Ship worms: description, features, class and characteristics

In this article we will consider the features of the structure of mollusks, which are called "shipworms". No, we were not mistaken - such animals do exist.

Ship worm: class and type of animals

The thing is that the ship worm, which is also called taredo, or woodworm, has undergone significant changes during evolution. Especially they relate to the external structure of the animal. Therefore, at first glance it is rather difficult to understand which class the ship worm belongs to. In fact, it is a representative of the multicellular sub-kingdom and the type of mollusks. The class that represents the ship worm is called "Bivalve".

External structure

The Teredo has a cylindrical body that reaches a length of about a meter. Since the shipworm belongs to the class of bivalve mollusks, it has inherent structural features. Where is his shell? It is located at the front end of the body and consists of two small leaves about 1 cm in size. With their help, the mollusc drills the wood. Each leaf is formed by three parts with jagged edges.

In other respects, the mollusk shipworm possesses the features of a structure typical of a given systematic unit. His body is flattened from the sides and consists of two parts: the trunk and legs. Since bivalve mollusks do not have a head, they lack the organs located on it. These are the tentacles, pharynx, tongue with a grater, jaws and salivary glands. The mantle covers the back of their body. There are also glands that secrete calcareous substances.

Almost the whole body of the ship's worm is in the wood. On the surface, it leaves only the rear end with a pair of siphons. Through them, the animal's relationship to the environment is realized. An interesting mechanism is the protection of terredo. Along with the siphons, at the posterior end of the body is a plate of solid carbohydrate chitin. In case of danger, the animal draws the siphons into the arboreal path. And the opening is closed with a chitin plate.

Habitat

All bivalve mollusks live in water. They can be found in all the seas, except for the coldest ones. This is due to the fact that they feed by filtration. The ship worm passes water through the siphons with the organic remains that are in it. Another source of nutrition taredo is wood. With the help of the reduced shell they make moves in it. Therefore, the teredos live in the wood of piers and ships, driftwood that has fallen on the bottom, and rhizomes of marine plants.

Internal structure

Like all mollusks, shipworms have a secondary body cavity. However, the spaces between the organs are filled with a loose connective tissue. The circulatory system of these animals is not closed. It consists of the heart and blood vessels. Blood from the arteries enters the body cavity. Here it mixes with the liquid and bathes all the organs. Gas exchange is carried out at this stage. In the heart, blood flows through the veins. The ship worm is a cold-blooded animal. Therefore, he can not live in very cold water.

The respiratory organs of the woodworm are the gills, by means of which it absorbs oxygen from the water. The excretory system is represented by the kidneys. They divide the exchange products into the circum-magnetic cavity. The ship worm has a nervous system of a diffuse-nodal type.

Features of life activity

Ship worms are in constant action. In a minute they make about ten boring movements. At the same time, they push apart the shutters, which with their jaggies destroy the wood. Dimensions of the shipworm moves increase with the growth of the animal itself. They can reach 2 meters in length with a diameter of 5 cm. With this way of life there is another related name - woodworms. Surprising is the fact that the movements of these mollusks never overlap. Scientists suggest that they hear the approaching sound of drilling a "neighbor" and change their direction. Such respect is shown by animals to each other!

To digest the complex carbohydrate of cellulose, from which the wood consists, certain enzymes are needed. The Teredos are not able to produce them on their own. A peculiarity of the structure of their digestive system is the presence of a long blind outgrowth of the stomach, in which the sawdust is constantly accumulating. Here live symbiotic bacteria. They also break down the cellulose to glucose monosaccharide. Another function of symbionts is the fixation of nitrogen in the water.

Reproduction and development

Ship worms are hermaphrodites. This means that one individual forms both male and female sex cells. Fertilized oocytes are first located in the gill cavity, which develops up to 3 weeks. They develop larvae. They go into the water and swim here for another 2 weeks. The foot of the mollusk begins to release a special protein substance in the form of a thread - bisus. With its help, the larva is attached to the wood. During this period taredo has a typical appearance of a bivalve mollusk. Most of his body is hidden by shells, from which a prominent leg protrudes. As the animal grows, it becomes like a worm.

Significance in nature and human life

Shipworms deservedly deserved fame. They really do a lot of harm, destroying the wood with their own moves. Especially dangerous these animals were in ancient times, when people still did not know about the methods of fighting them. Ship worms are able to completely destroy the bottom or sides of the ship, turn into a trumpet the supports of bridges and wharves, cause the death of marine plants. Now wood, which can become a "victim" of shipworms, is covered with special toxic substances that make it "inedible" for these mollusks.

So, ship worms, despite their name, are representatives of the class "Bivalve mollusks". They live in almost all the seas, settling on wood objects. These animals have an elongated soft body and two reduced shell flaps. With their help, they make wood in the way, thereby destroying it and causing great harm.