Argonauta argo

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Geographic Range

Warm temperate and tropical seas around the world.

Habitat

Likes to be near the surface of the water. It is an epipelagic oceanic species.

Physical Description

The maximum length of shell is 30 cm in females, but only 1.5-2 cm in males. The shell is coiled and laterally compressed with a narrow keel and numerous sharp nodules. Nodules toward the center of the coil are brown, but most of the shell is white.

Reproduction

The male uses a specialized arm called a 'hectocotylus' to fertilize the eggs. The hectocotylus is inserted into the females pouch and breaks off during mating. The female forms a "nacelle," a thin calcareous shell, with two of her legs (the others are used for swimming). This structure holds the eggs throughout development.

Behavior

The female is up to twenty times larger than the male. Normally these animals are solitary.

Food Habits

Feeds on plankton and small organisms on the surface of the water.

Economic Importance for Humans: Positive

Can be found in fish markets in India and Japan. The shell is praised by collectors because of its beauty, coloration, sculpture, and fragility.

Conservation Status

This animal is very common but is rarely spotted by humans. Every once and a while many of them may be washed up by a change in currents or chased into shallow waters by predators, allowing people to observe and catch them.

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

The species is heavily preyed upon by tunas, billfishes, and dolphin.

Contributors

Tyler Virden (author), University of Michigan-Ann Arbor.

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.

coastal

the nearshore aquatic habitats near a coast, or shoreline.

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.

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

References

Lane, Frank. 1960. Kingdom of the Octopus. Sheridan House, New York.

Verrill, A. !882. The Cephalopods. Govt. print. Washington.

Roper, C. 1984. Cephalopods of the World. National Museum, Washington.

Abbot, R. T. 1954. American Seashells. D. Van Nostrand Co., Inc.

Cousteau, Jacques. 1973. Octopus and Squid. Doubleday and Co., New York.