The underwater world is so diverse and unique that it is sometimes difficult to distinguish plants from animals. So bizarre are the creatures living there. Large marine giants and very microscopic planktonic crustaceans, colorful and bright, predators and herbivores are an insane variety of species of living organisms. One of these amazing creatures are sponges, which will be discussed later.
general information
It is possible to characterize the position of these animals in the system of the organic world as follows:
- Empire - Cellular;
- kingdom - Animals;
- kingdom - Multicellular;
- type - Sponges.
Today it is known that there are about 8 thousand species. 300 of them inhabit the vast seas of our country.
Classification
Sponge Type unites all famous representatives in four large classes.
- Calcarea, or Lime. The outer skeleton is formed in the form of deposited calcium salts.
- Ordinary, or Kremnerogovye. The main representative is a tramp.
- Glass (Six-beam). The class is small.
- Coral is a very poor class species.
All of these sponges have their own characteristics not only of the external, but also of the internal structure, lifestyle and economic importance in human life.
External structure
Perhaps the most unusual in all the characteristics of the animals in question will be the appearance. Features of the external structure of the sponge are determined by the variety of body shapes that are characteristic of them. So, representatives of different classes can be in the form of:
- glasses
- bowls;
- tree structure.
The symmetry of the body in single forms is bipolar axial, in colonial forms - mixed. Each individual has a special flat sole, with which it is attached to the bottom or other substrate. Sponges are most often motionless.
On the upper side of the body there is a special hole, which is called the "Oskulum". It serves to remove excess water from the internal cavity. Outside, the body is covered with a layer of cells - pinacoderm. They resemble in their structure the epithelial tissue of higher animals.
However, they also have distinctive features - the presence of wide pores. The structure of the sponge provides for the absorption of food particles not through the upper hole, but through numerous perforations that penetrate the entire body, which can contract and expand.
Two more are located under the outer layer, which we will consider in more detail later. The color scheme of both single and colonial forms is quite diverse. The following types of coloring are found:
- gray
- green
- Violet
- yellow;
- white
- red;
- brown;
- mixed.
The type of Sponge very animates the underwater world, making it even brighter, more colorful and attractive. Moreover, if we consider a single individual on the land surface, it will have a very unattractive appearance: a brownish slippery lump resembling a raw liver, emitting a not quite pleasant aroma.
The internal structure of representatives
The types of structure of sponges are similar, whether it be a single individual or attached to a colony. Immediately below the dermal outer layer of porous cells, there is a special intercellular substance that forms a fairly voluminous membrane. In it, the cells are located friable, and their shape is different. The tissue is somewhat reminiscent of adipose in higher terrestrial representatives. This structure is called "mesochil".
Under this layer is an internal cavity lined with a special row of cells. This is the gastric layer. All food gets here, and digestion takes place here. All waste products along with excess water are directed to the upper opening of the body and are brought out through it.
Also, the structure of the sponge necessarily includes a kind of skeleton. It is formed from calcareous, phosphoric, organic salts, which are produced in special mesochil cells. It not only gives the lips a certain shape of the body, but also is important for preservation from mechanical damage to the internal cavity.
The characterization of the type of Sponge will be incomplete, if you do not designate the main feature of these animals - their body does not have tissues, but only includes cells that form layers that are different in shape and structure . This is the main difference between the considered animals from all others.
The aquifer system of individuals is also interesting. In different classes, it may be different. There are three main types of it:
- Ascon - all communication with the external environment is carried out through a system of tubes through which water moves into special cell chambers. The most simplified aquifer system found in a few representatives.
- Sikon. A more advanced system, which includes a network of branched tubules and tubules that flow into special cell chambers with flagella.
- Leykon is a whole network of oskulums; this type of aquifer is characteristic only of colonial forms. The most complicated option compared to all the previous ones.
Reproduction in sponges occurs both sexually and asexually. Sex cells form in the layer of mesochil. Then the products go out through the pores of the body and with the flow of water enter the bodies of other sponges, where fertilization takes place. As a result, a zygote is formed, giving rise to a larva. Fry can be called in different ways: amphiblastula, parenchymal, celloblastula.
If we talk about asexual reproduction, then it is based on the process of budding, that is, the detachment of a part of the body with the subsequent regeneration of missing structures. For the most part, the type of Sponge includes hermaphroditic animals.
Lifestyle features
If we consider the whole variety of multicellular animals of the world, then sponges should be attributed to the most primitive stage in organization. However, these are also the most ancient animals that appeared many thousands of years ago. During the evolution of their organization, little has changed; they retain their characteristics over time. The life form of representatives has two manifestations:
Most often, massive accumulations of sponges are found among coral reefs. There are both freshwater species (their minority) and inhabitants of the seas and oceans (the overwhelming group of species).
The type of Sponge includes animals that feed on small organisms or their debris. In the structure of their body there are special collar cells with flagella. They just capture the floating particles of food, directing them into the inner paragastric cavity of the body. Digestion is carried out inside the cells.
By the method of extracting food, sponges can be called passive hunters. They lazily sit on an attached spot, waiting for floating nutrient particles. And only when they are very close, capture them through the pores and direct along with the flow of water into the body.
Some species are able to move, despite the fact that they still have a sole for attaching to the substrate. However, their speed is so small that for the whole day the individual is unlikely to advance further than a meter.
Variety of sponges
For such primitive animals, the diversity of representatives is quite impressive - there are about 8 thousand of them! And according to some modern data, this figure is already approaching 9 thousand. External diversity is explained by the difference in body shape, skeleton types and color of the body of individuals (or colonies).
Grade Glass Sponges
Glass sponges are very interesting in their external variety. They are not as numerous as others, but they have an unusual skeleton. This is one of the largest individuals, which includes the type of Sponge. The general characteristics of representatives of this class can be expressed in several paragraphs.
- The Latin name for the class is Hexactinellida.
- The skeleton is formed from silicon compounds, so it is very durable.
- The needle-like type of support of the body, in which six-pointed structures predominate.
- Larvae of the parenchymal or celoblastula species.
- An aquifer system such as a lacon.
- More often colonial than single forms.
- Sometimes up to 50 cm in height.
The most common representatives are such as:
- chialonema siboldi;
- euplectella.
Class Ordinary, or Cremorns, sponges
The type of Sponge, a photo of the representatives of which can be seen in this article, also includes the most numerous class in terms of the number of individuals - Kremnerogovye, or Ordinary. They got their name for the features in the structure of the skeleton - it consists of silica and spongina. The hardness is quite gentle and easily destroyed. The shape of the skeleton needles is very diverse:
- stars
- Anchors
- maces;
- sharp needles and so on.
The most common freshwater representative is the buggy - a sponge used as an indicator of the cleanliness of a reservoir. Outwardly unattractive, the color is brown-brown, sometimes dirty yellow. Used by man for various needs.
What other representatives are found among ordinary sponges?
- Mixers.
- Sea loaf.
- Baikal sponge.
- Sea brushes.
- Giant chondrocladium and others.
Class Lime Sponges
Representatives having a strong and beautiful calcareous skeleton belong to it. They live only in the seas and oceans. The color is pale or completely absent. Skeleton needles can have about three rays. Key representatives: Ascons, Sicons, leucandra.
Class Coral Sponges
The fewest representatives that look like coral twigs. This happens due to the formation of a powerful calcareous skeleton of different colors and patterned structures.
Representatives: Heratoporella Nicholson, Merliya. Only six species of such animals are described. For a long time they were not distinguished from the coral reef system, so they were discovered relatively recently.
Man using sponges
The economic importance of individuals included in the type of Sponge is also important. Representatives are used in the following needs:
- They are participants in the food chain, as they themselves serve as food for many animals.
- Used by people to make beautiful jewelry for the body and interior of the house.
- They contain substances that allow them to be used for medical purposes (the sponge of the body-boot has absorbable bruises and a wound-healing effect).
- They are used to create hygienic sponges - natural, natural products for the cosmetics industry.
- Used for technical and other purposes.