Nautilus

The nautilus is a sea animal.

It has a hard shell. The shell is a pretty shape. It has dark stripes on top. The bottom is white.

This helps it hide in the water. The shell has many small rooms inside. As the animal grows, it makes new rooms. It moves into the big rooms. It leaves the small rooms behind. It can even hide its whole body inside.

The nautilus is a very old animal.

The nautilus is a special sea animal. Many people call it a "living fossil." This is because it has stayed almost the same for millions of years.

It lives inside a hard, coiled shell. The shell has many small rooms inside. We call these rooms camerae.

As the animal grows, it builds new, larger rooms. It moves into the new space and seals the old room with a wall. This wall is called a septum.

The nautilus uses its shell to float. It has a tube called a siphuncle. This tube helps the animal change how it floats in the water. The shell also helps it hide. The top is dark with stripes. The bottom is white. This is called countershading. It helps the animal blend into the sea.

Nautiluses use tentacles to move and feel. They can have 50 to 90 tentacles. These tentacles do not have suckers. Instead, they use a sticky liquid to hold things.

The animal also has simple eyes. They work like a pinhole camera to see light.

The nautilus is a very special group of living things in the sea. They belong to a family called Nautilidae, which includes nine different species. Many people call them "living fossils." This is because they have stayed almost the same for hundreds of millions of years.

They are the only living members of a group called Nautiloidea. Most species live in the ocean and use their shells to stay safe.

To move and float, the nautilus uses a clever way of working. It has a coiled shell with many internal rooms called camerae.

A tube called a siphuncle runs through these rooms. This tube helps the animal change its buoyancy, which is how it floats. The siphuncle can move salt and liquid to change how heavy the animal feels in the water. To swim, the nautilus uses a part called a hyponome. It pushes water in and out to move through the sea using jet propulsion.

Scientists have studied these animals for a long time. We know about their history through fossils found in many places. One of the oldest fossils is kept at the Philippine National Museum.

The shells themselves are beautiful and have a special shape. This shape is called a logarithmic spiral. The shell has two layers. The outer layer is matte white with dark orange stripes. The inner layer is shiny and pearly.

There are many interesting facts about how a nautilus lives. A nautilus can have between 50 and over 90 tentacles. These tentacles do not have suckers like an octopus. Instead, they use a sticky liquid to hold onto things.

Their eyes are very simple and work like a pinhole camera. They do not have a clear lens to see sharp details. Most nautiluses live in deep water. The largest species is Nautilus pompilius. Some small versions, like those in the Sulu Sea, are very tiny.

Watching a nautilus helps us understand how life can last for ages. Their shell color is a type of camouflage called countershading. The dark top helps them hide when seen from above. The white bottom helps them hide from below. This helps them blend into the light and dark parts of the ocean. Their blood is even a different color than ours. It contains hemocyanin, which turns blue when it has oxygen. This makes the nautilus a truly amazing creature to study.

The nautilus is a unique marine animal belonging to the family Nautilidae. This family includes nine living species divided into two genera. The most well-known genus is Nautilus, which includes the species Nautilus pompilius. These animals are often called "living fossils" because they have remained relatively unchanged for hundreds of millions of years. They are the only living members of the subclass Nautiloidea. All species within this family are currently protected under CITES Appendix II.

The most striking feature of the nautilus is its external planispiral shell. This coiled shell is composed of two distinct layers. The outer layer is a matte white color with dark orange stripes. The inner layer is a striking, iridescent, pearlescent blue-gray material. This shell is divided into internal chambers called camerae. These chambers are separated by walls known as septa. A tube called the siphuncle pierces the center of each septum. As the nautilus grows, it builds new, larger camerae and moves into them. It then seals off the old, vacated space with a new septum.

Managing buoyancy is a complex process involving the siphuncle and the camerae. To stay at certain depths, the nautilus must control its density. The siphuncle extracts salt from the liquid inside the chambers. This salt then diffuses into the animal's blood. Through osmosis, the animal can either remove liquid from its chambers or allow liquid from its blood to refill them. This allows for long-term changes in buoyancy. However, the nautilus cannot manage sudden changes in pressure perfectly. If it goes too deep, the shell may implode at approximately 800 meters.

To move through the water, the nautilus uses a method called jet propulsion. It uses a muscular organ called the hyponome to draw water in and out of its living chamber. This method is considered less efficient than the fins used by some other marine animals. However, research suggests the nautilus is quite efficient compared to other jet-propelled animals like jellyfish. This efficiency might help the animal save energy while foraging at great depths.

The anatomy of a nautilus is very different from other cephalopods like octopuses. Instead of eight or ten arms, a nautilus can have between 50 and over 90 tentacles, known as cirri. These tentacles fall into three categories: ocular, digital, and labial. Ocular tentacles are located near the eyes and act as sensory organs. Digital tentacles form a ring around the mouth and provide adhesion. Unlike an octopus, the nautilus has no suckers. It uses a neutral mucopolysaccharide, a type of sticky liquid, to grip surfaces.

Sensory perception in the nautilus relies heavily on smell rather than sight. Their eyes are quite simple and function like a pinhole camera. Because they lack a solid lens, they cannot form highly focused or detailed images. Instead, they use olfaction, or smelling, to find food and mates. They also have structures called otocysts behind their nerve ring to help with balance. Their nervous system is centered around an oesophageal nerve ring. This ring lacks the complex, differentiated lobes found in the brains of squids or octopuses.

Nautiluses exhibit a form of camouflage called countershading. The dark, striped top of the shell helps the animal blend into the dark water when viewed from above. The white underside helps it blend into the bright surface water when viewed from below. This helps the animal remain hidden from predators. Sizes among species vary significantly. Nautilus pompilius is the largest, while Nautilus macromphalus is much smaller. Some populations, like those in the Sulu Sea, are even smaller, with a mean diameter of only 30 millimeters.