People have been exploring the nature of the planet for a long time. She is full of miracles and unexplored secrets. The animal and plant world is rich in various species. One of the most interesting marine inhabitants is nautilus (mollusk). Its amazing shell is so amazing in its beauty that people have learned how to make various jewelry from this material. This is a very ancient ocean dweller, as mysterious and mysterious as the eponymous submarine of Captain Nemo from the novel by Jules Verne.
general characteristics
Mollusk nautilus (from lat. Nautilus) is quite an 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 marine creatures such as octopuses, squids, and cuttlefish.
The mollusk nautilus looks quite original. It has a full sink. This is not a rudiment. Nautilus (mollusk) has a shell located outside. In other cephalopods, it is inside.
There are only 6 species of nautilus mollusks, which in their structure have much in common. Two of them are officially considered extinct. Of the cephalopod class, these are the most primitive creatures.
Shell structure
Nautilus is a cephalopod mollusk, the body of which is covered with a shell twisted in 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, whose subspecies is called pompilus. The smallest nautiluses are macromphalus.
The sink is twisted in one plane and has cameras. These compartments are interconnected by special valves. In the largest chamber is the body of the mollusk. All other compartments serve as ballast. To dive to a depth, a marine inhabitant fills the chambers with water, and to float up - with air.
The upper part of the shell has a dark color, and the bottom 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 fall to a depth below 500 m. They live at a depth of 20 to 100 m.
Mollusk structure
To understand what a mollusk nautilus looks like, you need to familiarize yourself with its structure. His body has a head and trunk. He is somewhat more primitive than his brothers. The head has a special blade to close the sink in case of danger. Here are the eyes and the mouth opening. Beside him are ninety tentacles. They perform the functions of the hands. There are suction cups on the tentacles; musculature is highly developed. They help the marine inhabitant to move around, catch prey and put it in his mouth.
From the shell of the mollusk, you can determine its life expectancy. For this, a chemical analysis is done. At the beginning of life, the nautilus has only seven chambers, and then, 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 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 ducts of the two-lobed liver open in it. From the stomach comes the rectum, passing into the colon. In the mantle cavity, it ends with the anus.
Body systems
The body systems that a nautilus has are worthy of special attention. The mollusk, whose structure is different from the cephalopod marine inhabitants similar to it, has two pairs of gills, four renal sacs and atria. Of the three ganglia consists of his nervous system.
This mollusk lacks iron, which produces ink fluid. The eyes are arranged quite primitively. There are no external photoreceptors, vitreous humor and lens. But the organs of smell are well developed. He uses them while hunting.
A muscular wall mantle covers the entire body of the nautilus. During contraction, this organ strongly pushes water through the mantle cavity. This throws the animal back. When relaxing, the cavity is again filled with water.
Breeding
Nautilus is a marine mollusk that reproduces in a spermatophore way. Individuals are dioecious. The male carries the spermatophore into the mantle region of the female. Fertilization is carried out here.
The female lays large eggs, from which new individuals appear after 6 months. They already have a fully formed shell and body. They do not differ from adult nautiluses.
When the female shell reaches 9 cm in diameter, and the male 11 cm, puberty begins. A man saw the embryo of a nautilus for the first time only in 1985. Such 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 unchanged for so many years, scientists can not yet say.
Interesting Facts
Nautilus (mollusk) has a shell twisted in accordance with the law of logarithmic progression. This animal used a mathematical formula many millions of years before it was described in 1638 by Rene Descartes.
From beautiful mother-of-pearl chambers people have been making beautiful decorative objects for many years. Contain animals in aquariums. The cost of one individual is quite high, and its content is even more expensive. Therefore, only large aquariums can afford such a pleasure.
Due to the increased human interest in such marine inhabitants, their abundance in the oceans over the past few decades has sharply decreased. Scientists sound the alarm and call this species of animals endangered. If they disappear, the ancient secrets of nature will disappear with them. But this cannot be allowed.
Having become acquainted with such a marine inhabitant as nautilus (mollusk), we can say that this is an interesting, mysterious view. It is shrouded in secrets and is especially interesting for naturalists with its ancient unchanging state, it can tell a lot about the distant past. Humanity is obligated to make every effort to save the Nautilus on the planet.