Skeleton of calcareous sponges. Sponges

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Including about 10,000 known species living on Earth today. Members of this phylum of animals are calcareous sponges, common sponges, and six-rayed sponges. Adult sponges are sedentary animals that live by attaching themselves to rocky surfaces, shells, or other underwater objects, while the larvae are free-swimming. Most sponges live in marine environments, but a few species can be found in freshwater bodies.

Description

Sponges are primitive multicellular animals that do not have digestive, circulatory or nervous systems. They do not have organs and the cells do not organize into a clearly defined structure.

There are three main classes of sponges. Glass sponges have a skeleton that consists of fragile, glassy needles formed from silica. Common sponges are often brightly colored and grow larger than other sponge species. Common sponges account for more than 90 percent of all living sponge species. Calcareous sponges are the only class of sponges that have spicules composed of calcium carbonate. Calcareous sponges are usually smaller than other members of the phylum.

The body of the sponge is like a bag, perforated with many small holes or pores. The body walls consist of three layers:

• outer layer of flat cells of the epidermis;
• the middle layer, which consists of a gelatinous substance and amoeboid cells migrating within the layer;
• the inner layer is formed from flagellar and collar cells (choanocytes).

Nutrition

Sponges feed by filtering water. They absorb water through pores located throughout the body wall in the central cavity. The central cavity is lined with collar cells, which have a ring of tentacles surrounding the flagellum. The movement of the flagellum creates a current that holds water flowing through the central cavity into an opening at the top of the sponge called the osculum. As water passes through the collar cells, food is captured by the rings of tentacles. Next, food is digested in food or amoeboid cells in the middle layer of the wall.

The flow of water also provides a constant supply of oxygen and removes nitrogenous waste. Water exits the sponge through a large hole at the top of the body called the osculum.

Classification

Sponges are divided into the following main taxonomic groups:

• Lime sponges (Calcarea);
• Ordinary sponges (Demospongiae);
• Six-beam sponges, or glass sponges (Hexactinellida, Hyalospongia).

The underwater world is so diverse and unique that sometimes it is even difficult to distinguish plants from animals. The creatures living there have such bizarre shapes. Large sea giants and very microscopic planktonic crustaceans, colorful and bright, predators and herbivores - an incredible variety of species of living organisms. One of these amazing creatures are sponges, which will be discussed further.

general information

The position of these animals can be characterized as follows:

• empire - Cellular;
• kingdom - Animals;
• subkingdom - 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

The Sponge type unites all known representatives into four large classes.

1. Calcarea, or Calcareous. Formed in the form of deposited calcium salts.
2. Ordinary, or Siliceous. The main representative is the badyaga.
3. Glass (Six-beam). The class size is small.
4. Corals are a very species-poor class.

All of these sponges have their own characteristics, not only external, but also internal structure, lifestyle and economic significance in human life.

External structure

Perhaps the most unusual thing in all the characteristics of the animals in question will be their external appearance. The features of the external structure of sponges are determined by the variety of body shapes that are characteristic of them. So, representatives of different classes can be in the form:

• glasses;
• bowls;
• tree structure.

The body symmetry in solitary forms is multipolar axial, while in colonial forms it is mixed. Each individual has a special flat sole, with which it is attached to the bottom or other substrate. Sponges most often lead a sedentary lifestyle.

On the upper side of the body there is a special opening called the “osculum”. It serves to remove excess water from the internal cavity. The outside of the body is covered with a layer of cells called 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 penetrating the entire body, capable of contracting and expanding.

Under the outer layer there are two more, which we will consider in more detail later. The color range of both single and colonial forms is quite diverse. The following types of coloring are available:

• gray;
• green;
• purple;
• yellow;
• white;
• red;
• brown;
• mixed.

The Sponge type greatly enlivens the underwater world, making it even more vibrant, colorful and attractive. Moreover, if we consider an individual individual on the surface of land, it will have a very unattractive appearance: a brownish, slippery lump reminiscent of raw liver, emitting a not entirely pleasant aroma.

Internal structure of representatives

The types of structure of sponges are similar, whether it is a single individual or attached to a colony. Immediately under the dermal outer layer of porous cells there is a special intercellular substance that forms a fairly voluminous membrane. In it, the cells are loosely located, and their shape is different. The tissue is somewhat reminiscent of adipose tissue in higher terrestrial representatives. This structure is called "mesohyl".

Under this layer there is an internal cavity lined with a special row of cells. This is the gastric layer. All food ends up here, and this is where digestion takes place. All waste products, along with excess water, are directed to the upper opening of the body and discharged out through it.

Also, the structure of a sponge necessarily includes a kind of skeleton. It is formed from calcareous, phosphorus, and organic salts, which are produced in special mesochyl cells. It not only gives the sponges a certain body shape, but is also important for the safety of the internal cavity from mechanical damage.

The characteristics of the Sponge type will be incomplete without identifying the main feature of these animals - their body does not have tissues, but only includes layers of different shapes and forming layers. This is the main difference between the animals in question and all others.

The aquifer system of the individuals is also interesting. It may not be the same for different classes. In total, there are three main types:

1. Askon - all communication with the external environment is carried out through a system of tubes through which water moves into special chambers. The most simplified aquifer system, found in only a few representatives.
2. Sicon. A more advanced system that includes a network of branched tubules and tubes flowing into special chamber cells with flagella.
3. Leukon is a whole network of osculums; this type of aquifer system is characteristic only of colonial forms. The most complicated option compared to all the previous ones.

Reproduction in sponges occurs both sexually and asexually. Germ cells are formed in the mesochyl layer. Then the products come out through the pores of the body and, with a stream of water, enter the bodies of other sponges, where fertilization occurs. As a result, a zygote is formed, giving rise to a larva. The fry can be called differently: amphiblastula, parenchymulus, celloblastula.

If we talk about it, it is based on the process of budding, that is, detachment with subsequent regeneration of missing structures. Most of the Sponge type includes hermaphroditic animals.

Lifestyle Features

If we consider all the diversity of multicellular animals in the world, then sponges should be classified as the most primitive stage in organization. However, these are also the most ancient animals, appearing many thousands of years ago. During their evolution, little has changed in their organization; they retain their characteristics over time. The life form of representatives has two manifestations:

• single;
• colonial.

Most often, massive accumulations of sponges are found among coral reefs. There are both freshwater species (their minority) and ocean species (the overwhelming group of species in terms of number of species).

The Sponge type includes animals that feed on small organisms or their remains. Their body structure contains special collar cells with flagella. They just capture floating food particles, directing them into the internal paragastric cavity of the body. Digestion takes place inside cells.

Based on their method of obtaining food, sponges can be called passive hunters. They lazily sit on an attached place, waiting for passing nutrient particles. And only when they are already very close, they capture them through the pores and direct them, 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 attachment to the substrate. However, their speed is so low that during the whole day an individual is unlikely to move further than a meter.

Variety of sponges

Quite impressive for such primitive representatives - after all, there are about 8 thousand species! And according to some modern data, this figure is already close to 9 thousand. External diversity is explained by differences in body shape, skeletal types and body colors of individuals (or colonies).

Class Glass sponges

Glass sponges are very interesting in their external diversity. They are not as numerous as others, but have an unusual skeleton. These are one of the largest individuals that the Sponge type includes. The general characteristics of representatives of this class can be expressed in several points.

1. The Latin name of the class is Hexactinellida.
2. The skeleton is formed from silicon compounds and is therefore very durable.
3. Needle-type body support, in which six-pointed structures predominate.
4. Larvae of the parenchymula or coeloblastula species.
5. Leukon-type aquifer system.
6. More often colonial than solitary forms.
7. Sometimes up to 50 cm in height.

The most common representatives are:

• Hyalonema siboldi;
• euplectella.

Class Ordinary, or Siliceous, sponges

The Sponge type, photos of which can be seen in this article, also includes the most numerous class in terms of the number of individuals - Siliceous, or Common. They got their name for the peculiarities in the structure of the skeleton - it consists of silica and spongin. In terms of hardness, it is quite delicate 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 badyaga - a sponge used as an indicator of the cleanliness of a reservoir. Outwardly unattractive, the color is brownish-brown, sometimes dirty yellow. They are used by humans for various needs.

What other representatives are found among common sponges?

1. Mixils.
2. Sea loaf.
3. Baikal sponge.
4. Sea brushes.
5. Giant chondrocladia and others.

Class Lime sponges

This includes representatives that have a durable and beautiful calcareous skeleton. They live only in seas and oceans. The color is pale or completely absent. Skeletal spines may have about three rays. Main representatives: Ascona, Sycona, Leucandra.

Class Coral sponges

The fewest representatives that look like coral branches. This happens due to the formation of a powerful calcareous skeleton of different colors and patterned structure.

Representatives: Nicholson's geratoporella, merlia. In total, only six species of such animals have been described. For a long time they were not distinguished from the coral reef system, so they were discovered relatively recently.

Human use of sponges

The economic importance of individuals belonging to the Sponge type is also important. Representatives are used for the following needs:

1. They are participants in the food chain, as they themselves serve as food for many animals.
2. They are used by people to make beautiful jewelry for the body and home interior.
3. They contain substances that allow them to be used for medical purposes (the bodyaga sponge has a bruise-absorbing and wound-healing effect).
4. They are used to create sanitary sponges - natural natural products for the cosmetics industry.
5. Used for technical and other purposes.

Sponges(Spongia) is a type of invertebrate animal. Sponges probably descend from colonial collared flagellated protozoans, forming a blind branch at the base of the phylogenetic tree of metazoans.

Sponges arose in the Precambrian (about 1 billion 200 million years ago!, i.e. these are very ancient organisms), and reached their greatest prosperity in the Mesozoic.

Sponges are predominantly marine organisms, but not many are freshwater. Outwardly, sponges are even difficult to mistake for animals. They sit completely motionless, attached to the substrate, and do not react in any way to irritation. Sponges are often colonial organisms, but solitary ones are also found. The sponges feel hard and tough to the touch. Freshwater sponges are gray or greenish, but sea sponges are often brightly colored. Color depends on the presence of pigment cells. Many sponges have a specific unpleasant taste and smell, so they are not edible and no one touches them.

Sponges have an extremely primitive organization. Their body doesn't have any symmetry, it formless. Inside the goblet or sac-shaped body (from a few mm to 1.5 m or more in height) of a typical sponge there is paragastric cavity opening at the top wellhead hole. Sponges do not have real organs and tissues, but their body consists of a variety of cellular elements. On the surface of the body there are flat cells - pinacocytes, from the inside the paragastric cavity is lined with flagellated collar cells, or choanocytes. Between the layer of pinacocytes and the layer of choanocytes lies a structureless substance - mesoglea, containing amebocytes, collencytes, scleroblasts and other cells. On the surface of the sponge's body there are many since then, leading to channels piercing the walls of the body. Depending on the degree of development of the canal system, the localization of choanocytes and the flagellar chambers formed by them, 3 types of sponge structure are distinguished: ascon, sicon And lacon.

Almost all sponges have skeleton, formed by flint or limestone needles In horny sponges, the skeleton consists of the protein substance spongin.

The life activity of sponges is associated with continuous by straining through the body of water, which, thanks to the beating of the flagella of many choanocytes, enters the pores and, having passed through a system of canals, flagellar chambers and the paragastric cavity, comes out through the mouth. Food particles (detritus, protozoa, diatoms, bacteria, etc.) enter the sponge with water and metabolic products are removed. Food is captured by choanocytes and canal wall cells.

Most sponges are hermaphrodites. A ciliated larva develops from the egg - parenchymula, or amphiblastula, which comes out, floats, then settles to the bottom and turns into a young sponge. During metamorphosis, a process of the so-called characteristic only of sponges is observed. perversions germinal leaflets, in which the cells of the outer layer migrate inward, and the cells of the inner layer end up on the surface. In addition, sponges have widespread budding and education gemmulus- types of asexual reproduction.

All sponges, as mentioned earlier, are aquatic, predominantly marine colonial, less often solitary animals leading a sedentary lifestyle. They are found from the coastal zone and almost to the maximum depths of the ocean; they are most diverse and numerous on the shelf (shelf is a flat, not deep zone of the seabed). Over 300 species live in the northern and Far Eastern seas of our country, about 30 species in the Black Sea, and 1 species of sponge in the Caspian Sea. In total, about 2,500 species have been described to date.

Sponge type is divided into 4 classes. The classification of sponges is based on their skeletal structure.

Class 1. Ordinary sponges(Demospongiae). In these sponges, the skeleton is formed by uniaxial or four-rayed flint spines. Channel system of leukonoid type. Usually colonial, less often solitary forms, predominantly marine forms. This most numerous class of modern sponges is represented by 2 orders: Siliceous sponges and Quadruped sponges.

In Silica sponges, the skeleton consists of flint uniaxial needles and organic matter - spongin or spongin fibers alone, forming a reticulate, less often tree-branched, support of the body. These are mainly colonial forms, having the appearance of cortical or cushion-shaped fouling, unevenly grown lumps, plates or various kinds of tubular, funnel-shaped, stalk-like, bushy and other formations, up to 0.5 m or more in height. Silica sponges include those known to us Badyagi and several types Toilet sponges. Toilet sponges are used for toilet, medical and technical purposes. The fishery for these sponges is developed in the Mediterranean and Red Seas, off the coast of the island. Madagascar, Philippines, in the Gulf of Mexico and the Caribbean Sea. The most valued is the so-called Greek sponge(Euspongia officinalis).

Four-rayed sponges have a spherical, ovoid, goblet-shaped, cushion-shaped body, usually up to 0.5 m in height. The skeleton is formed of flint, usually four-rayed (hence the name) or their derivatives - uniaxial needles located radially in the body. Also colonial, less often solitary forms. They live mainly to a depth of 400 m. The family of four-ray sponges belongs to Drilling jaws, or Clions. These sponges are capable of making passages inside any calcareous substrate, leaving round holes with a diameter of about 1 mm on its surface. It is believed that the drilling mechanism is due to the simultaneous action of carbon dioxide released by the surface cells of the drilling sponges and the contractile forces of these cells. About 20 species, mainly in the shallow waters of warm seas. In our country there are 3 species, in the Japanese, Black, White and Barents Seas. These sponges are dangerous pests of oyster jars.

Class 2. Lime sponges(Calcispongiae). The skeleton of these sponges is formed by three-, four-beam and uniaxial needles made of calcium carbonate. The body is often barrel-shaped or tube-shaped. The only class of sponges that includes sponges that have all 3 types of channel systems. Calcareous sponges are small solitary (up to 7 cm high) or colonial organisms. Over 100 species, distributed exclusively in seas of temperate latitudes, mainly in shallow waters. Representatives Sicon, Sikandra, Leucandra, Ascetta.

Class 3. Coral sponges(Sclerospongiae). Colonial sponges. The width of the colonies is up to 1 m, height - 0.5 m. Known from the Mesozoic. The skeleton consists of a basal mass of aragonite or calcite and flint uniaxial needles. Living tissue only covers the surface of coral sponges with a thin layer (about 1-2 mm thick). Channel system of leukonoid type. A total of 10 species live in shallow water among the coral reefs of the West Indies, the western parts of the Pacific and Indian Oceans, in the Mediterranean Sea and off the island. Madeira.

Class 4. Glass sponges, or Six-beam sponges (Hyalospongia, or Hexactinellida). Known since the Cambrian. They were most diverse and numerous in the Cretaceous period of the Mesozoic era. Skeleton made of flint six-rayed needles (or their derivatives) with rays lying in three mutually perpendicular planes. Mostly single, bag-shaped, tubular, goblet-shaped or barrel-shaped, up to 1.5 m high. About 500 species. Oceanic organisms that usually live at depths of over 100 m. Glass sponges are very beautiful and are used as decorations. For example, a sponge basket of Venus, Euplectella, Hyalonema.