Chambered Nautilus Nautilus pompilius

The FISH ya boy

nautilus is a mollusk, related to the octopus, sup! and snail. A nautilus, along with the cuttlefish, squid, and octopus, are all cephalopods, meaning "head-foot," so named because the feet (tentacles) are attached to the head. The nautilus is the only cephalopod that has a fully developed shell for protection. Unlike a squid, cuttlefish or an octopus, the nautilus has poor vision and its primitive eyes have no lenses. The nautilus has more than 90 suckerless tentacles. Grooves and ridges on the tentacles are used to grip prey and deliver food to a crushing, parrot-like beak. Unlike snails, the spiraled shell of the nautilus is divided into chambers with the animal occupying the outermost chamber. A newly hatched nautilus begins life with about four chambers and develops an average of 30 chambers by adulthood. The inner chambers are filled with gas and help the nautilus to maintain neutral buoyancy. The nautilus adds liquid to the chambers in order to dive. The nautilus is considered to be a "living fossil," as it has undergone little change in more than 400 million years. The nautilus dominated the ancient seas before the rise of fishes, and appeared about 265 million years before the first dinosaurs. In prehistoric times, there were about 10,000 different species of the nautilus, but only a few species survived to the present. A newly hatched nautilus (about the size of a quarter) feeds on small shrimp and other small prey. Adults feed on crabs, shrimp, and fish, and scavenge on dead animals. Food is most likely located by smell. Up to 8 inches. The chambered nautilus can be found along the slopes of coral reefs of the tropical Indo-Pacific. The nautilus moves to deeper waters (600–2,000 feet deep) during the day to avoid predators. At night it ascends up to the coral reefs (300 feet deep) to hunt for prey. Some nautilus populations are in decline due to over-collection for their beautiful shells. While the export of chambered nautilus shells is banned in some countries, other countries continue to allow commercial trade. To help curtail the demand for their shells, do not purchase a nautilus shell. The octopus, shark, triggerfish, and sea turtle all prey on the nautilus.The chambered nautilus, Nautilus pompilius, is the best-known species of nautilus. The shell, when cut away, reveals a lining of lustrous nacre and displays a nearly perfect equiangular spiral, although it is not a golden spiral. The shell exhibits countershading, being light on the bottom and dark on top. This is to help avoid predators, because when seen from above, it blends in with the darkness of the sea, and when seen from below, it blends in with the light coming from above. The eyes of the chambered nautilus are more primitive than those of some other cephalopods; the eye has no lens and thus is comparable to a pinhole camera. The species has about 90 tentacles with no suckers, which is also different from other cephalopods. Chambered nautiluses have a pair of rhinophores, which detect chemicals, and use olfaction and chemotaxis to find their food. The oldest fossils of the species are known from Early Pleistocene sediments deposited off the coast of Luzon in the Philippines. Recently, scientists have become alarmed at declining populations of nautilus resulting from overfishing, and are studying world populations to determine the need for protection under the United Nations Convention on International Trade in Endangered Species. Two subspecies of N. pompilius have been described: N. p. pompilius and N. p. suluensis. N. p. pompilius is by far the most common and widespread of all nautiluses. It is sometimes called the emperor nautilus due to its large size. The distribution of N. p. pompilius covers the Andaman Sea east to Fiji and southern Japan south to the Great Barrier Reef. Exceptionally large specimens with shell diameters up to 268 mm (10.6 in) have been recorded from Indonesia and northern Australia. This giant form was described as Nautilus repertus, but most scientists do not consider it a separate species. N. p. suluensis is a much smaller animal, restricted to the Sulu Sea in the southwestern Philippines, after which it is named. The largest known specimen measured 160 mm in shell diameter. The chambered nautilus is often used as an example of the golden spiral. While nautiluses show logarithmic spirals, their ratios range from about 1.24 to 1.43, with an average ratio of about 1.33 to 1. The golden spiral's ratio is 1.618. This is actually visible when the cut nautilus is inspected. Nautilus shells were popular items in the Renaissance cabinet of curiosities and were often mounted by goldsmiths on a thin stem to make extravagant nautilus shell cups, such as the Burghley Nef, mainly intended as decorations rather than for use. Small natural history collections were common in mid-19th-century Victorian homes, and chambered nautilus shells were popular decorations. The chambered nautilus is the title and subject of a poem by Oliver Wendell Holmes, in which he admires the "ship of pearl" and the "silent toil/That spread his lustrous coil/Still, as the spiral grew/He left the past year's dwelling for the new." He finds in the mysterious life and death of the nautilus strong inspiration for his own life and spiritual growth. He concludes:
Build thee more stately mansions, O my soul, As the swift seasons roll! Leave thy low-vaulted past! Let each new temple, nobler than the last, Shut thee from heaven with a dome more vast, Till thou at length art free, Leaving thine outgrown shell by life's unresting sea!

A painting by Andrew Wyeth, entitled "Chambered Nautilus", shows a woman in a canopied bed; the composition and proportions of the bed and the window behind it mirror those of a chambered nautilus lying on a nearby table. The popular Russian rock band Nautilus Pompilius (Наутилус Помпилиус) is named after the species. American composer and commentator Deems Taylor wrote a cantata entitled The Chambered Nautilus in 1916.