|Scientific name||Nautilidae||Weight||Maximum 1.27 kg (2.8 pounds)|
|Pronunciation||Nah-tee-lus||Length||16 to 25.4 centimeters (6.3 to 10 inches)|
|Classification||Mollusca, Cephalopoda, & Nautiloidea||Location||The Indo-Pacific|
With 400-million-year-old ancestors, timeless beauty, and an enigmatic nature, nautiluses are among the most fascinating deep-water creatures!
They’ve captured the attention, curiosity, and imagination of hundreds of scientists and wildlife enthusiasts.
Their popularity doesn’t end here, though! Over the centuries, their shells have been admired by hundreds of thousands of people and served as inspiration for multiple works of art.
As such, if you’re among those enchanted by these cephalopods, keep reading, as you’re about to learn some facts you’ll never forget!
Taxonomy and Classification
The term nautilus is used for the members of the Nautilidae family. It consists of eight genera, of which six are extinct. The extant genera are Allonautilus and Nautilus.
Allonautilus has two nautilus species: Allonautilus perforatus, commonly known as the Bali chambered nautilus, and Allonautilus scrobiculatus, or the crusty nautilus.
The Nautilus genus has seven species. The type species is Nautilus pompilius, or chambered nautilus.
These marine creatures are most closely related to living squid, octopuses, and cuttlefish. Ammonites are nautiluses’ closest extinct relatives.
Can you believe that nautiloids have been around for more than 400 million years?
Not only that, but they’ve even retained most of their characteristics over the years! They reached their diversity peak roughly 200 million years ago.
Most of them went extinct during the Cretaceous-Paleogene extinction event, which is why today there are only nine extant species.
The members of Nautilus and Allonautilus likely diverged during the Mesozoic in the Great Barrier Reef and around New Guinea.
Before discussing any more details, we must mention that argonauts (pelagic octopuses that form the Argonauta genus) are called paper nautiluses, but they are not true nautiluses.
Nautiluses are the only cephalopods with an external shell that protects their internal organs.
It is equipped with several chambers (up to 30), of which one serves as a living space for its owner.
Nautiluses can hide completely in the shell and close the entrance using their tentacles.
This shell is aragonitic (made of carbonate minerals) and nacreous (can be turned into pearls) and consists of two layers.
One (the outer layer) is matte white and decorated with orange stripes, and the other (the inner layer) is iridescent white.
The central part of the shell is a distinctive bluish-gray shade. The shell can differ slightly depending on the species.
For example, the fuzzy nautilus has a thick, hairy shell covered in periostracum, an organic, slime-like coating.
Nautilus tentacles are called cirri. They are long, soft, and lack the pads and suckers known in other coleoid cirri. Each nautilus has between 60 and 90 cirri.
These cephalopods have four ventricles, which transport their oxygenated blood to their internal organs.
Although their eye structure is well-developed, nautiluses do not have good eyesight because they lack the solid lens responsible for focused, clear images.
The images they see are often compared to those produced by pinhole cameras.
These cephalopods have a pair of rhinophores near the eyes. Rhinophores are ear-like structures that detect chemicals in the water.
Males and females are sexually dimorphic. If one were to observe their tentacle arrangements around the buccal cone, they’d notice something different between the two.
The female buccal cone is bilaterally symmetrical. Males, on the other hand, have an irregular cone due to the presence of a spadix, a secondary sexual organ.
Extant nautiluses aren’t as large compared to their extinct relatives. The largest living nautilus is Nautilus pompilius, with a maximum diameter of 25.4 centimeters (10 inches).
The smallest species (Nautilus macromphalus or the bellybutton nautilus) is almost half this size, reaching only 16 centimeters (6.3 inches) in diameter.
Habitat and Distribution
Nautiluses are endemic to the Indo-Pacific. They’re found in the waters between 90° E to 175° E longitude and 30° N to 30° S latitude.
They reside at different depths, the maximum recorded being 703 meters (2,306 feet).
The implosion depth is probably 800 meters (2,625 feet), and the maximum supported water temperature is 25 degrees Celsius (77 degrees Fahrenheit).
In several regions, nautiluses are spotted in shallow waters up to 5 meters (16.4 feet) deep.
However, most nautiluses prefer being active at depths of 100–300 meters (328–984 feet).
Behavior and Social Structure
While swimming, nautiluses draw water into and out of the main chamber by using a hyponome, which is the organ that produces locomotive force.
When seawater is inside the chamber, these cephalopods extract the salt from the water using their siphuncle’ a tissue that passes through their shell and connects the chambers. Then they diffuse the salt into the blood.
This siphuncle allows floating and helps maintain neutral buoyancy.
Unlike fish and crustaceans, nautiluses can withstand sudden pressure changes when brought to the water surface.
Nautiluses had long been thought to possess a poorly developed brain; in other words, scientists thought they weren’t too intelligent, or, at least, not as intelligent as squid or octopuses.
Recent studies, though, have shown that nautiluses are capable of memorizing things in a way similar to more developed cephalopods, although not for such a long period.
Octopuses, for example, probably remember things for several weeks, whereas nautiluses likely forget them within 24 hours.
These perplexing creatures can spend days in deeper areas, avoiding predators.
During the night, they may come closer to the surface to scavenge, upon which they return to safer depths.
Diet and Feeding
Nautiluses are opportunistic scavengers that feed on any animal remains they stumble upon.
Studies show that they primarily eat arthropod molts rich in organic integuments. Some specialists suggest they are active predators, but little evidence supports this.
These deep-water cephalopods feed with the help of their wide radula (a tongue-like structure) equipped with nine teeth.
Their mouths have two jaws that form a beak similar to that of a parrot. The jaws are powerful enough to rip food attached to rocks.
Nautiluses also rely on their cirri, or tentacles, to catch food. The cirri’s ridged surface allows for an excellent grip that makes grabbing prey a piece of cake.
Once nautiluses ingest the food, it reaches the crop, the largest organ of their digestive system then goes through the muscular stomach.
There, it is crushed into smaller pieces so that it can pass through the caecum and into the intestine.
Research shows that nautiluses are also capable of excavating food buried up to 25 millimeters deep in sediment.
They use the hyponome to blow the sediment away, then insert their tentacles to get to the food.
Reproduction and Life Cycle
Nautiluses reproduce by laying eggs. They likely do not have any particular courtship rituals.
On the contrary, male nautiluses will try to mate with anything they stumble upon that resembles a nautilus, even a rock!
If they’re lucky enough to find a female in the process, good for them!
During mating, males rely on the spadix, while females rely on the mantle. The spadix is used to transfer sperm into the mantle.
Afterward, the male does not release the female. Instead, he may hold onto her for hours!
Upon fertilization, females lay eggs in capsules. They are approximately 3–4 centimeters (1.2–1.6 inches) and are laid either isolated or in batches.
Females choose to attach the eggs to rocks. They may also lay the eggs in crevices between corals.
The preferred water temperature is between 21 and 25 degrees Celsius (70 and 77 degrees Fahrenheit).
The juveniles hatch roughly 8–12 months after the eggs are laid. Newly hatched nautiluses measure 3 centimeters (1.2 inches) in diameter.
It is believed that they do not have a larval stage, which is unusual for cephalopods.
Their shells start developing even before they hatch and breach the egg before the baby emerges, which is probably done by the use of the beak.
When born, nautiluses do not have as many shell chambers. Instead, the chambers develop as these cephalopods grow larger and older.
The living chamber is changed periodically when larger ones form.
Nautiluses have quite a long life expectancy. They probably reach maturity when they’re five, whereas sexual maturity is attained at 15 years of age.
It is thought they can live up to 20 years. Without a doubt, their resilience and lifespan are remarkable! Most other cephalopods do not live more than three years – not even in captivity!
Ecological Role and Interactions
Nautiluses are an important part of the marine ecosystem. Since they’re scavengers and feed on carrion, these cephalopods play a significant role in keeping their habitats healthy and clean.
Despite being small, nautiluses have few to no predators. Their strong shells, equipped with their lifestyle and location in the water, make for excellent defense mechanisms.
Although they have been seen preyed upon by octopuses, teleosts, and possibly deep-sea sharks, this doesn’t happen often – or, at least, scientists believe so.
On two occasions, specialists saw a large grouper (teleost) engulf a nautilus whole and then expel it. Afterward, the nautilus swam away.
Either way, there’s so much we don’t know yet about what happens 700 meters (feet) beneath the water surface!
Hopefully, future discoveries will reveal other jaw-dropping details about deep-sea habitats and their intra- and interspecific relationships.
Conservation Status and Threats
All nautilus species are added to CITES Appendix II, which controls international trade.
While other cephalopods are collected for their meat, nautiluses are prized for their shells, which are used as souvenirs, collectibles, and pearl substitutes.
The shells are highly valued decorative elements with a history spanning hundreds of years. Some of them are covered in artwork portraying complex historical scenes.
Although nautilus collection and shell trade may sustain a region’s economy, they negatively affect their populations.
Despite living a life of over 20 years, nautiluses have only five years to reproduce (since they reach sexual maturity at 15).
Above this, they do not have high fecundity rates, and the gestation period is unfavorably long.
These aspects make overexploitation for ornamental shells a threat to their population because, in time, nautiluses may not be able to recover.
Even though they were legally protected against trade in certain countries, people were still seeing nautilus shells for sale, which is why, in the end, all species were officially added to CITES Appendix II.
Hopefully, this will help save their population and lead to an increase in their numbers.
Unique Adaptations and Survival Strategies
A nautilus’ most notable adaptation is probably its ability to stay hidden deep in the water.
The fact that they can remain in their shells for long periods doesn’t hurt, either! They’ve also learned that it’s safer to scavenge during the night than during the day.
Although nautiluses do not have good eyesight, they compensate with their excellent sense of smell, which helps them forage and find mates.
Their rhinophores (ear-like structures) contain chemoreceptors (sensory receptors) that can also help them detect food.
Cultural Significance and Human Interactions
Since they’re among the oldest creatures that have survived till present times, nautiluses have undoubtedly earned the popularity they’re enjoying among scientists and wildlife enthusiasts.
They’re regarded as symbols of growth, renewal, and order amidst chaos. On the other hand, Palauans see them as symbols of fragility and vulnerability because they’re at a high risk of dying in rock collisions.
Besides their nature being explored for symbolistic and spiritual purposes, it is of major interest to painters, goldsmiths, historians, musicians, and poets.
They turned nautilus shells into decorative pieces that have become famous over the centuries.
During the Renaissance, nautilus shells were even displayed in cabinets of curiosities.
Additionally, goldsmiths mounted their shells on thin stems and created the famous nautilus shell cups, among which the Burghley Nef is the most notable.
Oliver Wendell Holmes, an American physician and poet, wrote a poem entitled Nautilus.
He described the cephalopod using the most beautiful terms, imagery, and metaphors, suggesting that nautiluses’ life and death served as inspiration for his growth.
There’s even a rock band called Nautilus Pompilius!
Cultural references do not end here, which is only natural considering how gorgeous and inspiring nautiluses are!
We won’t even mention all the media productions that found inspiration in the nature of nautiluses.
Unfortunately, nautiluses’ connection with humans doesn’t end on this positive note. We’re now heading toward the unpleasant part of our journey to unravel the uniqueness of these cephalopods.
As we’ve mentioned in a previous section, nautiluses have been extensively exploited for their shells.
Luckily, when the authorities noticed the degree to which they were collected and traded, they mobilized and added all species to CITES Appendix II.
We can only hope that this will save their population long-term; it would be a pity to have these cephalopods with ancestors dating back to 400 million years ago disappear, wouldn’t it?!
Future Prospects and Research
Although nautiluses are quite well-studied considering their lifestyle and location in the depths of the water, many aspects remain in the shadows, which is why further research is required and hoped for.
For example, scientists aren’t yet entirely sure if nautiluses are active predators. And if they are, how exactly do they hunt prey?
Additionally, males and females have some mysterious reproductive organs (Van der Hoeven’s organ for males; the Organ of Valenciennes; and Owen’s laminated organ for females). Scientists still have no idea what they serve!
As we’re approaching the end of this captivating journey, we’d like to remind you of the Nautilus Greatness, their prehistoric ancestry, and their remarkable adaptations to survive in the mysterious ocean depths.
Besides their physical beauty, nautiluses are employees of the ocean, as their scavenging nature helps clean the habitat and keep it healthy.
This is only one of the multiple reasons we should raise awareness and support the nautilus population. Don’t forget that even the smallest action matters!
What does nautilus mean?
The term nautilus comes from the Ancient Greek word for sailor.
Do nautiluses have venom?
There’s little scientific evidence to point out that nautiluses are venomous.
Does a nautilus have a brain?
A nautilus has a brain, although it’s simpler than that of its relatives.
Can a nautilus be kept as a pet?
Raising a nautilus in captivity is extremely difficult. They rarely even survive in public aquariums because scientists aren’t yet sure how to keep them healthy and happy in captivity. Not to mention that breeding them in captivity is almost impossible. Most of the young hatched in captivity died shortly after.