Mollusk | Chapter 3 | senses

There are mollusks that smell you coming across vast distances. Mollusks that see from a hundred directions through eyes made of stone. Blind mollusks that navigate by sensing the earth’s magnetic fields. Mollusks that can whirl and spin and always know which way is up.

From the deepest oceans to the highest mountains, mollusks have adapted to thrive in nearly every habitat on earth. They harness light, chemicals, and sound in ways that reveal to them a world completely different from the one we experience.

Squid tumble through the ocean as they fight, hunt, and flee in near darkness. They know which way they’re turning, how quickly they’re accelerating, and which way is up by using specialized organs called statocysts: balloon-like organs that orient them as they ride the ocean’s roller coaster.

When we spin, we become dizzy and fall. Compared to the squid in its vast underwater home, we are balance blind.

We walk around on the very edge of life: on top of the ground but not in the sky, over the water but rarely under it. The entire suite of our human perception – vision, but also touch, smell, hearing and taste – has evolved to help us survive in our extremely niche environment.

There are as many ways to experience the world as there are animals and niches. While we evolved to rove the land, a chiton could spend up to 40 years in the same tidepool, barely moving, bashed by waves and exposed to predators from above.

The chiton protects itself with a hard shell of eight overlapping plates, covered in hundreds of eyes. Each eye contains a tiny lens made of the mineral aragonite. The chiton can spot danger from every angle; the moment a shadow touches its armored back, it clamps down onto the rock with its sucking foot.

The armored chiton.  Randimal

The armored chiton. Randimal

Further out, in the calmer waters of the bay, the rose-colored sea slug Tritonia diomedea lives in a dancing world of smells. It follows odor plumes across the sandy seafloor, chasing food and lovers. When rough seas turn its path into a maelstrom of scents, the blind mollusk may rely on its compass: we think that tiny metal particles in its skin can detect the earth’s vast magnetic field, which stretches up into space and touches the solar winds. 

The rose-colored sea slug Tritonia diomedea.    Jon Gross      Photography

The rose-colored sea slug Tritonia diomedea. Jon Gross Photography

Be a mollusk for a moment. The world is projected onto your rock eyes in passing shadows, like a chiton. North is a feeling in your skin, a constant tingling like a sea slug. Or, as a squid, your hands and feet are covered in thousands of suckers full of chemoreceptors, like those in your human nose and mouth. You can taste your phone and your food with your fingertips. Your home is an ever-shifting galaxy of flashing light and tumbling motion. 

Reality extends beyond what any single species can perceive. Including us.

More Perception

Scallops have hundreds of dazzling blue eyes.
Sparkling blue mollusk blinkers.   Professor William Capman

Sparkling blue mollusk blinkers. Professor William Capman

When ships prospect for oil with compressed air guns, the noise bursts squids’ statocysts. No longer able to navigate in the deep, they wash onto the beaches in mass strandings.
Before going into space, astronauts have to learn to balance and control their bodies in the floating world of zero gravity. One of the places that they practice is a space station replica built underwater.
Humans are creatures of vision. Right now, in your brain, hundreds of millions of neurons—30 percent of your cortex—are devoted to visually processing what you are reading. Eight percent of it is paying attention to the object in your hands. Just three percent is listening to the sounds around you.