What is the mystery of the chambered nautilus?

Year after year beheld the silent toil
That spread his lustrous coil;
Still, as the spiral grew,
He left the past year’s dwelling for the new,
Stole with soft step its shining archway through,
Built up its idle door,
Stretched in his last-found home, and knew the old no more

Oliver Wendell Holmes (1804-1894)

The above is only an excerpt from the poem, “The Chambered Nautilus” by Holmes published in 1858. It only begins to hint at the marvel of this magnificent cephalopod. The chambered nautilus has become breathtaking subject matter for generations of artists and has become a commodity on the commercial trade industry.

The chambered nautilus is a squid that lives inside a shell marked with a brown and white zebra pattern. As the squid grows, the shell grows with it and creates compartments which are used as gas chambers and help the cephalopod rise or sink in the water column. The inside of the shell is lined with an iridescent pearl. In the last chamber of the shell are almost 90 tentacles and large eye peering out. Predators of the chambered nautilus include sharks, turtles, and octopus.

What makes the chambered nautilus so mysterious and sought after? Is it the mother of pearl that lines the inside of the animal’s shell? Is it that the animal represents a far off species only found tropical Indo-Pacific? Or is it that the inside compartments of the chambered nautilus each mirror its smaller and larger part exactly and therefore the animal is an example of the golden rectangle found in nature.

This harmonic progression is an illustration of Fibonacci’s sequence. This is a sequence where the first two numbers in the series are added to create the third number for a series of number that begins 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 and so on forever. This proportional pattern can be seen all over in nature: flower petals, pine cones, and even galaxies. Below is an illustration of the proportion as it relates to the chambered nautilus.

Image (c) top – seasky.org, bottom – http://2muchfun.info

Do you have another interesting question? E-mail info@beachchairscientist.com and let us know what you always ponder while digging your toes in the sand!

Why are there holes through some clam shells?

moonsnailholezd2The shell to the right with a hole through it was hinged to another shell of equal size with an animal living inside (in this case, a clam). Animals with two shells hinged together are known as bivalves. Often, in restaurants oysters and clams are shucked and served “on-the-half-shell” (Yum! I prefer them plain, but sometimes mix it up with ones with plenty of horseradish!).

Animals in the ocean do not have the luxury of someone shucking their prey, but rather use an adaptation called a radula. A radula is the sharp, drill-like tongue of some mollusks (e.g., whelk or conch). Radulas are found on every class of mollusk except for bivalves. A whelk or a conch would use their radula to drill into the clam and then slurp out its meal … Leaving behind a perfectly symmetrical hole. Moon snails and oyster drills are also well-known for using this technique to drill into clams for a feast.

Image (c) imageshack.us