Nautiluses: Characteristics, Shells and Species

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Nautilus in Thailand

Nautiluses are marine cephalopods — molluscs related to squid and octopus. But unlike other cephalopods, they are housed within a distinctive smooth, hard shell. Nautilus live in the open water in and around coral reefs in the Pacific and Indian Oceans. They have traditionally been harvested for their beautiful shells to make art and jewellery, but international trade is now regulated to protect them from over-exploitation. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Writers, artists, and engineers have long marveled at the nautilus’s beauty and swimming abilities. They use jet propulsion to roam the ocean deep. T The pearly nautilus grows to about 20 centimeters across and has remained virtually unchanged for 180 million years.

Although no regulations currently exist to protect them, the six living species of chambered nautilus appear to be in decline. They are trapped mostly for their attractive shells and also for the shell’s inner layer, called nacre, which is used as a pearl substitute in jewelry and trinkets. In 2013, NOAA Fisheries funded a University of Washington researcher to conduct population studies of the nautilus in Fiji and American Samoa. The research should provide a clearer picture of nautilus abundance in those areas. [Source: NOAA]

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal

Nautilus Taxonomy and Wher They Live

There are between six and nine specie of nautilus, including the chambered nautilus, Bali nautilus, Palau nautilus, white-patch nautilus, bellybutton nautilus and crusty nautilus. The issue of what constitutes a nautilus, a nautilus species and a nautilus subspecies is still hotly debated today. The term chambered nautilus can be used to describe one species or any member of the nautilus group.

Although their taxonomy is poorly resolved, the nautilus family, Nautilidae, is currently divided into two genera, Nautilus and Allonautilus, all which share the common name, chambered nautilus. Nautiluses can be found in shallow cooler waters in some locations when they feed. Generally, though they are found in deep water. The deepest nautilus ever observed was sighted at 703 meters (2,306) feet below the surface.

Nautiluses are found mostly in the Pacific between Fiji and Indonesia, with a large concentration of them around Palau, where they are often found at depths of around 680 meters (2,200 feet). They also commonly seen in the waters of the central Philippines, where fishermen set traps baited with chicken to catch them for food.

Nautilus History

Nautilus in Palau

Members of the Nautilidae family are known to have existed from the Late Triassic (237 million to 201 million years ago)., and appear to changed little since then. Darwin used the term “living fossils” to describe them. Its very difficult tell a dinosaur- era ancient Nautilus from a modern one. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Nautiluses come from a branch of mollusk that first appeared 550 million years ago and became mobile in the open sea by developing gas-filled flotation tanks. More than 3,500 nautilus species have been identified on the fossil record. Most of them lived in shallow seas. The largest one known had a nine-foot shell. Ancient nautiluses had parrotlike beaks surrounded by treacles. They were among the first animals known to seize prey, which appeared to have been shrimp.

Poems and stories have been written about the nautilus. A Jules Verne submarine was named after it and a famous Edward Westin photographs were taken of a split open one. For a while there was even a magazine devoted to them. Nautilus means “sailor” in Greek, so because they were among the first to find empty nautilus shell floating in the currents. Nautilus shells are exquisitely beautiful and admired for their mathematical sophistication as well as aesthetic delicacy. Some species are endangered because there were never many of them to begin with and many have been taken by shell collectors.

Nautilus Characteristics

Nautiluses are the only cephalopods that keep their shells outside of their soft bodies rather than in it. Residing inside a brown-patterned, mother-of-pearl-lined curling white shell, they look like a squid coming out of shell. They have 50 to 90 small suckerless tentacles, two long tentacles, primitive grooved eyes that working like pinhole cameras, and a water-spurting funnel. The spiraling gas-filled, airtight chambers in the shells act as buoyancy devices. The large final chamber is where the animal lives.

The pearly nautilus contains a tube that runs from the back of the body chamber into the flotation tanks allowing it to adjust its buoyancy by flooding or taking gas out of the tanks. The paper nautilus is really a kind of scallop.

Unlike other cephalopods, nautiluses are relatively long-lived, reaching ages of 15 to 20 years, or more. They grow slowly, maturing around 10 to 15 years of age, and produce a small number of eggs that require at least a year-long incubation period. [Source: NOAA]

Nautilus Shells

Nautilus cutaway logarithmic spiral
Nautiluses are the only cephalopods (squids, octopuses, and relatives) that have external shells. All the species and subspecies have beautiful, coiled shells, which can range in color, from white to orange, and even purple, with unique color patterns. [Source: Daniel Stokes, Dutch Shark Society, April 6, 2022]

The nautilus shell contains many sealed chambers, increasing in number as the animal grows. As each chamber seals, it is partially filled with gas, giving the animal its buoyancy. The chambers are perfectly proportioned mathematically and arranged in a logarithmic spiral. The pattern is widely used in art and design.

Externally the shell of the chambered nautilus is white with brown tiger-like stripes. The inside has a stunning mother-of- pearl finish. The beautiful pearlescent layers help disguises them in the sea and make their shell attractive to collectors and jewelry makers. [Source: Nicholas Argent, Citrus Reef]

The chambered nautilus (Nautilus pompilius), also called the pearly nautilus, is the largest and best-known species of nautilus. Among the most common types of nautilus shell are the natural nautilus, pearl nautilus, and center-cut nautilus.

Nautilus Shells and Buoyancy

Nautilus shells have many closed interior chambers or “compartments.” The animal resides in the shell’s largest chamber, while the other chambers function like the ballast tanks of a submarine. This is the secret to how the nautilus swims. As the animal grows new flotation chambers are added so the nautilus can increase its buoyancy as the animal became heavier. As the nautilus grows the animal moves forward in the expanding shell, and natural secretions from a partition, or septum, behind its fleshy body, seal the old chamber. Thus the nautilus creates a series of ever-larger chambers, at an estimated rate of one every few weeks or months. Shells with 38 chambers have been found.

Nautilus pompilius
The tissue in a canal called the siphuncle (pronounced sigh-funk-el) connects all of the interior chambers. As seawater pumps through the living chamber, the nautilus expels water by pulling its body into the chamber, thereby creating jet propulsion to thrust itself backwards and to make turns. While swimming up or down through the water column, the nautilus uses its siphuncle to suck fluid into, or draw it out of, the smaller sealed chambers, allowing the animal to adjust its overall buoyancy. [Source: NOAA]

Nautiluses eat fish, dead fish, lobster, crabs, and mollusks. They are hunters and pick up food scents in the water column with chemosensors on their tentacles. They search for prey with small stalked eyes and tentacles that are sensitive to taste and grasps prey with their tentacles and kills it with a bite form their sharp, parrot-beak-like mouth.

The soft-bodied nautilus lives inside a hard, chambered shell. Some float freely in the sea. Other times these seek refuge in the crevasse of rock or reefs. When the animal dies it sinks while the shell floats.Nautilus move around tube shaped water-expelling funnels like those on squids.

It uses the chambers to pump air and water in and out of its shell, creating jet propulsion to thrust itself backwards and to make turns. They possess a siphon tube, known as a hyponome, which runs the length of the shell. The hyponome allows the nautilus to control its buoyancy by regulating air and water in the shell chambers. [Source: NOAA]

Chambered Nautilus

Chambered Nautilus(Scientific name: Nautilus pompilius) are known for their beautiful, coiled shells. The shell can range in color, from white to orange, and even purple, with unique color patterns. Protruding from the shell are more than 90 suckerless tentacles. [Source: NOAA]

Chambered Nautilus weigh at least one kilograms (two pounds). Their shell is typically five to nine inches in length at maturity. Their lifespan is 15 to 20 years. They are mainly found in the western Pacific Ocean and coastal areas of the Indian Ocean. They have multiple predators, including sharks, bony fish, and octopuses.

Chambered nautiluses are sought after for their shells, which are sold commercially and traded internationally for use in art, furniture, jewelry, and other items. The chambered nautilus, is a highly vulnerable species because of its life history characteristics, including low reproductive rates, slow growth, and late maturity. This species is thought to occur in small, isolated populations throughout its range. They are also limited by both depth and temperature tolerances.

Three New Nautilus Species Discovered Off Fiji, Samoa and Vanuatu

In a study published on January 25, 2023 in the peer-reviewed journal ZooKeys, scientists announced they had dsivered three new nautilus species: 1) Nautilus vitiensis of Fiji, 2) Nautilus samoaensis of American Samoa, and 3) Nautilus vanuatuensis of Vanuatu. The classification of them as new new species highlight the concept of allopatric speciation — or biogeographic isolation — where populations are geographically separated from other populations, resulting in a barrier to gene flow. Over time, these populations eventually evolve into distinct species. [Source: Pensoft Publishers,, February 1, 2023

Nautilus anatomy

The Miami Herald reported: Their species diversity stems from the isolation of nautilus populations, researchers said. Because their shells will implode in the deep sea, and the surface water is too warm, they cluster themselves in habitable pockets of the ocean. Researchers said the three species were found on the eastern end of the Nautiluses’ habitat. Their discovery “provides insight into evolutionary radiation of the genus and clarification for future conservation practices,” according to the study. “The fact that we were able to combine the morphology and genetics to differentiate these species provides a foundation for managers and other officials to begin to efficiently identify distinct species of nautilus shells that may come through as trade products,” the study said. [Source: Brendan Rascius, Miami Herald, February 22, 2023]

For the study Baited traps were dropped several hundred meters into the ocean in order to catch the creatures, which were then hauled onto boats. After the specimens were photographed and sampled, they were dropped back into the water and escorted home by attentive divers who “burped” them, researchers said. “When we take nautiluses out of the water, they are still using their hyponome (funnel) to ventilate,” Gregory Barord, one of the study’s authors, said. “When this happens, air can get trapped in the shell and if it is not burped out, the nautilus becomes positively buoyant and cannot jet down back to its home, 300 meters below.” Following the expedition, shell characteristics, such as size, pigmentation and stripe patterns were analyzed and used to identify three unique species, researchers said, adding that there are likely many more waiting to be discovered. Currently, there are no known fisheries in Fiji, American Samoa, or Vanuatu so the risk of these populations decreasing from fisheries is low, at the moment.

Threats to Nautiluses

Chambered nautiluses have been listed as threatened throughout Its range since 2018 by U.S. Fish and Wildlife . Endangered Species Act (ESA). The Convention on International Trade in Endangered Species (CITES) places them in Appendix II, which lists species not necessarily threatened with extinction now but may become so unless trade is closely controlled: Throughout Its range.

The primary threat to nautiluses is overfishing through commercial harvest to meet the demand for the international nautilus shell trade. Chambered nautilus shells, which have a distinctive coiled interior, are traded as souvenirs to tourists and shell collectors and also used in jewelry and home décor items (where either the whole shell is sold as a decorative object or parts are used to create shell-inlay designs). The trade in the species is largely driven by the international demand for their shells and shell products since fishing for nautiluses has been found to have no cultural or historical relevance. [Source: NOAA]

While all nautilus species are found in international trade, N. pompilius, being the most widely distributed, is the species most commonly traded. Given their slow growth, late maturity, low reproductive output, and low mobility, chambered nautiluses are particularly vulnerable to overfishing. Efforts to address overutilization of the species through regulatory measures appear inadequate, with evidence of targeted fishing of and trade in the species, particularly in Indonesia, Philippines, and China, despite prohibitions.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023

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