Mollusk | Chapter 4 | BRAINS

Coquina clams have no brains, but they can surf.

Small hair-like sensors on their gills quiver with the movement of large waves. Connected to distributed nerve-clusters called ganglia, the quivering triggers a muscle response – a reflex. The clams leap out of the sand, surfing toward richer water as the tides ebb and flow.

Clams don’t wonder which wave to surf. They quiver, and they leap. Tap your knee in just the right spot and watch your leg kick. That reflex was involuntarily triggered by nerves in your spine.

We often overlook intelligence when it doesn’t fit our schema, seeing an enormous planet of twitchy knees reacting to stimuli. But reflexes keep the clams alive.

At its heart, evolution is a long game of call and response across time. Each adaptation is a question: will this work? The brain is just one of many possible design solutions. Hundreds of millions of years ago, as clams put their energy into building stronger shells, octopuses began shedding theirs and investing in intelligence. Soft-bodied, vulnerable, the octopus relies on its wits to survive.

The wiliest invertebrate we’ve observed, octopuses can mimic other animals. They learn. They play. They have likes and dislikes. They might have feelings about you. In captivity, octopuses can remember the faces of their human keepers.

Do you remember me? Octopus observing humans from inside its tank at the Kelly Tarlton Aquarium, New Zealand.

Do you remember me? Octopus observing humans from inside its tank at the Kelly Tarlton Aquarium, New Zealand.

The main problem we face when thinking about animal cognition is our own lack of imagination: how can we get inside their minds when their bodies are so different from our own?

Only 10 percent of an octopus’s neurons are in its central brain, which is shaped like a donut encircling its throat. 20 percent of its neurons are located in its optic lobes, and the other 70 percent are spread out across its arms, a flickering distributed mind. When an octopus is hungry, each arm can begin the hunt in a different way.

Observing how octopuses behave, some arms reaching out recklessly while others hide in the rocks, researchers are starting to ask what we can learn from this multifaceted intelligence. Does each arm have its own personality? What is the octopus thinking as it watches us through the glass of the tank? As it sucks gently on our arms?

More Brains

In April 2016, Inky the Octopus in the New Zealand Aquarium escaped from his tank, crossed the aquarium floor, and squeezed himself into a 164-foot-long drainpipe that dropped him back in the Hawke’s Bay.
A severed octopus arm will keep on trying to catch food to feed to its phantom mouth. It can survive for up to an hour before it dies from lack of oxygen. Within six weeks, the remaining octopus re-grows a whole new intelligent arm.
Benthoctopus sp. looking into NOAA's diving gear.   Bruce Strickrott, Expedition to the Deep Slope 2006

Benthoctopus sp. looking into NOAA's diving gear. Bruce Strickrott, Expedition to the Deep Slope 2006

Humans have decided that only two of the seven classes of mollusks have brains, cephalopods and gastropods…but researchers are still trying to figure out what a brain is.
Brains are expensive. Human brains burn 20 percent of our bodies’ daily energy needs, more than any other organ in our body.

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