Information about Argonaut (animal)

Argonauts Fossil range: Miocene – Recent
Eggcases of various Argonauta species
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Order: Octopoda Superfamily: Argonautoida Family: Argonautidae Genus: Argonauta Linnaeus, 1758
Species
†Argonauta absyrtus Argonauta argo (type) Argonauta bottgeri Argonauta cornuta* Argonauta hians †Argonauta itoigawai †Argonauta joanneus Argonauta nodosa Argonauta nouryi Argonauta pacifica* †Argonauta tokunagai *Species status questionable.
Synonyms
Argonautarius Dumeril, 1806 Todarus nom. nud. Rafinesque, 1815 Todarus Rafinesque, 1840 Trichocephalus Chiaje, 1827 in 1823-1831

The argonauts (genus Argonauta, the only extant genus in the Argonautidae family) are a group of pelagic octopuses. They are also called paper nautiluses, 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 Argonauta.^[1]

Argonauts are found in tropical and subtropical waters worldwide; they live in open ocean. Like most octopuses, they have a rounded body, eight arms and no fins. However, unlike most octopuses, argonauts live close to the sea surface rather than on the seabed. Argonauta species are characterised by very large eyes and small distal webs. The mantle-funnel locking apparatus is a major diagnostic feature of this taxon. It consists of knob-like cartilages in the mantle and corresponding depressions in the funnel. Unlike the closely allied genera Ocythoe and Tremoctopus, Argonauta species lack water pores.

Of its names, "argonaut" means "sailor on the Argo", and "nautilus" is Greek νаυτιλος = "sailor", because it was formerly supposed to use its shell-secreting arms as sails when it was on the surface.

The chambered nautilus was later named after the argonaut.

Physical description

Sexual dimorphism and reproduction

Argonauts exhibit extreme sexual dimorphism in size and lifespan. Females grow up to 10 cm and make shells up to 30 cm, while males rarely surpass 2 cm. The males only mate once in their short lifetime, whereas the females are iteroparous. In addition, the females have been known since ancient times while the males were only described in the late 19th Century.

The males lack the dorsal tentacles used by the females to create their eggcases. The males use a modified arm, the hectocotylus, to transfer sperm to the female. For fertilization, the arm is inserted into the female's pallial cavity, then is detached from the male. The hectocotylus was originally described as a parasitic worm.^[2]

Mature female A. nodosa

Juvenile female A. hians

Immature male A. hians

Eggcase

Female argonauts produce a laterally-compressed calcareous eggcase in which they reside. This "shell" has a double keel fringed by two rows of alternating tubercles. The sides of the eggcase are ribbed with the centre either flat or having winged protrusions. The eggcase curiously resembles the shells of extinct ammonites. It is secreted by the tips of the female's two greatly expanded dorsal tentacles (third left arms) before egg laying. After she deposits her eggs in the floating eggcase, the female takes shelter in it, often along with the male's detached hectocotylus. She is usually found with her head and tentacles protruding from the opening, but she retreats deeper inside if disturbed. These ornate curved white eggcases are occasionally found floating on the sea, sometimes with the female argonaut clinging to it. It is not made of aragonite as most other shells are, but of calcite, with a 3-layered structure^[3] and a higher proportion of magnesium carbonate (7%) than other cephalopod shells.^[4]

The egg case contains a bubble of gas used for buoyancy similar to shelled cephalopods, although it does not have a chambered phragmocone as in other shelled cephalopods.^[4]

Most other octopuses lay eggs in caves; it is speculated that, before ammonites died out during the Cretaceous–Tertiary extinction event, the argonauts may have evolved to use ammonite shells for their egg laying, eventually becoming able to mend the shells and perhaps make their own shells.^[5] However, this is uncertain and it is unknown whether this is the result of convergent evolution.

Argonauta argo is the largest species in the genus and also produces the largest eggcase, which may reach a length of 300 mm.^[6][7] The smallest species is Argonauta bottgeri, with a maximum recorded size of 67 mm.^[8][9]

Female A. nodosa with its eggcase	The eggcase of A. argo	The eggcase of A. nodosa	The eggcase of A. hians

Beak

The beaks of Argonauta species are distinctive, being characterised by a very small rostrum and a fold that runs to the lower edge or near the free corner. The rostrum is 'pinched in' at the sides, making it much narrower than in other octopuses, with the exception of the closely allied monotypic genera Ocythoe and Vitreledonella. The jaw angle is curved and indistinct. Beaks have a sharp shoulder, which may or may not have posterior and anterior parts at different slopes. The hood lacks a notch and is very broad, flat, and low. The hood to crest ratio (f/g) is approximately 2-2.4. The lateral wall of the beak has no notch near the wide crest. Argonaut beaks are most similar to those of Ocythoe tuberculata and Vitreledonella richardi, but differ in 'leaning back' to a greater degree than the former and having a more curved jaw angle than the latter.^[9]

Feeding and defense

Feeding mostly occurs during the day. Argonauts use tentacles to grab prey and drag it toward the mouth. It then bites the prey to inject it with poison from the salivary gland. They feed on small crustaceans, molluscs, jellyfish and salps. If the prey is shelled, the argonaut uses its radula to drill into the organism, then inject the poison.

Argonauts are capable of altering their color. They can blend in with their surroundings to avoid predators. They also produce ink, which is ejected when the animal is being attacked. This ink paralyzes the olfaction of the attacker, providing time for the argonaut to escape. The female is also able to pull back the web covering of her shell, making a silvery flash, which may deter a predator from attacking.

Argonauts are preyed upon by tunas, billfishes, and dolphins. Shells and remains of argonauts have been recorded from the stomachs of Alepisaurus ferox and Coryphaena hippurus.^[9]

Male argonauts have been observed residing inside salps, although little is known about this relationship.^[10]

Classification

The genus Argonauta contains up to seven extant species. Several extinct species are also known.

†Argonauta absyrtus
Argonauta argo (type)
Argonauta bottgeri
Argonauta cornuta*
Argonauta hians
†Argonauta itoigawai
†Argonauta joanneus
Argonauta nodosa
Argonauta nouryi
Argonauta pacifica*
†Argonauta tokunagai

*Species status questionable.

The extinct species Obinautilus awaensis was originally assigned to Argonauta, but has since been transferred to the genus Obinautilus.^[11]

Dubious or uncertain taxa

The following taxa associated with the family Argonautidae are of uncertain taxonomic status:^[12]

Binomial name and author citation	Current systematic status	Type locality	Type repository
Argonauta arctica Fabricius, 1780	Undetermined	Unresolved; ?Tullukaurfak, Greenland	Unresolved
Argonauta bibula Roding, 1798	Undetermined	Unresolved	Unresolved
Argonauta compressa Blainville, 1826	Undetermined	Mer de Indes	Unresolved; [other Blainville types at MNHN] [not reported by Lu et al. (1995)]
Argonauta conradi Parkinson, 1856	Species of uncertain status [fide Robson (1932:200)]	"New Nantucket, Pacific Ocean"	Unresolved
Argonauta cornu Gmelin, 1791	Undetermined	Unresolved	Unresolved; LS?
Argonauta cymbium Linne, 1758	Non-cephalopod; foraminiferous shell [fide Von Martens (1867:103)
Argonauta fragilis Parkinson, 1856	Species of uncertain status [fide Robson (1932:200)]	Not designated	Unresolved
Argonauta geniculata Gould, 1852	Species of uncertain status [fide Robson (1932:200)]	Near Sugarloaf [Mountain] Rio [de] Janeiro [Brazil]	Type not extant [fide Johnson (1964:32)]
Argonauta maxima Dall, 1871	Nomen nudum
Argonauta navicula Lightfoot, 1786	Species dubium [fide Rehder (1967:11)]	Not designated	Unresolved
Argonauta rotunda Perry, 1811	Non-cephalopod; Carcinaria sp. [fide Robson (1932:201)]
Argonauta rufa Owen, 1836	Incertae sedis [fide Robson (1932:181)]	"Indian seas" ["South Pacific ocean" fide Owen (1842:114)]	Unresolved; Museum of the Royal College of Surgeons? Holotype
Argonauta sulcata Lamarck, 1801	Nomen nudum
Argonauta tuberculata f. aurita Von Martens, 1867	Undetermined	Unresolved	ZMB
Argonauta tuberculata f. mutica Von Martens, 1867	Undetermined	Coast of Brazil	ZMB Holotype
Argonauta tuberculata f. obtusangula Von Martens, 1867	Undetermined	Not designated	ZMB Syntypes
Argonauta vitreus Gmelin, 1791	Undetermined	Not designated	Unresolved; LS?
Octopus (Ocythoe) raricyathus Blainville, 1826	Undetermined [Argonauta?]	Not designated	MNHN Holotype; specimen not extant [fide Lu et al. (1995:323)]
Ocythoe punctata Say, 1819	Argonauta sp. [fide Robson (1929d:215)]	Atlantic Ocean near the North American coast (from stomach of dolphin)	Unresolved; ANSP? Holotype [not traced by Spamer and Bogan (1992)]
Tremoctopus hirondellei Joubin, 1895	Argonauta or Ocythoe [fide Thomas (1977:386)]	(Atlantic Ocean)	MOM Holotype [station 151] [fide Belloc (1950:3)]

Trivia

• Argonauts are featured in Twenty Thousand Leagues Under the Sea, noted for their ability to use their tentacles as sails. There is no evidence for this.
• A female argonaut is also described in Marianne Moore's poem "The Paper Nautilus."
• Paper nautiluses were caught in the The Swiss Family Robinson novel.
• Argonauts gave their name to an Arabidopsis mutant and by extension to Argonaute proteins.

References

External links

• CephBase: Argonauta
• Tree of Life web project: Argonauta

Argonauta species

A. argo • A. bottgeri • A. cornuta • A. hians • A. nodosa • A. nouryi • A. pacifica

The Miocene Epoch is a period of time that extends from about 23.03 to 5.332 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain.
..... Click the link for more information.

Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
..... Click the link for more information.

Editing of this page by unregistered or newly registered users is currently disabled until (UTC) due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or
..... Click the link for more information.

Mollusca
Linnaeus, 1758

Classes

Caudofoveata
Aplacophora
Polyplacophora
Monoplacophora
Bivalvia
Scaphopoda
Gastropoda
Cephalopoda
† Rostroconchia
† Helcionelloida
† ?Bellerophontida
The molluscs
..... Click the link for more information.

Cephalopoda
Cuvier, 1797

Orders

Subclass Nautiloidea

• †Plectronocerida
• †Ellesmerocerida
• †Actinocerida
• †Pseudorthocerida
• †Endocerida
• †Tarphycerida
• †Oncocerida

..... Click the link for more information.

Octopoda
Leach, 1818

Suborders

†Pohlsepia (incertae sedis)
†Proteroctopus (incertae sedis)
†Palaeoctopus (incertae sedis)
Cirrina
Incirrina
Synonyms

..... Click the link for more information.

Argonautoida
Naef, 1912

Families

Alloposidae
Argonautidae
Ocythoidae
Tremoctopodidae

Argonautoida is a superfamily of the suborder Incirrina.
..... Click the link for more information.

Argonautidae
Tryon, 1879

Genera

Argonauta
†Izumonauta
†Kapal
†Mizuhobaris
†Obinautilus

Argonautidae
..... Click the link for more information.

Carolus Linnaeus (Carl von Linné)

Carl von Linné, Alexander Roslin, 1775. Currently owned by and hanging at the Royal Swedish Academy of Sciences.
..... Click the link for more information.

species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
..... Click the link for more information.

A. absyrtus

Binomial name
Argonauta absyrtus
Martill & Barker, 2006

Argonauta absyrtus is an extinct species of octopus assigned to the genus Argonauta.

A.
..... Click the link for more information.

A. argo

Binomial name
Argonauta argo
Linnaeus, 1758

Synonyms

• Argonauta papyracea
  Roding, 1798
• Argonauta grandiformis
  Perry, 1811
• ?Argonauta striata

..... Click the link for more information.

A type species fixes the name of a genus (or of a taxon in a rank lower than genus).

Strictly speaking, a type species exists only in zoological nomenclature. As set in article 42.
..... Click the link for more information.

A. bottgeri

Binomial name
Argonauta bottgeri
Maltzan, 1881

Synonyms

• Argonauta boettgeri orth. var.

..... Click the link for more information.

A. cornuta

Binomial name
Argonauta cornuta
Conrad, 1854

Synonyms

• ?Argonauta dispar
  Conrad, 1854
• Argonauta expansa
  Dall, 1872

Argonauta cornuta
..... Click the link for more information.

A. hians

Binomial name
Argonauta hians
Lightfoot, 1786

Synonyms

• Argonauta gondola
  Dillwyn, 1817
• ?Argonauta haustrum
  Dillwyn, 1817
• ?Ocythoe cranchii

..... Click the link for more information.

A. itoigawai

Binomial name
Argonauta itoigawai
Tomida, 1983

Argonauta itoigawai is an extinct species of octopus.
..... Click the link for more information.

A. joanneus

Binomial name
Argonauta joanneus
Hilber, 1915

Argonauta joanneus is an extinct species of octopus assigned to the genus Argonauta.
..... Click the link for more information.

A. nodosa

Binomial name
Argonauta nodosa
Lightfoot, 1786

Synonyms

• ?Argonauta oryzata
  Meuschen, 1787
• Argonauta tuberculata
  Roding, 1798

..... Click the link for more information.

A. nouryi

Binomial name
Argonauta nouryi
Lorois, 1852

Synonyms

• Argonauta gruneri
  Dunker, 1852

Noury's Argonaut (Argonauta nouryi
..... Click the link for more information.

A. pacifica

Binomial name
Argonauta pacifica
Dall, 1871

Synonyms

• Argonauta pacifica nom. nud.

..... Click the link for more information.

A. tokunagai

Binomial name
Argonauta tokunagai
Yokoyama, 1913

Argonauta tokunagai is an extinct species of octopus.
..... Click the link for more information.

In scientific nomenclature, synonyms are different scientific names used for a single taxon. Usage and terminology are different for zoology and botany.

Zoology

In zoological nomenclature, synonyms are different scientific names that pertain to the same taxon, for example
..... Click the link for more information.

genus (plural: genera) is part of the Latinized name for an organism. It is a name which reflects the classification of the organism by grouping it with other closely similar organisms.
..... Click the link for more information.

Extant is a term commonly used to refer to taxa, species, genera or families that are still in existence (living). For example, Brandt's Cormorant is an extant species, while the Spectacled Cormorant is an extinct species.
..... Click the link for more information.

Argonautidae
Tryon, 1879

Genera

Argonauta
†Izumonauta
†Kapal
†Mizuhobaris
†Obinautilus

Argonautidae
..... Click the link for more information.

The pelagic zone is the part of the open sea or ocean that is not near the coast. In contrast, the neritic zone comprises the water that is near to (and is significantly affected by) the coast or the continental shelf.
..... Click the link for more information.

Octopoda
Leach, 1818

Suborders

†Pohlsepia (incertae sedis)
†Proteroctopus (incertae sedis)
†Palaeoctopus (incertae sedis)
Cirrina
Incirrina
Synonyms

..... Click the link for more information.

tropics are the geographic region of the Earth centered on the equator and limited in latitude by the Tropic of Cancer in the northern hemisphere, at approximately 23°30' (23.5°) N latitude, and the Tropic of Capricorn in the southern hemisphere at 23°30' (23.5°) S latitude.
..... Click the link for more information.

The subtropics are the zones of the Earth immediately north and south of the tropic zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitude 23.5 ° north and south.
..... Click the link for more information.