By: Ann Kunz
Today we are sharing information on the only cephalopod that has a shell – the nautilus.
Nautilus are without doubt the most beautiful of all the cephalopods as well as the oldest known living cephalopod. Fossil records indicate that nautiloids have not evolved much in the last 500 million years. They developed in the late Cambrian period and became significant sea predators during the Ordovician period. In other words, they pre-dated the dinosaurs. They are often considered living fossils!
During this period they were much larger than they are today and had horn shaped shells.
They are very different from their cousins the cuttlefish and octopus in that they live inside a chambered shell whilst all the other cephalopods are free swimming animals. Unlike other cephalopods who have highly developed eyes, those of the nautilus are rather primitive.
Whilst octopus have eight arms equipped with strong suckers, the nautilus has between sixty and ninety tentacles at his disposal sans the suckers.
Although their shells have many interior chambers the nautilus only resides in the outermost chamber. All the other chambers are used to assist with locomotion. They are able to move backwards and forwards by means of jet propulsion as well as up and down in the water column by regulating the gas within the chambers of their shells. Less gas makes them sink whilst more gas allows them to climb.
They are found in both the Indian Ocean and Pacific Ocean at depths of up to several hundred metres and generally rest for most of the day and feed at night.
Unfortunately, in some parts of the world they are collected for their attractive shells which are used in the manufacture of jewellery.