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


Nautiluses usually inhabit depths of about {{convert|300|m}}, in some localities rising to around {{convert|100|m}} at night to feed, mate and lay [[Egg (biology)|eggs]].{{fact|date=April 2012}} Individuals have occasionally been sighted at depths exceeding 700&nbsp;m; implosion depth for nautilus shells is thought to be around 800&nbsp;m.<ref name="Dunstan et al. 2011" /> Only in [[New Caledonia]], the [[Loyalty Islands]], and [[Vanuatu]] can nautiluses be observed in very shallow water.<ref name=Ward1987 /> 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.<ref name=Ward1987 />
Nautiluses usually inhabit depths of several hundred metres. It has long been believed that nautiluses rise at night to feed, mate and lay [[Egg (biology)|eggs]], but it appears that, in at least some populations, the vertical movement patterns of these animals are far more complex.<ref name=vertical>{{cite doi|10.1371/journal.pone.0016311}}</ref> The greatest depth at which a nautilus has been sighted is 703&nbsp;m, for two specimens of ''N.&nbsp;pompilius''.<ref name=vertical /> Implosion depth for nautilus shells is thought to be around 800&nbsp;m.<ref name="Dunstan et al. 2011" /><ref name=vertical /> Only in [[New Caledonia]], the [[Loyalty Islands]], and [[Vanuatu]] can nautiluses be observed in very shallow water (at a depth of as little as 5&nbsp;m).<ref name=Ward1987 /><ref name=vertical /> 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&nbsp;m).<ref name=Ward1987 /><ref name=vertical /> Nautiluses generally avoid water temperatures above 25°C.<ref name=vertical />


There is growing concern that nautiluses are being greatly overfished.<ref>{{cite news |title=Loving the Chambered Nautilus to Death |author=Broad WJ |url=http://www.nytimes.com/2011/10/25/science/25nautilus.html?_r=4 |newspaper=New York Times |date=24 October 2011 |accessdate=25 October 2011}}</ref> Their limited ecological range and the late onset of their sexual maturity combined with this overfishing has led to recent investigations into the need to protect them from possible endangerment or extinction.<ref>{{cite journal |author=Dunstan AJ; Bradshaw CJA; Marshall NJ |title=Nautilus at Risk – Estimating Population Size and Demography of ''Nautilus pompilius''. |journal=PLoS ONE |volume=6 |issue=2 |pages=e16716 |year=2011 |month=February |doi=10.1371/journal.pone.0016716 |url=http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016716}}</ref>
There is growing concern that nautiluses are being greatly overfished.<ref>{{cite news |title=Loving the Chambered Nautilus to Death |author=Broad WJ |url=http://www.nytimes.com/2011/10/25/science/25nautilus.html?_r=4 |newspaper=New York Times |date=24 October 2011 |accessdate=25 October 2011}}</ref> Their limited ecological range and the late onset of their sexual maturity combined with this overfishing has led to recent investigations into the need to protect them from possible endangerment or extinction.<ref>{{cite journal |author=Dunstan AJ; Bradshaw CJA; Marshall NJ |title=Nautilus at Risk – Estimating Population Size and Demography of ''Nautilus pompilius''. |journal=PLoS ONE |volume=6 |issue=2 |pages=e16716 |year=2011 |month=February |doi=10.1371/journal.pone.0016716 |url=http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016716}}</ref>

Revision as of 19:56, 1 April 2012

For other uses, see Nautilus (disambiguation).

Nautilus
Temporal range: Triassic–Present[1]
Nautilus belauensis
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Cephalopoda
Subclass:
Nautiloidea
Order:
Nautilida
Superfamily:
Nautilaceae
Family:
Nautilidae

Genera

†Carinonautilus
†Cenoceras
†Eutrephoceras
†Pseudocenoceras
†Strionautilus
Allonautilus
Nautilus

Synonyms[2]
  • Eutrephoceratidae Miller, 1951

Nautilus (from Greek ναυτίλος, 'sailor') is the common name of marine creatures of cephalopod family Nautilidae, 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 species of the Nautilidae.

Nautilidae, both extant and extinct, are characterized by involute or slightly evolute shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle.[3] Having survived relatively unchanged for millions of years, nautiluses represent the only living members of the subclass Nautiloidea, and are often considered "living fossils."

The name "Nautilus" originally referred to the Argonauta, otherwise known as paper nautiluses, because the ancients believed these animals used their two expanded arms as sails.[4] However, this octopus is not closely related to the Nautiloidea.

Anatomy

Two drawings of nautilus
The anatomy of Nautilus. The top figure is dissected; the bottom just has the shell removed.

The nautilus is similar in general form to other cephalopods, with a prominent head and tentacles. 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. There are two pairs of gills. These are the only remnants of the ancestral metamerism to be visible in extant cephalopods.[5]: 56 

Nautilus pompilius is the largest species in the genus. One form from northwestern Australia, once called Nautilus repertus, may reach 26.8 centimetres (10.6 in) in diameter.[6] However, most nautilus species never exceed 20 centimetres (7.9 in). Nautilus macromphalus is the smallest species, usually measuring only 16 centimetres (6.3 in). A dwarf population from the Sulu Sea (Nautilus pompilius suluensis) is even smaller, with a mean shell diameter of 115.6 mm.[7]

Shell

Nautilus hemishell showing the camerae in a logarithmic spiral

Nautiluses are the sole living cephalopods whose bony body structure is externalized as a 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,[8] nacreous and pressure resistant, imploding at a depth of about 800 metres (2,600 ft). The nautilus shell is composed of 2 layers: a matte white outer layer, and a striking white iridescent inner layer. The innermost portion of the shell is a pearlescent blue-gray. The osmena 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 four at the moment of hatching to thirty or more in adults.

The shell colouration 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 named 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.

Tentacles

Nautilus tentacles differ from those of other cephalopods. Lacking pads, the tentacles stick to prey by virtue of their ridged surface.[9] Nautiloids have a powerful grip. Attempts to take an object already seized by a nautilus may tear away the creature's tentacles, which remain firmly attached to the surface of the object.[9] Two pairs of tentacles are separate from the other 90-ish, the pre-ocular and post-ocular, situated before and behind the eye. These are more evidently grooved, with more pronounced ridges. They are extensively ciliated and serve an olfactory purpose.[9][10][11]

Physiology

Buoyancy and movement

Nautilus locomotion
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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. 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.[7] The maximum depth at which they can regulate buoyancy by osmotic removal of chamber liquid is not known.[12]

Senses

Head of Nautilus pompilius showing the eye

Unlike many other cephalopods, they do not have good vision; their eye structure is highly developed but lacks a solid lens. They have a simple "pinhole" eye open to the environment.

Instead of vision, the animal is thought to use olfaction as the primary sense for foraging, locating or identifying potential mates.[13]

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 octopuses 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.[14][15][16]

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.[14][15][16] 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 simply be 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.[16]

Reproduction and lifespan

Nautiluses reproduce by laying eggs. Gravid females attach the fertilized eggs to rocks in shallow waters, whereupon the eggs take eight to twelve months to develop until the 30 millimetres (1.2 in) juveniles hatch. Females spawn once per year and regenerate their gonads, making nautiluses the only cephalopods to present iteroparity or polycyclic spawning.[17]

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.Attention: This template ({{ref jstor}}) is deprecated. To cite the publication identified by jstor:2400210, please use {{cite journal}} with |jstor=2400210 wrapped in <ref> instead. 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 (only one study from the Philippines found females to be more abundant, with males representing only 32% of the population).[7]

The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod.[18] However, nautiluses typically reach sexual maturity when they are about 15 years old.[7]

Left: Frequency distribution of Nautilus 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.[7]
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).[7]

Ecology

Range, habitat, and status

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. No specimens were recovered from a depth of less than 150 m during 18 trapping efforts.[7]

Nautiluses are only found in the Indo-Pacific, from 30° N to 30° S latitude and 90° 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.[19] The greatest depth at which a nautilus has been sighted is 703 m, for two specimens of N. pompilius.[19] Implosion depth for nautilus shells is thought to be around 800 m.[7][19] Only in New Caledonia, the Loyalty Islands, and Vanuatu can nautiluses be observed in very shallow water (at a depth of as little as 5 m).[12][19] 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).[12][19] Nautiluses generally avoid water temperatures above 25°C.[19]

There is growing concern that nautiluses are being greatly overfished.[20] Their limited ecological range and the late onset of their sexual maturity combined with this overfishing has led to recent investigations into the need to protect them from possible endangerment or extinction.[21]

Diet

Nautiluses are scavengers and opportunistic predators.[22][23] They eat molts of lobsters, hermit crabs, and carrion of any kind.[12]

Evolution

Shell characters of the genera Allonautilus and Nautilus

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 metres (8 ft 2 in) 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. Extinct relatives of the nautilus include ammonites, such as the baculites and goniatites.

The Nautilidae has its origin in the Trigonocerataceae (Centroceratina), specifically in the Syringonautilidae of the Late Triassic[3] and continues to this day with Nautilus, the type genus, and its close relative, Allonautilus.

Fossil genera

Eutrephoceras dorbignyanum

The Nautilidae begin 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 subgobular, 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.

Taxonomy

Photo of profiles of three progressively larger nautilus shells
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.[7]

Dubious or uncertain taxa

The following taxa associated with the family Nautilidae are of uncertain taxonomic status:[24]

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 Linne, 1758 Non-cephalopod; Foraminifera [fide Frizzell and Keen (1949:106)]
N. calcar Linne, 1758 ?Non-cephalopod; Foraminifera Lenticulina Adriatic Sea Unresolved; Linnean Society of London?
N. crispus Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. crista Linne, 1758 Non-cephalopod; Turbo [fide Dodge (1953:14)]
N. fascia Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. granum Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. lacustris Lightfoot, 1786 Non-cephalopod; Helix [fide Dillwyn (1817:339)]
N. legumen Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. micrombilicatus Joubin, 1888 Nomen nudum
N. obliquus Linne, 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 Linne, 1758 ?Non-cephalopod; Foraminifera Nodosaria Adriatic Sea Unresolved; Linnean Society of London?
N. raphanistrum Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society of London?
N. raphanus Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society of London?
N. semi-lituus Linne, 1758 Undetermined Liburni, Adriatic Sea Unresolved; Linnean Society of London?
N. sipunculus Linne, 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)]

In popular culture

Main article: Chambered Nautilus § In literature and art

The nautilus shell features prominently in the official emblem of New Caledonia.

See also

Template:Wikipedia-Books

References

Notes
  1. ^ Attention: This template ({{cite jstor}}) is deprecated. To cite the publication identified by jstor:1306604, please use {{cite journal}} with |jstor=1306604 instead.
  2. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1017/S0954102005002671, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1017/S0954102005002671 instead.
  3. ^ 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.
  4. ^ cf. Aristotle Historia Animalium 622b
  5. ^ Wingstrand, KG (1985). "On the anatomy and relationships of Recent Monoplacophora" (Link to free full text + plates). Galathea Rep. 16: 7–94.
  6. ^ Nautilus repertus ID:118764. Shell Encyclopedia, Conchology, Inc.
  7. ^ a b c d e f g h i Dunstan AJ; Ward PD; Marshall NJ (2011). "Nautilus pompilius life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia". PLoS ONE. 6 (2): e16312. doi:10.1371/journal.pone.0016312. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  8. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1111/j.1365-3091.1981.tb01691.x, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1111/j.1365-3091.1981.tb01691.x instead.
  9. ^ a b c Willey, Arthur (1897). "The Pre-ocular and Post-ocular Tentacles and Osphradia of Nautilus". Quarterly Journal of Microscopical Science. 40 (1): 197–201.
  10. ^ Fukuda, Y. 1987. Histology of the long digital tentacles. In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. Springer Netherlands. pp. 249–256. doi:10.1007/978-90-481-3299-7_17
  11. ^ Kier, W.M. 1987. Template:PDFlink In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. Springer Netherlands. pp. 257–269. doi:10.1007/978-90-481-3299-7_18
  12. ^ a b c d Ward, P.D. (1987). The Natural History of Nautilus. Allen and Unwin, London.
  13. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1159/000258669, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1159/000258669 instead.
  14. ^ a b Ewen Callaway (2 June 2008). "Simple-Minded Nautilus Shows Flash of Memory". New Scientist. Retrieved 7 March 2012.
  15. ^ a b Kathryn Phillips (15 June 2008). "Living Fossil Memories" (PDF). Inside JEB. 211: iii. doi:10.1242/jeb.020370.
  16. ^ a b c Robyn Crook & Jennifer Basil (2008). "A biphasic memory curve in the chambered nautilus, Nautilus pompilius L. (Cephalopoda: Nautiloidea)" (PDF). The Journal of Experimental Biology. 211: 1992–1998. doi:10.1242/jeb.018531.
  17. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1017/S1464793101005681, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1017/S1464793101005681 instead.
  18. ^ Saunders WB (1984). "Nautilus Growth and Longevity: Evidence from Marked and Recaptured Animals". Science. 224 (4652): 990–992. doi:10.1126/science.224.4652.990. PMID 17731999. {{cite journal}}: Unknown parameter |month= ignored (help)
  19. ^ a b c d e f Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1371/journal.pone.0016311, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1371/journal.pone.0016311 instead.
  20. ^ Broad WJ (24 October 2011). "Loving the Chambered Nautilus to Death". New York Times. Retrieved 25 October 2011.
  21. ^ Dunstan AJ; Bradshaw CJA; Marshall NJ (2011). "Nautilus at Risk – Estimating Population Size and Demography of Nautilus pompilius". PLoS ONE. 6 (2): e16716. doi:10.1371/journal.pone.0016716. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  22. ^ Template:Cite JSTOR
  23. ^ Template:Cite DOI
  24. ^ Sweeney, M.J. 2002. Taxa Associated with the Family Nautilidae Blainville, 1825. Tree of Life web project.
Bibliography

External links

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