nautiluses

Nautiluses are marine mollusks in the cephalopod family Nautilidae and the sole living representatives of the subclass Nautiloidea. They are distinguished by an external spiral shell divided into gas-filled chambers and a soft body occupying the final chamber. They possess numerous slender tentacles instead of suckers and lack the ink sacs and advanced eyes seen in other cephalopods.

The chambers are connected by a siphuncle, allowing the animal to regulate buoyancy by adjusting gas and liquid within the chambers. This enables slow, vertical movement and hovering in the water column. Jet propulsion provides primary locomotion.

Nautiluses inhabit Indo-Pacific waters, often around reefs and rocky slopes at depths of about 100–300 meters. They are nocturnal predators, feeding on crustaceans and other small animals with their tentacles.

Reproduction is sexual. Females lay eggs in the substrate; embryos develop within the eggs and hatch as free-swimming juveniles that bear a small shell. Growth proceeds as the animal adds new chambers to its shell.

Conservation concerns stem from slow growth, late maturity, and vulnerability to overharvesting for shells, as well as habitat disturbance. Several Nautilus species are listed as threatened or of concern in regional assessments, underscoring the need for sustainable management.