of
complex learning: something only backboned "vertebrates" can do.
In work published in 2007, Jean Boal
of Millersville University in Pennsylvania placed California two-spot octopuses
in two different mazes.
In each case they had to travel from the middle
of a brightly-lit tank to reach a dark den, an environment they
To get there they had to avoid a false burrow, which was
blocked by an upside-down glass jar.
After five trial runs, most
of the octopuses had learned to recognise which maze they were in and
immediately headed for the correct burrow.
This, Boal concluded, meant octopuses do have conditional discrimination abilities
A mimic octopus (Thaumoctopus mimicus)
(Credit: Jeff Rotman/naturepl.com)
In many ways, octopuses' brains are rather like ours.
have folded lobes, similar to those of vertebrate brains, which are
thought to be a sign of complexity.
What's more, the electrical patterns
they generate are similar to those of mammals.
Octopuses also have monocular vision
meaning they favour the vision from one eye over that from the other.
This trait tends to arise in species where the two halves of the brain
have different specialisations.
It was originally considered uniquely
human, and is associated with higher cognitive skills such as language.
Octopuses even store memories in a similar way to humans
They use a process called long-term potentiation, which strengthens the links between brain cells.
similarities are startling.
The last common ancestor of humans and
octopuses lived a long time ago, probably quite early in the history of
multicellular life, and was a simple animal.
That means the similarities
in brain structure have evolved independently.
Even more fascinating than the similarities, however, are the differences.
than half of an octopus's 500 million nervous system cells are in their
That means the eight limbs can either act on their own or in
coordination with each other.
Researchers who cut off an octopus's arm found that it recoiled when they pinched it
, even after an hour detached from the rest of the octopus.
Clearly, the arms can act independently to some extent.
the human brain can be seen as a central controller, octopus
intelligence may be distributed over a network of neurons, a little bit
like the internet.
If this is true, the insights octopuses offer
extend way beyond their advanced cognitive and escapology abilities.
Inky and his relatives may force us to think in a new way about the
nature of intelligence.
Post a Comment