The Chambered Nautilus is the most well known nautilus, and unlike most cephalopods, its ~90 tentacles have no ‘suckers’. It’s shell, which exhibits countershading to protect from predators, displays a nearly perfect logarithmic spiral on its interior, and is lined with mother of pearl (nacre). They have a pair of rhinophores which use olfaction and chemotaxis in order to find their food.
To swim, the nautilus draws water into and out of the living chamber with its hyponome (siphon), which uses jet prepulsion. While water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood. The animal adjusts its buoyancy by osmotically pumping gas and fluid into or out of the camerae along the siphuncles. This limits them; they cannot operate under the extreme hydrostatic pressures found at depths greater than approximately 800 metres (2,600 ft). In the wild, nautiluses usually inhabit depths of about 300 metres (980 ft), rising to around 100 metres (330 ft) at night to feed, mate and to lay eggs.
Reblogged from nemosfin 1 year ago