I have never ever seen one of these,
and yet the shape and name is kind of iconic. I don’t think I’ve ever seen one in an aquarium or even on a nature special.
I apologize if this entry is a little dry, but admitting that one knows nothing about a whole family of creatures leads to the need for a whole lot of somewhat dry information to get started. I will bold the section markers to make it easier to skim.
According to some wikipedia scavenging, they are cephalopods, like octopus, squid and cuttlefish, but a separate, older branch in their evolution, with an external shell. They have survived nearly unchanged for hundreds of millions of years.
“Nautiluses are predators that feed mainly on small fish, shrimp, and other crustaceans, which are captured by the tentacles. Due to the limited energy they expend in swimming, nautiloids only need to eat once a month.” And just to inject some editorializing they have way more tentacles that their cousins. They may have up to 90 tentacles! Now there’s a bad dream waiting to happen. Bleck.
The website Tonmo.com is dedicated to all things cephalopod and has a great article on the origin of Nautiloids. “The first cephalopods had appeared in the Late Cambrian, about 515 million years ago.”
Explaining the shell and the buoyancy of the nautilus, “The shell of the nautiloid or phragmocone, was divided into many chambers that would have contained gases provided by a connecting tube known as asiphuncle. The siphuncle works by drawing water out of the saturated chambers of the nautilus into the bloodstream and gas seeps out of the blood to fill the empty space in the chamber. When the nautilus completes a new chamber it is initially filled with water. The nautilus will then increase the salt content and acidity in its bloodstream flowing through the siphuncle. The increase in salt levels sets up an osmotic gradient causing the water in the chamber to move to the more concentrated blood. As the water levels drop in the chamber and the pressure reduces, gases are diffused from the siphuncle to fill the space creating buoyancy.”
“To swim, the nautilus draws water into and out of the living chamber with its hyponome, which uses jet propulsion.” “Unlike many other cephalopods, they do not have good vision; their eye structure is highly developed but lacks a solid lens. They have a simple “pinhole” eye open to the environment.” It is thought that they use olfaction, aka smell, “as the primary sense for foraging, locating or identifying potential mates”
I am also grateful to the blog Strange Animals for loads of interesting info in far more common language and thoughtfully prepared for a novice user. Bless you: “The chambered nautilus can be found in tropical waters that extend from the Andaman Sea east to Fiji and from southern Japan to the Great Barrier Reef. This weird creature’s habitat usually lies in locations where the coral reef slopes go down into deep waters. ”
:There are two known subspecies of the Chambered Nautilus: Nautilus pompilius pompilius and Nautilus pompilius suluensis
N. p. pompilius is the most common and widespread subspecies. It is also called “Emperor Nautilus” due to its large size. Its natural habitat covers the Andaman Sea east to Fiji and southern Japan south to the Great Barrier Reef. Remarkably large specimens with a shell diameter of up to 268 mm (10.3 inches) have been reported from Indonesia and northern Australia. This giant nautilus was firstly described as Nautilus repertus, however most scientists believe that it is not a separate species.
N. p. suluensis is much smaller in size, found only to the Sulu Sea in the southwestern Philippines. The largest specimen ever recorded had a shell diameter of 148 mm (5,5 inches):
“Although the Nautilus is heavily harvested for the shell trade, the animal appears to be doing rather well and is very widespread around the Pacific. In fact, the animal may even be diversifying; the Papua New Guinean Allonautilus differs in its physiology so much from Nautilus, mainly in the creases and encrusting layer on its shell, size of its gills and variation in reproductive structures that in 1997 it was declared by Ward and Saunders to be a separate genus. Following DNA studies it is believed that Allonautilus scrobiculatus may be a recent offshoot of Nautilus. If so, this would indicate that the Nautilida is undergoing speciation again. If so, the Nautilus in one form or another may be around for a long time yet to come.”
The Chambered Nautilus is the title and subject of a poem by Oliver Wendell Holmes in which 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!
Finally, how cute are these lamps!
Furthermore on another tangent, mathematics has a great deal of gratitude to offer these ancient scavenging cephalopods. According to the scienceclassroom.wikispaces.com, ” Look at any new text book in almost any school and on the cover of each will likely be a piece of photography or a graphic rendering of one of the