Chambered Nautilus

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This animal is not currently on exhibit at the aquarium.

The chambered nautilus (Nautilus pompilius) has been around for about 500 million years and changed little during that time, two facts that often earn it the label “living fossil.” But it would be just as fair (and much more polite) to describe it as a living feat of engineering: The nautilus literally builds itself a home as it grows, adding new internal chambers in a spiral pattern while always occupying the outermost one. The chambers, which increase from four to about 30 over the course of a lifetime, are coated in iridescent nacre, or mother-of-pearl; they also contain gases that provide buoyancy, and connect through a system of tubes that regulates density as nautili move around.

And move they do: Nautili spend their days in dark, cool water down to 2,000 feet deep; at night they rise to between 300 and 500 feet below the surface to scavenge for dead or dying fish and crustaceans. Due to their poor vision—like pinhole cameras, their eyes have no lenses—they rely on a generous set of unusual, suckerless tentacles to find and ingest bits of food, which they then crush with a powerful beak. When it’s time to change location, nautili move by jet propulsion, shooting out pressurized water through a tube near the tentacles.

Chambered nautili are skilled at evading most (non-human) predators. In the wild, they can live up to 20 years—an unusually long time for cephalopods.

Range and Conservation Status

Chambered nautili are found off the coasts of Southeast Asia and Australia, in tropical spots where coral reefs descend into deeper waters. Overfishing by humans is a threat (the iridescence and spiral pattern of their shells makes for an especially desirable commodity), and the species is late and slow to reproduce, but due to a lack of sufficient population data, chambered nautili are currently not protected by any international body. Further research is pending.

Defenses

Many of the nautilus’s traits double as techniques to avoid predators. Its armor-like shell, for example, supports the complex network of internal chambers but also limits its natural predators to animals that can crack it (such as sharks, turtles, and octopuses). Its coloration, meanwhile, exhibits a phenomenon called countershading: the nautilus is dark on top and light beneath, making it difficult to distinguish from the water when viewed from overhead, and from the sky when viewed from below.

Symbolism

Though the pattern of the nautilus’s chambers only approximates the geometric marvel of the golden spiral, it enjoys a reverence beyond the decorative (or mathematical) arts. The nineteenth-century poet Oliver Wendell Holmes, Sr., even wrote a meditation in which he takes spiritual inspiration from the “lustrous coil” of its “ship of pearl,” urging the human soul to grow as the nautilus does: “Let each new temple, nobler than the last, /Shut thee from heaven with a dome more vast.”