Nautilus

The nautilus is a pelagic marine mollusk belonging to the Nautilidae family of cephalopods. The nautilus is the only living member of the Nautilaceae superfamily and its tiny but nearly equal suborder, Nautilina. It consists of six live species divided into two genera, the most common of which being the Nautilus genus. The word chambered nautilus is used for any of the Nautilidae, albeit it is more precisely applied to the species Nautilus pompilius. Appendix II of the Convention on International Trade in Endangered Species protects all of them.

Extant and extinct members of the Nautilidae family have smooth involute or more or less convolute shells with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle. Nautiluses are the only living members of the subclass nautiloidea and are commonly referred to as "living fossils" since they have lived virtually unmodified for hundreds of millions of years.

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Scientific Classification of Nautilus:

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Subclass: Nautiloidea

Order: Nautilida

Superfamily: Nautilaceae

Family: Nautilidae Blainville, 1825

The name nautilus comes from the Greek word nautlos, which originally referred to the paper nautilus of the genus Argonauta, which are actually octopuses. Because paper nautiluses were assumed to employ two of their arms as sails, the name nautlos literally means "sailor."

Anatomy 

Cirri

The nautili's "tentacles'’ are actually cirri (singular: cirrus), which are made up of long, soft, flexible appendages that may be retracted into hardened sheaths. Unlike coleoid cephalopods, which have 8–10 head appendages, nautiluses have a large number of cirri. A single molluscan foot divides into 60–90 cirri into the early embryonic phases of nautilus development, different even within a species. Nautilus cirri tentacles are likewise non-elastic and lack pads or suckers, unlike those of some coleoids. Instead, nautilus cirri use their ridged surface to stick to prey.

Sheaths cohere into a single hard fleshy mass as the major cirri develop. The pair of cirri in front of the eye (pre-ocular) and the pair of cirri behind the eye (post-ocular) are also distinct. These have more pronounced ridges and are more visibly grooved. They have a lot of cilia and are thought to have an olfactory function.

Digestive System

The radula is a long, narrow structure with nine teeth. The animal's mouth is made up of a parrot-like beak with two interlocking jaws capable of pulling crustaceans from the rocks to which they are stuck.

The arrangement of tentacles surrounding the buccal cone can be used to distinguish males from females. Males have a spadix organ (formed like a spike or shovel) on the left side of the cone, which makes the cone look irregular, whilst females' buccal cones are bilaterally symmetrical.

Nervous System

The oesophageal nerve ring, a collection of ganglia, commissures, and connectives that form a ring around the animal's oesophagus, is the major component of the nautilus nervous system. All nerves branch out from this ring, leading to the mouth, tentacles, and funnel in the front, the eyes and rhinophores in the middle, and the remaining organs in the back.

Circulatory System

The nautilus' blood, like that of all cephalopods, includes hemocyanin, which is blue when oxygenated. The only remains of the original metamerism that can be seen in extant cephalopods are two pairs of gills. Oxygenated blood enters the heart through four ventricles, goes out to the animal's organs via separate aortas, and then returns through veins that are too small and variable to be detailed in detail. The vena cava, a single big vein running along the underside of the crop into which nearly all other vessels carrying deoxygenated blood empty, is the only exception. After leaving the vena cava and before reaching the gills for re-oxygenation, all blood goes through one of the four sets of filtering organs (one pericardial appendage and two renal appendages). Blood waste is discharged into the pallial cavity through a series of matching holes.

Nautilus Shell

1. Nautili are the only living cephalopods with a planispiral shell that covers their bony body. The animal may enter its shell completely and shut the hole with a leathery hood made of two specially folded tentacles. Coiled, aragonitic, nacreous, and pressure-resistant, the shell implodes at a depth of roughly 800 metres (2,600 ft). The nautilus shell is made up of two layers: a matte white outer layer and an iridescent white interior layer. The shell's innermost layer is a pearlescent blue-gray. Contrary to its name, the osmena pearl is not a pearl, but a jewellery item made from this section of the shell.

2. The shell is divided into chambers on the inside, with the chambered section known as the phragmocone. Septa separate the divisions, each of which is punctured in the middle by a duct called a siphuncle. As the nautilus becomes older, it develops a new, larger camerae and puts its developing body into them, sealing the vacated chamber with a new septum. The camerae expand in number from roughly 4 when they hatch to 30 or more when they reach adulthood.

3. The animal's shell colouring helps keep it hidden in the water. The shell is deeper in colour and has uneven stripes when viewed from above, which helps it blend into the dark water below. The animal's underside is almost totally white, blending in with the brighter waters near the top. Countershading is the term for this type of camouflage.

4. Although it is not a golden spiral, the nautilus shell is one of the best natural examples of a logarithmic spiral. A nautilus shell, you may learn about the use of nautilus shells in art and literature.

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Movement of Nautilus 

1. To swim, the nautilus employs its hyponome, which uses jet propulsion to suck water into and out of the living chamber. This style of propulsion is often considered inefficient when compared to fin propulsion or undulatory locomotion; but, when compared to other jet-propelled marine organisms like squid and jellyfish, or even salmon at low speeds, the nautilus has been proven to be very efficient. This is assumed to be linked to the utilisation of asymmetrical contractile cycles, and it could be an adaptation to reduce metabolic needs and defend against hypoxia while feeding at depth.

2. The siphuncle absorbs salt from the water inside the chamber and diffuses it into the blood. Only in long-term density changes does the animal alter its buoyancy by osmosis, withdrawing liquid from its chambers or allowing water from the siphuncle's blood to gently replenish the chambers. This is done in reaction to rapid variations in buoyancy caused by predatory fish assaults that can break off pieces of the shell. This restricts nautiluses' ability to work in intense hydrostatic pressures seen at depths more than 800 metres (2,600 feet), and they actually implode at that depth, killing them instantly. At sea level, the gas enclosed in the chambers is slightly below atmospheric pressure. It is unknown what depth they can adjust buoyancy through osmotic removal of chamber liquid.

3. The nautilus possesses the highly unique ability to survive being dragged to the surface from its deep native habitat without showing any signs of harm. Whereas fish or crustaceans brought up from such depths will almost always die, a nautilus will remain unaffected by pressure changes of up to 80 atmospheres (1,200 psi). The exact causes for this capacity, which is assumed to be coincidental rather than functional, are unknown, though the animal's vena cava's perforated structure is thought to play a key part.

Senses 

Unlike many other cephalopods, nautiluses lack what most people consider decent vision; their eye structure is highly developed but lacks a solid lens. While a sealed lens allows for the construction of highly focused and clear, detailed surrounding vision, nautiluses have a simple pinhole eye that is open to the surroundings and only allows for the generation of similarly simple imagery.

Foraging and discovering and recognising possible mates are assumed to be done primarily by olfaction (smell) rather than vision.

Reproduction 

1. Laying eggs is how nautiluses reproduce. Gravid females attach fertilised eggs to rocks in warmer waters (21-25 degrees Celsius), where they develop for eight to twelve months until the 30-millimetre (1.2 in) juveniles hatch. Nautiluses are the only cephalopods that have iteroparity, or polycyclic spawning. Females spawn once a year and regenerate their gonads.

2. Males have four tentacles modified into an organ called the "spadix," which transfers sperm into the female's mantle during mating. Nautiluses are sexually dimorphic in that males have four tentacles modified into an organ called the "spadix," which transfers sperm into the female's mantle during mating. When a male reaches sexual maturity, his shell grows slightly larger than a female's. Males have been found to outweigh females in almost all published investigations, accounting for 60 to 94 percent of all individuals observed at various sites.

3. Nautiluses have a lifespan of up to 20 years, which is unusually long for a mollusk, as many survive less than three years even in captivity and under optimal living conditions. However, nautiluses do not attain sexual maturity until about the age of 15, restricting their reproductive lives to less than five years.

Range and Habitat 

1. Only the Indo-Pacific region, from 30° N to 30° S latitude and 90° E to 175° E longitude, is home to nauplii. They live on coral reefs' deep slopes.

2. Nautiluses normally live at depths of hundreds of metres. Although it has long been assumed that nautiluses ascend at night to feed, mate, and lay eggs, it appears that their vertical mobility patterns are significantly more complex in at least some populations. A nautilus has been spotted at a depth of 703 metres (2,306 feet) (N. pompilius).

3. Nautilus Shell:

The depth of implosion for nautilus shells is estimated to be around 800 metres (2,600 ft). Nautiluses can only be found in very shallow water in New Caledonia, the Loyalty Islands, and Vanuatu, at depths as low as 5 metres (15 ft). This is owing to the cooler surface waters found in these southern hemisphere habitats, as opposed to the various equatorial habitats of other nautilus groups, which are typically restricted to depths more than 100 metres (300 ft). Water temperatures exceeding 25 °C (75 °F) are generally avoided by nautiluses.

Diet 

Nautiluses are opportunistic predators and scavengers. They devour lobster moults, hermit crabs, and any form of carrion.

Evolution 

During the last 500 million years, nautiloids have not evolved much, according to fossil records. Many, like the extinct genus Lituites, had straight shells at first. During the Ordovician epoch, they evolved into a prominent group of sea predators. Some species grew to be above 2.5 metres (8 feet) tall. Coleoidea, the other cephalopod subclass, split from the nautiloids a long time ago, and the nautilus has stayed largely unchanged since then. 200 million years ago, nautiloids were much more numerous and varied. Ammonites, such as baculites and goniatites, are extinct relatives of the nautilus.

Facts 

The shell of the Nautilus is made up of isolated chambers; Nautiluses are born with four chambers and add to them over time and hence known as chambered nautilus. A fully grown nautilus has about 30 chambers. The monster (which resembles a small octopus) resides in the newest and largest room. To maintain buoyancy, the other compartments are filled with air and water. The siphuncle is a tube that runs through each chamber and is used to transport liquids and gases from one to the other. The gas is first diluted in liquid in one chamber before being released at a low pressure in a second chamber. It's the same as opening a can of soda.

1. Nautilus is propelled by a jet that blows water out through a syphon. The nautilus's direction is determined by the position of the syphon: front, rear, upward, or below.

2. The tentacles of the Nautilus are located outside the shell and are used to catch and manipulate its prey.

3. Nautilus, like other members of the octopus family, has a beak that chops their food (crabs, shrimps, and fish).

4. When the sun goes down, the Nautilus spends the day at depths and then migrates to shallow water to hunt.

5. Only once a year do nautiluses mate. Only 25% of the nautilus captured for research are females, whereas 75% are males. Researchers are baffled as to why this is.

6. For up to 30 hours at a time, a couple of nautiluses can have sex. Males frequently bite females on the mantle during intercourse, leaving a mark on their partner's shell.

The nautilus is a type of pelagic marine mollusk that belongs to the Nautilidae cephalopod family. The only extant member of the Nautilaceae superfamily and its small but nearly equal suborder, Nautilina, is the nautilus. The name nautilus comes from the Greek word nautlos, which originally referred to the octopus-like paper nautilus of the genus Argonauta. The term nautlos literally means "sailor" since paper nautiluses were thought to use two of their arms as sails. The only surviving cephalopods having a planispiral shell covering their bony body are the nautili. The animal can entirely enter its shell and close it with a leathery hood formed of two specially folded tentacles. The shell implodes at a depth of around 800 metres, coiled, aragonitic, nacreous, and pressure-resistant (2,600 ft).