Tropical to warm temperate latitudes of the east Indian and west Pacific oceans
Open ocean near the seafloor
Class Cephalopoda (octopuses, squids, and relatives), Family Nautilidae (nautiluses)
The chambered nautilus is one of six species of nautilus, the only cephalopods (squids, octopuses, and relatives) that have external shells. Like in most shelled animals, this species can retract completely into its shell when threatened. The chambered nautilus lives in deep waters of the open ocean and is one of very few species of shelled invertebrates that live in the water column instead of in contact with the seafloor or reef surface. The animal only lives in the outermost chamber of the shell. The other chambers are filled with gas that helps the chambered nautilus remain neutrally buoyant, giving it the ability to hover in the water.
The chambered nautilus is both an active predator and a scavenger. It typically hunts for benthic crustaceans or other invertebrates, but it is not selective when scavenging. This species has as many as 90 appendages, unlike the octopuses and squids, which have eight or ten. Furthermore, the chambered nautilus does not have suckers on its tentacles, and obtains food by wrapping several tentacles around its prey and pulling the prey toward its mouth.
This species reproduces via internal fertilization. Males have modified tentacles that they use to pass sperm to females. Females then attach fertilized eggs to hard substrates on the seafloor, where they remain for up to a full year before hatching. Newly hatched juveniles already have well developed (though tiny) shells. The chambered nautilus is one of the longest living cephalopods, reaching ages of over 20 years old. The nautiluses are also the only cephalopods that reproduce multiple times. Squids, octopuses, and other cephalopods die after they reproduce once.
The conservation status and population trends of the chambered nautilus are not known, as there are little data on numbers of this species. Some individual scientists fear that they are being overharvested for their shells. This species is not offered legal protection anywhere in its range and fishing activities are not actively managed, so overharvesting is a legitimate concern. Monitoring chambered nautilus populations is an important first step in determining whether or not this is a species of concern.