Nautilus (shellfish): description, structure and interesting facts

People have been exploring the nature of the planet for a long time. It is full of miracles and uncharted secrets. The animal and plant world is rich in various species. One of the most interesting marine inhabitants is the Nautilus (mollusk). Its amazing shell is so amazing with its beauty that people have learned to make various ornaments from this material. This is a very ancient inhabitant of the ocean, as mysterious and mysterious as Captain Nemo's eponymous submarine from the novel by Jules Verne.

general characteristics

The nautilus shellfish (from the Latin Nautilus) is a fairly ancient inhabitant of our planet. This species has existed for more than 500 million years. Nautiluses belong to the class of cephalopods. They are distant relatives of such marine creatures as octopus, squid and cuttlefish.

The nautilus shell looks quite original. It has a full sink. This is not a rudiment. Nautilus (shellfish) has a shell located outside. In other cephalopods, it is located inside.

There are only 6 types of mollusks nautilus, which in their structure have much in common. Two of them are officially considered extinct. Of the class of cephalopods, these are the most primitive creatures.

The structure of the shell

Nautilus is a cephalopod mollusk, whose body is covered with a spiral sink. Depending on the type of this creature, it has a size in diameter from 16 to 25 cm. The largest shells of the imperial nautilus, the subspecies of which are called pompilus. The smallest nautilus are macromphalus.

The shell is twisted in one plane and has chambers. These compartments are interconnected by special valves. In the largest chamber there is a body of a mollusc. All other compartments serve as ballast. To dive deep, the marine man fills the chambers with water, and to float - with air.

The upper part of the shell has a dark color, and the lower part is light. This allows you to mask to avoid encounters with predators. The inside of the shell is pearly.

This amazing creation of nature is quite fragile. Therefore nautilus do not descend to a depth below 500 m. They live at a depth of 20 to 100 m.

The structure of the mollusk

To understand what the nautilus shellfish looks like, it is necessary to familiarize yourself with its structure. His body has a head and a trunk. He is somewhat more primitive than his brothers. The head has a special vane to cover the shell in case of danger. Here are the eyes and mouth. Near it are ninety tentacles. They perform the functions of the hands. There are suckers on the tentacles, musculature is highly developed. They help the marine inhabitant to move, catch prey and send it to the mouth.

On the shell of the mollusk you can determine the duration of his life. For this, chemical analysis is done. At the beginning of life, the Nautilus has only seven chambers, and then, after every three weeks, another compartment is added to them. This growth slows down only to ten years of life.

The mouth has two jaws. This allows a snack of hard food. There is a muscular pharynx with salivary glands. It passes into the esophagus, which leads to the stomach. It opens the ducts of a double-lobed liver. From the stomach goes the rectum, which passes into the large intestine. In the mantle cavity, it ends with an anal opening.

Body systems

Deserve a special attention to the body system, which has nautilus. The mollusk, the structure of which differs from similar cephalopods of marine inhabitants, has two pairs of gills, four renal sacs and auricles. Of the three ganglia consists of his nervous system.

This mollusc lacks iron, which produces an ink fluid. The eyes are rather primitive. There are no external photoreceptors, vitreous body and lens. But the organs of smell are well developed. He uses them during the hunt.

A mantle with a muscular wall covers the entire body of the nautilus. When contracted, this organ strongly pushes water through the mantle cavity. This throws the animal back. With relaxation, the cavity is again filled with water.

Reproduction

Nautilus is a marine mollusk that multiplies by the spermatophore way. Individuals are dioecious. The male transfers the spermatophore to the mantle area of the female. Fertilization is carried out here.

The female lays large eggs, which appear after 6 months of new individuals. They have a fully formed shell and body. They do not differ from adult nautilus.

When the female reaches 9 cm in diameter, and the male has 11 cm, the period of puberty begins. A man saw the embryo of the Nautilus for the first time only in 1985. This viability of this species is explained by great genetic variability. It is twice as large as in humans. However, why this species has been preserved in its unchanged form for so many years, scientists can not say yet.

Interesting Facts

Nautilus (shellfish) has a shell, twisted according to the law of the logarithmic progression. This animal used the mathematical formula for many millions of years before it was described in 1638 by Rene Descartes.

From beautiful mother-of-pearl cameras, people have made beautiful decorative objects for many years. They also contain animals in aquariums. The cost of one individual is quite high, and its content is even more expensive. Therefore, to afford such a pleasure can only large oceanariums.

Because of the increased interest of man to such marine life, their numbers in the world's oceans have declined sharply in the past few decades. Scientists sound alarm and call this species of animals dying out. If they disappear, the ancient secrets of nature will disappear along with them. And this can not be tolerated.

Having become acquainted with such a marine creature as a nautilus (mollusk), we can say that this is an interesting, mysterious sight. It is shrouded in secrets and is especially interesting for naturalists with its ancient immutable state, much can tell about the distant past. Mankind has to make every effort to preserve the Nautilus on the planet.