The chambered nautilus
It is an underwater living that lives in deep waters of the open ocean and it is one of very few species of shelled invertebrates which live in the water column instead of in contact with the seafloor or reef surface. The chambered nautilus only lives in the outermost chamber of the shell. The other chambers are filled with gas that helps the chambered nautilus remain neutrally buoyant and that give it the ability to hover in the water.
The chambered nautilus is an active predator and also a scavenger. It typically hunts for benthic crustaceans or other invertebrates, but when scavenging it is not selective. This species has as many as 90 appendages, the octopuses and squids have only eight or ten. Also, 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 by internal fertilization. Males have modified tentacles and they use them to pass sperm to females. Females then attach fertilized eggs to hard substrates on the seafloor, where they remain for up to about a full year before hatching. Newly hatched juveniles will have well developed 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. Other species like Squids, octopuses, and other cephalopods die after they reproduce once.
The conservation and population trends of the chambered nautilus are not popular , because there are little data on numbers of this species. Some individual scientists are afraid 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 considered an important first step in determining whether or not this is a species of concern.
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