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Mussel: external and internal structure, the useful properties of the mollusk

The genus Mussels belongs to the class of bivalve mollusks, which includes about 20 thousand species. These invertebrates are common in almost all water areas – including ocean depths, seas, and freshwater rivers and lakes.

Even in the Arctic Ocean there are quite a lot of representatives of this numerous genus. The structure of mussels differs depending on the habitat; however, it also has features common to all bivalve mollusks.

The genus Mussels belongs to the class of bivalve mollusks, which includes about 20 thousand species

Mussels are considered to be bottom coastal animals, preferring to attach themselves to rocks washed by the surf, artificial structures and reefs. Reliable fastening is caused by byssal threads, allowing mollusks to be in places with strong and fast current and waves.

The extensive distribution area of ​​mussels made of them in the process of evolution of completely unpretentious creatures. They are able to live among the ice and in the tropics, in fresh water and in reservoirs with a high salt content.

In nutrition, they also do not differ fastidiousness. Their diet includes:

  • unicellular and multicellular algae;
  • bacteria;
  • phytoplankton.

Mussels are considered to be bottom coastal animals, preferring to attach themselves to the rocks washed by the surf.

Mussels, like other mollusks, have the ability to clean the water tank in which they live, thanks to the type of food – they, like a live filter, pass water through themselves, filtering it from edible particles.

Depending on the living conditions, the life span of these bivalves varies greatly. Mussels live in the Black Sea and freshwater bodies for 5 years, in cold seas and oceans – 10, but mollusks living in the Pacific Ocean are considered to be the champions – their age often reaches 30 years.

These stormy animals owe their stunning abundance and spread throughout the planet’s waters to their amazing ability to adapt to any, even constantly changing, environmental conditions, as well as reproduction characteristics. Mussels are able to lay millions of eggs, which they retain under their gills right up to the moment of hatching.

The life span of mussels living in the Pacific Ocean reaches 30 years

Small mussels are born without a shell and at first swim in the water column together with plankton, gradually overgrown with a shell. Under the gradually increasing weight of the formed calcium flaps, they soon lose their ability to swim and sink to depth, attaching themselves to rocks, reefs and shells of other mollusks.

Among the variety of mussels are two main categories – freshwater and marine. The first can grow in length to 15−20 cm, whereas the second – only up to 5−7.

If the water space does not allow settling over large areas, these invertebrates cling to any free area of ​​solid surface with numerous colonies consisting of several thousand individuals. Such formations are called mussel banks.

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The bodies of all species of mollusks are slippery elastic substance, penetrated by blood vessels and nerve fibers. In many species of these animals, the shell is twisted spiral-shaped – in the form of an elongated spiral or a flat coil.

Bivalves have a slightly different structure, although it does not deprive them of the main features of mollusks.

Externally, the mussel is a shell that has a shape that is flattened on both sides, slightly elongated or almost round, two-sidedly symmetrical. Many mollusks have a head and a leg on their bodies; in the Midievs these parts are almost absent.

The leg was practically reduced due to the “sedentary” lifestyle, the head was also not very necessary – all vital parts of the body were hidden inside the shell, including the mouth and internal organs.

Sash connected on one side with the help of muscle tissue. The muscles of absolutely all bivalve mollusks are incredibly strong, so it is not at all easy to open the conch with your bare hands, without using any devices.

Such powerful muscles are necessary mussels to slam the sash in time, not allowing the predator to get to the tender body inside.

Externally, the mussel is a shell that is flattened on both sides.

The color of the shell varies depending on the species and habitat conditions, from light gray and brown to almost black. From the inside, the valves have a beautiful pearl-colored overflow, thanks to which they have always been used as material for creativity in the manufacture of figurines, jewelry and clothing.

In addition, mother of pearl allows you to get pearls. In fact, these gems are merely sea sand grains that once fell between the shell and the mantle (the upper layer of the mollusk’s body) and overgrown with numerous mother-of-pearl layers. Although not all mussels are capable of producing pearls.

In addition, created by different representatives of this family, it differs in properties and appearance.

The outer surface of the mussel is decorated with peculiar lines – these are annual rings with which you can determine the age of the caught individual.

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Mussels are not very complex internal structure. The absence of the head and some of the digestive organs familiar to other animals is due to anatomical features.

At the base of the foot is a mouth that connects to the small esophagus, which opens the passage to the stomach. A specific feature of mussels are unusual glands that produce strong thread-like protein formations consisting of synthesized liquid collagen, which freeze and are used for attachment to extraneous objects, byssuses.

The leathery mantle is represented by folds of muscle and connective tissue, covering the body on both sides of the valves and fused at the back. It can change its shape and position, stretching and contracting.

The outer shell of the mantle epithelium is made shell shutters. All layers of this cover perform several important functions:

  • protection of the body against foreign objects and various damages;
  • sensory;
  • mucocyte – is responsible for the secretion of mucus, which is involved primarily in enveloping and removing toxins from the body.

In addition to these functions, the epithelium of the mantle is able to absorb oxygen directly from the water, and also helps its circulation. This body accumulates nutrients that the body mussels stores in the process of absorption and processing of food.

In the back there are special siphons:

  • The air serves to take water for the purpose of extracting oxygen from it with the help of internal gills, the ctenidia. Every day for proper breathing, the mussel drives about 70 liters of water through itself. The gills are covered with the finest outgrowths – cilia, which direct edible microorganisms, filtered from the water, to the mouth.
  • Food siphon is used to remove inedible filtration elements and waste products of mollusk out.

Located on both sides of the oral opening, 4 triangular lobes – labial palps, guide incoming food into the mouth, through which it passes into the esophagus, and then into the stomach, resembling a sack in shape. It stretches along the back of the body.

Around the stomach are the lobes of the liver – diverticula. The liver (hepatopancreas) is developed, consists of paired lobes with many small lobes.

Hepatic ducts open in the stomach and are actively involved in digestion. There are mussels and cecum in the digestive system, which synthesize special enzymes for qualitative dissolution and assimilation of food.

The sense organs have the appearance of oral lobes, as well as sensitive cells located along the rim of the mantle, on the gills

From the stomach is the middle gut of curved shape, which passes into the back, penetrating the heart through the ventricle and out in the form of a food (excretory) siphon to the outside.

The miniature heart of mussels consists of two atria and a ventricle. The unclosed circulatory system is represented by two aorta, divided further into several arteries.

The primitive, underdeveloped nervous system of the mollusk is represented by 3 pairs of ganglia — the nerve ganglia participating in all the vital processes of the body.

The sense organs have the appearance of oral lobes, as well as sensory cells located along the rim of the mantle, on the gills and muscular leg.

The structure of the mussel body allows you to successfully adapt to changes in water parameters, fluctuations in the level of salinity and temperature.

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