Nautilus
Nautilus belauensis
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Subclass: Nautiloidea Order: Nautilida Suborder: Nautilina Agassiz, 1847 Family: Nautilidae Blainville, 1825
Genera
Allonautilus Nautilus

Nautilus (from Greek ναυτίλος, 'sailor') is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. The Palau Nautilus ( Nautilus belauensis) is a species of Nautilus native to the waters around the Pacific Island nation of Palau Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Nautilida is an order of mostly prehistoric Cephalopods that includes the modern Nautiluses and their immediate ancestors and relatives Jean Louis Rodolphe Agassiz ( May 28 1807 — December 14 1873) was a Swiss - American Zoologist, Glaciologist Henri Marie Ducrotay de Blainville ( September 12, 1777 - May 1, 1850) was a French Zoologist and Anatomist. A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic The Genus Allonautilus contains two species of Nautiluses which differ significantly in terms of morphology from those placed in the sister Taxon Nautilus is a Genus of Cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by It comprises six species in two genera, the type of which is the genus Nautilus. In biology the phrase type genus is used differently depending on the nomenclatural ''Code'' that applies In zoological nomenclature, a type Nautilus is a Genus of Cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of Though it more specifically refers to the species Nautilus pompilius, the name chambered nautilus is also used for any species of the Nautilidae.

Having survived relatively unchanged for millions of years, nautiluses represent the only living members of the subclass Nautiloidea, and are often considered to be "living fossils. Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Living fossil is an informal term for any living Species (or Clade) of organism which appears "

The name "Nautilus" originally referred to the Argonauta, otherwise known as paper nautiluses, because they allegedly use their two expanded arms as sails (cf. The argonauts ( Genus Argonauta, the only extant genus in the Argonautidae family are a group of Pelagic Octopuses Aristotle Historia Animalium 622b). Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great.

Description

The nautilus is similar in general form to other cephalopods, with a prominent head and tentacles. Tentacles can refer to the elongated flexible organs that are present in some animals especially Invertebrates and sometimes to the hairs of the leaves of some insectivorous Nautiluses typically have more tentacles than other cephalopods, up to ninety. These tentacles are arranged into two circles and, unlike the tentacles of other cephalopods, they have no suckers, are undifferentiated and retractable. The radula is wide and distinctively has nine teeth. The radula is a toothed Chitinous ribbon typically used for scraping cutting and chewing food before it enters the Esophagus. There are two pairs of gills. A gill is an anatomical structure found in many aquatic organisms

Nautilus pompilius is the largest species in the genus. One form from western Australia may reach 26. For a topic outline on this subject see List of basic Australia topics. 8 cm in diameter. However, most other nautilus species never exceed 20 cm. Nautilus macromphalus is the smallest species, usually measuring only 16 cm. The Bellybutton Nautilus ( Nautilus macromphalus) is a species of Nautilus native to the waters off New Caledonia, the Loyalty Islands, and

The shell

Nautilus shells: N. macromphalus (left), A. scrobiculatus (centre), N. pompilius (right)

Nautiluses are the sole cephalopods whose bony structure of the body is externalized as a shell. The animal can withdraw completely into its shell, closing the opening with a leathery hood formed from two specially folded tentacles. Tentacles can refer to the elongated flexible organs that are present in some animals especially Invertebrates and sometimes to the hairs of the leaves of some insectivorous The shell is coiled, calcareous, nacreous and pressure resistant (imploding at a depth of about 800 m). Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer The nautilus shell is composed of 2 layers: the outer layer is a matte white, while the inner layer is a striking white with iridescence. Iridescence is an Optical phenomenon in which Hue changes with the angle from which a surface is viewed The innermost portion of the shell is a pearlescent blue-gray. The osmena pearl, contrarily to its name, is not a pearl, but a jewelry product derived from this part of the shell. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. Jewellery (also spelled jewelry, see spelling differences) is a personal Ornament, such as a necklace ring or bracelet made from Gemstones

The shell is internally divided into chambers, the chambered section being called the phragmocone. The phragmocone is the chambered portion of the shell of a Cephalopod. The phragmocone is divided into camerae by septa, all of which are pierced in the middle by a duct, the siphuncle. In Biology, Camera can refer to Camera (anatomy, spaces or chambers enclosed between two adjacent septa in the Phragmocone Septa (singular septum) are thin walls or partitions between the internal chambers ( Camerae) of the shell of a Cephalopod, namely Nautiloids The siphuncle is a strand of tissue passing longitudinally through the shell of a Cephalopod Mollusk. As the nautilus matures its body moves forward, sealing the camerae behind it with a new septum. The last fully open chamber, also the largest one, is used as the living chamber. The number of camerae increases from around four at the moment of hatching to thirty or more in adults. Hatching ( hachure in French) and cross-hatching are artistic techniques used to create tonal or shading effects by drawing (or painting or scribing closely

The shell coloration also keeps the animal cryptic in the water. In Ecology, crypsis is the ability of an organism to avoid observation When seen from the top, the shell is darker in color and marked with irregular stripes, which makes it blend into the darkness of the water below. On the contrary, the underside is almost completely white, making the animal indistinguishable from brighter waters near the ocean surface. This mode of camouflage is named countershading. Camouflage is a method of cryptic or concealing coloration that allows an otherwise visible Organism Countershading, or Thayer’s Law, is a form of Camouflage. Countershading in which an animal’s pigmentation is darker dorsally, is often thought

The nautilus shell presents one of the finest natural examples of a logarithmic spiral. Definition In Polar coordinates ( r, θ the curve can be written as r = ae^{b\theta}\ or \theta (It is sometimes incorrectly claimed to be a golden spiral as well. In Geometry, a golden spiral is a Logarithmic spiral whose growth factor b is related to &phi the Golden ratio. )

A nautilus shell viewed from above (left), from underneath (centre), and a hemishell showing the camerae in a logarithmic spiral (right)

Buoyancy and movement

Nautilus locomotion
• File format: Ogg multiplexed audio/video file, Theora/Vorbis • File size: 1. Definition In Polar coordinates ( r, θ the curve can be written as r = ae^{b\theta}\ or \theta 29 MB • Duration: 5. 0s

Nautilus with extended tentacles and hyponome visible

In order to swim, the nautilus draws water into and out of the living chamber with the hyponome, which makes use of jet propulsion. The hyponome or siphon is the organ used by Cephalopods for locomotion specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to When water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants When water is pumped out, the animal adjusts its buoyancy with the gas contained in the chamber. In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is Buoyancy can be controlled by the osmotical pumping of gas and fluid into or from the camerae along the siphuncles. Osmosis is the Diffusion of a solvent (frequently water through a semi-permeable membrane, from a solution of low solute concentration (high water potential The control of buoyancy in this manner limits the nautilus; they cannot operate under extreme hydrostatic pressures. Fluid statics (also called hydrostatics) is the Science of Fluids at rest and is a sub-field within Fluid mechanics.

In the wild, nautiluses usually inhabit depths of about 300 m, rising to around 100 m at night for feeding, mating and egg laying. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. The shell of the nautilus cannot withstand depths greater than approximately 800 m.

Diet and sensory system

Nautiluses are predators and feed mainly on shrimp, small fish and crustaceans, which are captured by the tentacles. True shrimp are swimming decapod Crustaceans classified in the Infraorder Caridea, found widely around the world in both fresh Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting However, due to the very little energy they devote to swimming, they need only eat once a month. Unlike other cephalopods, they do not have good vision; their eye structure is highly developed but lacks a solid lens. The lens is a transparent biconvex structure in the Eye that along with the Cornea, helps to Refract Light to be focused They have a simple "pinhole" lens through which water can pass. A' pinhole camera' is a very simple Camera with no lens and a single very small Aperture. Instead of vision, the animal is thought to use olfaction as the primary sensory means during foraging, locating or identifying potential mates. Olfaction (also known as olfactics or smell) refers to the Sense of smell. Foraging theory is a branch of Behavioral ecology that studies the foraging behavior of animals in response to the environment in which the animal lives

Reproduction and lifespan

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. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. Nautiluses reproduce by laying eggs. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. Gravid females attach the fertilized eggs to rocks in shallow waters, whereupon the eggs take eight to twelve months to develop until the 30 mm juveniles hatch. Females spawn once per year and regenerate their gonads, making nautiluses the only cephalopods to present iteroparity or polycyclic spawning. The gonad is the organ that makes Gametes The gonads in males are the Testes and the gonads in Females are the Ovaries. Reproduction is the Biological process by which new individual Organisms are produced Reproduction is the Biological process by which new individual Organisms are produced The lifespan of nautiluses is about 20 years, which is exceptionally long for a cephalopod.

Classification

The genus Nautilus contains six extant species and several extinct species. Extant is a term commonly used to refer to Taxa (such as Species, genera or families) that are still in existence (living

• Genus Allonautilus
  • Allonautilus perforatus
  • Allonautilus scrobiculatus
• Genus Nautilus
  • Nautilus belauensis
  • †Nautilus clarkanus
  • †Nautilus cookanum
  • Nautilus macromphalus
  • Nautilus pompilius (type)
    • Nautilus pompilius pompilius
    • Nautilus pompilius suluensis
  • †Nautilus praepompilius
  • Nautilus stenomphalus

Dubious or uncertain taxa

The following taxa associated with the family Nautilidae are of uncertain taxonomic status:^[1]

Distribution

Nautiluses are only found in the Indo-Pacific, from 30° N to 30° S latitude and 90° to 185° W longitude. The Genus Allonautilus contains two species of Nautiluses which differ significantly in terms of morphology from those placed in the sister Taxon Allonautilus perforatus is a Species of Nautilus native to the waters around Bali, Indonesia. The Crusty Nautilus ( Allonautilus scrobiculatus) is a species of Nautilus native to the waters around New Guinea, specifically New Britain Nautilus is a Genus of Cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of The Palau Nautilus ( Nautilus belauensis) is a species of Nautilus native to the waters around the Pacific Island nation of Palau Nautilus clarkanus is an extinct species of Nautilus. It lived during the Lower Carboniferous. Nautilus cookanum is an extinct species of Nautilus. It lived during the Eocene Epoch. The Bellybutton Nautilus ( Nautilus macromphalus) is a species of Nautilus native to the waters off New Caledonia, the Loyalty Islands, and In Taxonomy, a type species is the species that originally defined a genus. Nautilus praepompilius is an extinct species of Nautilus. It lived during the late Eocene and Oligocene Epochs The White-patch Nautilus ( Nautilus stenomphalus) is a species of Nautilus native to the Great Barrier Reef. A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to Queensland is a state of Australia, occupying the north-eastern corner of the mainland continent For a topic outline on this subject see List of basic Australia topics. The Foraminifera, ("Hole Bearers" or forams for short are a large group of Amoeboid Protists with reticulating Pseudopods fine The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine. The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history Helix is a Genus of terrestrial pulmonate Snails native to Europe and the regions around the Mediterranean Sea. The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The phrase nomen nudum is a Latin term meaning "naked name" The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history New Guinea, located just north of Australia, is the world's second largest island, having become separated from the Australian mainland when the area now known New Guinea, located just north of Australia, is the world's second largest island, having become separated from the Australian mainland when the area now known New Guinea, located just north of Australia, is the world's second largest island, having become separated from the Australian mainland when the area now known The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Liburnians (or Liburni, Greek: Λιβυρνοί were an ancient people inhabiting the district called Liburnia, a coastal region of the northeastern The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The Linnean Society of London is the World 's premier society for the study and dissemination of Taxonomy and natural history The phrase nomen nudum is a Latin term meaning "naked name" The Indo-Pacific is a biogeographic region of the earth's seas comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean They inhabit the deep slopes of coral reefs. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water

Natural history

Fossil records indicate that nautiluses have not evolved much during the last 500 million years, and nautiloids were much more extensive and varied 200 million years ago. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Many were initially straight-shelled, as in the extinct genus Lituites. Lituites is an extinct Genus of the Nautiloids and is one of the most primitive known Cephalopods It originated in the Ordovician They developed in the Cambrian period and became a significant sea predator in the Ordovician period. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 Certain species reached over 2. 5 meters in size. The other cephalopod subclass, Coleoidea, diverged from the Nautilidae long ago and the nautilus has remained relatively unchanged since. Subclass Coleoidea is the grouping of Cephalopods containing all the primarily soft-bodied creatures Extinct relatives of the nautilus include ammonites, such as the baculites and goniatites. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class Goniatites is genus of the Goniatitaceae superfamily They are an extinct group of ammonoid, which are shelled Cephalopods related to

See also

The nautilus shell features prominently in the official emblem of New Caledonia. For the former North American fur-trading district see New Caledonia (Canada, and for the Scottish colony in Panama see Darien scheme.

• Cephalopod size, for maximum shell diameters
• The Chambered Nautilus, a poem of Oliver Wendell Holmes
• Coelacanth, another "living fossil"

References

• Ward, P. D. 1988. In Search of Nautilus. Simon and Schuster.

External links

• CephBase: Nautilidae
• Nautilidae discussion forum at TONMO.com
• Waikïkï Aquarium: Marine Life Profile: Chambered Nautilus
• A molecular and karyological approach to the taxonomy of Nautilus