Which of the following ocean creatures looks like a squid with a shell?
And the answer is: nautilus.
Found in coastal reefs around Southeast Asia and Australia, the nautilus is a type of cephalopod, which is a group of animals that includes the squid, octopus, and cuttlefish. One noticeable characteristic is that most of the nautilus' body is contained inside a spiral shell, which makes swimming a little awkward, but manageable.
The nautilus is an ancient creature. These shelled cephalopods have been perusing the ocean's deep waters for around for some 500 million years, yet their unique anatomy makes them a continuous source of intrigue in the scientific community. Interestingly, the nautilus is what's known as a "living fossil" as due to the fact that their anatomy has gone relatively unchanged in the millions of years they have been on Earth.
Unlike squids or octopi, the nautilus do not hunt for their prey. The creatures propel themselves forward by using water pressure with the chambers of air trapped in their shell– operating not unlike a submarine. As a result, nautilus' swimming ability is meager at best; they are unable to lunge or attack the same way as their shell-less cousins. Instead, these cephalopods' way of life depends on scavenging. Helpfully, they have up to 90 retractable, suckerless tentacles to help in obtaining food and attaching to the reef during rest.
The nautilus lay few eggs, and experience a relatively latent maturity– these creatures reach their peak after about 20 years of life. However, this makes them prime subjects for overfishing. The ancient nautilus faces endangerment into the modern day. Yet, there is still much to learn. Scientists will continue to study their habits and life for as long as they're around.
Check out this Museum of Natural History video to learn more.