nautilid

The nautilid is a marine mollusc belonging to the order Nautilida. These cephalopods are characterized by their external, chambered shell, which they use for buoyancy control. Nautilids are among the oldest surviving cephalopod lineages, with a fossil record stretching back hundreds of millions of years. They are found in the Indo-Pacific region of the ocean.

Nautilids possess multiple tentacles, arranged in two whorls, which they use for capturing prey and locomotion. Unlike their coleoid relatives such as squid and octopus, nautilids have a shell and lack suckers on their tentacles. Their diet consists primarily of small crustaceans and fish.

The shell of a nautilid is divided into chambers by septa. The animal lives in the outermost chamber, while the inner chambers are filled with gas and liquid, allowing the nautilid to adjust its buoyancy and depth. As the nautilid grows, it adds new chambers to the shell.

Reproduction in nautilids involves the laying of eggs, typically attached to the seabed or other surfaces. The development of young nautilids is direct, meaning they hatch as miniature versions of the adult, without a larval stage. Despite their ancient lineage, nautilids are considered vulnerable or endangered in some areas due to overfishing and habitat destruction.