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Nautiluses

Nautilidae Blainville, 1825

 

 
Palau Nautilus (Nautilus belauensis): Rock Islands Southern Lagoon World Heritage Site, Palau,
Micronesia. Photo: Kai Squires (iNaturalist).
Contents

Introduction

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Nautilus macromphalus: Bourail, New Caledonia.
Photo: Pauline Fey (iNaturalist). Enlarge Image!		  
The chambered nautiluses (Nautilidae) hold a unique place among today's cephalopods. Although they share the characteristic traits that define them as such, most notably their numerous tentacles and their method of moving by jet propulsion, they are noticeably different from all other extant members of the group known to us, living on earth today.

Nautiluses are the only extant cephalopods that still have a complete external shell. The tiny ram's horn squids (Spirulidae) also do have one, but it is almost entirely enclosed by the mantle. Paper nautiluses or argonauts (Argonautidae), on the other hand, may superficially look like a nautilus, hence their name, but they are in fact pelagic octopus-like cephalopods. They do not have a true shell at all. Instead, the female produces a delicate calcareous egg case, which she uses to protect her brood.

Unlike the other living cephalopods of the Coleoidea group, which include such well known creatures like squids, cuttlefish and octopuses, nautiluses even today retain a number of characteristics, that are generally regarded as primitive:

 
Nautilus macromphalus: Passe de Dumbea, New Caledonia.
Photo: Johan Bas (iNaturalist). Enlarge Image!
Apart from their external shell, the most conspicuous of these features is the large number of their tentacles: Depending on the species, a nautilus can have between 50 and 90 tentacles, as compared to the eight or ten arms of other living cephalopods. Nautiluses also have two pairs of gills, while their more derived relatives only retain a single pair.

American Museum of Natural History: How is a nautilus different from a squid?

The eyes of today's far developed coleoid cephalopods, squids, cuttlefish and octopuses, are counted among the most highly developed visual organs in the animal kingdom. Nautiluses, on the other hand, are provided with relatively simple pinhole-camera eyes.

Because of these and several other ancestral characteristics, nautiluses are often regarded as living fossils, since today there are only two extant genera left on earth, Nautilus and Allonautilus. All other species of the Nautiloidea subclass are only known by their remains from the fossil record.

The family Nautilidae, as it is known today, is first known from the Eocene (34 - 56 mio. years ago), the evolutionary lineage of the Nautiloidea, however, reaches much further back in geological history and probably can be traced back into the Late Cambrian and Early Ordovician. This means nautiloids ancestry much further in time than, for example, that of the geologically are noticeably older than their younger, but much better known, ammonite and belemnite relatives ( Geological Time Periods).

Animal Fact Files: Nautilus Facts: Older than Dinosaurs!

Description

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Even if nautiluses certainly are a part of the cephalopod class, they are distinctly different from the rest of their relatives in several characteristics, which make them look like a relic from a long bygone era:

The Shell


From left to right: Nautilus pompilius, Allonautilus scrobiculatus, Nautilus macromphalus.
Photo: MGiganteus1 (Source).		  
The most obvious first characteristi is the nautiluses' large, well-developed external shell. Apart from the aforementioned ram's horn squid (Spirula spirula, Family Spirulidae), nautiluses are the only living cephalopods that retain a complete shell. Unlike the egg case of the paper nautiluses or argonauts (Argonautidae), however, this is a true molluscan shell, superficially resembling that of a snail (Gastropoda). The shell of a nautilus is likewise spirally coiled and composed of several layers. Apart from the main calcareous shell layer (ostracum), the shell is covered externally by an organic periostracum that protects it from chemical erosion. Internally on the other hand, it is lined by a hypostracum made from iridescent calcium carbonate crystals known as nacre, which can also be seen in many mussels and clams (Bivalvia).

 
A Nautilus shell cut open. Photo: Chris76 (Source).

On the right: Opened shell of Nautilus pompilius with opened chambers
and siphuncle channel (arrow). Photo: Anne Laudisoit (iNaturalist).		  
At this point, however, the similarities with gastropod shells largely are at an end: Contrary to a snail shell, which is coiled asymmetrically to one side, the shell of a nautilus is coiled concentrically. While the apical side of a snail shell with the tip can usually easily be told apart from the umbilical side with its navel (umbilicus), the shell of a nautilus basically looks the same from either side.

The coiled shell of Gastropods.

In live nautiluses, the upper side of the shell is darker than the lower side, providing camouflage against the light coming in from above - a phenomenon known as "countershading" or "Thayer's Law". However, because a live nautilus swims "upside down", with the shell aperture facing upwards, the ventral side of the shell is actually darker than the dorsal side, like a shark swimming on its back.

Although the shell of a nautilus does have a nacreous inner layer or hypostracum, it does not produce pearls. The so-called Osmeña pearls, traded particularly in the Philippines, are not true pearls, contrary to those produced by various bivalves, such as oysters. Instead, those are crafted by cutting up a nautilus shell and then grinding and polishing the parts.

Wikipedia: Osmeña Pearl.

Submarines Named Nautilus


SSN-571 Nautilus on her maiden voyage in 1955. (Source: US NHHC).

As early as in 1800, Robert Fulton, an American inventor, presented to the British and French with his submarine by the name Nautilus. Though he was able to sink several ships with it, in the end the idea was not accepted.

During World War II, the US-Navy performed an amphibious operation with Special Forces on the Pacific Island of Makin, using the submarines USS Nautilus (S168) and Argonaut (S166).

In August 1958, the Americans astonished the World in the times of the Cold War, when the nuclear subarine USS Nautilus (SSN 571) under the command of William T. Anderson, as first vessel reached the North Pole - under water.

The most famous ship by the Name Nautilus, however, is ficticious: The submarine commanded by the legendary Captain Nemo from Jules Verne's 1870 novel "Twenty Thousand Leagues Under the Seas".

Cephalopods in Myths and Legends.

Source: Wikipedia: List of ships named Nautilus.		  
The internal structure of the nautilus shell is even more markedly different from that of a gastropod, those showing that the cephalopod shell developed on a different path than that of a gastropod or other shell-bearing molluscs ( Fossil History of the Nautiloids). It is divided into a series of chambers which, in the living animal, may contain a mixture of gases and water. Through an opening in each of the concave walles (septa) separating the chambers runs the siphuncle, a tubular strand of living tissue. This is the only part of the soft body that extends through all chambers. By actively transporting salts and creating osmotic gradients between the chamber fluid and the blood, the nautilus gradually removes water from the chambers and replaces it with gas. In this way, it generates buoyancy, allowing it to hover in the water column, unlike its shell-less relatives.

While the nautilus achieves this through osmotic processes, man-made submarines also operating on the principle of boyancy must resort to mechanical pumps to expel water from their ballast tanks in order to surface. Actually, several submarines throughout naval history have thus been named Nautilus, including the USS Nautilus (SSN-571), the world's first nuclear-powered submarine, which was the first vessel to reach the North Pole beneath the Arctic ice in 1958 (see box on the left).

 
Cenoceras lineatum, a fossil Nautiloid from the middle Jurassic (ca. 200
mio. years ago). Picture: Nobu Tamura (Source).
The position of the siphuncle also tells nautiloids apart from the ammonoids (ammonites and their relatives). In nautiloids, the siphuncle passes through the centre of each septum, whereas in ammonoids it is positioned close to the shell wall. In addition, nautiloid septa are relatively simple and thus produce correspondingly simple sutures on the shell surface, while ammonoid septa are highly folded and so are the reason for the complex suture patterns ammonites are famous for.

Geo Girl: Mollusca (Pt 3)- Cephalopods- Invertebrate Paleontology.

However, water pressure increasing with depth does impose limits on the nautilus' ability to regulate buoyancy. At depths below approximately 250 m, water gradually seeps into the shell chambers, forcing the animal to return periodically to shallower waters around 200 m to restore neutral buoyancy. The maximum diving depth of a nautilus shell is estimated around 800 m; beyond this point implosion would inevitably kill the animal. Deep-water areas surrounding coral reefs thus isolate nautilid populations from one another, since also nautiluses have no free-swimming larval stage, which renders them unable to cross such expanses ( Threat Situation).


 		 Dunstan, A.J.; Ward, P.D.; Marshall, N.J. (2011): Vertical Distribution and Migration Patterns of Nautilus pompilius. PLoS ONE 6 (2): e16311. (Link).

Evidence from the earliest cephalopod fossils of the Cambrian suggests that the chambered shell was one of the key innovations in cephalopod evolution. By enabling active buoyancy control, it allowed these molluscs to abandon a purely benthic existence and adopt a free-swimming lifestyle. The fact that cephalopods have thus far survived multiple global extinction events and repeatedly underwent major evolutionary radiations demonstrates the success of this strategy, even though some gastropods, such as the pteropods, have independently evolved a pelagic lifestyle, as well, and even certain bivalves are capable of limited swimming.

Wikipedia: Evolution of Cephalopods.
Geo Girl: Why Ammonoids Went Extinct at the End Cretaceous While Nautiloids Survived?
Fossil History of the Nautiloids.

Eyes and other Sensory Organs

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Schematic of an abalone's (Haliotis tuberculata)
pinhole camera eye. Quelle: Wikipedia.		  
The eye of a Nautilus belauensis. Notice the rhinophore in front of and
behind the eye! Photo: Kai Squires (iNaturalist).
The eyes of nautiluses are equally remarkable. Compared to those of other more derived cephalopod groups, such as cuttlefish, squids and octopuses, the eyes of nautiluses are relatively simple and function after the principle of a pinhole camera (camera obscura). Light enters through a small pupil opening, and the narrow aperture breaks the light, projecting an image onto the retina. However, compared to the highly developed lens eyes of other cephalopods, this type of eye has the disadvantage of a projected image either dark or poorly focused, as image sharpness and brightness are inversely related, depending on the size of the pupil opening.

Therefore it is generally assumed that nautiluses rely primarily on their sense of smell for orientation, especially because much of their diet consists of carrion, although they are absolutely capable of capturing small marine animals and will do so. To provide it with the necessary olfactory information, a nautilus has a pair of olfactory organs at its disposal, known as rhinophores, positioned on either side of the head.


 		 Basil, J.A.; Hanlon, R.T.; Sheikh, S.I.; Atema, J. (2000): "Three-dimensional odor tracking by Nautilus pompilius". Journal of Experimental Biology. 203 (9): 1409 - 1414. (Abstract).

Nautiluses also possess a pair of statocysts - fluid-filled sensory vesicles located behind the pedal ganglia within the ring-shaped brain. They contain small calcareous particles that respond to movement and vibration and thus allow the nautilus to detect changes in orientation and water movement and even might contribute to the perception of low-frequency sounds.

Tentacles and Locomotion


The head of a Palau Nautilus (Nautilus belauensis): Palau, Micronesia.
Photo: Kai Squires (iNaturalist). Enlarge Image!		  
Unlike the ten-armed cuttlefish and squids and the eight-armed octopuses, nautiluses have a far greater number of appendages at their disposal. Depending on the species and sex, they may bear between 50 and 90 tentacles. As do their simple eyes, this represents another "primitive" feature, suggesting that the Nautiloidea are evolutionarily much older than the more derived and highly specialised Coleoidea  ( Cephalopod Systematics).

 
Frontal view of a Nautilus pompilius.
Photo: Hans Hillewaert (Source).
Each tentacle of a nautilus consists of a slender cirrus (the actual tentacle) that can be withdrawn into a protective sheath (see picture on the left). Unlike the arms of modern coleoids, these so-called cirri bear no sucker cups. Instead, they are equipped with adhesive ridges that help secure prey. In the midst of the tentacles the funnel (siphon or hyponome) is positioned, which enables locomotion by means of the characteristic cephalopod jet propulsion. By expelling water from the mantle cavity through the funnel, the nautilus generates thrust and moves through the water.

Although jet propulsion is generally regarded as less energy-efficient than locomotion using fins (as in squids) or the undulating mantle seam (as in cuttlefish), nautiluses employ it remarkably efficiently: They also possess no real other way of propulsion and must also take into account their relatively low metabolic rate and the reduced oxygen content in the deeper and denser water layers.

Nautiluses use two different methods of locomotion: For a slow forward movement, the funnel is directed backwards, causing the animal to move gently forwards. During rapid escape responses, however, the funnel is swung forwards, ejecting a powerful jet of water and retreating the nautilus out of danger fast.


 		 Neil, T.R.; Askew, G.N. (2018): "Swimming mechanics and propulsive efficiency in the chambered nautilus". Royal Society Open Science. 5 (2) 170467. (Link).

Ecology

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Nautilus macromphalus: Lifou, New Caledonia, Pacific.
Photo: Pauline Fey (iNaturalist). Enlarge Image!		  
Nautiluses are scavengers and opportunistic predators. They locate their food primarily by smell, feeding on carrion as well as small crustaceans, worms and fishes. They will also consume the freshly shed exoskeletons (exuviae) of larger crustaceans such as lobsters. It is therefore not uncommon to observe several nautiluses gathering around the carcass of a dead marine animal. The nautilus also uses calcium obtained from crustacean exoskeletons to grow and repair its own shell.

Phil Eyden: Nautiloids - The First Cephalopods (The Octopus News Magazine Online, 2020).
Ward, P.D.: "The Natural History of Nautilus". Allen and Unwin, London, 1987.

Compared with their much more agile shell-less relatives, nautiluses are relatively slow-moving animals. They prefer cooler waters and are generally absent from habitats where temperatures exceed 25°C. It was long assumed that nautiluses spend the daytime in deeper waters and ascend into shallower depths at night to restore buoyancy, search for food and reproduce. However, observations by Dunstan et al. (2011) suggest that this is not a universal pattern. Experiments tracking several individuals of Nautilus pompilius revealed considerable variation, with different animals showing both diurnal and nocturnal activity patterns.

Dunstan, A.J.; Ward, P.D.; Marshall, N.J. (2011): Vertical Distribution and Migration Patterns of Nautilus pompilius. PLoS ONE 6 (2): e16311. (Link).
EV Nautilus: First nautiloids spotted from E/V Nautilus on last dive of season!. ( YouTube Video).

 
Nautilus pompilius. Photo: Vladimír Motyčka (biolib.cz).		  
Palau Nautilus (Nautilus belauensis) in a cage, Palau, Micronesia.
Photo: Lee R. Berger (Source). Enlarge Image!
Although the shell is assumed to withstand depths of up to approximately 800 m, the deepest recorded observation of Nautilus pompilius was made at 703 m. The depths nearest to the surface still regularly inhabited by nautilids generally are around 100 m, with the exception of regions around New Caledonia and Vanuatu, where nautilids have been observed at considerably shallower depth levels because surface waters in this region are cooler than those of more equatorial seas. Throughout their area of presence, nautilids show a clear preference for cooler water and are rarely found where the water temperature exceeds 25°C.

Reproduction and Development

Compared to most other cephalopods, nautilids have a remarkably long lifespan: Nautilus pompilius may live for up to 20 years, however sexual maturity is reached only after about 12–15 years. Female nautiluses can be distinguished from males by their wider shell aperture.

Unlike many other cephalopods, male nautiluses do not possess a hectocotylus. Instead, they carry a specialised reproductive organ known as the spadix (Latin: "spade"), which is derived from four modified tentacles and is likewise used to transfer a spermatophore to the female during mating.

Following fertilisation, the female lays comparatively few eggs, typically only 10–12 per year. Embryonic development is unusually slow and may take between 10 and 12 months. Unlike most other cephalopods, however, nautilids do not pass through a free-swimming planktonic larval stage. Instead, fully formed juvenile nautiluses hatch and begin feeding independently almost immediately.

Species and Distribution

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Palau Nautilus (Nautilus belauensis): Palau, Micronesia.
Photo: Lee R. Berger (Source) Enlarge Image!		  
The Palau Nautilus (Nautilus belauensis)

The Palau Nautilus, endemic to the Palau Archipelago (Nautilus belauensis, see above), as by MolluscaBase is considered a "Taxon inquirendum", meaning the species is considered unclear by several scientists, since it cannot simply be distinguished from other species and data are (so far) insufficient for an conclusive identification (As of: 05.06.2026).

Source: MolluscaBase (2025): Nautilus belauensis Saunders, 1981.		  
Nautiluses live on the steep outer slopes of Indo-Pacific coral reefs, across a range extending roughly from 30°N to 30°S latitude and from 90°E to 175°E longitude. The depths at which the animals are present vary between species and are also influenced by age and local water temperatures (see Ecology).

Although their way of life has remained largely unchanged over millions of years of evolutionary history, nautiluses are no longer nearly as abundant as they were during earlier geological periods. Their distribution has contracted considerably, particularly since the expansion of seals (pinnipeds) during the late Cenozoic and especially since the Pleistocene ( Geological Time Periods).

Today, nautiluses are almost exclusively found in regions where seals are absent.

Genus Nautilus

 

Class Cephalopoda Cuvier, 1795

Subclass Nautiloidea
Order Nautilida

Superfamily Nautiloidea
Family Nautilidae

Nautilus Linnaeus, 1758
Nautilus macromphalus G. B. Sowerby II, 1849
Nautilus pompilius Linnaeus, 1758
Nautilus samoaensis Barord et al., 2023
Nautilus stenomphalus G. B. Sowerby II, 1849
Nautilus vanuatuensis Barord et al., 2023
Nautilus vitiensis Barord et al., 2023

Allonautilus Linnaeus, 1758
Allonautilus scrobiculatus ([Lightfoot], 1768)

Source: MolluscaBase (2025): Nautilidae Blainville, 1825, simplified.
At present, six living species are recognised within the genus Nautilus, three of which were described only in 2023. In addition, one recognised species belongs to the genus Allonautilus ( Simplified Systematics on the right).

Several further nautilus populations assigned to the genus Nautilus remain taxonomically unresolved.


 		 Animal Fact Files: Nautilus Facts: Older than Dinosaurs! ( YouTube Video).

 		 MolluscaBase (2021): Nautilus Linnaeus, 1758.

 		 Saunders, W.B.; Mapes, R.H.; White, M.M.; Hastie, L.C.; Yaqin, K. (2017): "Descriptions of Nautilus pompilius Linnaeus, 1758 from the Type Area, Ambon, Molucca Islands, and from Sumbawa - Lombok Islands, Indonesia," American Malacological Bulletin 35 (1), 1 - 14. (Abstract).

As with gastropod shells, species identification relies primarily on shell morphology, including shell size, shape and the proportions of the aperture and umbilicus relative to the entire shell. The size and shape of the callus, a thickened calcareous layer partially covering the umbilicus, are also important diagnostic characters. Geographic distribution is equally significant, since many species are restricted to relatively small areas.

The Fuzzy Nautilus (Allonautilus scrobiculatus)


Allonautilus scrobiculatus: Ndrova Island, Papua New Guinea.
Photo: Peter Ward (Source). Enlarge Image! 		  
Allonautilus scrobiculatus is the only widely accepted species of the genus Allonautilus and thus the only living member of the family Nautilidae that is not a part of the genus Nautilus. A second putative species, Allonautilus perforatus, is known only from a small number of shells and is currently regarded as taxonomically uncertain.

MolluscaBase (2025): Allonautilus Ward & Saunders, 1997.
Wikipedia: Allonautilus scrobiculatus.

Although Nautilus scrobiculatus had already been described from a shell collection in 1786, its rarity and scattered distribution within a narrow depth range meant that no living specimen was observed until 1984, first by W. B. Saunders and shortly afterwards by Peter Ward. For many years thereafter, no further sightings were reported and the species was even assumed extinct. In 2015, however, Peter Ward once again managed to find living specimens near Ndrova Island in Papua New Guinea. Additional observations from the nearby Bismarck Archipelago have since been recorded, including video footage shown in a YouTube Video. To date, fewer than ten confirmed observations of living Allonautilus scrobiculatus are believed to have taken place.

 
Nautilus pompilius (above) and Allonautilus scrobiculatus: Ndrova Island,
Papua New Guinea. Photo: Peter Ward (Source). Enlarge Image!
   
 
Peter Ward with a Nautilus pompilius (left) and an Allonautilus scrobi-
culatus (right): Manus Island, Papua New Guinea, 2015.

 		 Saunders, W.B.; Davis, L.E.; Knight, R.L. (1987): "Sympatric species of Nautilus (N. pompilius and N. scrobiculatus) in the Admiralty Islands, Papua New Guinea". Nautilus 101 (2), 93 - 99. (Link).

 		 Cool Green Science (2015): Searching for Rare Nautilus in the Bismarck Sea. ( YouTube Video).

 		 James Urton (2015): Rare nautilus sighted for the first time in three decades.

 		 Hamilton, R.; Barord, G.; Devantier, L. (2019): "First record of the 'golden nautilus' (Allonautilus scrobiculatus) from Solomon Islands". Reef Encounter. (Link).
Description

Like other nautilids, Allonautilus scrobiculatus has a coiled external shell, numerous tentacles or cirri, and two pairs of gills rather than the single pair found in other living cephalopods. Beyond these similarities, however, it is noticeably different from species of Nautilus.

The shell surface is strongly ribbed, hence the species name. The outer organic shell layer, or periostracum, is exceptionally well developed and covers most of the shell, giving it a rough, shaggy and somewhat crusted appearance. This has led to the English vernacular names "Fuzzy Nautilus" and "Crusty Nautilus". The surface of the hood is also covered with conspicuous white papillae of irregular, often multi-pointed shape. The shell typically grow to about 18 cm in diameter, although specimens exceeding 20 cm have been recorded.

Anatomically, the species differs from other nautilids in several respects, most notably in the structure of the gills, which are smaller and bear fewer lamellae, as well as in aspects of the reproductive system.

Distribution

Allonautilus scrobiculatus is known from the waters surrounding Papua New Guinea and the Solomon Islands. It is particularly sensitive to water temperature and is therefore confined to a relatively narrow depth range of approximately 150 - 400 m. The upper limit is determined by the warm surface waters of its habitat, which exceed the species' thermal tolerance. At greater depths, its distribution is ultimately constrained by the pressure limits of the shell.

Although its range today appears to be somewhat larger than originally assumed, the species remains highly vulnerable because of its fragmented distribution and small, isolated populations.

Systematics

The species was first mentioned in 1786 by Lightfoot as Nautilus scrobiculatus ("the ribbed nautilus") in the catalogue of a natural history collection. The conspicuous periostracum was unsurprisingly not noted then, since it is usually preserved only in living or recently deceased specimens, much alike to many gastropods. Thus, the much more apparent strongly ribbed shell surface attracted particular attention during the original description.

Linnaeus had previously described Nautilus umbilicatus from Indonesia in 1758, although it remains uncertain if this taxon might represent a synonym of Allonautilus scrobiculatus. Only in 1997 did Ward and Saunders place the species in its own genus, Allonautilus, recognising that its numerous morphological and anatomical differences from Nautilus warranted separate generic status.

Ward, P.D.; Saunders, W.B. (1997): "Allonautilus: a new genus of living nautiloid cephalopod and its bearing on phylogeny of the Nautilida". Journal of Paleontology 71 (6), 1054 - 1064. (Abstract).

Economic Importance and Threat Situation

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Nautilus shells cut open in Bali.
Photos: Vincent Nijman.		  
A chess set made from Nautilus shell.		  
Nautiluses are only of marginal importance for human consumption, mainly as a local food resource or an occasional exotic delicacy. Their greatest commercial significance, however, lies elsewhere: Living animals are traded internationally for the aquarium and pet trade, while shells and shell products, both worked and unworked, are widely marketed. They are sold as curiosities and souvenirs, but also used in the jewellery, furniture, and fashion industries. Among the best-known products are the so-called Osmeña pearls, which are not even true pearls at all (see above). Instead, they are handcrafted from pieces of nautilus shell that are cut, polished, and shaped into pearl-like ornaments.

Like many other mollusc shells, nautilus shells have been collected and traded for centuries. Their shape closely resembles a logarithmic spiral, often associated with the so-called Golden Ratio, and as early as during the Renaissance era they were fashioned into elaborate chalices and other decorative objects. While only relatively small numbers of shells were collected during that period, the demand of modern industries is far greater. According to Nijman et al. (2025), a single piece of furniture decorated with nautilus mother-of-pearl from Indonesia may require the processing of up to one hundred shells, resulting in severe overexploitation of local populations.

Most of today's nautilus trade originates from fishery in the Philippines, with increasing contributions from Indonesia and New Caledonia. Recent studies (Dunstan et al., 2011) have shown that nautilus fishery in the Philippines has experienced a decline of approximately 80% within only 10–20 years, despite the fact that fishing effort is generally low and often involves only three to four fishers at a given site. Existing regulations in the countries concerned, particularly the Philippines and Indonesia, are often inadequately enforced.

 
Nautilus chalice (Germany, 16. century), Sforza Castle, Milano, Italy.
Photo: Giovanni Dall'Orto (Source).
Several biological characteristics make nautiluses especially vulnerable to overfishing: Their distribution, as mentioned before, is restricted to the Indo-Pacific, where they live on steep coral reef slopes at depths ranging from the surface to about 700 m. In most regions, however, the upper limit of their distribution lies closer to 100 m because the shallow surface waters are too warm. Rising sea temperatures associated with climate change are also likely to exacerbate this restriction.

In addition, nautiluses are benthic animals whose dispersal is limited by the maximum diving depth of their shells of about 800 m. Without a free-swimming larval stage which would be able of crossing deeper oceanic areas, populations on individual reef systems are often isolated from one another. Thus, local population losses cannot easily be compensated, for example by immigration from neighbouring areas. Although nautiluses may live for two decades or more, they only reach sexual maturity at an advanced age. They also produce relatively few eggs, while embryonic development takes many months before hatching ( Reproduction and Development).

All taken together, isolated populations, sensitivity to environmental change, particularly rising sea temperatures, and a low reproductive rate make nautiluses highly susceptible to human influence. Overfishing, especially where regulations are insufficiently enforced, remains one of the most significant threats in countries such as the Philippines and Indonesia. Beyond direct exploitation, the continuing degradation and destruction of coral reef habitats through both human activities and environmental change must also be regarded as a major factor affecting the long-term survival of these remarkable cephalopods.

Dunstan, A.; Bradshaw, C.J.; Marshall, J. (2011): "Nautilus at risk - estimating population size and demography of Nautilus pompilius". PLoS One 6 (2): e16716. (Link).
Nijman, V.; Campera, M.; Balestri, M. et al. (2025): "Protection, policies, prisoners and prosecutions linked to nautilus shells in traditional handicrafts". Discover Animals 2, 60. (Link).

Links

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Literature

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Latest Change: 20.06.2026 (Robert Nordsieck).
Latest Link Check: 24.05.2026.