Nautilus

About the Nautilus

Living fossils that have remained virtually unchanged for 500 million years - they survived all five mass extinctions. They can regulate their buoyancy by pumping gas and fluid in and out of their shell chambers. They have 90 tentacles, unlike octopus which have 8. They have primitive pinhole eyes with no lens. They live at 200-700 meters depth, coming shallower at night to feed. Their shells display a near-perfect logarithmic spiral (golden ratio). Overfishing for their shells has depleted populations. Their blood is blue due to hemocyanin. They are the only cephalopods with external shells.