Have you ever seen a nautilus? Probably not—most people haven't. (And no, I'm not talking about Captain Nemo's ship). But I'm willing to bet that you have seen an octopus, if not in person then at least in a Disney cartoon or on the Discovery channel, when the Discovery channel had actual educational programs and not just reality TV shows.
So what is this strange creature of the deep? In the late twentieth century, fossils of ancient nautiluses that date back to the Late Eocene period (56 to 33.9 million years ago) were discovered off the coast of Cape Flattery on the Olympic Peninsula in Washington state. These creatures slowly evolved into the nautiluses we know today, mollusks with close ties to other cephalopods, such as octopuses and squid. The nautilus shares many anatomical similarities with the octopus, such as tentacles, eyes, and a siphon for jet-propulsion and respiration, but this is where the obvious resemblances end.
Objet Trouvé I: The Nautilus
Like the octopus, the nautilus has a type of "tentacle," but only a type; unlike the octopus, the tentacles of the nautilus lack suction pads, and instead derive their grip from their ridged structure. And while the octopus has—you guessed it—eight tentacles, the nautilus can have up to ninety, including two tentacles that double as olfactory organs. Good thing too, given that the nautilus has poor eyesight. While the octopus is known for its keen eyesight (some species even have color vision), the nautilus, with its simple pinhole eye, is as good as blind, instead relying on its strong sense of smell to navigate its surroundings. Given their poor sense of sight, olfactory organs, such as the two tentacles closest to their eyes, are essential as they navigate the ocean. Their extra keen sense of smell is particularly important given that unlike octopuses or squid,
which use jet-propulsion to propel themselves forward, the nautilus propels itself backwards through the ocean, with the butt of its hard shell protecting its vital organs from predators and other oncoming traffic. As the nautilus jet propels itself through the ocean, it is quite literally flying blind.While all these qualities are enough to differentiate it from the octopus, the nautilus really sets itself apart with its remarkable shell. Like the octopus, the nautilus is soft-bodied, yet it lives in a hard, chambered shell, which has a pearl-like coating called nacre, a material that is highly sought after by jewelers and merchants for its natural beauty. Beyond its beauty, the nautilus shell is also remarkable for containing a structure capable of effecting the fish’s buoyancy, an ability necessary for the fish to navigate the ocean and escape predators. While the majority of the nautilus can be found in the shell’s largest chamber, the rest of the nautilus’s 30 or so chambers act like the tanks of a submarine, holding and discharging water by means of osmosis and a complex regulation of gases, which changes the animal’s density. As water moves out of the chambers, pressure created by gases such as nitrogen, oxygen, and carbon dioxide lowers, and the nautilus becomes less dense; as water is drawn into the chambers, the nautilus becomes more dense.The nautilus shell is an extraordinary example of form meets function in nature. Its mathematical structure alone, known as a logarithmic spiral, has been a subject of beauty and awe for those who have studied it, inspiring countless tracts and odes. That it allows for a complex system of buoyancy is even more remarkable. This is not your average cephalopod; in fact, its unlike anything else in this world.