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Nautilus

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Nautilus
Temporal range: Triassic–present 230–0 Ma[1]
Nautilus Palau.JPG
Nautilus belauensis
CITES Appendix II (CITES)
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Nautiloidea
Order: Nautilida
Superfamily: Nautilaceae
Family: Nautilidae
Blainville, 1825
Genera

Carinonautilus
Cenoceras
Eutrephoceras
Pseudocenoceras
Strionautilus
Allonautilus
Nautilus
† = Extinct

Synonyms[2]
  • Eutrephoceratidae Miller, 1951

The nautilus (from Latin nautilus 'paper nautilus', from Ancient Greek ναυτίλος nautílos 'sailor')[3] is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.

It comprises six living species in two genera, the type of which is the genus Nautilus. Though it more specifically refers to species Nautilus pompilius, the name chambered nautilus is also used for any of the Nautilidae. All are protected under CITES Appendix II.[4] Depending on species, adult shell diameter is between 10 and 25 cm (4 and 10 inches).

Nautilidae, both extant and extinct, are characterized by involute or more or less convolute shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle.[5] Having survived relatively unchanged for hundreds of millions of years, nautiluses represent the only living members of the subclass nautiloidea, and are often considered "living fossils".

The first and oldest fossil of Chambered Nautilus displayed at Philippine National Museum.
The first and oldest fossil of Chambered Nautilus displayed at Philippine National Museum.

The word nautilus is derived from the Greek word ναυτίλος nautílos "sailor", it originally referred to a type of octopus of the genus Argonauta, also known as 'paper nautilus', which were thought to use two of their arms as sails.[6][7]

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Argonaut (animal)

Argonaut (animal)

The argonauts are a group of pelagic octopuses. They are also called paper nautili, referring to the paper-thin eggcase that females secrete. This structure lacks the gas-filled chambers present in chambered nautilus shells and is not a true cephalopod shell, but rather an evolutionary innovation unique to the genus. It is used as a brood chamber, and to trap surface air to maintain buoyancy. It was once speculated that argonauts did not manufacture their eggcases but utilized shells abandoned by other organisms, in the manner of hermit crabs. Experiments by pioneering marine biologist Jeanne Villepreux-Power in the early 19th century disproved this hypothesis, as Villepreux-Power successfully reared argonaut young and observed their shells' development.

Cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Nautilaceae

Nautilaceae

The Nautilaceae form one of five superfamilies that make up the Nautilida according to Bernard Kummel (1964), and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae, Cymatoceratidae, Hercoglossidae, and Aturiidae. Shimanskiy (1957) separated the Paracenoceratidae and Pseudonautilidae from his near equivalent Nautilina and added them to the Lyroceratina, expanding the equivalent Clydonautilaceae and bringing it into the Jurassic. The Nautilaceae are represented by Nautilus and Allonautilus, genera included in the Nautilidae.

Nautilina

Nautilina

The Nautilina is the last suborder of the Nautilida and the only nautiloids living since the end of the Triassic. The Nautilina, proposed by Shimanskiy, is basically the Nautilaceae of Kummel, 1964, defined by Furnish and Glenister, but differs in omitting two families, the Paracenoceratidae and Pseudonautilidae which instead are placed in the Liroceratina.

Type genus

Type genus

In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name.

Nautilus (genus)

Nautilus (genus)

Nautilus is a genus of cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of morphology from those placed in the sister taxon Allonautilus. The oldest fossils of the genus are known from the Late Eocene Hoko River Formation, in Washington State and from Late-Eocene to Early Oligocene sediments in Kazakhstan. The oldest fossils of the modern species Nautilus pompilius are from Early Pleistocene sediments off the coast of Luzon in the Philippines.

Chambered nautilus

Chambered nautilus

The chambered nautilus, also called the pearly nautilus, is the best-known species of nautilus. The shell, when cut away, reveals a lining of lustrous nacre and displays a nearly perfect equiangular spiral, although it is not a golden spiral. The shell exhibits countershading, being light on the bottom and dark on top. This is to help avoid predators, because when seen from above, it blends in with the darkness of the sea, and when seen from below, it blends in with the light coming from above.

Involute

Involute

In mathematics, an involute is a particular type of curve that is dependent on another shape or curve. An involute of a curve is the locus of a point on a piece of taut string as the string is either unwrapped from or wrapped around the curve.

Whorl (mollusc)

Whorl (mollusc)

A whorl is a single, complete 360° revolution or turn in the spiral or whorled growth of a mollusc shell. A spiral configuration of the shell is found in numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the ammonites.

Siphuncle

Siphuncle

The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the septa (walls) dividing the camerae (chambers). Some older studies have used the term siphon for the siphuncle, though this naming convention is uncommon in modern studies to prevent confusion with a mollusc organ of the same name.

Living fossil

Living fossil

A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossils commonly are of species-poor lineages, but they need not be. While the body plan of a living fossil remains superficially similar, it is never the same species as the remote relatives it resembles, because genetic drift would inevitably change its chromosomal structure.

Anatomy

Diagram of the anatomical structure of a female N. pompilius including most of its internal organs.
Diagram of the anatomical structure of a female N. pompilius including most of its internal organs.

Cirri

The "tentacles" of the nautili are actually cirri (singular: cirrus), composed of long, soft, flexible appendages which are retractable into corresponding hardened sheaths. Unlike the 8–10 head appendages of coleoid cephalopods, nautiluses have many cirri. In the early embryonic stages of nautilus development a single molluscan foot differentiates into a total of 60–90 cirri, varying even within a species.[8] Nautilus cirri also differ from the tentacles of some coleoids in that they are non-elastic and lack pads or suckers. Instead, nautilus cirri adhere to prey by means of their ridged surface. Nautili have a powerful grip, and attempts to take an object already grasped by a nautilus may tear away the animal's cirri, which will remain firmly attached to the surface of the object.

The main cirri emerge from sheaths which cohere into a single firm fleshy mass. Also, the pair of cirri before the eye (pre-ocular) and the pair of cirri behind the eye (post-ocular) are separate from the others. These are more evidently grooved, with more pronounced ridges. They are extensively ciliated and are believed to serve an olfactory purpose.[9][10][11]

Digestive system

The radula is wide and distinctively has nine teeth.

The mouth consists of a parrot-like beak made up of two interlocking jaws capable of ripping the animal's food— mostly crustaceans— from the rocks to which they are attached.[12]: p. 105  Males can be superficially differentiated from females by examining the arrangement of tentacles around the buccal cone: males have a spadix organ (shaped like a spike or shovel) located on the left side of the cone making the cone look irregular, whereas the buccal cone of the female is bilaterally symmetrical.[12]: pp. 115–130 

The crop is the largest portion of the digestive tract, and is highly extensible. From the crop, food passes to the small muscular stomach for crushing, and then goes past a digestive caecum before entering the relatively brief intestine.

Circulatory system

Like all cephalopods, the blood of the nautilus contains hemocyanin, which is blue in its oxygenated state. There are two pairs of gills which are the only remnants of the ancestral metamerism to be visible in extant cephalopods.[13]: 56  Oxygenated blood arrives at the heart through four ventricles and flows out to the animal's organs through distinct aortas but returns through veins which are too small and varied to be specifically described. The one exception to this is the vena cava, a single large vein running along the underside of the crop into which nearly all other vessels containing deoxygenated blood empty. All blood passes through one of the four sets of filtering organs (composed of one pericardial appendage and two renal appendages) upon leaving the vena cava and before arriving at the gills for re-oxygenation. Blood waste is emptied through a series of corresponding pores into the pallial cavity.

Nervous system

The central component of the nautilus nervous system is the oesophageal nerve ring which is a collection of ganglia, commissures, and connectives that together form a ring around the animal's oesophagus. From this ring extend all of the nerves forward to the mouth, tentacles, and funnel; laterally to the eyes and rhinophores; and posteriorly to the remaining organs.

The nerve ring does not constitute what is typically considered a cephalopod "brain": the upper portion of the nerve ring lacks differentiated lobes, and most of the nervous tissue appears to focus on finding and consuming food (i.e., it lacks a "higher learning" center). Nautili also tend to have rather short memory spans, and the nerve ring is not protected by any form of brain case.[14]

Shell

Nautilus half-shell showing the camerae in a logarithmic spiral
Nautilus half-shell showing the camerae in a logarithmic spiral
Section cut of a nautilus shell
Section cut of a nautilus shell
A nautilus shell viewed from above (left), and from underneath  (right)
A nautilus shell viewed from above (left), and from underneath  (right)
A nautilus shell viewed from above (left), and from underneath (right)

Nautili are the sole living cephalopods whose bony body structure is externalized as a planispiral shell. The animal can withdraw completely into its shell and close the opening with a leathery hood formed from two specially folded tentacles. The shell is coiled, aragonitic,[15] nacreous and pressure-resistant, imploding at a depth of about 800 m (2,600 ft). The nautilus shell is composed of two layers: a matte white outer layer with dark orange stripes,[16] and a striking white iridescent inner layer. The innermost portion of the shell is a pearlescent blue-gray. The osmeña pearl, contrarily to its name, is not a pearl, but a jewellery product derived from this part of the shell.

Internally, the shell divides into camerae (chambers), the chambered section being called the phragmocone. The divisions are defined by septa, each of which is pierced in the middle by a duct, the siphuncle. As the nautilus matures, it creates new, larger camerae and moves its growing body into the larger space, sealing the vacated chamber with a new septum. The camerae increase in number from around 4 at the moment of hatching to 30 or more in adults.

The shell coloration also keeps the animal cryptic in the water. When seen from above, the shell is darker in color and marked with irregular stripes, which helps it blend into the dark water below. The underside is almost completely white, making the animal indistinguishable from brighter waters near the surface. This mode of camouflage is called countershading.

The nautilus shell presents one of the finest natural examples of a logarithmic spiral, although it is not a golden spiral. The use of nautilus shells in art and literature is covered at nautilus shell.

Size

N. pompilius is the largest species in the genus. One form from Indonesia and northern Australia, once called N. repertus, may reach 25.4 cm (10.0 in) in diameter.[17] However, most nautilus species never exceed 20 cm (8 in). Nautilus macromphalus is the smallest species, usually measuring only 16 cm (6+12 in). A dwarf population from the Sulu Sea (Nautilus pompilius suluensis) is even smaller, with a mean shell diameter of 11.56 cm (4.55 in).[18]

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Cirrus (biology)

Cirrus (biology)

In biology, a cirrus SIRR-əs, plural cirri, SIRR-eye, is a long, thin structure in an animal similar to a tentacle but generally lacking the tentacle's strength, flexibility, thickness, and sensitivity.

Coleoidea

Coleoidea

Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less". Unlike its extant sister group, Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal cuttlebone, gladius, or shell that is used for buoyancy or support. Some species have lost their cuttlebone altogether, while in some it has been replaced by a chitinous support structure. A unique trait of the group is the ability to edit their own RNA.

Olfactory system

Olfactory system

The olfactory system, or sense of smell, is the sensory system used for smelling (olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli.

Radula

Radula

The radula is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus. The radula is unique to the molluscs, and is found in every class of mollusc except the bivalves, which instead use cilia, waving filaments that bring minute organisms to the mouth.

Cephalopod beak

Cephalopod beak

All extant cephalopods have a two-part beak, or rostrum, situated in the buccal mass and surrounded by the muscular head appendages. The dorsal (upper) mandible fits into the ventral (lower) mandible and together they function in a scissor-like fashion. The beak may also be referred to as the mandibles or jaws.

Spadix (zoology)

Spadix (zoology)

In the field of zoology, a spadix is a secondary sexual organ found in some cephalopods and hydrozoans. In the genus Nautilus, the spadix is a composite erectile organ in the male located in the oral region which is composed of four highly modified tentacles and which is paired with a somewhat smaller antispadix that is also composed of four tentacles. The spadix is normally a concealed organ but quickly becomes distended upon the animal's death. The exact function of the spadix and antispadix in Nautilus is not yet known.

Hemocyanin

Hemocyanin

Hemocyanins (also spelled haemocyanins and abbreviated Hc) are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O2). They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not confined in blood cells but are instead suspended directly in the hemolymph. Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form.

Gill

Gill

A gill is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Branchia is the zoologists' name for gills.

Metamerism (biology)

Metamerism (biology)

In biology, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions. In animals, metameric segments are referred to as somites or metameres. In plants, they are referred to as metamers or, more concretely, phytomers.

Commissure

Commissure

A commissure is the location at which two objects abut or are joined. The term is used especially in the fields of anatomy and biology.The most common usage of the term refers to the brain's commissures, of which there are five. Such a commissure is a bundle of commissural fibers as a tract that crosses the midline at its level of origin or entry. The five are the anterior commissure, posterior commissure, corpus callosum, commissure of fornix, and habenular commissure. They consist of fibre tracts that connect the two cerebral hemispheres and span the longitudinal fissure. In the spinal cord there are the anterior white commissure, and the gray commissure. Commissural neurons refer to neuronal cells that grow their axons across the midline of the nervous system within the brain and the spinal cord. Commissure also often refers to cardiac anatomy of heart valves. In the heart, a commissure is the area where the valve leaflets abut. When such an abutment is abnormally stiffened or even fused, valvular stenosis results, sometimes requiring commissurotomy. The term may also refer to the junction of the upper and lower lips. It may refer to the junction of the upper and lower mandibles of a bird's beak, or alternately, to the full-length apposition of the closed mandibles, from the corners of the mouth to the tip of the beak. It may refer to the nasal and temporal meeting points of the upper and lower eyelids. In female genitalia, the joining points of the two folds of the labia majora create two commissures - the anterior commissure just anterior to the prepuce of the clitoris, and the posterior commissure of the labia majora, directly posterior to the frenulum of the labia minora and anterior to the perineal raphe.

Rhinophore

Rhinophore

A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea hares (Aplysiomorpha), and sap-sucking sea slugs (Sacoglossa).

Logarithmic spiral

Logarithmic spiral

A logarithmic spiral, equiangular spiral, or growth spiral is a self-similar spiral curve that often appears in nature. The first to describe a logarithmic spiral was Albrecht Dürer (1525) who called it an "eternal line". More than a century later, the curve was discussed by Descartes (1638), and later extensively investigated by Jacob Bernoulli, who called it Spira mirabilis, "the marvelous spiral".

Physiology

Buoyancy and movement

Nautilus locomotion
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Nautilus with extended tentacles and hyponome visible
Nautilus with extended tentacles and hyponome visible

To swim, the nautilus draws water into and out of the living chamber with its hyponome, which uses jet propulsion. This mode of propulsion is generally considered inefficient compared to propulsion with fins or undulatory locomotion, however, the nautilus has been found to be particularly efficient compared to other jet-propelled marine animals like squid and jellyfish, or even salmon at low speeds.[19] It is thought that this is related to the use of asymmetrical contractile cycles and may be an adaptation to mitigate metabolic demands and protect against hypoxia when foraging at depth.[20] While water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood.

The animal adjusts its buoyancy only in long term density changes by osmosis, either removing liquid from its chambers or allowing water from the blood in the siphuncle to slowly refill the chambers. This is done in response to sudden changes in buoyancy that can occur with predatory attacks of fish, which can break off parts of the shell. This limits nautiluses in that they cannot operate under the extreme hydrostatic pressures found at depths greater than approximately 800 metres (2,600 ft), and in fact implode at about that depth, causing instant death.[18] The gas also contained in the chambers is slightly below atmospheric pressure at sea level.[21] The maximum depth at which they can regulate buoyancy by osmotic removal of chamber liquid is not known.[22]

The nautilus has the extremely rare ability to withstand being brought to the surface from its deep natural habitat without suffering any apparent damage from the experience. Whereas fish or crustaceans brought up from such depths inevitably arrive dead, a nautilus will be unfazed despite the pressure change of as much as 80 standard atmospheres (1,200 psi). The exact reasons for this ability, which is thought to be coincidental rather than specifically functional, are not known, though the perforated structure of the animal's vena cava is thought to play an important role.[12]: p. 188 

Senses

Head of N. pompilius showing the rudimentary eye, which functions similarly to a pinhole camera
Head of N. pompilius showing the rudimentary eye, which functions similarly to a pinhole camera

Unlike many other cephalopods, nautiluses do not have what many consider to be good vision; their eye structure is highly developed but lacks a solid lens. Whereas a sealed lens allows for the formation of highly focused and clear, detailed surrounding imagery, nautiluses have a simple pinhole eye open to the environment which only allows for the creation of correspondingly simple imagery.

Instead of vision, the animal is thought to use olfaction (smell) as the primary sense for foraging and for locating and identifying potential mates.[23]

The "ear" of the nautilus consists of structures called otocysts located immediately behind the pedal ganglia near the nerve ring. They are oval structures densely packed with elliptical calcium carbonate crystals.

Brain and intelligence

Nautiluses are much closer to the first cephalopods that appeared about 500 million years ago than the early modern cephalopods that appeared maybe 100 million years later (ammonoids and coleoids). They have a seemingly simple brain, not the large complex brains of octopus, cuttlefish and squid, and had long been assumed to lack intelligence. But the cephalopod nervous system is quite different from that of other animals, and recent experiments have shown not only memory, but a changing response to the same event over time.[24][25][26]

In a study in 2008, a group of nautiluses (N. pompilius) were given food as a bright blue light flashed until they began to associate the light with food, extending their tentacles every time the blue light was flashed. The blue light was again flashed without the food 3 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours later. The nautiluses continued to respond excitedly to the blue light for up to 30 minutes after the experiment. An hour later they showed no reaction to the blue light. However, between 6 and 12 hours after the training, they again responded to the blue light, but more tentatively. The researchers concluded that nautiluses had memory capabilities similar to the "short-term" and "long-term memories" of the more advanced cephalopods, despite having different brain structures.[24][25][26] However the long-term memory capability of nautiluses was much shorter than that of other cephalopods. The nautiluses completely forgot the earlier training 24 hours later, in contrast to octopuses, for example, which can remember conditioning for weeks afterwards. However, this may be simply the result of the conditioning procedure being suboptimal for sustaining long-term memories in nautiluses. Nevertheless, the study showed that scientists had previously underestimated the memory capabilities of nautiluses.[26]

Reproduction and lifespan

Nautiluses reproduce by laying eggs. Gravid females attach the fertilized eggs, either singly or in small batches, to rocks in warmer waters (21-25 Celsius), whereupon the eggs take eight to twelve months to develop until the 30-millimetre (1.2 in) juveniles hatch.[27] Females spawn once per year and regenerate their gonads, making nautiluses the only cephalopods to present iteroparity or polycyclic spawning.[28]

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. At sexual maturity, the male shell becomes slightly larger than the female's.[29] Males have been found to greatly outnumber females in practically all published studies, accounting for 60 to 94% of all recorded individuals at different sites.[18]

The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod, many of whom live less than three even in captivity and under ideal living conditions.[30] However, nautiluses typically do not reach sexual maturity until they are about 15 years old, limiting their reproductive lifespan to often less than five years.[18]

Left: Frequency distribution of N. pompilius shell diameter at Osprey Reef, part of the Coral Sea Islands, based on  2067 captured individuals. Shells ranged in size from 76 to 145 mm, with a mean of 128.6±28.01 mm.[18]
Right: Shell diameter of mature male and female N. pompilius caught at Osprey Reef. Males (n = 870) had a mean shell diameter of 131.9±2.6 mm, compared to 118.9±7.5 mm in females (n = 86). The Osprey Reef N. pompilius population is the second smallest known in terms of mean shell diameter, after the dwarf form from the Sulu Sea (130.7 mm and 115.6 mm, respectively).[18]
Left: Frequency distribution of N. pompilius shell diameter at Osprey Reef, part of the Coral Sea Islands, based on  2067 captured individuals. Shells ranged in size from 76 to 145 mm, with a mean of 128.6±28.01 mm.[18]
Right: Shell diameter of mature male and female N. pompilius caught at Osprey Reef. Males (n = 870) had a mean shell diameter of 131.9±2.6 mm, compared to 118.9±7.5 mm in females (n = 86). The Osprey Reef N. pompilius population is the second smallest known in terms of mean shell diameter, after the dwarf form from the Sulu Sea (130.7 mm and 115.6 mm, respectively).[18]
Left: Frequency distribution of N. pompilius shell diameter at Osprey Reef, part of the Coral Sea Islands, based on 2067 captured individuals. Shells ranged in size from 76 to 145 mm, with a mean of 128.6±28.01 mm.[18]
Right: Shell diameter of mature male and female N. pompilius caught at Osprey Reef. Males (n = 870) had a mean shell diameter of 131.9±2.6 mm, compared to 118.9±7.5 mm in females (n = 86). The Osprey Reef N. pompilius population is the second smallest known in terms of mean shell diameter, after the dwarf form from the Sulu Sea (130.7 mm and 115.6 mm, respectively).[18]

Discover more about Physiology related topics

Jet propulsion

Jet propulsion

Jet propulsion is the propulsion of an object in one direction, produced by ejecting a jet of fluid in the opposite direction. By Newton's third law, the moving body is propelled in the opposite direction to the jet. Reaction engines operating on the principle of jet propulsion include the jet engine used for aircraft propulsion, the pump-jet used for marine propulsion, and the rocket engine and plasma thruster used for spacecraft propulsion.

Squid

Squid

True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.

Jellyfish

Jellyfish

Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larvae that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.

Salmon

Salmon

Salmon is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic and North Pacific basin. Other closely related fish in the same family include trout, char, grayling, whitefish, lenok and taimen.

Hypoxia (environmental)

Hypoxia (environmental)

Hypoxia refers to low oxygen conditions. Normally, 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure. In water, oxygen levels are much lower, approximately 7 ppm or 0.0007% in good quality water, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface.

Siphuncle

Siphuncle

The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the septa (walls) dividing the camerae (chambers). Some older studies have used the term siphon for the siphuncle, though this naming convention is uncommon in modern studies to prevent confusion with a mollusc organ of the same name.

Salt

Salt

Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantities in seawater. The open ocean has about 35 g (1.2 oz) of solids per liter of sea water, a salinity of 3.5%.

Buoyancy

Buoyancy

Buoyancy, or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid.

Osmosis

Osmosis

Osmosis is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential to a region of low water potential, in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves across a selectively permeable membrane separating two solutions of different concentrations. Osmosis can be made to do work. Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.

Pinhole camera

Pinhole camera

A pinhole camera is a simple camera without a lens but with a tiny aperture —effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the camera obscura effect. The size of the images depends on the distance between the object and the pinhole.

Eye

Eye

Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons (neurones). In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

Foraging

Foraging

Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavior of animals in response to the environment where the animal lives.

Ecology

Range and habitat

Number of captured N. pompilius at various depths around the Osprey Reef Seamount, Coral Sea. The data was collated from 271 trapping events spread across all months of the year. Nautiluses were most common at 300–350 m (1,000–1,100 ft). No specimens were recovered from a depth of less than 150 m (500 ft) during 18 trapping efforts.[18]
Number of captured N. pompilius at various depths around the Osprey Reef Seamount, Coral Sea. The data was collated from 271 trapping events spread across all months of the year. Nautiluses were most common at 300–350 m (1,000–1,100 ft). No specimens were recovered from a depth of less than 150 m (500 ft) during 18 trapping efforts.[18]

Nautiluses are only found in the Indo-Pacific, from 30° N to 30° S latitude and 90° E to 175° E longitude. They inhabit the deep slopes of coral reefs.

Nautiluses usually inhabit depths of several hundred metres. It has long been believed that nautiluses rise at night to feed, mate, and lay eggs, but it appears that, in at least some populations, the vertical movement patterns of these animals are far more complex.[31] The greatest depth at which a nautilus has been sighted is 703 m (2,306 ft) (N. pompilius).[31] Implosion depth for nautilus shells is thought to be around 800 m (2,600 ft).[18][31] Only in New Caledonia, the Loyalty Islands, and Vanuatu can nautiluses be observed in very shallow water, at depths of as little as 5 m (15 ft).[22][31] This is due to the cooler surface waters found in these southern hemisphere habitats as compared to the many equatorial habitats of other nautilus populations – these usually being restricted to depths greater than 100 m (300 ft).[22][31] Nautiluses generally avoid water temperatures above 25 °C (75 °F).[31]

A pair of N. pompilius feeding on two-spot red snapper (Lutjanus bohar) bait during daytime at 703 m (2,306 ft) depth. This observation constitutes the deepest record of any nautilus species.
A pair of N. pompilius feeding on two-spot red snapper (Lutjanus bohar) bait during daytime at 703 m (2,306 ft) depth. This observation constitutes the deepest record of any nautilus species.

Diet

Nautiluses are scavengers and opportunistic predators.[32][33] They eat molts of lobsters, hermit crabs, and carrion of any kind.[22]

Discover more about Ecology related topics

Coral Sea

Coral Sea

The Coral Sea is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends 2,000 kilometres (1,200 mi) down the Australian northeast coast. Most of it is protected by the French Natural Park of the Coral Sea and the Australian Coral Sea Marine Park. The sea was the location for the Battle of the Coral Sea, a major confrontation during World War II between the navies of the Empire of Japan, and the United States and Australia.

Indo-Pacific

Indo-Pacific

The Indo-Pacific is a vast biogeographic region of Earth.

Coral reef

Coral reef

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.

New Caledonia

New Caledonia

New Caledonia is a sui generis collectivity of overseas France in the southwest Pacific Ocean, south of Vanuatu, about 1,210 km (750 mi) east of Australia, and 17,000 km (11,000 mi) from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Chesterfield Islands, the Belep archipelago, the Isle of Pines, and a few remote islets. The Chesterfield Islands are in the Coral Sea. French people, especially locals, call Grande Terre "Le Caillou".

Vanuatu

Vanuatu

Vanuatu, officially the Republic of Vanuatu, is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is 1,750 km (1,090 mi) east of northern Australia, 540 km (340 mi) northeast of New Caledonia, east of New Guinea, southeast of Solomon Islands, and west of Fiji.

Lobster

Lobster

Lobsters are a family of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others. Highly prized as seafood, lobsters are economically important and are often one of the most profitable commodities in coastal areas they populate.

Hermit crab

Hermit crab

Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs' soft (non-calcified) abdominal exoskeleton means they must occupy shelter produced by other organisms or risk being defenseless.

Carrion

Carrion

Carrion is the decaying flesh of dead animals, including human flesh.

Evolution

Shell characters of the genera Nautilus and Allonautilus
Shell characters of the genera Nautilus and Allonautilus
Section cut of a nautilus shell
Section cut of a nautilus shell

Fossil records indicate that nautiloids have not evolved much during the last 500 million years. Many were initially straight-shelled, as in the extinct genus Lituites. They developed in the Late Cambrian period and became a significant group of sea predators during the Ordovician period. Certain species reached over 2.5 m (8 ft) in size. The other cephalopod subclass, Coleoidea, diverged from the nautiloids long ago and the nautilus has remained relatively unchanged since. Nautiloids were much more extensive and varied 200 million years ago. The ancestors of all Coleoidea (shell-less Cephalopods) once possessed shells, and many early Cephalopod species are only known from shell remains. Following the K-Pg extinction event most Nautiloid species went extinct, while members of Coleoidea managed to survive. Following the mass extinction the Nautilus became the only extant species of Nautiloids.[34][35] Extinct relatives of the nautilus include ammonites, such as the baculites and goniatites.[36]

The family Nautilidae has its origin in the Trigonocerataceae (Centroceratina), specifically in the Syringonautilidae of the Late Triassic[5] and continues to this day with Nautilus, the type genus, and its close relative, Allonautilus.

Fossil genera

The fossil record of Nautilidae begins with Cenoceras in the Late Triassic, a highly varied genus that makes up the Jurassic Cenoceras complex. Cenoceras is evolute to involute, and globular to lentincular; with a suture that generally has a shallow ventral and lateral lobe and a siphuncle that is variable in position but never extremely ventral or dorsal. Cenoceras is not found above the Middle Jurassic and is followed by the Upper Jurassic-Miocene Eutrephoceras.

Eutrephoceras is generally subglobular, broadly rounded laterally and ventrally, with a small to occluded umbilicus, broadly rounded hyponomic sinus, only slightly sinuous sutures, and a small siphuncle that is variable in position.

Next to appear is the Lower Cretaceous Strionautilus from India and the European ex-USSR, named by Shimankiy in 1951. Strionautilus is compressed, involute, with fine longitudinal striations. Whorl sections are subrectangular, sutures sinuous, the siphuncle subcentral.

Also from the Cretaceous is Pseudocenoceras, named by Spath in 1927. Pseudocenoceras is compressed, smooth, with subrectangular whorl sections, flattened venter, and a deep umbilicus. The suture crosses the venter essentially straight and has a broad, shallow, lateral lobe. The siphuncle is small and subcentral. Pseudocenoceras is found in the Crimea and in Libya.

Carinonautilus is a genus from the Upper Cretaceous of India, named by Spengler in 1919. Carinonautilus is a very involute form with high whorl section and flanks that converge on a narrow venter that bears a prominent rounded keel. The umbilicus is small and shallow, the suture only slightly sinuous. The siphuncle is unknown.

Obinautilus has also been placed in Nautilidae by some authorities, though it may instead be an argonautid octopus.[37][38]

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Fossil

Fossil

A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the fossil record.

Lituites

Lituites

Lituites is an extinct nautiloid genus from the Middle Ordovician and type for the Lituitidae that in some more recent taxonomies has been classified with the orthocerids and listed under the order Lituitida. Fossils have been found in New York, Argentina, Norway, Sweden, Estonia, and China.

Cambrian

Cambrian

The Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biology surpasses that of some later periods.

Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.

Coleoidea

Coleoidea

Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less". Unlike its extant sister group, Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal cuttlebone, gladius, or shell that is used for buoyancy or support. Some species have lost their cuttlebone altogether, while in some it has been replaced by a chitinous support structure. A unique trait of the group is the ability to edit their own RNA.

Species

Species

In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined.

Nautiloid

Nautiloid

Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). Only a handful of rare coiled species, the nautiluses, survive to the present day.

Extinction

Extinction

Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.

Goniatite

Goniatite

Goniatids, informally goniatites, are ammonoid cephalopods that form the order Goniatitida, derived from the more primitive Agoniatitida during the Middle Devonian some 390 million years ago. Goniatites (goniatitids) survived the Late Devonian extinction to flourish during the Carboniferous and Permian only to become extinct at the end of the Permian some 139 million years later.

Syringonautilidae

Syringonautilidae

Syringonautilidae is a family of Nautiloidea from the middle to late Triassic. Syringonautilidae comprise the last of the Trigonoceratoidea and are the source for the Nautilaceae which continued the Nautiloidea through the Mesozoic and into the Cenozoic right down to the recent. Syringonautilidae is a strictly Triassic family, derived early in the Triassic from the Grypoceratidae.

Late Triassic

Late Triassic

The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 Ma and 201.3 Ma. It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian Ages.

Nautilus (genus)

Nautilus (genus)

Nautilus is a genus of cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of morphology from those placed in the sister taxon Allonautilus. The oldest fossils of the genus are known from the Late Eocene Hoko River Formation, in Washington State and from Late-Eocene to Early Oligocene sediments in Kazakhstan. The oldest fossils of the modern species Nautilus pompilius are from Early Pleistocene sediments off the coast of Luzon in the Philippines.

Taxonomy

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

The family Nautilidae contains up to six extant species and several extinct species:

Recent genetic data has pointed to there being only three extant species: A. scrobiculatus, N. macromphalus, and N. pompilius, with N. belauensis and N. stenomphalus both subsumed under N. pompilius, possibly as subspecies.[18]

Dubious or uncertain taxa

The following taxa associated with the family Nautilidae are of uncertain taxonomic status:[39]

Binomial name and author citation Current systematic status Type locality Type repository
N. alumnus Iredale, 1944 Species dubium [fide Saunders (1987:49)] Queensland, Australia Not designated [fide Saunders (1987:49)]
N. ambiguus Sowerby, 1848 Species dubium [fide Saunders (1987:48)] Not designated Unresolved
N. beccarii Linné, 1758 Non-cephalopod; Foraminifera [fide Frizzell and Keen (1949:106)]
N. calcar Linné, 1758 ?Non-cephalopod; Foraminifera Lenticulina Adriatic Sea Unresolved; Linnean Society of London?
N. crispus Linné, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. crista Linné, 1758 Non-cephalopod; Turbo [fide Dodge (1953:14)]
N. fascia Linné, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. granum Linné, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. lacustris Lightfoot, 1786 Non-cephalopod; Helix [fide Dillwyn (1817:339)]
N. legumen Linné, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. micrombilicatus Joubin, 1888 Nomen nudum
N. obliquus Linné, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. pompilius marginalis Willey, 1896 Species dubium [fide Saunders (1987:50)] New Guinea Unresolved
N. pompilius moretoni Willey, 1896 Species dubium [fide Saunders (1987:49)] New Guinea Unresolved
N. pompilius perforatus Willey, 1896 Species dubium [fide Saunders (1987:49)] New Guinea Unresolved
N. radicula Linné, 1758 ?Non-cephalopod; F. Nodosaria Adriatic Sea Unresolved; Linnean Society of London?
N. raphanistrum Linné, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. raphanus Linné, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. semi-lituus Linné, 1758 Undetermined Liburni, Adriatic Sea Unresolved; Linnean Society of London?
N. sipunculus Linné, 1758 Undetermined "freto Siculo" Unresolved; Linnean Society of London?
N. texturatus Gould, 1857 Nomen nudum
Octopodia nautilus Schneider, 1784 Rejected specific name [fide Opinion 233, ICZN (1954:278)]

Discover more about Taxonomy related topics

Allonautilus

Allonautilus

The genus Allonautilus contains two species of nautiluses, which have a significantly different morphology from those placed in the sister taxon Nautilus. Allonautilus is now thought to be a descendant of Nautilus, rendering the latter genus paraphyletic.

Allonautilus perforatus

Allonautilus perforatus

Allonautilus perforatus also known as the Bali chambered nautilus, is a species of nautilus native to the waters around Bali, Indonesia. It is known only from drifted shells and, as such, is the least studied of the six recognized nautilus species. Thus, not much is known about it outside of the shell.

Nautilus (genus)

Nautilus (genus)

Nautilus is a genus of cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of morphology from those placed in the sister taxon Allonautilus. The oldest fossils of the genus are known from the Late Eocene Hoko River Formation, in Washington State and from Late-Eocene to Early Oligocene sediments in Kazakhstan. The oldest fossils of the modern species Nautilus pompilius are from Early Pleistocene sediments off the coast of Luzon in the Philippines.

Nautilus cookanum

Nautilus cookanum

Nautilus cookanum is an extinct species of nautilus. It lived during the Eocene epoch. N. cookanum placed within the genus Nautilus, together with extant species based on their shared shell characters. Fossils of the species from the Late Eocene Hoko River Formation are noted as one of the two oldest occurrences for the genus.

Nautilus praepompilius

Nautilus praepompilius

Nautilus praepompilius is an extinct species of nautilus. It lived from the Late Paleocene through Oligocene epochs. The first fossil specimens discovered in the Late Eocene to Oligocene-aged Chegan Formation of Kazakhstan: an additional, older specimen was found in the Late or Latest Paleocene-aged Pebble Point Formation in Victoria, Australia. N. praepompilius has been grouped into a single genus together with extant species based on their shared shell characters. It is morphologically closest to N. pompilius, hence the name. The nepionic constriction shows that the hatching size was approximately 23 mm, close to that for N. pompilius. N. praepompilius, along with aff. N. cookanum fossils from the late Eocene Hoko River Formation in Washington state are the oldest occurrences of the genus.

Subspecies

Subspecies

In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species have subspecies, but for those that do there must be at least two. Subspecies is abbreviated subsp. or ssp. and the singular and plural forms are the same.

Taxon

Taxon

In biology, a taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.

Tom Iredale

Tom Iredale

Tom Iredale was an English-born ornithologist and malacologist who had a long association with Australia, where he lived for most of his life. He was an autodidact who never went to university and lacked formal training. This was reflected in his later work; he never revised his manuscripts and never used a typewriter.

Nomen dubium

Nomen dubium

In binomial nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application.

Queensland

Queensland

Queensland is a state situated in northeastern Australia, and is the second-largest and third-most populous of the Australian states. It is bordered by the Northern Territory, South Australia and New South Wales to the west, southwest and south respectively. To the east, Queensland is bordered by the Coral Sea and the Pacific Ocean; to its north is the Torres Strait, separating the Australian mainland from Papua New Guinea. With an area of 1,852,642 square kilometres (715,309 sq mi), Queensland is the world's sixth-largest sub-national entity; it is larger than all but 15 countries. Due to its size, Queensland's geographical features and climates are diverse, including tropical rainforests, rivers, coral reefs, mountain ranges and sandy beaches in its tropical and sub-tropical coastal regions, as well as deserts and savanna in the semi-arid and desert climatic regions of its interior.

Australia

Australia

Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of 7,617,930 square kilometres (2,941,300 sq mi), Australia is the largest country by area in Oceania and the world's sixth-largest country. Australia is the oldest, flattest, and driest inhabited continent, with the least fertile soils. It is a megadiverse country, and its size gives it a wide variety of landscapes and climates, with deserts in the centre, tropical rainforests in the north-east, and mountain ranges in the south-east.

Carl Linnaeus

Carl Linnaeus

Carl Linnaeus, also known after his ennoblement in 1761 as Carl von Linné, was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the modern system of naming organisms. He is known as the "father of modern taxonomy". Many of his writings were in Latin; his name is rendered in Latin as Carolus Linnæus and, after his 1761 ennoblement, as Carolus a Linné.

Conservation status and human use

Nautilus are collected or fished for sale as live animals or to carve the shells for souvenirs and collectibles, not for just the shape of their shells, but also the nacreous inner shell layer, which is used as a pearl substitute.[40][41][42] Nautilus shells were popular items in the Renaissance and Baroque cabinet of curiosities and were often mounted by goldsmiths on a thin stem to make extravagant nautilus shell cups. The low fecundity, late maturity, long gestation period and long life-span of nautiluses suggest that these species are vulnerable to over-exploitation and demand for the ornamental shell is causing population declines.[43] The threats from trade in these shells has led to countries such as Indonesia legally protecting the chambered nautilus with fines of up to US $8,500 and/or 5 years in prison for trading in this species. Despite their legal protection, these shells were reported to be openly sold at tourist areas in Bali as of 2014.[40] The continued trade of these animals has led to a call for increased protection[44] and in 2016 all species in Family Nautilidae[45] were added to CITES Appendix II, regulating international trade.[46][47]

Discover more about Conservation status and human use related topics

Pearl

Pearl

A pearl is a hard, glistening object produced within the soft tissue of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carbonate in minute crystalline form, which has deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The finest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable.

Renaissance

Renaissance

The Renaissance is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ideas and achievements of classical antiquity. It occurred after the Crisis of the Late Middle Ages and was associated with great social change. In addition to the standard periodization, proponents of a "long Renaissance" may put its beginning in the 14th century and its end in the 17th century.

Baroque

Baroque

The Baroque is a style of architecture, music, dance, painting, sculpture, poetry, and other arts that flourished in Europe from the early 17th century until the 1750s. In the territories of the Spanish and Portuguese empires including the Iberian Peninsula it continued, together with new styles, until the first decade of the 19th century. It followed Renaissance art and Mannerism and preceded the Rococo and Neoclassical styles. It was encouraged by the Catholic Church as a means to counter the simplicity and austerity of Protestant architecture, art, and music, though Lutheran Baroque art developed in parts of Europe as well.

Cabinet of curiosities

Cabinet of curiosities

Cabinets of curiosities, also known as cabinets of wonder and wonder-rooms, were collections of notable objects. Although more rudimentary collections had preceded them, the classic cabinets of curiosities emerged in the sixteenth century. The term cabinet originally described a room rather than a piece of furniture. Modern terminology would categorize the objects included as belonging to natural history, geology, ethnography, archaeology, religious or historical relics, works of art, and antiquities. In addition to the most famous and best documented cabinets of rulers and aristocrats, members of the merchant class and early practitioners of science in Europe formed collections that were precursors to museums.

Goldsmith

Goldsmith

A goldsmith is a metalworker who specializes in working with gold and other precious metals. Nowadays they mainly specialize in jewelry-making but historically, goldsmiths have also made silverware, platters, goblets, decorative and serviceable utensils, and ceremonial or religious items.

Fecundity

Fecundity

Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to produce offspring, measured by the number of gametes (eggs), seed set, or asexual propagules.

Oliwa

Oliwa

Oliwa is a northern district of the city of Gdańsk, Poland. From east it borders Przymorze and Żabianka, from the north Sopot and from the south with the districts of Strzyża, VII Dwór and Brętowo, while from the west with Matarnia and Osowa. It is known for its medieval monastery, the 1627 Battle of Oliwa and the 1660 Treaty of Oliva.

Museo Poldi Pezzoli

Museo Poldi Pezzoli

The Museo Poldi Pezzoli is an art museum in Milan, Italy. It is located near the Teatro alla Scala, on Via Manzoni 12.

Source: "Nautilus", Wikipedia, Wikimedia Foundation, (2023, January 25th), https://en.wikipedia.org/wiki/Nautilus.

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See also
References

Notes

  1. ^ 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. doi:10.1017/S0022336000036039. JSTOR 1306604. S2CID 87319305.
  2. ^ Cichowolski, M.; Ambrosio, A.; Concheyro, A. (2005). "Nautilids from the Upper Cretaceous of the James Ross Basin, Antarctic Peninsula". Antarctic Science. 17 (2): 267. Bibcode:2005AntSc..17..267C. doi:10.1017/S0954102005002671. S2CID 128767860.
  3. ^ Lewis, Charlton T.; Short, Charles (1879). "nautĭlus or nautĭlŏs". A Latin Dictionary. Perseus Digital Library.
  4. ^ "Checklist of CITES species". CITES. Retrieved 24 June 2020. (please fill in 'Nautilus' in the search-box).
  5. ^ a b Kümmel, B. 1964. Nautiloidae-Nautilida, in the Treatise on Invertebrate Paleontology, Geological Society of America and Univ of Kansas Press, Teichert and Moore eds.
  6. ^ Liddell, Henry George; Scott, Robert (1940). "ναυτίλος". A Greek-English Lexicon. Perseus Digital Library.
  7. ^ "Origin of nautilus". Dictionary.com Unabridged. 2017. Retrieved 15 November 2017.
  8. ^ Staaf, Danna (3 October 2017). Squid Empire: The Rise and Fall of the Cephalopods. Lebanon, NH: University Press of New England. pp. 10–11. ISBN 9781512601282.
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