nautilus

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nautilus

, in zoology

nautilus or chambered nautilus, cephalopod mollusk belonging to the sole surviving genus (Nautilus) of a subclass that flourished 200 million years ago, known as the nautiloids. The spirally coiled shell consists of a series of chambers; as the nautilus grows it secretes larger chambers, sealing off the old ones with thin septa. The animal lives in the largest and newest chamber, with a tubular elongation of the body, known as the siphuncle, extending through the septa to the apex of the shell. The siphuncle removes liquid from the chambers and replaces it with gas, giving the animal the buoyancy that permits it to swim (backwards except when feeding), which it accomplishes by ejecting water through a funnel.

The nautilus breathes by means of two pairs of gills; it feeds on crabs and other animals, which it catches with its long, slender tentacles (numbering more than 90) that encircle the mouth. There is a thickened area over the head, called the hood, that acts as a protective lid when the animal withdraws into the shell. The nautilus lives in deep water in the S Pacific and Indian oceans. It is active at night; during the day it stays hidden in coral crevices. It is hunted for its shell, which is used in jewelry and ornaments.

The paper nautilus, which is not a true nautilus, is a close relative of the octopus, belonging to the order Octopoda. The true nautilus is classified in the phylum Mollusca, class Cephalopoda, order Nautilida, family Nautilidae.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Nautilus

 

a genus of invertebrates of the superorder Nautiloidea and the class Cephalopoda.

Nautilus is now the only living group of the subclass Tetrabranchia. The shell is large (up to 30 cm in diameter) and external, spirally coiled in a single plane, and divided by partitions into a series of chambers. The body of the mollusk is located in the last and largest chamber. The chambers serve the animal as a hydrostatic apparatus. To descend, it fills them with water to varying degrees, while to rise it fills them with a gas with a high content of nitrogen. There are several species, which are found in the Indian Ocean and the western part of the Pacific. Nautilus crawls along the bottom (at shallow depths) or swims on the surface of the water. It feeds on small crabs and fish.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

Nautilus

[′nȯd·ə·ləs]
(invertebrate zoology)
The only living genus of the molluscan subclass Nautiloidea, containing the only living cephalopods with an external chambered shell and numerous cephalic tentacles, six species live in the western Pacific and around the East Indies.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Nautilus

submarine in which its builder, Captain Nemo, cruises around the world. [Fr. Lit.: Jules Verne Twenty Thousand Leagues Under the Sea]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.

nautilus

1. any cephalopod mollusc of the genus Nautilus, esp the pearly nautilus
2. short for paper nautilus
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
The Chambered Nautilus never looked more handsomely masculine, its prose glittering like the back of a surfacing whale.
Unlike its namesake the chambered nautilus, which is permanently attached within its shell, the paper nautilus uses its specialized tentacles to hold onto its "shell" and keep it from washing away.
It's very mysterious, as this ratio appears in unrelated works and natural phenomena, from the chambered nautilus to galaxies to artwork and architecture.
Oliver Wendell Holmes's "The Chambered Nautilus" (1858)--another renowned excursion into cephalopodic lyricism-presents the nautilus's step-by-step construction of its shell as an inspirational example: "Build thee more stately mansions, O my soul." But where Holmes's poem celebrates incrementalism, "The Kraken" rejects it altogether.
Some of the unusual sea life that visitors can glimpse at "Oddwater" include the chambered nautilus, which is notable for its unusual movement.
SHELL-STOCKED From pillows to picture frames and this mother-of-pearl jewel box ($450) topped with chambered nautilus shell, FantaSea celebrates the sea's beauty.
Seashell, 31 indeed resembles a chambered nautilus cut into being with crisp, angular shapes of pinks, reds, and plums in warm electric tones; Damaged, 46 is formally attired in pitch black, grays, and white and recalls shattered crystal.
The deepest layer contains traces of seafloor burrows and large numbers of phosphate nodules that include the fossils of ammonites, the extinct relatives of today's chambered nautilus.
The sloping and tilting roof gains width as it surrounds the circular welcoming center and is indicative of a number of different forms in nature and in Native American culture -- the beginning of a spider web, the shape of a pine cone as it unfolds, or the form of a Chambered Nautilus' shell.