People have been exploring the nature of the planet for a long time. It is full of wonders and unknown 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 striking in its beauty that people have learned to make various decorations from this material. This is a very ancient inhabitant of the ocean, as mysterious and enigmatic as Captain Nemo's submarine of the same name from Jules Verne's novel.
General characteristics
The nautilus mollusk (from lat. Nautilus) is a fairly ancient inhabitant of our planet. This species has existed for over 500 million years. Nautiluses belong to the class of cephalopods. They are distant relatives of marine life such as octopus, squid and cuttlefish.
The nautilus clam looks quite original. It has a full shell. It's not a vestige. Nautilus (mollusk) has a shell located outside. Other cephalopods have it inside.
There are only 6 types of nautilus molluscs, which have a lot in common in their structure. Two of them are officially considered extinct. From the class of cephalopods, these are the most primitive creatures.
Structure of a shell
Nautilus is a cephalopod mollusk whose body is covered with a shell twisted in the form of a spiral. Depending on the type of this creature, it has a diameter of 16 to 25 cm. The largest shells are in the imperial nautilus, a subspecies of which is called pompilus. The smallest nautiluses are macromphaluses.
The sink is twisted in one plane and has chambers. These compartments are interconnected by special valves. The body of the mollusk is located in the largest chamber. All other compartments serve as ballast. To dive to the depths, a marine inhabitant fills the chambers with water, and to emerge - with air.
The upper part of the shell is dark in color, and the lower part is light. This allows you to disguise yourself to avoid encounters with predators. The inside of the shell is mother-of-pearl.
This amazing creation of nature is quite fragile. Therefore, nautiluses do not descend below 500 m. They live at a depth of 20 to 100 m.
The structure of a mollusk
To understand what the nautilus mollusk looks like, you need to familiarize yourself with its structure. His body has a head and a torso. It is somewhat more primitive than its counterparts. The head has a special blade to close the shell in case of danger. Here are the eyes and the mouth opening. Ninety tentacles are located next to it. They performhand functions. There are suckers on the tentacles, muscles are highly developed. They help the sea dweller to move, catch prey and put it in the mouth.
It is possible to determine the duration of its life by the shell of a mollusk. This is done by chemical analysis. At the beginning of life, the nautilus has only seven chambers, and then, every three weeks, another chamber is added to them. This growth slows down only by the age of ten.
The mouth has two jaws. This allows you to snack on solid foods. There is a muscular pharynx with salivary glands. It passes into the esophagus, which leads to the stomach. The bilobed liver ducts open into it. From the stomach comes the rectum, which passes into the large intestine. In the mantle cavity, it ends with an anus.
Body systems
Deserve special attention to the systems of the body, which has a nautilus. The mollusk, whose structure differs from similar cephalopod marine inhabitants, has two pairs of gills, four renal sacs and atria. His nervous system consists of three ganglia.
This mollusk lacks a gland that produces an inky liquid. 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 while hunting.
A mantle with a muscular wall covers the entire body of a nautilus. When contracting, this organ strongly pushes water through the mantle cavity. This throws the animal back. When relaxing the cavity againfills with water.
Reproduction
Nautilus is a marine mollusk that reproduces by the spermatophore method. Individuals are dioecious. The male carries the spermatophore to the mantle region of the female. Fertilization takes place here.
The female lays large eggs, from which new individuals appear after 6 months. They already have a fully formed shell and body. They are no different from adult nautiluses.
When the female's shell reaches 9 cm in diameter, and the male's 11 cm, puberty begins. A man saw the embryo of a nautilus for the first time only in 1985. Such resilience of this species is due to the great genetic variability. It is twice that of humans. However, why this species has been preserved in its unchanged form for so many years, scientists cannot yet say.
Interesting facts
Nautilus (mollusk) has a shell, twisted in accordance with the law of logarithmic progression. This animal used the mathematical formula many millions of years before René Descartes described it in 1638.
For many years, people have been making beautiful decorative objects out of beautiful mother-of-pearl chambers. They also keep animals in aquariums. The cost of one individual is quite high, and its maintenance is even more expensive. Therefore, only large aquariums can afford such pleasure.
Due to the increased human interest in such marine life, their numbers in the world's oceans have declined sharply in the past few decades. Scientists sound the alarm and call thisendangered animal species. If they disappear, the ancient secrets of nature will disappear with them. And this cannot be allowed.
Acquainted with such a marine life as a nautilus (mollusk), we can say that this is an interesting, mysterious species. It is shrouded in secrets and is of particular interest to naturalists for its ancient unchanging state, which can tell a lot about the distant past. Humanity must make every effort to save the nautilus on the planet.
