Nautilus Facts

Scientific Name: Nautilus pompilius

chambered nautilus, Nautilus pompilius, Palau

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The chambered nautilus (Nautilus pompilius) is a large, mobile cephalopod which is called a "living fossil" and has been the subject of poetry, artwork, math, and jewelry. They have even inspired the names of submarines and exercise equipment. These animals have been around for about 500 million years—even before the dinosaurs.

Fast Facts: Chambered Nautilus

  • Scientific Name: Nautilus pompilius
  • Common Name: Chambered nautilus
  • Basic Animal Group: Invertebrate
  • Size: 8–10 inches in diameter
  • Weight: Maximum of 2.8 pounds
  • Lifespan: 15–20 years
  • Diet: Carnivore
  • Habitat: Oceans in the Indo-Pacific region
  • Conservation Status: Not Evaluated

Description

Nautiluses are invertebrates, cephalopods, and mollusks related to octopus, cuttlefish, and squid. Of all the cephalopods, nautiluses are the only animal to have a visible shell. The shell is not only beautiful, but it also provides protection. The nautilus can withdraw into the shell and seal it closed with a fleshy trapdoor called a hood.

Nautilus shells can reach up to 8–10 inches in diameter. They are white on the underside with brown stripes on its upper side. This coloration helps the nautilus blend into its surroundings.

The shell of an adult nautilus contains over 30 chambers which form as the nautilus grows, following a genetically-hardwired shape known as a logarithmic spiral. The nautilus's soft body is located in the largest, outermost chamber; the remainder of the chambers are ballast tanks that help the nautilus maintain buoyancy.

When a nautilus approaches the surface, its chambers fill with gas. A duct called the siphuncle connects the chambers so that, when necessary, the nautilus can flood the chambers with water to make itself sink again. This water enters the mantle cavity and is expelled through a siphon.

Chambered nautiluses have many more tentacles than their squid, octopus and cuttlefish relatives. They have about 90 thin tentacles, which do not have suckers. Squid and cuttlefish have two and octopus have none.

Cross-section model of chambered nautilus
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Species

These several species are in the Nautilidae family, including five species in the genus Nautilus (Nautilus belauensis, N. macromphalus, N. pompilius, N. repertus, and N. stenomphelus) and two species in the genus Allonautilus (Allonautilus perforatus and A. scrobiculatus). The largest of the species is N. repertus (the emperor nautilus), with a shell measuring from 8 to 10 inches in diameter and soft body parts weighing nearly 2.8 pounds. The smallest is the bellybutton nautilus (N. macromphalus), which only grows 6–7 inches. ​

Allonautilus was recently re-discovered in the South Pacific after thought extinct for some 30 years. These animals have a distinctive, fuzzy-looking shell. 

Habitat and Distribution

Nautilus pompilius is only found in the dimly lit tropical and warm temperate waters of the Indo-Pacific region in southeast Asia and Australia. It is the most widespread of any of the nautiluses and like most of the species, it spends most of the day at depths up to 2,300 feet. At night it migrates slowly up the coral reef slopes to forage for food at about 250 feet deep.

Diet and Behavior

Nautiluses are primarily scavengers of dead crustaceans, fish, and other organisms, even other nautiluses. However, they do prey on (living) hermit crabs and dig in the soft sediments of the sea floor for small prey pieces.

Nautiluses have poor vision with two large but primitive pinhole eyes. Under each eye is a fleshy papilla about a tenth of an inch long called a rhinophore that the nautilus uses to detect its prey. When a dead fish or crustacean is detected by the nautilus, it extends its thin tentacles and swims towards the prey. The nautilus grips the prey with its tentacles and then rips it into shreds with their beak before passing it to the radula.

A nautilus moves by jet propulsion. Water enters the mantle cavity and is forced out the siphon to propel the nautilus backward, forward, or sideways.

Reproduction and Offspring

With a lifespan of 15–20 years, nautiluses are the longest-living cephalopods. They take from10 to more than 15 years to become sexually mature. Nautiluses must move into warmer tropical waters to mate, and then they mate sexually when the male transfers his sperm packet to the female using a modified tentacle called a spadix.

The female produces between 10 and 20 eggs each year, laying them one at a time, a process that may last throughout the year. It can take up to a year for the eggs to hatch. 

Two nautiluses
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Evolutionary History

Long before dinosaurs roamed the Earth, giant cephalopods swam in the sea. The nautilus is the oldest cephalopod ancestor. It hasn't changed much over the last 500 million years, hence the name living fossil. 

At first, prehistoric nautiloids had straight shells, but these evolved into a coiled shape. Prehistoric nautiluses had shells up to 10 feet in size. They dominated the seas, as fish hadn't yet evolved to compete with them for prey. The nautilus's main prey was likely a type of arthropod called the trilobite.

Threats

None of the nautiluses are listed as threatened or endangered by the International Union for Conservation of Nature (IUCN). However, ongoing threats to nautiluses are recognized, including over-harvesting, habitat loss, and climate change. One climate change-related issue is ocean acidification, which affects the nautilus's ability to build its calcium carbonate-based shell.

Nautilus populations in some areas (such as in the Philippines) are declining due to over-fishing. Nautiluses are caught in baited traps to be sold as live specimens, meat, and shells. Shells are used to make handicrafts, buttons, and jewelry, while the meat is consumed and live animals are collected for aquariums and scientific research. According to the U.S. Fish and Wildlife Service, more than half a million nautiluses were imported into the U.S. from 2005–2008. 

Intensive nautilus fisheries are short-lived and devastating to local populations. Within about a decade or two, the locations become commercially nonviable. Nautiluses are especially vulnerable to over-fishing due to their slow development and reproduction rates. Populations also seem to be isolated, with little gene flow between populations and less able to recover from a loss.

Although the IUCN has not yet reviewed nautilus for inclusion on the Red List due to lack of data, in January 2017, the entire family of chambered nautiluses (Nautilidae) was listed in the U.S. CITES Appendix II. This means that CITES documentation will be required for import and re-export of these species and items made from them. 

Saving the Nautilus

To help nautiluses, you can support nautilus research and avoid purchasing products made of a nautilus shell. These include the shells themselves as well as "pearls" and other jewelry made from the nacre from the nautilus's shell. 

Diver watching Palau nautilus
Westend61/Westend61/Getty Images

Sources