"This is the ship of pearl, which poets feign, sails the unshadowed main / and its dim dreaming life was wont to dwell /as the frail tenant of its growing shell."
Oliver Wendell Holmes described this remarkable creature in his 1858 poem “The Chambered Nautilus.” Holmes was a doctor, essayist, Harvard professor and Supreme Court justice.
However, the brilliant Holmes got the chambered nautilus wrong. It is not "a frail tenant." Not at all. Far from it.
The chambered nautilus is a robust survivor. A "living fossil." It has been around, relatively unchanged, for hundreds of millions of years. Two hundred and sixty-five million years before the dawn of the dinosaurs, the chambered nautilus was jet-propelling itself on the hunt for food with its long slim tentacles.
Those tentacles—of which it can have up to 90—are a giveaway to its ancestry. The nautilus is a cephalopod mollusk, a relative of octopus, squid, oyster and clam.
Yet, unlike its cousin, the famous giant Pacific octopus, the chambered nautilus has small eyes, blurry eyesight and sucker-less tentacles. It cannot open jars.
However, what it lacks in showmanship, it makes up for in beauty and longevity. It can live up to 16 years, while the giant Pacific octopus lives only three to five. At more than an inch in length, its eggs are among the largest of any invertebrate. Those eggs also have an extremely long incubation period: from six months to a year.
Nautilus are scavengers. They hunt by using their tentacles as chemical sensors—in effect smelling the deep reefs of the tropical Indo-Pacific carrion, dead and decaying crabs and fish, and occasionally other nautilus.
Now, about that shell—it's the only cephalopod to have one, and it is remarkable. Mathematical. A cross-section of the nautilus shell reveals that its chambers are arranged in a perfect logarithmic spiral.
Through a geometric principle called the golden ratio, these spirals are found frequently in nature. In sunflowers, for example. In hurricanes. In galaxies. And in the elegant lustrous mother-of-pearl whorl of a nautilus shell.
But that shell isn't just for show. It's functional. It provides shelter, defense, and it is a nifty swim aid.
The chambered nautilus can change its buoyancy in the water by adjusting the ratio of gas to saline solution in the chambers of its shell, much like a submarine uses its ballast tanks. In fact, the first nuclear powered submarine, launched in 1954, was named USS Nautilus.
The chambered nautilus can dive very deep, migrating 2,000 feet to cold, deep waters during the day to avoid predators like turtles, octopus and sharks, and then rising at night to feed in shallower, warmer waters.
We might love the nautilus's shell too much. In 2011, the New York Times called the harvest of their shells for jewelry and ornaments a "horrendous slaughter.” Sadly, nautiluses are heavily fished, and face possible extinction in the places where competition for the shell trade is fiercest, like the Philippines.
After surviving mass extinctions over millions of years, they are now at risk because we humans see a pretty shell, not the beauty of a survivor that’s stood the test of time.
To learn more about the nautilus and its shell’s golden ratio, please visit aqua.org/ablueview.