FunNature & AnimalMeet the nautilus, a living fossil

Meet the nautilus, a living fossil

What kind of animal is the nautilus?

Nautiluses (Nautiloidea) are cephalopods, like octopuses, cuttlefish or squid , but much more primitive. Although they have a very different appearance, they share the presence of the parrot’s beak, a pair of jaws that they use to tear prey; and the radula, a specialized structure for scraping food. In addition, they also have a kind of tentacles, called cirrus, connected directly to the head.

Why is it considered a living fossil?

The genus Nautilus sp. It has been on Earth for about 500 million years , since the early Paleozoic. In all this time these animals have hardly changed.

How are they different from other living cephalopods?

The most notable differential feature is the presence of an external shell ; which is divided into several septa and the animal is housed in the most recent chamber, the most external. In the rest of the cephalopods, the lake has been reduced throughout history, it has become internal (cuttlefish and calmers) or it has completely disappeared (octopuses). In addition, instead of eight tentacles, nautiluses can be as long as ninety and lack suction cups.

What functions does its outer shell have?

Apart from fulfilling a structural and protective function , the pond serves to fill or empty itself with gas or water, to contribute to the buoyancy of the animal , so that it can go up or down in the water column.

What do they feed on?

Nautiluses are carnivores and often feed on other mollusks . They are capable of secreting sticky mucus on their tentacles to hold on to their prey. In addition, the parrot beak allows them to break the shell of a bivalve.

Who eats them?

Octopuses and triggerfish attack the outer shell of the nautiluses , eventually breaking it up and devouring them. As victims they can only hide in their shell and wait for the danger to pass.

How do they reproduce?

Although at the moment this behavior has only been observed in captivity, it is known that nautiluses lay 10 to 20 eggs in 3-4 cm capsules . Before laying, during the mating ritual, the male may cling to the female for hours, while passing a package full of sperm to her with a special tentacle called a spadix. Something curious that has been observed in samplings around the world is that 95% of captured individuals are males . The reason for this phenomenon is still unknown.

Where can they be seen?

The five existing species of nautilus, two of the genus Allonautilus sp . and three of the Nautilus sp., live in the Indian and Pacific oceans. However, they are somewhat difficult to see, since during the day they rest at a depth of 300-400 m and at night they climb up to 100 m to feed or mate. In remote occasions they can be seen a little closer to the surface, will you be the lucky one?

One last curiosity …

Jules Verne, a well-known 19th century French writer, named the submarine Nautilus that appeared in his novel ‘20,000 Leagues Under the Sea ‘ in honor of these mollusks, since both control their buoyancy by flooding cavities.

 

References:

Saunders, B. W., & Landman, N. (2016). Nautilus: The Biology and Paleobiology of a Living Fossil, Reprint with additions (Topics in Geobiology, 6) (Softcover reprint of the original 2nd ed. 2010 ed.). Springer.

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