Nautilus

The nautilus is the only cephalopod that has a fully developed shell.

 Chambered nautilus

 Unlike a squid, cuttlefish or an octopus, the nautilus has poor vision.

 Its primitive eyes have no lenses. They work like pinhole cameras.

The nautilus has more than 90 suckerless tentacles. 

 Grooves and ridges on the tentacles are used to grip prey.

 They deliver food to a crushing, parrot-like beak.

The spiraled shell of the nautilus is divided into chambers with the animal occupying the outermost chamber. 

 A newly hatched nautilus begins life with about four chambers.

 It develops an average of 30 chambers by adulthood. 

 The inner chambers are filled with gas.

 They help the nautilus to maintain buoyancy. 

 The nautilus adds liquid to the chambers in order to dive.

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