One of the weirder facts about the animal kingdom is that
octopuses are actually quite smart. Octopuses exhibit all kinds of
impressive behavior when tested. They can solve fairly complex spatial
problems and remember patterns for later. They can learn and work toward
a goal over time. They even engage in elaborate hunting behavior to
trap or lure prey. The question is: why would octopuses be so much
smarter than the animals around them, and how did they get that way?
A new study published in Nature
has sequenced the octopus genome in order to discover just that. It
looked at several different types of octopus tissue, analyzing the
octopus’ surprisingly large genome. It contains many times more genetic
information about making certain types of proteins, particularly those
governing the growth and interaction of neurons. They have some 33,000
protein-coding genes to a human’s 25,000 — and those octopuses are
smarter than they look. This still proves that when it comes to genome
size, it really is all about how you make use of what you’ve been given.
Yet, unlike many large genomes, this one has not been
duplicated. Some species of fruit fly have enormous genomes, but this is
due to multiple duplications of their entire genome — they simply have
more than they need. The octopus genome seems to have grown and
elaborated the honest way, though genuine natural selection. This
incredible evolutionary achievement has allowed a mollusk to become one
of the apex predators of the sea.
The enormous and oddly diverse collection of genes makes the
octopus genome a true oddity. University of Chicago researcher Clifton
Ragsdale told Nature that “It’s the first sequenced genome from
something like an alien,” referring to how unusual its proportions are.
This study shows octopuses to have the second-largest gene family yet
discovered, with 18,000 genes coding for versions of the zinc finger
transcription factors — this is second only to elephants, with over
20,000 genes in the olfactory receptor family. Transcription factor
adjust the expression of other genes, and the octopus seems to use these
zinc finger genes in its most specialized tissues, like its suckers and
camouflaging skin.
The squid is also surprisingly intelligent, for what it is, but still nowhere near as smart as the octopus.
One particularly interesting discovery is that octopuses
seem to have biochemical systems in place that allow them to modify
proteins on the fly, potentially changing their functions. Scientists
speculate that this could allow the octopus to adapt its neural network
to different tasks, allowing a plasticity that leads to the octopus’s
incredible abilities in learning and memory. By some measures, its
abilities can match those of a dog; the study features the example of an
octopus opening a jar to get at the crab within.
The brain of an octopus is large, in terms of the number of
neurons — the molluscs can have several times more neurons in their
bodies than a mouse or rat. However, many of those neurons are
distributed over the creature’s entire body, rather than being
centralized in the cerebral cortex. A portion of the octopus-thinking
hardware extend down the arms, allowing each one to do some basic
thinking on its own. This may allow the octopus to use all its different
limbs simultaneously, since they can each nominally detect and respond
to their own surroundings.
Even a severed octopus limb can do basic “thinking” in the
form of directed grasping. It’s sort of a super-charged version of our
own spinal reflexes, which for instance allow us to unconsciously
withdraw our hand from a hot surface before the brain has even
registered any heat. The hardware for basic heat-response thinking
exists in our upper spine, outside the brain, and the hardware for basic
grip-finding and other tasks seems to exist in each of the octopus’
swirling limbs.
All this could help scientists learn not only how the
octopus walked this remarkable evolutionary path, but perhaps more
importantly, why.
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