What is an Argonaut? An Argonaut is a free-swimming cephalopod that lives in oceans. The Argonaut argo or also known as the Greater Argonaut is one of those species of creatures and, are a very unique species. The Argonauts are most famous for their beautiful brittle white shells.
Only the females have the shell which is used to carry the eggs, while the males go without. The shell is white with a black crest and on the end of the shell. The shape of the shell is ridged and bumpy. Amazingly the female Greater Argonaut holds on to its shell with its suckers. They also have eight arms with two rows of suckers. They have closed eye with lens and two gills. The beak is made out of a horny material. Females develop a shell very early in life at a size of approximately 7 mm mantle length. Also, the females in this species can grow to around 40 cm long. The females’ shell grows up to 45 centimeters large, the male-only reaches less than 2 centimeters size. The male is much smaller than the female.
Their habitat is in tropical and temperate oceans around the world. In the Mediterranean Sea, there has been a form of a dwarf of the Argonaut argo, but it is described as Argonauta argo mediterranea.
They eat small live fish, shrimp, pelagic molluscs and crustaceans.
Argonaut argo is prey to many. The predators of the Argonauts are commonly fast-moving creatures, also to the streamlined, oceanic fishes including lancet fishes, dolphinfishes, mackeral, tunas, swordfish, marlins, sailfishes and whaler sharks. Also are a diet ot the catsharks, dolphins, small toothed whales, fur seals, penguins, terns, petrels, albatrosses and tropicbirds. In the Australian waters have been reported in the diets of Southern Bluefin Tuna, Australian Fur Seal, and the Shy Albatross.
To avoid these predators, the Great Argonauts have developed defense strategies like inking and countershading. They can shoot a minimum of five shots of dark gray, ink that hangs in the water and slowly extend. This move disorients predators while the Great Argonaut quickly escapes with jet propulsion. Countershading, or Thayer’s law, also know as camouflage, is also an effective predator avoidance tactic.
Interesting Facts
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They have 3 hearts.
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To swim by jet propulsion, using powerful jets of water squirting through their funnel.
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The females shell is paper thin, and very fragile.
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This species name in Chinese translates as "White Sea-horse's Nest".
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The Argonaut argo is the largest Argonaut in its genus, and also produces the largest eggcase.
Author: Amanda M.
Published: 2/2008
Resources
http://researchdata.museum.vic.gov.au/argosearch/index.html
http://www.weichtiere.at/Mollusks/Kopffuesser/argonauta.html
http://www.thecephalopodpage.org/MarineInvertebrateZoology/Argonautaargo.html
http://en.wikipedia.org/wiki/Greater_Argonaut
Picture credit: David Paul
http://researchdata.museum.vic.gov.au/argosearch/index.html