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Nautilus stenomphalus

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Nautilus stenomphalus
Nautilus stenomphalus (white-patch nautilus) (Mindanao, Philippines) 2 (24078294661).jpg
CITES Appendix II (CITES)[1]
Scientific classification edit
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Nautiloidea
Order: Nautilida
Family: Nautilidae
Genus: Nautilus
Species:
N. stenomphalus
Binomial name
Nautilus stenomphalus
Sowerby, 1848

Nautilus stenomphalus, also known as the white-patch nautilus, is a species of nautilus native to the Great Barrier Reef. N. stenomphalus is very similar to N. pompilius and may in fact represent a subspecies. It is separated by the absence of a thickened callus and the presence of white patches in the umbilical and shoulder regions of the shell. The sheaths of this species have scalloped edges compared with the smooth sheaths of N. pompilius. N. stenomphalus also differs slightly in hood ornamentation. The shell is usually up to around 180 mm in diameter, although the largest specimen ever recorded measured 201 mm.[2]

Discover more about Nautilus stenomphalus related topics

Nautilus

Nautilus

The nautilus 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.

Great Barrier Reef

Great Barrier Reef

The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef is located in the Coral Sea, off the coast of Queensland, Australia, separated from the coast by a channel 100 miles wide in places and over 200 feet deep. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps. It supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN labelled it one of the Seven Natural Wonders of the World in 1997. Australian World Heritage places included it in its list in 2007. The Queensland National Trust named it a state icon of Queensland in 2006.

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.

Callus (mollusc)

Callus (mollusc)

A callus is an anatomical feature that exists in some mollusk shells, a thickened area of shell material that can partly or completely cover the umbilicus, or can be located as a coating on the body whorl near the aperture of the shell.

Umbilicus (mollusc)

Umbilicus (mollusc)

The umbilicus of a shell is the axially aligned, hollow cone-shaped space within the whorls of a coiled mollusc shell. The term umbilicus is often used in descriptions of gastropod shells, i.e. it is a feature present on the ventral side of many snail shells, including some species of sea snails, land snails, and freshwater snails.

Distribution

Nautilus stenomphalus are pelagic molluscs belonging to the Nautilidae cephalopod family predominantly found across coral reefs along the Indo-Pacific region.[3] N. stenomphalus is specifically known to inhabit the Great Barrier Reef, whereas other members

Description

N. stenomphalus are scavengers that utilize two chemosensory rhinophores, rod-shaped structures located below the eye, to locate dead meat and consuming low-nutrients from the ocean floor.[3] They dwell in darker waters in depths up to 300 meters, though moving towards shallower waters to scavenge at night.[4] Though possessing primitive eyes, N. stenomphalus predominantly rely on chemoreception in order to locate food in their habitat. N. stenomphalus share many morphological similarities with its close relative N. pompilius such as “zigzag” shell color pattern

Morphology

Sexual dimorphism

N. stenomphalus express sexual dimorphism, with mature males predominantly being larger and are significantly more abundant than females.[5]

Sensory organs

N. stenomphalus possess digital tentacles which are able to detect chemosensation, though its preocular and postocular tentacles are more sensitive and also are believed to function for tactile purposes.[4] When perceiving odor stimulation through its rhinophore, its digital tentacles are often spread out laterally in a “cone of search” to identify the source of the stimulus. Nautilus expresses this distinct pattern of behavior when attempting to locate the source of an odor, swaying its tentacles in a cone shape to detect and move towards the substrate. N. stenomphalus also rely on olfaction through rhinophores, chemosensory structures that are similar to other olfactory organs expressed by other members in the cephalopod family such as Octopus. Rhinophores are situated inside the Nautilus and are exposed to the external environment through pores located below the eyes.[4]

Taxonomy and evolution

Members of the Nautilus genus are believed to have evolved to their current form between seven and ten million years ago, though some estimates place their divergence from their Mesozoic ancestors as early as 40 million years ago.[6] Though Nautilus stenomphalus is classified as an individual species compared to its much more abundant relative Nautilus pompilius, closer DNA analysis of the relationship between N. stenomphalus and N. pompilius reveals that they cannot be identified as independent lineages due to their shared DNA positions and synapomorphies. Moreover, stenomphalus and pompilius hybrid species exhibit less than one percent deviation from the DNA sequences of both parent species. Phylogenetic reconstructions identify both N. stenomphalus and N. pompilius as belonging to the Australian/Papua-New Guinean clade, providing insight that both species may have arisen from sympatric speciation.[7] Few studies have sought to identify the DNA sequence differences between the species, moreover the genetic distinction of N. stenomphalus and N. pompilius remains unresolved.[6]

Phylogeny

Due to the striking similarities between Nautilus and its subspecies from their identical DNA sequence sections and synapomorphies, there is significant evidence to suggest that Nautilus pompilius exhibits phenotypic plasticity. Namely, Nautilus subspecies identification through taxonomic features is difficult between populations as many features that were thought to be unique may overlap across different Nautilus populations. Other subspecies such as N. belauensis, N. macromphalus, and N. scrobiculatus are regionally bound and known to inhabit areas around Palau, New Caledonia, and Papua-New Guinea respectively.[7] N. pompilius represents the type species as it is the most common and widely distributed member of the Nautilus family, and is used as a point of comparison to other Nautilus members. Phylogenetic analysis conducted utilizing DNA and morphological data between members suggests that N. pompilius represents a paraphyletic group of Nautilus members, though not including N. scrobiculatus.[7]

Source: "Nautilus stenomphalus", Wikipedia, Wikimedia Foundation, (2022, January 24th), https://en.wikipedia.org/wiki/Nautilus_stenomphalus.

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References
  1. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  2. ^ Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. p. 93.
  3. ^ a b Ward, Peter, Frederick Dooley, and Gregory Jeff Barord. "Nautilus: biology, systematics, and paleobiology as viewed from 2015." Swiss Journal of Palaeontology 135.1 (2016): 169-185.
  4. ^ a b c Basil, Jennifer, et al. "The function of the rhinophore and the tentacles of Nautilus pompilius L.(Cephalopoda, Nautiloidea) in orientation to odor." Marine and Freshwater Behaviour and Physiology 38.3 (2005): 209-221.
  5. ^ Dunstan, Andrew J., Peter D. Ward, and N. Justin Marshall. "Nautilus pompilius life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia." PLOS ONE 6.2 (2011)
  6. ^ a b Vandepas, Lauren E., et al. "A revisited phylogeography of Nautilus pompilius." Ecology and evolution 6.14 (2016): 4924-4935.
  7. ^ a b c Wray, Charles G., et al. "Genetic divergence and geographic diversification in Nautilus." Paleobiology 21.2 (1995): 220-228.
  • Norman, M. 2000. Cephalopods: A World Guide. Hackenheim, ConchBooks, p. 31.
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