Argonaut (animal)

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Argonauts
Temporal range: Miocene – Recent
Papierboot Argonauta 200705181139.jpg
Female Argonauta argo with its eggs bulging out of its damaged shell
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Family: Argonautidae
Genus: Argonauta
Linnaeus, 1758
Type species
Argonauta argo
Linnaeus, 1758
Species

*Species status questionable.

Synonyms

The argonauts (genus Argonauta, the only extant genus in the family Argonautidae) are a group of pelagic octopuses. They are also called paper nautili, referring to the paper-thin eggcase that females secrete; however, as octopuses, they are only very distant relatives of true nautili. Their 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. [1] 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. [2]

Contents

Argonauts are found in tropical and subtropical waters worldwide. They live in the open ocean, i.e. they are pelagic. Like most octopuses, they have a rounded body, eight limbs (arms) and no fins. However, unlike most octopuses, argonauts live close to the surface rather than on the seabed. Argonauta species are characterised by very large eyes and small webs between the arms. The funnel–mantle 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 of the Argo". [3] "Paper nautilus" is derived from the Greek ναυτίλος nautílos, which literally means "sailor", as paper nautili were thought to use two of their arms as sails. [4] This is not the case, as argonauts swim by expelling water through their funnels. [5] The chambered nautilus was later named after the argonaut, but belongs to a different cephalopod order, Nautilida.

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, capable of having offspring many times over the course of their lives. 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 and then becomes detached from the male. The hectocotylus when found in females was originally described as a parasitic worm. [6]

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 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 retaining 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 three-layered structure [7] and a higher proportion of magnesium carbonate (7%) than other cephalopod shells. [8]

The eggcase contains a bubble of air that the animal captures at the surface of the water and uses for buoyancy, similarly to other shelled cephalopods, although it does not have a chambered phragmocone. [7] Once thought to contribute to occasional mass strandings on beaches, the air bubble is under sophisticated control, evident from the behaviour of animals from which air has been removed under experimental diving conditions. [9] [10] [11] This system to attain neutral buoyancy is effective only at the relatively shallow depths of the upper 10 meters of the water column. Young females with mantle lengths less than 9 millimeters are shell-less like the males, with both having been found in waters between 50 and 200 meters. [12]

Most other octopuses lay eggs in caves; Neale Monks and C. Phil Palmer speculate that, before ammonites died out during the Cretaceous–Paleogene extinction event, the argonauts may have evolved to use discarded ammonite shells for their egg laying, eventually becoming able to mend the shells and perhaps make their own shells. [13] 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. [14] [15] The smallest species is Argonauta boettgeri , with a maximum recorded size of 67 mm. [14] [16]

Beak

Argonauta argo lower beak (side view).jpg
Argonauta argo upper beak (side view).jpg
Lower (left) and upper beaks of female Argonauta argo (63 mm ML) in lateral view
3d glasses red cyan.svg 3D red cyan glasses are recommended to view this image correctly.

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. [16]

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 venom 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 toxin.

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 . [16]

Male argonauts have been observed residing inside aggregate salps (Pegea socia), although little is known about this relationship. [17]

Classification

Fossilised eggcase of the extinct Miocene species Argonauta joanneus (lateral and keel views) Argonauta joanneus.jpg
Fossilised eggcase of the extinct Miocene species Argonauta joanneus (lateral and keel views)
Eggcases of six extant Argonauta species Argonauta species.PNG
Eggcases of six extant Argonauta species

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

Four extant species are widely considered valid: [18]

Several additional taxa are either treated as valid species or regarded as nomina dubia :

A number of extinct species have also been described:

The extinct species Obinautilus awaensis was originally assigned to Argonauta, but has since been transferred to the genus Obinautilus . [20]

Dubious or uncertain taxa

The following taxa associated with the family Argonautidae are of uncertain taxonomic status: [21]

Binomial name and author citationCurrent systematic statusType localityType repository
Argonauta arctica Fabricius, 1780UndeterminedUnresolved; ?Tullukaurfak, Greenland Unresolved
Argonauta bibula Röding, 1798UndeterminedUnresolvedUnresolved
Argonauta compressa Blainville, 1826UndeterminedMer de IndesUnresolved; [other Blainville types at MNHN] [not reported by Lu et al. (1995)]
Argonauta conradi Parkinson, 1856Species of uncertain status [fide Robson (1932:200)]"New Nantucket, Pacific Ocean"Unresolved
Argonauta cornu Gmelin, 1791UndeterminedUnresolvedUnresolved; LS?
Argonauta cymbium Linné, 1758Non-cephalopod; foraminiferous shell [fide Von Martens (1867:103)
Argonauta fragilis Parkinson, 1856Species of uncertain status [fide Robson (1932:200)]Not designatedUnresolved
Argonauta geniculata Gould, 1852Species of uncertain status [fide Robson (1932:200)]Near Sugarloaf Mountain, Rio de Janeiro, Brazil Type not extant [fide Johnson (1964:32)]
Argonauta maxima Dall, 1871Nomen nudum
Argonauta navicula Lightfoot, 1786Species dubium [fide Rehder (1967:11)]Not designatedUnresolved
Argonauta rotunda Perry, 1811Non-cephalopod; Carcinaria sp. [fide Robson (1932:201)]
Argonauta rufa Owen, 1836Incertae 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, 1801Nomen nudum
Argonauta tuberculata f. aurita Von Martens, 1867UndeterminedUnresolvedZMB
Argonauta tuberculata f. mutica Von Martens, 1867UndeterminedCoast of Brazil ZMB Holotype
Argonauta tuberculata f. obtusangula Von Martens, 1867UndeterminedNot designatedZMB Syntypes
Argonauta vitreus Gmelin, 1791UndeterminedNot designatedUnresolved; LS?
Octopus (Ocythoe) raricyathus Blainville, 1826Undetermined [Argonauta?]Not designatedMNHN Holotype; specimen not extant [fide Lu et al. (1995:323)]
Ocythoe punctata Say, 1819Argonauta 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, 1895Argonauta or Ocythoe [fide Thomas (1977:386)] 44°28′56″N46°48′15″W / 44.48222°N 46.80417°W / 44.48222; -46.80417 (Atlantic Ocean)MOM Holotype [station 151] [fide Belloc (1950:3)]

In design

The argonaut was the inspiration for a number of classical and modern art and decorative forms including use on pottery and architectural elements. Some early examples are found in Bronze Age Minoan art from Crete. [22] A variation known as the double argonaut design was also found in Minoan jewelry. [23] This design was also transposed and adapted in both gold and glass in contemporary Mycenaean contexts, as seen both at Mycenae and the Tholos at Volo. [24]

In literature and etymology

Argonauts surrounding the Nautilus, in Jules Verne's novel Twenty Thousand Leagues Under the Sea Nemo Aronax sail-fish.jpg
Argonauts surrounding the Nautilus , in Jules Verne's novel Twenty Thousand Leagues Under the Sea

Related Research Articles

<span class="mw-page-title-main">Squid</span> Superorder of cephalopod molluscs

A squid is a mollusc 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.

<span class="mw-page-title-main">Cephalopod</span> Class of mollusks

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.

<span class="mw-page-title-main">Nautilus</span> Family of molluscs

The nautilus is an ancient pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina.

<span class="mw-page-title-main">Argonautidae</span> Family of molluscs

The Argonautidae are a family of pelagic cephalopods that inhabit tropical and temperate oceans of the world. The family encompasses the modern paper nautiluses of the genus Argonauta along with several extinct genera of shelled octopods. Though argonauts are derived from benthic octopuses, they have evolved to depart the sea floor and live their life-cycle in the open seas.

<i>Ocythoe tuberculata</i> Species of cephalopods

Ocythoe tuberculata, also known as the tuberculate pelagic octopus or football octopus, is a pelagic octopus. It is the only known species in the family Ocythoidae.

<i>Argonauta argo</i> Species of cephalopod known as the greater argonaut

Argonauta argo, also known as the greater argonaut, is a species of pelagic octopus belonging to the genus Argonauta. The Chinese name for this species translates as "white sea-horse's nest".

<span class="mw-page-title-main">Hectocotylus</span> Cephalopod sex organ

A hectocotylus is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male may use it merely as a conduit to the female, analogously to a penis in other animals, or he may wrench it off and present it to the female.

<i>Argonauta nouryi</i> Species of mollusc

Argonauta nouryi, also known as Noury's argonaut, is a species of pelagic octopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The shell is usually approximately 80 mm in length, although it can exceed 90 mm in exceptional specimens; the world record size is 95.5 mm.

<i>Argonauta hians</i> Species of mollusc

Argonauta hians, also known as the winged argonaut, muddy argonaut or brown paper nautilus, is a species of pelagic octopus. The common name comes from the grey to brown coloured shell. The Chinese name for this species translates as "Grey Sea-horse's Nest". The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The eggcase is characterised by a wide keel that gives it a square appearance, few rounded tubercles along the keel, and less than 40 smooth ribs across the sides of the shell. The shell is usually approximately 80 mm in length, although it can exceed 120 mm in exceptional specimens; the world record size is 121.5 mm.

<i>Argonauta cornuta</i> Species of mollusc

Argonauta cornuta is a species of pelagic octopus belonging to the genus Argonauta. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus reminiscent of the way a nautilus lives in its shell. The shell is usually approximately 80 mm in length, although it can exceed 90 mm in exceptional specimens; the world record size is 98.6 mm.

<i>Argonauta pacifica</i> Species of mollusc

Argonauta pacifica, also known as the Pacific argonaut, is a species of pelagic octopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The shell is usually approximately 150 mm in length, although it can exceed 200 mm in exceptional specimens; the world record size is 220.0 mm.

<span class="mw-page-title-main">Argonauta nodosa</span> Species of mollusc

Argonauta nodosus [previously known as Argonauta nodosa], also known as the knobby or knobbed argonaut, is a species of pelagic octopus. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell. The shell is usually approximately 150 mm in length, although it can exceed 250 mm in exceptional specimens; the world record size is 292.0 mm. A. nodosus produces a very characteristic shell, which is covered in many small nodules on the ridges across the shell, hence the specific epithet nodosus and common name. These nodules are less obvious or even absent in juvenile females, especially those under 5 cm in length. All other argonaut species have smooth ridges across the shell walls.

<i>Argonauta bottgeri</i> Species of mollusc

Argonauta bottgeri, also known as Böttger's argonaut, is a species of pelagic octopus belonging to the genus Argonauta. The female of the species, like all argonauts, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell.

<i>Nautilus</i> (genus) Genus of molluscs

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.

<span class="mw-page-title-main">Incirrata</span> Suborder of octopuses

Incirrata is a suborder of the order Octopoda. The suborder contains the classic "benthic octopuses," as well as many pelagic octopus families, including the paper nautiluses. The incirrate octopuses are distinguished from the cirrate octopuses by the absence in the former of the "cirri" filaments for which the cirrates are named, as well as by the lack of paired swimming fins on the head, and lack of a small internal shell.

<span class="mw-page-title-main">Octopodiformes</span> Superorder of molluscs

Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid. All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid or modifying the tentacles into thin filaments. Octopodiformes is often considered the crown group of octopuses and vampire squids, including all descendants of their common ancestor. Some authors use the term Vampyropoda for the same general category, though others use "Vampyropoda" to refer to the total group. Another term is Octobranchia, referring to cephalopods without prominent tentacles.

<i>Obinautilus</i> Extinct genus of molluscs

Obinautilus is an extinct genus of shelled cephalopod that has been variously identified as an argonautid octopod or a nautilid. It is known from the Late Oligocene to Pliocene of Japan. The shell is discoidal and very involute, with rapidly expanding and compressed whorls, fine radial ribs, a rounded venter with a shallow furrow, and almost closed umbilicus.

<span class="mw-page-title-main">Common blanket octopus</span> Species of cephalopod

The common blanket octopus or violet blanket octopus is a large octopus of the family Tremoctopodidae found worldwide in the epipelagic zone of warm seas. The degree of sexual dimorphism in this species is very high, with females growing up to two meters in length, whereas males grow to about 2.4 cm. The first live specimen of a male was not seen until 2002 off the Great Barrier Reef. Individual weights of males and females differ by a factor of about 10,000 and potentially more.

<span class="mw-page-title-main">Cephalopod limb</span> Limbs of cephalopod molluscs

All cephalopods possess flexible limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles.

<span class="mw-page-title-main">Argonautoidea</span> Superfamily of octopuses

Argonautoidea is a superfamily of the suborder Incirrata containing all known argonautoids.

References

  1. ↑ Naef, A. (1923). "Die Cephalopoden, Systematik". Fauna Flora Golf. Napoli (35) (in German). 1: 1–863.
  2. ↑ Scales, Helen (2015). Spirals in Time: The Secret Life and Curious Afterlife of Seashells. Bloomsbury.
  3. ↑ "Word Origin and History for Argonaut". Online Etymology Dictionary. 2010. Retrieved 2017-11-15.
  4. ↑ "Origin of nautilus". Dictionary.com Unabridged. 2017. Retrieved 2017-11-15.
  5. ↑ Figuier, Louis (1869). The Ocean World: Being a Descriptive History of the Sea and Its Living Inhabitants. London: Cassell, Petter and Galpin. pp.  329.
  6. ↑ Delle Chiaje, S. (1825). Memorie sulla storia e notomia degli animali (in Italian). Senza Vertebre del Regno di Napoli. I.
  7. 1 2 Nixon, M.; Young, J. Z. (2003). The Brains and Lives of Cephalopods. Oxford University Press.[ page needed ]
  8. ↑ Saul, L.; Stadum, C. (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. ISSN   0022-3360. JSTOR   4095022. S2CID   131373540.
  9. ↑ Finn, J. K. & Norman, M. D. The argonaut shell: gas-mediated buoyancy control in a pelagic octopus. Proceedings of the Royal Society B: Biological Sciences, published online May 19, 2010. doi : 10.1098/rspb.2010.0155
  10. ↑ "Museum Victoria 'Argonaut buoyancy' video" Archived 2012-07-13 at the Wayback Machine museumvictoria.com.au. URL accessed on 19 May 2010.
  11. ↑ Pidcock, R. 2010. Ancient octopus mystery resolved. BBC News, May 19, 2010.
  12. ↑ The argonaut shell: gas-mediated buoyancy control in a pelagic octopus
  13. ↑ Monks, N.; Palmer, C. P. (2002). Ammonites. Smithsonian Institution Press, Washington D.C.
  14. 1 2 Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. p. 12.
  15. ↑ (in Russian) Nesis, K. N. 1982. Abridged key to the cephalopod mollusks of the world's ocean. Light and Food Industry Publishing House, Moscow, 385+ii pp. [Translated into English by B. S. Levitov, ed. by L. A. Burgess (1987), Cephalopods of the world. T. F. H. Publications, Neptune City, NJ, 351 pp.]
  16. 1 2 3 Clarke, M. R. (1986). A Handbook for the Identification of Cephalopod Beaks. Oxford University Press. pp. 273 pp.
  17. ↑ Banas, P. T.; D. E. Smith & D. C. Biggs (1982). "An association between a pelagic octopod, Argonauta sp. Linnaeus 1758, and aggregate salps". Fish. Bull. 80: 648–650.
  18. ↑ Serge Gofas (2015). "Argonauta Linnaeus, 1758". World Register of Marine Species. Flanders Marine Institute. Retrieved 5 February 2018.
  19. ↑ Ponzi, G. (1876). Cefalopodi. [p. 932 + pl. III 1a–b ] In: I fossili del Monte Vaticano. Atti della Reale Accademia dei Lincei, series 2, 3(2): 925–959 + 3 pls. (in Italian)
  20. ↑ Martill, D.M. & M.J. Barker (2006). A paper nautilus (Octopoda, Argonauta) from the Miocene Pakhna Formation of Cyprus. Palaeontology49 (5): 1035-1041.
  21. ↑ Sweeney, M. J. Taxa Associated with the Family Argonautidae Tryon, 1879. Tree of Life web project.
  22. ↑ Eleni M. Konstantinidi, 2001, Jewellery Revealed in the Burial Contexts of the Greek Bronze Age, Hadrian Books, 322 pages ISBN   1-84171-165-9
  23. ↑ C.Michael Hogan, Knossos Fieldnotes, The Modern Antiquarian (2007)
  24. ↑ Higgins, Reynold; Higgins, Reynold Alleyne (1980-01-01). Greek and Roman Jewellery. University of California Press. ISBN   978-0-520-03601-7.
  25. ↑ Johann David Wyss and Jenny H. Stickney, The Swiss Family Robinson, Ginn & Co., 1898, 364 pages.
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