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Overview

Brief Summary

Introduction

The pearly nautilus is unusual among living cephalopods in having a large calcareous external shell divided into chambers (phragmocone) that are pierced by a siphuncle. The animal lives in the largest and most recently formed chamber. The shell acts as a protective and buoyancy device. The nautilus can withdraw into the shell and seal the entrance with a large tough hood. Buoyancy is controlled by pumping fluid in and out of the chambers using an osmotic mechanism. The osmotic pump must operate against hydrostatic pressure and a depth limit for this mechanism seems to be around 300 m (Saunders and Ward, 1987). It can only exceed this depth for short periods of time. At a depth of approximately 800 m the shell implodes.

Pearly nautiluses are very muscular but slow swimers. They swim by jet propulsion provided by contraction of the large funnel and the "piston action" resulting from withdrawal of the head into the living chamber. They are restricted to the Indo-Pacific from 30° N lat. to 30° S lat. and 90° to 185° W long. (Saunders, 1987). Their numerous tentacles with adhesive ridges that are used to grab prey are quite different from the 8 or 10 sucker-bearing arms of coleoid cephalopods. The pearly nautiluses are partially, at least, scavengers that can hold an occasional windfall of up to 20% of the body weight in their large crop. Some species undergo vertical migrations, moving along steeply sloping bottoms from around 300 m during the day to 100 m at night. One of their predators is their distant relative, the octopus, which is able to bore a hole through the shell and inject a poison.

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Comprehensive Description

Nomenclature

A list of all nominal genera and species in the living Nautilidae can be found here. The list includes the current status and type species of all genera, and the current status, type repository and type locality of all species and all pertinent references.

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Characteristics

  1. External chambered shell.
  2. Eyes without lenses; form images via a pin-hole opening.
  3. Funnel formed by overlapping flaps.
  4. Beaks: Descriptions can be found here.

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Physical Description

Diagnostic Description

Description

The only cephalopod family including species with external true shells. The shells are large, light in weight and resemble a round-bottomed boat. They are distinguished, above all, by being partitioned or chambered internally, the partitions being linked by a tube known as siphuncle. The chambers are filled with a gas allowing the shell to float; the animal controls its buoyancy by introducing water into or removing it from the chambers. Two genera, six or seven species, all from the Indo-Pacific.
  • MASDEA (1997).
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© WoRMS for SMEBD

Source: World Register of Marine Species

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Life History and Behavior

Life Cycle

Life History

Figure. Embryo of Nautilus sp. removed from the egg case. Photograph by J. Arnold.

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Evolution and Systematics

Functional Adaptations

Functional adaptation

Gas-storage chamber controls buoyancy: nautilus
 

The inner chambers of a nautilus allow for buoyancy control via different mixtures of stored air and water.

     
  "The body of the mollusc inhabits the very last of a spiralling series of chambers inside the shell. By filling the inner chambers with a mixture of air and water, the nautilus achieves perfect buoyancy, allowing it to rise effortlessly during its nightly migration from the depths of the Pacific Ocean to the surface." (Downer 2002:17)
  Learn more about this functional adaptation.
  • Downer, J. 2002. Weird Nature: An Astonishing Exploration of Nature's Strangest Behavior. Ontario: Firefly Books.
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© The Biomimicry Institute

Source: AskNature

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:460Public Records:42
Specimens with Sequences:459Public Species:2
Specimens with Barcodes:421Public BINs:2
Species:2         
Species With Barcodes:2         
          
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© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

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Barcode data

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Wikipedia

Nautilus

Nautilus (from Greek ναυτίλος, 'sailor') is the common name of pelagic marine mollusks of the 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 pelagic octopuses of the genus Argonauta, otherwise known as paper nautiluses, as the ancients believed these animals used their two expanded arms as sails.[citation needed]

Anatomy[edit]

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

The nautilus is similar in general form to other cephalopods, with a prominent head and tentacles, each composed of a long, soft, flexible cirrus and corresponding hardened sheath. 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, and 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.[4]:56

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.[5]: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 it look irregular, whereas the buccal cone of the female is bilaterally symmetrical.[5]:pp. 115–130

Like all cephalopods, the blood of the nautilus contains hemocyanin, which is blue in its oxygenated state. Unlike others, however, the nautilus does not have an ink sac and depends on its shell for protection from predators rather than on diversionary clouds of ink.

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][7] 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.[8]

Shell[edit]

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

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,[9] nacreous and pressure resistant, imploding at a depth of about 800 metres (2,600 ft). The nautilus shell is composed of two 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 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 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[edit]

Nautilus tentacles differ from those of other cephalopods. Lacking pads, the tentacles stick to prey by virtue of their ridged surface.[10] 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.[10] The main tentacles emerge from sheaths which cohere into a single firm fleshy mass. 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.[10][11][12]

Physiology[edit]

Buoyancy and movement[edit]

Nautilus locomotion
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File size: 1.29 MB
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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.[8] The maximum depth at which they can regulate buoyancy by osmotic removal of chamber liquid is not known.[13]

Senses[edit]

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.[14]

The "ear" of the nautilus is contained within a structure called an otocyst located immediately behind the pedal ganglia. It is an oval structure densely packed with elliptical calcium carbonate crystals.

Brain and intelligence[edit]

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.[15][16][17]

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.[15][16][17] 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.[17]

Reproduction and lifespan[edit]

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.[18]

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.[19] 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 males to be more abundant, with females representing only 32% of the population).[8]

The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod.[20] However, nautiluses typically reach sexual maturity when they are about 15 years old.[8]

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.[8]

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).[8]

Ecology[edit]

Range and habitat[edit]

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.[8]

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.[21] The greatest depth at which a nautilus has been sighted is 703 m (N. pompilius).[21] Implosion depth for nautilus shells is thought to be around 800 m.[8][21] 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).[13][21] 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).[13][21] Nautiluses generally avoid water temperatures above 25°C.[21]

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

Status[edit]

There is growing concern that nautiluses are being greatly overfished not just for the shape of their shells, but also for the nacreous inner shell layer, which is used as a pearl substitute. Because there are currently no national or international regulations protecting this ancient creature, biologist Peter Ward, from the University of Washington, says "there is a horrendous slaughter going on out there."[22] 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 though no regulations yet exist and thus the nautilus remains unprotected.[23]

Diet[edit]

Nautiluses are scavengers and opportunistic predators.[24][25] They eat molts of lobsters, hermit crabs, and carrion of any kind.[13]

Evolution[edit]

Shell characters of the genera Nautilus and Allonautilus

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[edit]

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.

Obinautilus has also been placed in Nautilidae by some authorities, though it may instead be an argonautid octopus.[26][27]

Taxonomy[edit]

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.[8]

Dubious or uncertain taxa[edit]

The following taxa associated with the family Nautilidae are of uncertain taxonomic status:[28]

Binomial name and author citationCurrent systematic statusType localityType repository
N. alumnus Iredale, 1944Species dubium [fide Saunders (1987:49)]Queensland, AustraliaNot designated [fide Saunders (1987:49)]
N. ambiguus Sowerby, 1848Species dubium [fide Saunders (1987:48)]Not designatedUnresolved
N. beccarii Linne, 1758Non-cephalopod; Foraminifera [fide Frizzell and Keen (1949:106)]
N. calcar Linne, 1758 ?Non-cephalopod; Foraminifera LenticulinaAdriatic SeaUnresolved; Linnean Society of London?
N. crispus Linne, 1758UndeterminedMediterranean SeaUnresolved; Linnean Society of London?
N. crista Linne, 1758Non-cephalopod; Turbo [fide Dodge (1953:14)]
N. fascia Linne, 1758UndeterminedAdriatic SeaUnresolved; Linnean Society of London?
N. granum Linne, 1758UndeterminedMediterranean SeaUnresolved; Linnean Society of London?
N. lacustris Lightfoot, 1786Non-cephalopod; Helix [fide Dillwyn (1817:339)]
N. legumen Linne, 1758UndeterminedAdriatic SeaUnresolved; Linnean Society of London?
N. micrombilicatus Joubin, 1888Nomen nudum
N. obliquus Linne, 1758UndeterminedAdriatic SeaUnresolved; Linnean Society of London?
N. pompilius marginalis Willey, 1896Species dubium [fide Saunders (1987:50)]New GuineaUnresolved
N. pompilius moretoni Willey, 1896Species dubium [fide Saunders (1987:49)]New GuineaUnresolved
N. pompilius perforatus Willey, 1896Species dubium [fide Saunders (1987:49)]New GuineaUnresolved
N. radicula Linne, 1758 ?Non-cephalopod; Foraminifera NodosariaAdriatic SeaUnresolved; Linnean Society of London?
N. raphanistrum Linne, 1758UndeterminedMediterranean SeaUnresolved; Linnean Society of London?
N. raphanus Linne, 1758UndeterminedAdriatic SeaUnresolved; Linnean Society of London?
N. semi-lituus Linne, 1758UndeterminedLiburni, Adriatic SeaUnresolved; Linnean Society of London?
N. sipunculus Linne, 1758Undetermined"freto Siculo"Unresolved; Linnean Society of London?
N. texturatus Gould, 1857Nomen nudum
Octopodia nautilus Schneider, 1784Rejected specific name [fide Opinion 233, ICZN (1954:278)]

In Popular Culture[edit]

See also[edit]

References[edit]

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 (Paleontological Society) 71 (6): 1054–1064. doi:10.2307/1306604. JSTOR 1306604.  edit
  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. doi:10.1017/S0954102005002671.  edit
  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. ^ Wingstrand, KG (1985). "On the anatomy and relationships of Recent Monoplacophora" (Link to free full text + plates). Galathea Rep. 16: 7–94. 
  5. ^ a b Griffin, Lawrence E. (1900). The anatomy of Nautilus pompilius 8. Washington, D.C.: Government Printing Office. doi:10.5962/bhl.title.10466. OCLC 18760979. 
  6. ^ Nautilus repertus ID:118764. Shell Encyclopedia, Conchology, Inc.
  7. ^ Harasewych, M.G. & F. Moretzsohn (2010). The Book of Shells: A lifesize guide to identifying and classifying six hundred shells. A & C Black Publishers, London.
  8. ^ a b c d e f g h i Dunstan AJ; Ward PD; Marshall NJ (February 2011). "Nautilus pompilius life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia". In Solan, Martin. PLoS ONE 6 (2): e16312. Bibcode:2011PLoSO...616312D. doi:10.1371/journal.pone.0016312. PMC 3037366. PMID 21347356. 
  9. ^ Buchardt, B.; Weiner, S. (1981). "Diagenesis of aragonite from Upper Cretaceous ammonites: a geochemical case-study". Sedimentology 28 (3): 423–438. Bibcode:1981Sedim..28..423B. doi:10.1111/j.1365-3091.1981.tb01691.x.  edit
  10. ^ 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. 
  11. ^ 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
  12. ^ Kier, W.M. 1987. The functional morphology of the tentacle musculature of Nautilus pompilius. PDF 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
  13. ^ a b c d Ward, P.D. (1987). The Natural History of Nautilus. Allen and Unwin, London.
  14. ^ Grasso, F.; Basil, J. (2009). "The evolution of flexible behavioral repertoires in cephalopod molluscs". Brain, Behavior and Evolution 74 (3): 231–245. doi:10.1159/000258669. PMID 20029186.  edit
  15. ^ a b Ewen Callaway (2 June 2008). "Simple-Minded Nautilus Shows Flash of Memory". New Scientist. Retrieved 7 March 2012. 
  16. ^ a b Kathryn Phillips (15 June 2008). "Living Fossil Memories". Inside JEB 211 (12): iii. doi:10.1242/jeb.020370. 
  17. ^ a b c Robyn Crook & Jennifer Basil (2008). "A biphasic memory curve in the chambered nautilus, Nautilus pompilius L. (Cephalopoda: Nautiloidea)". The Journal of Experimental Biology 211 (12): 1992–1998. doi:10.1242/jeb.018531. 
  18. ^ Rocha, F.; Guerra, Á.; González, Á. F. (2001). "A review of reproductive strategies in cephalopods". Biological Reviews of the Cambridge Philosophical Society 76 (3): 291–304. doi:10.1017/S1464793101005681. PMID 11569786.  edit
  19. ^ Bruce Saunders, W.; Spinosa, C. (1978). "Sexual Dimorphism in Nautilus from Palau". Paleobiology 4 (3): 349–358. doi:10.2307/2400210. JSTOR 2400210.  edit
  20. ^ Saunders WB (June 1984). "Nautilus Growth and Longevity: Evidence from Marked and Recaptured Animals". Science 224 (4652): 990–992. Bibcode:1984Sci...224..990S. doi:10.1126/science.224.4652.990. PMID 17731999. 
  21. ^ a b c d e f Dunstan, A. J.; Ward, P. D.; Marshall, N. J. (2011). "Vertical distribution and migration patterns of Nautilus pompilius". In Solan, Martin. PLoS ONE 6 (2): e16311. doi:10.1371/journal.pone.0016311. PMC 3043052. PMID 21364981.  edit
  22. ^ Broad WJ (24 October 2011). "Loving the Chambered Nautilus to Death". New York Times. Retrieved 25 October 2011. 
  23. ^ Dunstan AJ; Bradshaw CJA; Marshall NJ (February 2011). "Nautilus at Risk – Estimating Population Size and Demography of Nautilus pompilius". In Solan, Martin. PLoS ONE 6 (2): e16716. Bibcode:2011PLoSO...616716D. doi:10.1371/journal.pone.0016716. PMC 3037370. PMID 21347360. 
  24. ^ Saunders, W.B. (1984). "The role and status of Nautilus in its natural habitat: Evidence from deep-water remote camera photosequences". Paleobiology 10 (4): 469–486. JSTOR 2400618.  edit
  25. ^ Wells, M. J.; Wells, J.; O'Dor, R. K. (2009). "Life at low oxygen tensions: The behaviour and physiology of Nautilus pompilius and the biology of extinct forms". Journal of the Marine Biological Association of the United Kingdom 72 (2): 313–328. doi:10.1017/S0025315400037723.  edit
  26. ^ Teichert, C. & T. Matsumoto (2010). The Ancestry of the Genus Nautilus. In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. Springer. pp. 25–32. doi:10.1007/978-90-481-3299-7_2
  27. ^ Saul, L.R. & C.J. Stadum (2005). Fossil argonauts (Mollusca: Cephalopoda: Octopodida) from Late Miocene siltstones of the Los Angeles Basin, California. Journal of Paleontology 79(3): 520–531. doi:10.1666/0022-3360(2005)079<0520:FAMCOF>2.0.CO;2
  28. ^ Sweeney, M.J. 2002. Taxa Associated with the Family Nautilidae Blainville, 1825. Tree of Life web project.
  29. ^ "Firefall Creatures - Nautilus". Red 5 Studios. Retrieved 16 February 2014. 
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