Argonaut - a relative of the octopus living in a shell

Nutrition

Octopuses usually go out at night to search for food.
The highly intelligent mollusk hides in ambush and carefully examines the surroundings. Enough for the victim to approach him at a fairly close distance, he makes a lightning-fast jump and grabs her with tentacles. With the prey, the hunter hurries to his home to dine in a cozy home environment. On the way, he can catch some other living creatures and hide them in the folds of his mantle. The octopus paralyzes the caught victim with the poison of the salivary glands.

In the shells of crabs, it gnaws a hole with its beak-like jaws, into which it injects digestive juices. After some time, a kind of “meat broth” forms in the crab’s body, which the smart cephalopod drinks with pleasure.

It either cracks the shells of other mollusks with strong tentacles or crushes them using a tongue studded with small teeth called a radula.

Appearance and features

The deepest-sea octopus has puzzled scientists

Photo: Nautilus pompilius

Nautilus pompilius has several features that help distinguish it from other species in the genus Nautilus. As mentioned earlier, today there are the largest individuals, the diameter of which reaches 25 centimeters. The Nautilus pompilius we are considering is precisely this species.

Let's talk about the animal shell first. It twists in a spiral, and inside it is divided into chambers. The largest section serves for the body of the mollusk, and the rest are used by it for immersion or ascent. These chambers can be filled with water, which allows the nautilus to descend to greater depths, or with air, which allows it to rise higher. The animal's shell has a tiger color.

The body of the mollusk, like that of most other animals, is bilaterally symmetrical, however, it also has its differences. As we know, most cephalopods have suckers on their arms or tentacles, but this does not apply to the species we are considering. Their limbs are mainly used to grab prey and move through the water. The mouth of Nautilus pompilius has more than 90 arms.

The eyes on the animal’s head are located, like those of other representatives of the genus, but they do not have a lens. Also in this part of the body there are several olfactory tentacles that react to the external environment.

Clam House Features

The shell of the sea creature is very fragile. The nautilus (mollusk), as a rule, does not descend deeper than 500 m, since its chambers are not able to withstand high water pressure and burst in an instant. In such cases, nothing can help the nautilus; it will never surface again. Due to their characteristics and features, all nautiluses live close to the surface. They usually scurry around in search of food at a depth of 20-100 m and near coral reefs. Nautilus pompilius, a mollusk whose photo is presented in the article, leads a benthic lifestyle. Its diet includes carrion and plants. He can go hungry for a very long time, going without food for about a month.

Notes

1. ↑ Akimushkin I.I. Cephalopods of the seas of the USSR M.: Publishing House of the USSR Academy of Sciences, 1963. - 236 p.
2. Nesis K. N. Cephalopods: smart and swift. - M.: Octopus Publishing House, 2005. - 208 p.
3. ↑ Large encyclopedic dictionary "Biology". — ed. M. S. Gilyarova, M.: Great Russian Encyclopedia, 1998. ISBN 5-85270-252-8
4. ↑ Ruppert E. E., Fox R. S., Barnes R. D., Invertebrate zoology: functional and evolutionary aspects. T. 2: Lower coelomic animals. - M.: Publishing House, 2008. - 448 p.
5. Raff R., Coffman T. Embryos, genes and evolution. M., Mir, 1986, p. 175—176
6. ↑
7. ↑ Nesis K.N. Oceanic cephalopods. Distribution, life forms, ecology. M., 1985, p.49

Octopus

Where does the octopus live?

Sea clam in shell

Photo: Octopus in the sea

They can be found in the warm waters of seas and oceans at various depths.

Octopuses choose the following places for comfortable settlement:

• deep bottom, where it comfortably disguises itself as stones and sand;
• sunken objects with many secluded places;
• reefs;
• rocks.

Octopuses hide in small crevices and secluded places, and can also hunt there. Sometimes an octopus can climb into a shell left by crustaceans and sit there, but octopuses themselves never establish permanent homes.

The maximum depth at which octopuses can comfortably live is 150 m, although deep-sea representatives of the genus can descend 5 thousand meters down, like squid. Occasionally, octopuses can be found in cold waters, where they behave extremely sleepy.

They are considered to be nocturnal creatures, since during the daytime they hide in their shelters. Occasionally, being half asleep, an octopus can grab prey swimming by and, almost without waking up, eat it.

Octopuses can swim, although they don't like to do so - swimming creates a vulnerable situation where the octopus is easy to grab. Therefore, they move along the bottom using tentacles. There are no obstacles for octopuses in the form of steep rocks and vertical surfaces - the octopus makes its way along them using suction cups and grabbing onto any objects with its tentacles.

When swimming, they move slowly because they use the cuttlefish method: they take water into their mouth and push it out. Due to their slowness, they mostly hide in shelters and move when absolutely necessary.

Interesting fact

The nautilus mollusk, as we have already found out, is a close relative of animals such as octopuses and squids. They are smart, agile, dexterous and move with the help of a “jet stream”, pushing water out behind them under strong pressure. This helps them get food, swim out and descend to depth. A hollow tube in the middle of the body (funnel) acts like a siphon, through which liquid is sucked in or released. The siphon can only pass a small amount of water, so the mollusk moves quite slowly and in peculiar jerks. It seems to freeze in the depths of the sea, somewhat reminiscent of an ancient airship. A unique feature of this animal is that it moves backwards.

Appearance

Female Argonauts have the unique ability to build a shell with their tentacle-arms using a liquid composition secreted from her glands. The fragile shell is loosely placed on its back, not attached to anything and capable of being discarded by the mollusk. The female continues to build the shell throughout her life, laying and bearing offspring.

Argonaut mollusk photo

Externally, this is a calcareous device, consisting of one chamber, having a flat keel with two rows of tubercles, the sides of the shell are compressed, and have a ribbed surface. The body length of the female is about 12 cm, the size of the males is about 2 cm including tentacles.

The Argonaut mollusk has a conical mantle with smooth muscles. In the female it is curved towards the helix of the shell. Long tentacle-like arms with suction cups arranged in two rows. There is no membrane between the tentacles. The dorsal arms of females are equipped with a skin fold capable of strong stretching. With the help of this organ, the female secretes and forms a shell.

The female is inside the shell, hiding all her arms inside. Two wide blades of tentacles are spread across the entire surface of the structure. Large eyes, a beak and the final part of another organ of the mollusk, a powerful funnel, the design of which facilitates the movement of the mollusk. Argonaut is brown or purple in color.

Hands spread over the ship shell remain snow-white, but their color can instantly change and become burgundy.

External links [edit]

• Web project “Tree of Life”: Argonauta
• Absurd Creature of the Week: A beautiful octopus whose gender is dismemberment.

Description

Adults reach a body length of 30-50 cm and weigh up to 1.5 kg. The long body has a streamlined shape. The upper side of the body is colored reddish-brown.

Small dark specks are scattered on the lighter background of the lower side. The mollusk has 10 tentacles: 8 short and 2 long grasping ones. Each of the tentacles is equipped with suction cups.

Between the tentacles and the head, clearly separated from the rest of the body, there is a mouth opening with strong jaws, with which the squid can easily crush the shells of its victims. There is a special grater in the throat for grinding food.

The underdeveloped shell in the form of a keratinized shelf is completely hidden by the folds of the mantle. On both sides of the body there are 2 sail-like fins.

On the lower side there is a siphon through which water is pushed out from the mantle cavity, creating jet thrust. This species has very large eyes, which are the most advanced organ of vision among all invertebrates.

The lifespan of common squid does not exceed 2-3 years on average.

Taxonomy

The genus includes several fossils and up to 8 modern species:

• Argonauta argo Linnaeus, 1758typus - A tropical-subtropical cosmopolitan species found in the world's oceans up to approximately 35-43° N. w. and Yu. sh., also inhabits the Gulf of Mexico, the Caribbean and Mediterranean Seas. Predominantly distant neritic (or neritoceanic) species.
• Argonauta bottgeri
• Argonauta cornuta Conrad, 1854—species status disputed;
• Argonauta cygnus Monterosato
• Argonauta hians Solander in Dillwyn, 1817
• Argonauta nodosa - Tropical and south-subtropical Indo-West Pacific from the Red Sea and southern Japan to southern Africa, Tasmania and New Zealand, east to Polynesia, with doubt in Chile. Predominantly distant-neritic (or neritic-oceanic) species.
• Argonauta nouryi Lorois, 1852 - species status disputed
• Argonauta pacifica Dall, 1871 - species status disputed

• †Argonauta absyrtus
• †Argonauta itoigawai
• †Argonauta joanneus
• †Argonauta tokunagai

Synonyms

As synonyms for the generic name Argonauta

consider Argonautarius Dumeril, 1806, Todarus nom. nud. Rafinesque, 1815, Todarus Rafinesque, 1840, Trichocephalus Chiaje, 1827

Taxonomy

The genus includes several fossils and up to 8 modern species:

• Argonauta argo Linnaeus, 1758typus - A tropical-subtropical cosmopolitan species found in the world's oceans up to approximately 35-43° N. w. and Yu. sh., also inhabits the Gulf of Mexico, the Caribbean and Mediterranean Seas. Predominantly distant neritic (or neritoceanic) species.
• Argonauta bottgeri
• Argonauta cornuta Conrad, 1854—species status disputed;
• Argonauta cygnus Monterosato
• Argonauta hians Solander in Dillwyn, 1817
• Argonauta nodosa - Tropical and south-subtropical Indo-West Pacific from the Red Sea and southern Japan to southern Africa, Tasmania and New Zealand, east to Polynesia, with doubt in Chile. Predominantly distant-neritic (or neritic-oceanic) species.
• Argonauta nouryi Lorois, 1852 - species status disputed
• Argonauta pacifica Dall, 1871 - species status disputed

• †Argonauta absyrtus
• †Argonauta itoigawai
• †Argonauta joanneus
• †Argonauta tokunagai

Synonyms

As synonyms for the generic name Argonauta

consider Argonautarius Dumeril, 1806, Todarus nom. nud. Rafinesque, 1815, Todarus Rafinesque, 1840, Trichocephalus Chiaje, 1827

Reproduction

During the mating season, males gather in fairly large flocks. At this time, one of their tentacles, located in a special sac on the head, begins to increase in size. When it is fully formed, it breaks away from the body and begins to drift autonomously in the water column. This floating organ is called a hectocotylus, and it contains spermatophores.

The female lays about 500 eggs inside the shell, after which the hectocotylus explodes and fertilizes them. The mother selflessly protects the laid eggs and does not part with them throughout the entire maturation process. The exact period of embryo development is still unknown. It is believed that it can vary from several weeks to several months depending on the water temperature.

The babies emerging from the eggs are exact miniature copies of adult Argonauts. They immediately leave the mother's shell and begin an independent life.

When do octopuses reproduce?

Spawning occurs all year round, usually in the cold half of the year. Most often, octopuses reproduce

near the coast. Before spawning, the female completely and forever stops feeding (she stops producing digestive enzymes). The female chooses a spacious hole, cleans it and lays eggs there.

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origin of name

In ancient Greek mythology, these mollusks became famous for helping Jason escape from the angry inhabitants of Colchis after stealing the Golden Fleece. They clung to the sides of the Argo ship and spread their tentacles in the wind. A fair wind blew, and the Greeks managed to break away from their pursuers, who preferred to work with oars the old fashioned way rather than using sail propulsion.

Together with the crew of the ship, the mollusks received the proud name of Argonauts in honor of this event. The great storyteller Aristotle, better known as the great philosopher, in his writings also attributed such an extravagant method of movement to this creature.

Aristotle's speculations were elevated by the Christian church to the rank of unshakable truth, so this view lasted in scientific circles for almost 2000 years. Naturalists bravely waited for the end of the fires of the Inquisition and only at the end of the 18th century began to directly study the life of cephalopods in natural conditions.

In literature and etymology[edit]

Argonauts surrounding Nautilus

, in Jules Verne's novel
Twenty Thousand Leagues Under the Sea

• The Argonauts are featured in Twenty Thousand Leagues Under the Sea
  , famous for their ability to use their tentacles as sails, although this is a widespread myth.
• The female Argonaut is also described in Marianne Moore's poem "The Paper Nautilus".
• "Argonauta" is the title of a chapter in Gift of the Seas
  .
• Paper nautiluses ended up in the novel The Swiss Family Robinson
  . [22]
• Argonauts give their name to the Arabidopsis thaliana
  and the resulting Argonaute proteins.
• The animal has no relation to the heroes, the Argonauts, in Greek mythology. Their name comes from their ship Argo, named after its builder Argus.

Interesting facts about octopuses

1. Due to its body shape, this solitary cephalopod is recognized as the most amazing creation of nature.
2. Its skull contains a donut-shaped brain, but is completely missing any bones.
3. The eyes of an octopus are rectangular in shape.
4. Although nature has endowed it with several modes of movement, the octopus mainly walks or crawls. He swims less often.
5. All existing species of octopuses emit ink for protection. They can harm other inhabitants of the sea, but humans will not suffer from them. The emitted ink cloud not only hides the octopus, but also neutralizes odors. There is only one specimen of such a mollusk, the blue-ringed octopus, the ink discharge of which can kill a person.
6. This specimen of mollusks mainly hunts at night. Its prey is fish, crustaceans and small mollusks, which it takes out of shells. If that doesn't work, he uses a toxin that dissolves the shell.
7. Captivity for an octopus most often ends in death.
8. As research has proven, these creatures have memory, short-term and long-term.
9. In nature there is a wide variety of octopuses of various sizes, but their behavior is the same.
10. Due to the lack of a skeleton, this deep-sea mollusk has access to any crevices. It can be four times the size of the hole it can enter.
11. Octopuses are given superiority in intelligence among all invertebrates. They can be trained. They remember their “teachers” and are capable of recognizing figures and unscrewing cans. The octopus Paul proved the presence of intelligence in cephalopods by predicting all the results of matches of the German football team.
12. Before eating, the octopus tastes food with the help of taste buds, as if with sensors. He has more than 10,000 of them.
13. Scientists know more than 300 species of octopuses. But they are convinced that not all species are known to science.
14. Blood moves through the body of the mollusk due to the presence of three hearts. Two hearts send blood to the gills, and one circulates blood throughout the body. There is a lot of copper in the blood of this creature, which is why it is “aristocratic,” that is, blue.
15. In addition to the fact that the color of the octopus can change depending on the mood and location as a means of protection, they are able to scare away predators by imitating their behavior.
16. When its tentacles are torn off, after some time they grow back at the site of loss. In moments of danger, an octopus, like a lizard throwing away its own tail, can break its tentacles itself.
17. This mollusk has no hearing, and no species has vocal communication.
18. The lifespan of different types of octopuses ranges from six months to five years. Mating is often the leading cause of death for males. They can also be eaten by females. Females die after the offspring appear. It itself must fight for survival. But even among the octopuses who are “indifferent” to the future of their “children,” there are exceptions. Thus, the Pacific striped mollusk does not leave the female for a long time; it “has mercy” on her for several months. And the mother takes care of the babies for more than one month.
19. These mollusks mate only once in their entire lives.
20. The female leaves about 200,000 eggs, but the survival rate of the emerging young is no more than 30%.
21. The Pacific Ocean is famous for the largest specimens of octopuses. There you can find specimens weighing up to 45 kg. The smallest California cephalopod measures 2.5 cm.
22. Octopuses are clean inhabitants of the deep sea. Instead of a broom, they “sweep away” the dirt with water released in a stream from a funnel on the body. The remaining food is always in one special place.

Octopuses are unusual sea creatures, which are also called cephalopods: their arms, or legs, or rather, tentacles grow from their heads. Whatever they are called, humanity likes not only their unusual appearance. People like octopus as a product rich in many elements necessary for the body.

“Important: all information on the site is provided for informational purposes only. Before applying any recommendations, consult with a specialized specialist. Neither the editors nor the authors are responsible for any possible harm caused by the materials.”

Nautilus macromphalus. Allonautilus and Nautilus - modern nautilids

Anyone interested in paleontology is well aware of the modern nautilus, “the last representative of the external shells” or “the last of the nautilids” as they like to call it in popular literature. This is Nautilus pompilius, truly the most abundant and most famous of the modern Nautilida. But not everyone knows that Nautilus pompilius is not the only representative of living nautilids, and even the genus Nautilus is not the only genus of the family Nautilidae that has survived to this day. There is no point in analyzing the biology of the nautilus in detail in this publication - many books and articles are devoted to it. It is worth briefly mentioning that modern nautiluses have very simple eyes (much simpler than those of coleoids - squids, sepia, spirula and octopuses), many thin tentacles (and their number varies from individual to individual), a leathery hood on the head that covers the mouth at the moment of danger, a strong beak as jaws and a powerful, but primitively constructed funnel. It is held in the living chamber of its shell by retractor muscles attached to the walls and special ligaments in the back of the body. Also in the front part of the living chamber, near the mouth, the mantle is attached to the edge of the shell. The attachment points of the retractor muscles are called “muscle imprints,” and the area of ​​tissue attachment at the last septum is called the annular region (annular elevation). Until recently, paleontologists automatically extrapolated all the structural details of the nautilus to the Paleozoic nautiloids, considering Nautilus pompilius a kind of living fossil, preserved by nature for hundreds of millions of years. But recently it turned out that the numerous tentacles, and most likely the hood, formed from fused tentacles and parts of the mantle, are the nautiluses’ own “evolutionary inventions.” Scientists have not yet figured out exactly when this fragmentation of the tentacles occurred and when the hood was formed, but it is clear that the ancient nautiloids had nothing like this. It is also quite possible that four gills (instead of two in all other cephalopods) are also an evolutionary innovation that allowed nautiluses to master oxygen-poor deep layers of water, unsuitable for the life of fish and other cephalopods.

Notes

1. ↑ Encyclopedic Dictionary of F. A. Brockhaus and I. A. Efron: In 86 half-volumes with illustrations and additional materials. - St. Petersburg, 1890-1907.
2. Korobkov N. A.
   Paleontological descriptions (methodological manual). - L.: Nedra, 1971. - 200 p.
3. Brem A.
   Animal life / Preface and comments by M. S. Galina and M. B. Kornilova. - M.: OLMA-PRESS, Red Proletarian, 2004. - 1192 p. — 5000 copies. — ISBN 5-224-04422-7. ISBN 5-85197-214-9.
4. Complete zoological and botanical dictionary in French, Russian and Latin. Addition to the French-Russian dictionary compiled by V. Ertel. - St. Petersburg: Printing house N. Grech, 1843. - 404 p.
5. ↑ Norman M.
   Cephalopods: A World Guide (undefined). - ConchBooks, 2000. - pp. 189-195.
6. Nesis K. N. Cephalopods: smart and swift. - M.: Octopus Publishing House, 2005. - 208 p.
7. Ruppert E. E., Fox R. S., Barnes R. D., Invertebrate zoology: functional and evolutionary aspects. T. 2: Lower coelomic animals. - M.: Publishing House, 2008. - 448 p.
8. Pisor, D.L.
   Registry of World Record Size Shells (English)Russian. (undefined). — 4th. - Snail's Pace Productions and ConchBooks, 2005. - P. 12.
9. (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.

Description

The body length of adult females is 20-30 cm, and that of males is 1.5-2 cm. The baggy body is short and dense, covered with a fold of skin - the mantle.

In the female, out of eight tentacles armed with suckers, two are very flattened and form a shell. The outer shell is boat-shaped and is not connected to the body. On the side there is a large funnel through which water is pushed out of the mantle cavity.

A pair of large eyes indicates well-developed vision.

The life expectancy of Argonauts is about 6-8 years.

Almost all cephalopods mate and reproduce once in their lives.

Although reports periodically appear about the possibility of repeated spawning in nature in some octopuses, this has not yet been documented.

After reaching reproductive age, octopuses begin to look for a partner, and until this moment they prefer to live separately from their relatives.

In adult males, by this time “packets” with sperm develop in the mantle cavity (in cephalopods they are called spermatophores), which during the breeding season are carried out through a funnel along with streams of water. During mating, the male holds the female with his tentacle hand, and uses a special genital tentacle to introduce spermatophores into the mantle cavity of the female.

Researchers have noticed some facts of octopus reproduction. Namely, during reproduction, males of some species try to mate with any representative of their genus, regardless of gender and age. Of course, in this case the eggs will not be fertilized, and the mating process itself is not as long as with a female of the appropriate age.

In the blue-ringed octopus, mating continues until the female gets tired of it and she forcibly tears the overexcited male away from her.

Mating occurs even more unusual in Argonaut octopuses.

The male has a sexual tentacle called a hectocotylus. It develops in a special pouch between the fourth and second hands on the left side.

It is described as follows: “The males of this species are not destined to experience satisfaction. This is because nature has endowed them with a very strange penis. After the octopus produces a sufficient amount of seminal fluid, the organ miraculously separates from the body and swims off into the depths of the sea in search of a suitable female Argonaut octopus. Finds it - by smell and taste - catches up, crawls under her mantle and there independently does everything that is needed, without distracting the former owner from thoughts of the eternal: the spermatophores burst, and the liquid from them fertilizes the eggs.

The ex-owner can only watch how his reproductive organ mates with the “beautiful half”. After some time, the penis grows back.

After fertilization, the female makes a nest in a hole or cave in shallow water, where she lays up to 80 thousand eggs. For spawning, some females choose cavities or burrows in rocks, gluing the eggs to the ceiling or walls. Most species of octopus lay their eggs at night, one at a time.

The nest is a hole in the ground, lined with a rampart of stones and shells. The eggs are spherical, connected in groups of 8-20 pieces.

Others prefer to carry a bunch of eggs glued together with them.

The female always takes care of the eggs: she constantly ventilates them, washing them with a stream of water from the siphon. She uses her tentacles to remove foreign objects and dirt. During the entire period of egg development, the female remains at the nest without food and often dies after the young hatch.

Three-week-old octopuses in eggs under the protection of a dying mother.

The duration of development of octopus eggs varies, on average up to 4-6 months, but sometimes it can reach a year, and in rare cases several years. All this time, the female octopus incubates the eggs, does not hunt or eat. Studies have shown that before reproduction, octopuses undergo a restructuring of the body; shortly before spawning, they stop producing the enzymes necessary for digesting food. Soon after the juveniles emerge from the eggs, the female dies, and the newborn octopuses are able to take care of themselves.

Structure of the mollusk

To understand what a nautilus mollusk looks like, you need to familiarize yourself with its structure. His body has a head and a torso. It is somewhat more primitive than its counterparts. The head has a special blade to close the shell in case of danger. The eyes and mouth opening are also located here. Ninety tentacles are located next to it. They perform the functions of hands. The tentacles have suckers and highly developed muscles. They help the sea dweller move, catch prey and put it in his mouth.

From the shell of a mollusk you can determine its lifespan. For this purpose, a chemical analysis is done. At the beginning of life, the nautilus has only seven chambers, and then, every three weeks, another compartment is added to them. This growth slows down only at the age of ten.

The mouth has two jaws. This allows you to snack on solid foods. There is a muscular pharynx with salivary glands. It passes into the esophagus, which leads to the stomach. The ducts of the bilobed liver open into it. From the stomach comes the rectum, which passes into the large intestine. In the mantle cavity it ends with the anus.

The smartest mollusk

Octopuses have only a cartilaginous capsule containing a highly developed brain as a memory of their distant past.

These cephalopods are superior in intelligence to many marine animals, not to mention other invertebrates.

Thanks to the presence of a rudimentary cerebral cortex, they have short-term and long-term memory, distinguish and remember the geometric shapes of objects, are able to use available means for their own purposes and, if necessary, independently build their own homes on the bottom of the sea.

To get to food, this amazing creature is able to open cans, bottles and various boxes. The octopus understands what threads are and can unscrew caps, remembers the way in the most complex maze, and is even able to solve some puzzles.

Historical value

Nautilus is a cephalopod that is related to octopuses, cuttlefish and squids. The shells of these sea inhabitants were discovered by the ancient Greeks, but the mystery of their structures could not be understood until 1892. It was then that Richard Owen (the famous paleontologist and zoologist) asked a doctor friend who was heading to the Pacific Ocean to bring a sample of the creature that lives in this shell. The doctor managed to obtain a live nautilus and immediately sent it to Owen for further research. The scientist was able to find out that this species of animal belongs to cephalopods. This means that the nautilus is a marine mollusk with a large head and many “arms”. In most cephalopods the shell is hidden in the middle of the body, but in our nautiluses it is external.

Taxonomy[edit | edit code]

The genus includes several fossils and up to 8 modern species:

• Argonauta argo Linnaeus, 1758typus - A tropical-subtropical cosmopolitan species found in the world's oceans up to approximately 35-43° N. w. and Yu. sh., also inhabits the Gulf of Mexico, the Caribbean and Mediterranean Seas. Predominantly distant neritic (or neritoceanic) species.
• Argonauta bottgeri
• Argonauta cornuta Conrad, 1854—species status disputed;
• Argonauta cygnus Monterosato
• Argonauta hians Solander in Dillwyn, 1817
• Argonauta nodosa - Tropical and south-subtropical Indo-West Pacific from the Red Sea and southern Japan to southern Africa, Tasmania and New Zealand, east to Polynesia, with doubt in Chile. Predominantly distant-neritic (or neritic-oceanic) species.
• Argonauta nouryi Lorois, 1852 - species status disputed
• Argonauta pacifica Dall, 1871 - species status disputed

• †Argonauta absyrtus
• †Argonauta itoigawai
• †Argonauta joanneus
• †Argonauta tokunagai

Synonymsedit | edit code

As synonyms for the generic name Argonauta

consider Argonautarius Dumeril, 1806, Todarus nom. nud. Rafinesque, 1815, Todarus Rafinesque, 1840, Trichocephalus Chiaje, 1827

Argonaut octopuses – information for those interested

Argonauts (lat. Argonauta) are the only modern genus of octopuses from the family Argonautidae. They live in the surface waters of the World Ocean in tropical and subtropical zones. They feed mainly on other pelagic mollusks. Representatives have pronounced sexual dimorphism. The body length of females reaches 10 cm, males are usually much smaller. Insemination is spermatophoric: the tentacle (hectocotyl) carrying packets of sperm breaks away from the male’s body and independently migrates into the mantle cavity of the female. Unlike other cephalopods, they are capable of repeated reproduction. Females rise to the surface of the water at night and drift passively, usually clinging to floating objects.

Octopus Argonaut

Female argonauts, unlike other modern octopuses, have a single-chambered calcareous shell, which is secreted by specialized lobes at the ends of the dorsal tentacles. This formation, therefore, is not homologous to the shells of other mollusks, which are secreted by the epithelium of the mantle. Due to the lack of a rigid attachment between the body and the shell, the mollusk is forced to hold it with its tentacles.

The shells of Argonauts are thin-walled and rather fragile (one of the names is “paper boats”), in some species they are up to 25-30 cm in size. They function not as a skeleton (like in other mollusks), but as a brood chamber in which the female lays eggs. eggs (tens of thousands). Small males in some cases settle in the shells of females.

Another function of the shell is to regulate buoyancy. Rising to the surface of the water, female Argonauts capture a certain volume of air with their shell, lock it with their hands and dive to depth. Active regulation of gas compression allows mollusks to achieve zero buoyancy at various depths and, possibly, to compensate for the significant increase in weight of the embryos developing in the shell during the breeding season.

Behavior

Argonauts swim on the sea waves and rarely descend into the depths of the ocean. At the same time, if necessary, they can dive to depths of several hundred meters.

Males and females are very different from each other. Males lack shells and do not exceed 2 cm in length. They prefer to stay in small flocks. Females lead a solitary lifestyle. The upper pair of their tentacles resemble wide blades. The epithelium of these tentacles secretes a liquid substance that hardens and forms a spiral-twisted shell.

The shell serves as a means of transportation for the mollusk, like a small boat.

It is not attached to the body in any way and he has to constantly support it like a big hat. If necessary, the Argonaut can discard it at any time.

Gas accumulates inside the shell, which helps the mollusk float on the surface of the water. Females almost always drift in the water. Sometimes they abandon their floating homes and begin to swim on their own or crawl clumsily along the bottom. Usually, after having had enough of a walk, the young lady returns to her sink.