Argonauta nodosa

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Geographic Range

Argonauta nodosa lives in all the different oceans and seas with a warm, tropical climate. However, it is most abundant in the South Australian waters. (Wu 1989;Hall 1997; Mangold and Young 1996)

Habitat

Argonauta nodosa prefers to live near the surface level in the open-ocean, which has lower temperatures and fewer predators than a gulf. Pelagic.

(Hall 1997; Wu 1989)

Physical Description

Argonauta nodosa is closely related to the octopus. It has eight tentacles with suckers on them. It has a closed circulatory system. It moves by using a siphon to pump water, pushing it forward. Like the octopus, it has the ability to shoot ink made by an ink gland in the intestine. Argonauta nodosa has many different shades of color, since it is able to change color to match its environment.

Male and Female Argonauta nodosa show sexual dimorphism. The male is much smaller than the female. The female size is about 30 cm in length, and the male size is about 3 in length. The female also makes a shell, which the male does not create.

The shell of the female is 12-15 cm on average. The dorsal arms of the female both have a large flap, which are enlarged membranes. These membranes have glands that secret the calcareous shell. Each arm makes half of the shell, creating a double keel where each side meets. The shell has rows of knobs on the keel, which are called tubercules. The tubercules can be many different colors, such as brown or purple. The shell itself is usually transparent and flexible. In the Argonauta nodosa the keel is wider than in the Argonauta argo, the more common nuatilus, and it's nodules are stouter and spaced farther apart. The flaps on the arms also cover the shell like a web. The shell is not connected to the Paper Nautilus by any type of muscle, but is supported by the dorsal arms of the female.

The male Argonauta nodosa displays a long tentacle called the hectocotylus. This extended arm is absent in the female. The hectocotylus contains spermatophore, and is used for reproduction. Each season a new hectocotylus is formed.

(Wu 1989; Mangold and Young 1996; Hall 1997; Grzimek 1972; Alling 1996; Lorimer 1995; Lorimer 1996)

Reproduction

Reproduction of the Argonauta nodosa is sexual, and fertilization is internal. A male is ready for reproduction when the hectocotylus is fully developed. At this time the hectocotylus, which develops in a sac, breaks out of the sac and is exposed. The hectocotylus is a specialized, extended tentacle used to store spermatophore, the male gamete. The male transfers the spermatophores to the female by putting it's hectocotylus into a cavity in the mantle of the female. This mantle cavity is known as the pallial cavity. This is the only contact the male and female have with each other during copulation, and it can be at a distance. During copulation, the hectocotylus breaks off the male. The funnel-mantle locking apparatus on the hectocotylus keeps it lodged in the pallial cavity of the female. This helps to ensure the fertilization of the female. In addition, the spermatophore remains active for a long time to help ensure fertilization. The female Argonauta nodosa is only able to mate once in her lifetime, whereas the male is able to reproduce multiple times. After fertilization, the female deposits the eggs into the "brood chamber," which is her shell. In the brood chamber, the eggs develop until they are ready to enter the open ocean.

(Wu 1989; Grzimek 1972; Rosenblum 1995; Alling 1996)

Behavior

When feeding Argonauta nodosa uses its tentacles to grab its prey, and drag it toward its mouth. Then it bites the prey, injecting it with poison made in the salivary gland. If the prey is shelled, Argonauta nodosa uses its radula, a tongue-like appendage, to drill into a shelled organism. Then it will inject the poison into its prey.

Argonauta nodosa have defenses against other organisms seeking to prey on them. Argonauta nodosa has the capability to alter its color. It can effectively blend in with its surroundings to avoid predators. Argonauta nodosa also makes ink, which it ejects when it is being attacked. This ink is used to paralyze the sense of smell of the predator, providing Argonauta nodosa time to escape. The female is also able to pull back the web covering of the shell, making a silvery flash. This might deter a predator from attacking.

Argonauta nodosa is usually a solitary animal, but it is occasionally in a school. This usually occurs during the mating season.

During mating the males will sometimes fight to mate with the female. The winner of the fight mates with the female. When the female Argonauta nodosa produces her eggs, those eggs are stored in her brood shell. As the eggs grow larger, they begin to force the mother out of her shell. When she is out of the shell, the young can be released. Soon after she is forced out, she dies. Then the female Argonaut nodosa, once forced out of her shell, will drift to a shallow area, and die.

(Hall 1997;Wu 1989; Grzimek 1972; Rosenblum 1995)

Food Habits

The Argonauta nodosa eats crayfish, crabs, and other types of bivalves.

(Grzimek 1972)

Economic Importance for Humans: Positive

Argonauta nodosa shells are fairly rare, and they are prized by shell collectors. People make money from the sale of the shells of this species.

(Hall 1997)

Economic Importance for Humans: Negative

There are no adverse affects to humans.

Conservation Status

Other Comments

Argonauta nodosa is preyed upon by animals such as tuna, dolphin, and bullfishes.

Though it is not endangered, Argonauta nodosa is rarely seen by humans because it lives in the open ocean. It is usually seen when it has washed onto the shore.

(Wu 1989; Hall 1997)

Contributors

Michael Rutledge (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Alling, G. 1996. Argonaut. Pp. 278 in P Bayer, C Peckaitis, B Cole, H Tench, B Feinberg, eds. Encyclopedia Americana. Danbury, Connecticut: Grolier Incorporated.

Grzimek, B. 1972. The Cephalopods. Volume 3. Pp. 217-225 in B Grzimek, M Abs, S Ali, R Altevogt, R Angermann, eds. Grzimek's Animal Life Encyclopedia. New York, New York: Van Nostrand Reinhold Company.

Hall, P. 1997. The Paper Nautilus Argonauta and The Chambered Nautilus Nautilus. Marine Life Society of Southern Australia, 1997: 2-5.

Lorimer, L. 1995. Octopus. Pp. 348 in J Cox, S France, C Mankin, S Moll, S Randel, eds. Academic American Encyclopedia. Danbury, Connecticut: Grolier Incorporated.

Lorimer, L. 1996. Octopus. Pp. 631-632 in P Bayer, C Peckaitis, B Cole, H Tench, B Feinberg, eds. Encyclopedia Americana. Danbury, Connecticut: Grolier Incorporated.

Mangold, .., .. Vecchione, .. Young. August 5, 1999. "Tree of Life" (On-line). Accessed Febuary 19, 2000 at http://www.soest.hawaii.edu/tree/ce...lies/argonautidae/argonautidae.html.

Rosenblum, E. 1995. Octopus. Pp. 67-68 in L Bloomfield, C Waff, T Zinn, S Mage, P Quigley, eds. Collier's Encyclopedia. New York, New York: Collier's.

Wu, N. 1989. The Paper Nautilus. Sea Frontiers, March-April, 1989: 94-96.