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).

They can be solitary animals, but much more often they form colonies. For a long time, sponges were classified as zoophytes - intermediate forms between plants and animals. The belonging of sponges to animals was first proven by R. Ellis in 1765, who discovered the phenomenon of water filtration through the body of sponges and the holozoic type of nutrition. R. Grant (1836) was the first to distinguish sponges into an independent type of Sponge (Porifera).

In total, 5,000 species of sponges are known. This is an ancient group of animals known since the Precambrian.

General characteristics of the type of sponges. Sponges combine the characteristics of primitive multicellular animals with a specialization for a sedentary lifestyle. The primitiveness of the organization of sponges is evidenced by such signs as the absence of tissues, organs, high regenerative ability and interconvertibility of many cells, and the absence of nerve and muscle cells. They are characterized only by intracellular digestion.

On the other hand, sponges exhibit features of specialization for a sedentary lifestyle. They have a skeleton that protects the body from mechanical damage and predators. The skeleton can be mineral, horny or mixed in nature. An obligatory component of the skeleton is the horny substance - spongin (hence one of the names of the type - Spongia). The body is riddled with pores. This is reflected in the synonym for the name of the type - Porifera (rop - pores, fera - load-bearing). Through the pores, water enters the body with suspended food particles. With the flow of water through the body of the sponges, all functions of nutrition, respiration, excretion, and reproduction are passively carried out.

In the process of ontogenesis, perversion (inversion) of the germinal layers occurs, that is, the primary outer layer of cells takes the position of the inner layer, and vice versa.

There are three classes of sponges: the Calcareous sponges class (Calcispongiae), the Glass sponges class (Hyalospongiae), and the Common sponges class (Demospongiae).

External and internal structure of sponges. In the simplest case, single sponges have the shape of a glass, for example Sycon (Fig. 70, 1). This shape has heteropolar axial symmetry. The goblet sponge has a sole, with which it is attached to the substrate, and on the upper pole there is an aperture - the osculum.

There is a constant flow of water through the body of the sponge: water enters the sponge through the pores and leaves the mouth. The direction of water flow in the sponge is determined by the movement of the flagella of special collar cells. Colonial sponges have many mouths (osculums) and axial symmetry is broken.

The body wall of sponges consists of two layers of cells (Fig. 71): integumentary cells (pinacocytes) and an inner layer of flagellar collar cells (choanocytes), which perform the function of water filtration and phagocytosis. Choanocytes have a funnel-shaped collar around the flagellum. The collar is formed from interlocking microvilli. Between the layers of cells there is a gelatinous substance - mesoglea, in which individual cellular elements are located. These include stellate supporting cells (collencytes), skeletal

Rice. 71. Structure of the Ascon sponge (according to Hadorn): A - longitudinal section, B, C - choanocytes; 1 - skeletal needles at the osculum, 2 - choanocyte, 3 - pore, 4 - skeletal needle, 5 - porocyte, 6 - pinacocytes, 7 - amoebocytes, 8, 9 - mesoglea with cellular elements

Rice. 72. Types of morphological structure of sponges (according to Hesse): A - ascon, B - sicon, C - leucon. Arrows show the direction of water flow in the sponge body

cells (sclerocytes), motile amoeboid cells (amebocytes) and undifferentiated cells - archaeocytes, which can give rise to any other cells, including germ cells. Sometimes weakly contracting cells - myocytes - are present. Among pinacocytes, special cells are distinguished - porocytes with a through pore. The porocyte is capable of contraction and can open and close the pore. Pores are scattered throughout the body of the sponge or form clusters.

There are three types of morphological structure of sponges: ascon, sicon, leucon (Fig. 72). The simplest of them is ascon. Asconoid sponges are small solitary sponges in which water enters through the pores and pore canals penetrating the body wall into the atrial cavity lined with choanocytes, and then exits through the osculum. Sicon type sponges are larger, with thicker walls, which contain flagellar chambers. The flow of water in syconoid type sponges occurs along the following path: pores, pore canals, flagellar chambers, atrial cavity, osculum. Unlike asconoid sponges, in siconoid sponges, choanocytes do not line the atrial cavity, but numerous flagellar pockets in the thickness of the body wall. This increases the digestive surface of the sponges and increases the efficiency of phagocytosis. The atrial cavity in siconoids is lined with pinacocytes. The most complex type of structure is leukon. These are colonial sponges with numerous osculums. There are many skeletal elements in the thick layer of mesoglea. Wall

Rice. 73. Shape of sponge needles (according to Dogel): A - uniaxial needle, B - triaxial, C - quadriaxial, D - multiaxial, E - complex triaxial needle or florik of glass sponges, E - irregular needle

the body is penetrated by a network of canals connecting numerous flagellar chambers. The flow of water in the leukonoid sponge occurs along the following paths: pores - pore canals - flagellar chambers - efferent canals - atrial cavity - osculum. Leuconoid sponges have the largest digestive surface area.

The type of structure of sponges does not reflect their systematic relationship. Different classes of sponges have representatives with different morphological structures. This indicates parallel evolutionary paths in different classes of sponges. The advantage of increasing the complexity of the structure of sponges was that with an increase in the size of the body of the sponges, the digestive surface of the choanocyte layer increased and the intensity of filtration increased. For example, a 7 cm Leuconia sponge filters 22 liters of water per day.

Skeleton sponges are internal and are formed in the mesoglea. The skeleton can be mineral (calcareous or silicon), horny, or mixed - silicon-horny.

The mineral skeleton is represented by needles (spicules) of various shapes: 1-, 3-, 4- and 6-axial and of a more complex structure (Fig. 73). Part

The skeleton includes an organic horn-like substance - spongin. In the case of reduction of the mineral skeleton, only spongine filaments remain.

Examples of sponges with skeletons of different composition: Leucandra has a calcareous skeleton; glass sponge (Hyalonema) - silicon; the sponge sponge (Spongilla) is silicon-horny, and the toilet sponge (Euspongia) is horny, or sponginous.

Calcareous sponge needles are calcite crystals with an admixture of other elements (Ba, Sr, Mn, Mg, etc.). The outside of the needles is covered with an organic sheath.

Silicon needles consist of amorphous silica arranged in concentric layers around an axial organic filament.

Mineral needles are formed due to the activity of cells - sclerocytes, while calcareous needles are formed extracellularly due to the secretions of several sclerocytes, and silicon needles are formed intracellularly. Large silicon spines are formed by several scleroblasts or intracellular syncytium with several nuclei.

Spongin fibers are formed extracellularly due to the release of fibrillar filaments by cells - spongiocytes. Spongin fibers cement the needles within the silicon-horn skeleton.

Horny and non-skeletal sponges are a secondary phenomenon.

Physiology of sponges. The lips are motionless. However, it is known that porocytes bearing pores and osculums of sponges can slowly narrow and expand due to contractions of myocyte cells and the cytoplasm of some other cells surrounding these openings. Motile cells include amebocytes, which perform a transport function in the mesoglea. They transport food particles from choanocytes to other cells, remove excreta, and during the breeding season they transport sperm through the mesoglea to the eggs. The flagella of choanocytes are constantly active. Thanks to the synchronous movement of the flagella, a constant flow of water is created in the sponge, delivering food particles and fresh portions of water with oxygen. Choanocytes capture food with pseudopodia, some of the food particles are digested themselves, and some are transferred to amoebocytes, which perform the main digestive and transport functions in the body of sponges.

Reproduction and development of sponges. Reproduction in sponges can be asexual or sexual. Asexual reproduction is carried out by external or internal budding. In the first case, a protrusion forms on the body of the sponge, at the top of which the osculum breaks through. In solitary sponges, the buds separate from the mother's body and form independent organisms, while in colonial sponges, budding leads to the growth of the colony. Freshwater sponges (Spongilla) are capable of internal

Rice. 74. Gemmules of freshwater sponges (according to Rezvoy): 1 - gemmule of badyagi - Spongilla lacustris, 2 - gemmule of Ephydatia blembingia. The section shows the cellular contents, a double sponginous membrane with rows of microsclera, it is time

budding. In this case, internal buds - gemmules - are formed in the mesoglea (Fig. 74). Typically, the formation of gemmules begins in the fall before the death of the mother colony. In this case, archaeocytes form clusters in the mesoglea, around which sclerocytes form a double spongin membrane with silicon needles or complex skeletal elements - amphidisks.

In the spring, archaeocytes emerge from the gemmule through a special pore and begin to divide. Subsequently, all types of sponge cells are formed from them. From the many gemmules in the skeletal framework of the mother colony, a new daughter colony is formed. Gemmules also perform the function of settlement, as they are carried by shadows. When fresh water bodies dry out, gemmules can be transported by the wind to other bodies of water. The formation of gemmules is the result of sponges adapting to life in fresh waters.

Sexual reproduction has been described for calcareous and siliceous horn sponges. Sponges are usually hermaphroditic, less often dioecious. Germ cells are formed in the mesoglea from undifferentiated cells - archaeocytes. Cross fertilization. Spermatozoa from the mesoglea exit into the atrial cavity and out of it. With the flow of water, sperm drop out through the pores into the body of another sponge, and then penetrate into the mesoglea, where fusion with the eggs occurs. As a result of crushing the zygote, a larva is formed, which leaves the body of the mother sponge, then settles to the bottom and turns into an adult sponge. Features of embryogenesis and types of larvae are different for different sponges.

In some calcareous sponges, for example in Clathrina (Fig. 75, A), as a result of fragmentation of the zygote, a coeloblastula larva is formed, consisting of cells of the same size with cords. The coeloblastula enters the water, and then some of its cells immigrate into the blastocoel.

Rice. 75. Development of sponges (from Malakhov): A - phases of development of the Clathrina sponge: 1 - zygote, 2 - uniform fragmentation of the embryo, 3 - coeloblastula larva (in water), 4 - parenchymula (in water), 5 - settled larva (pupa) with inversion of layers, 6 - formation of a sponge with flagellar chambers. B - phases of development of the sponge Leucosolenia: 1 - zygote, 2, 3 - uneven fragmentation of the embryo, 4 - formation of a stomoblastula with micromeres and macromeres (flagella of micromeres facing inward), 5 - eversion (excurvation) of the stomoblastula through fialopores, 6 - formation of an amphiblastula and temporary invagination of macromeres into the blastocoel, 7 - restoration of the amphiblastula to a spherical shape and its release into water, 8 - transformation of the settled larva into a sponge with inversion of layers

They lose their flagella and acquire an amoeboid shape. This is how a two-layer parenchymal larva is formed with flagellar cells on the surface and amoeboid cells inside. It settles to the bottom, after which the process of cell immigration occurs again: flagellated cells plunge inside, giving rise to choanocytes, and amoeboid cells emerge to the surface, forming integumentary cells - pinacocytes. At the end of metamorphosis, a young sponge is formed. The process of changing the position of cell layers in sponge embryogenesis is called layer inversion. The outer flagellar cells, which performed the motor function in the larvae, turn into the inner layer of choanocyte cells, which ensure the flow of water inside the sponge and the capture of food. Conversely, internal phagocytic cells in larvae subsequently form a layer of integumentary cells.

In other calcareous and siliceous sponges, development is more complex and involves the formation of an amphiblastula larva. Thus, in the calcareous sponge Leucoslenia (Fig. 75, B), as a result of uneven fragmentation of the egg, a single-layer stomoblastula embryo with an opening - a fialopore - is formed. Large cells are located along the edges of the fialopore, and the rest of the stomoblastula consists of small cells with flagella directed into the cavity of the embryo. Subsequently, the stomoblastula is turned “inside out” through the fialopore, after which it closes. This process of everting the embryo is called excurvation. A single-layered spherical larva is formed - an amphiblastula. One half of this sphere is formed by small flagellated cells - micromeres, and the other - by large cells without flagella - macromeres. After excurvation, the amphiblastula experiences temporary gastrulation - invagination of macromeres inward. Before the larva exits into the external environment, the macromeres protrude back, and it again acquires a spherical shape. Amphiblastulae swim forward with flagellar cells, then settle to the bottom and begin secondary gastrulation. Only now flagellar cells are invaginated, which are then transformed into choanocytes, and from large macromeres integumentary cells and cellular elements in the mesoglea are formed. Metamorphosis ends with the formation of a sponge. In the development of this sponge, the phenomenon of inversion of layers, common to all types of sponges, is observed. If during the first gastrulation of the amphiblastula the position of the outer layer is occupied by flagellar micromeres, and the inner layer by macromeres, then after the second gastrulation the cell layers change their position to the diametrically opposite one. Compared to the development of the Clathrina sponge, Leucoslenia has a more progressive method of gastrulation, occurring not by immigration of individual cells, but by invagination of the cell layer.

The inversion of layers in the embryogenesis of sponges indicates the functional plasticity of the cell layers, which should not be identified with the germ layers of higher multicellular organisms.

Review of classes of sponges, ecology and practical significance.

The division of sponges into classes is based on the characteristics of the chemical state and skeletal structure.

Class Calcareous sponges (Calcispongiae, or Calcarea)

These are sea sponges with a calcareous skeleton. Skeletal spines can be triaxial, quadriaxial or uniaxial. Among calcareous sponges there are single goblet-shaped or tubular forms, as well as colonial ones. Their dimensions do not exceed 7 cm in height. Representatives of this class can be the goblet sponge Sycon and the colonial Leucandra (Fig. 70, 1).

Class Glass sponges
(Hyalospongiae, or
Hexaclinellida)

These are predominantly large, deep-sea marine forms with a silicon skeleton consisting of six-axial spines. Sometimes individual spines are reduced, and in some cases the spines are soldered together and form amphidisks or complex lattices (Fig. 76). Glass sponges have a beautiful openwork skeleton and are used as collectible objects and souvenirs. For example, the sponge - Venus basket (Euplectella asper) in the shape of an openwork cylinder, the glass sponge - Hyalonema (Hyalonema) with a long tail rod made of thick silicon needles is very valuable. The body of some representatives

Rice. 76. Deep-sea glass sponges on the left - Venus basket Euplectella asper, on the right - Hyalonema sieboldi

Rice. 77. Silica sponges: on the left - Neptune's cup Poterion neptuni, on the right - toilet sponge Spongia officinalis

Glass sponges reach about 1 m in length, and the bundle of needles with which the sponge is fixed in soft soil can be up to 3 m. Glass sponges are fished mainly off the coast of Japan.

Class Common sponges (Demospongiae)

The class under consideration includes the vast majority of modern sponge species. They have a silicon skeleton combined with spongine threads. But in some species the silicon spines are reduced and only the spongine skeleton remains. Silicon needles are four-axis or single-axis.

Ordinary sponges are varied in shape, size, and color. In the surf, sponges usually have the form of growths, mats, and pillows. These are the spherical sea sponges Geodia, sea oranges (Tethya), and cork sponges (Subrites). At great depths, sponges can be branched or tubular, goblet-shaped. Among the beautiful sponges, Neptune's Cup (Poterion neptuni, Fig. 77) stands out. Commercial sponges include the toilet sponge (Spongia zimocca) with soft spongine. skeleton. The toilet sponge fishery is developed in the Mediterranean and Red Seas, as well as in the Caribbean Sea and the Indian Ocean. Created off the coast of Florida and Japan

artificial plantations. Toilet sponges are used not only for washing, but also as polishing material or filters. Among the sponges there are drilling forms (Cliona), which damage the calcareous shells of mollusks, including commercial species (oysters, mussels).

The group of freshwater sponges is represented by badyagi sponges. We have about 20 species of freshwater sponges, most of which live in Lake Baikal. The most common in our rivers is the badyaga (Spongilla lacustris) of a lumpy or bushy form (Fig. 78). It settles on stones, snags, and pieces of wood. Previously, badyagu was used in medicine as a remedy for rheumatism and bruises.

Most sponges are active biofilters, freeing food from suspended organic and mineral particles. For example, a finger-sized sponge filters 3 liters of water per day. Sponges are important in the biological treatment of marine and fresh waters. Recently, biologically active substances have been discovered in some sponges that will find wide application in pharmacology.

Sponges are aquatic sessile multicellular animals. There are no real tissues and organs. They have no nervous system. The body, in the form of a bag or glass, consists of a variety of cells performing various functions and intercellular substance.

The body wall of the sponges is penetrated by numerous pores and channels extending from them, communicating with the internal cavity. The cavities and canals are lined with flagellated collar cells. With few exceptions, sponges have a complex mineral or organic skeleton. Fossil remains of sponges are already known from Proterozoic rocks.

Lime and glass sponges:

1 - Polymastia corticata; 2 - sea ​​loon sponge (Halichondria panicea); 3 - Neptune's cup (Poterion neptuni); 4 - Baikal sponge (Lubomirskia baikalensis);

5, 6 - Clathrina primordialis; 7 - Pheronema giganteum; 8 - Hyalonema sieboldi

About 5 thousand species of sponges have been described, most of them live in the seas. The phylum is divided into four classes: calcareous sponges, siliceous or common sponges, glass sponges or six-rayed sponges and coral sponges. The latter class includes a small number of species that live in grottoes and tunnels among coral reefs and have a skeleton consisting of a massive calcareous base of calcium carbonate and flint uniaxial spines.

As an example, consider the structure of a lime sponge. Its body is sac-like, its base is attached to the substrate, and its opening, or mouth, is directed upward. The paragastric region of the body communicates with the external environment through numerous channels beginning with external pores.

In the body of an adult sponge there are two layers of cells - ecto- and ento-dermis, between which lies a layer of structureless substance - mesoglea - with cells scattered in it. Mesoglea occupies most of the body, contains the skeleton and, among other things, germ cells. The outer layer is formed by flat ectodermal cells, the inner layer by collar cells - cho-anocytes, from the free end of which a long flagellum protrudes. Cells freely scattered in the mesoglea are divided into stationary - stellate, performing a supporting function (collencytes), skeletal mobile (scleroblasts), engaged in digesting food (amebocytes), reserve amoeboid, which can turn into any of the above types, and sexual cells. The ability of cellular elements to transform into each other indicates the absence of differentiated tissues.

Based on the structure of the body wall and canal system, as well as the location of sections of the flagellate layer, three types of sponges are distinguished, the simplest of which is ascon and the more complex ones are sycon and leucon.

Different types of structure of sponges and their channel system:

A - ascon; B - sicon; IN - lacon. Arrows show the flow of water in the body of the sponge

The skeleton of sponges is formed in the mesoglea. The mineral (calcareous or flint) skeleton consists of individual or fused needles (spicules) that form inside scleroblast cells. The organic (spongin) skeleton is composed of a network of fibers similar in chemical composition to silk and formed intercellularly.

Sponges are filtrate organisms. There is a continuous flow of water through their body, caused by the action of collar cells, the flagella of which shoot in one direction - towards the paragastric cavity. Collar cells capture food particles (bacteria, unicellular organisms, etc.) from the water passing by them and swallow them. Some of the food is digested on the spot, some is transferred to amebocytes. Filtered water is expelled from the paragastric cavity through the orifice.

Sponges reproduce both asexually (by budding) and sexually. Most sponges are hermaphrodites. Germ cells lie in the mesoglea. Spermatozoa enter the canals, are excreted through the mouth, penetrate other sponges and fertilize their eggs. The zygote fragments, resulting in the formation of a blastula. In non-calcareous and some calcareous sponges, the blastula consists of more or less identical flagellar cells (coeloblastula).

Subsequently, some of the cells, losing their flagella, plunge inside, filling the cavity of the blastula, and as a result, a parenchymal larva appears.

More often, sponges live in colonies, resulting from incomplete budding. Only a few sponges are solitary. Secondarily single organisms are also found. Their importance in the life of reservoirs is very great. By filtering huge amounts of water through their bodies, they help cleanse it of particulate matter.

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Sponges are a type of aquatic, predominantly marine, immobile primitive animal. In terms of the complexity of their structure, they occupy an intermediate place between colonial protozoa and coelenterates. Usually they are not studied in a school biology course, although in terms of the number of species (about 8 thousand) this is a fairly large group.

Previously, people used sponges in everyday life (as washcloths).

Now we have learned how to make artificial sponges, but from them you can get an idea of ​​how animal sponges work. Their distinctive feature is their porous body structure, capable of passing large amounts of water through it.

In the body of sponges there are different cells that perform different functions and differ from each other in their structure. On this basis, sponges differ from colonial protozoa. However, sponge cells are weakly connected to each other, do not fully lose their ability to be independent, are almost not controlled together, and do not form organs.

Therefore, it is believed that sponges do not have tissues. In addition, they do not have true nerve or muscle cells.

The body shape of sponges can be different: like a bowl, a tree, etc. Moreover, all sponges have a central cavity with a fairly large hole (mouth) through which water comes out. The sponge absorbs water through smaller holes (tubules) in its body.

The figure above shows three options for the structure of the aquifer system of sponges.

In the first case, water is sucked into a common large cavity through narrow side channels. In this common cavity, nutrients (microorganisms, organic residues; some sponges are predators and are capable of capturing animals) are filtered from the water. The capture of food and the flow of water are carried out by the cells shown in red in the figure. In the figure in the second and third cases, the sponges have a more complex structure.

There is a system of channels and small cavities, the inner walls of which form cells responsible for nutrition. The first variant of the sponge body structure is called ascon, second - sicon, third - lacon.

Cells shown in red are called choanocytes.

They have a cylindrical shape, with a flagellum facing a chamber-cavity. They also have a so-called plasmatic collar, which traps food particles. Choanocyte flagella push water in one direction.

Sponges have a number of other cell types.

The diagram above shows part of the body of an ascona. Cover cells are indicated in yellow ( pinacocytes). They perform a protective function. Between the choanocytes and pinacocytes there is a fairly thick layer mesochyla(shown in grey). It has a non-cellular structure, it is a fibrous gelatinous substance in which all other types of cells and various formations are located.

Archaeocytes(light green cell in the diagram) - are amoeba-like motile undifferentiated cells capable of transforming into all others. When a sponge loses a part of its body, it is thanks to the division and differentiation of archaeocytes that the regeneration process occurs.

Article: The concept of a sponge

Archaeocytes also perform the function of transporting substances between cells (for example, from choanocytes to pinacocytes). There are also many other types of cells in the mesochyl (reproductive cells, cells containing nutrients, collagen, etc.). Also in the mesochyl there are needles that perform a supporting skeleton-forming function; they allow the sponge to maintain its shape. The needles have a crystalline structure.

Sponges reproduce both asexually and sexually. Asexual reproduction occurs by budding.

Daughter individuals can remain attached to the mother. As a result, colonies are formed. During sexual reproduction, sperm from one sponge enter the canals and chambers of the other. Fertilization of eggs (oocytes) occurs. The resulting zygote begins to divide, a larva is formed, which leaves the mother’s body with a flow of water and subsequently settles in a new place. In its structure, the larva does not have germ layers, but resembles a colony of unicellular flagellates.

The larva does not swim passively, but with the help of flagella. After it settles in a new place, it twists so that the flagella turn inward, and the larva begins to grow, turning into a sponge.

SPONGS (Spongia, Porifera) - a type of multicellular invertebrate aquatic animals. G. is characterized by cellular differentiation with little intercellular coordination, as a result of which individual cells of the body are practically independent of each other.

G.'s body consists of ento- and ectoderm and the gelatinous substance lying between them - mesoglia; muscle and nerve cells characteristic of higher animals are absent. The skeleton of G. consists of calcareous or silica formations of different sizes and shapes - spicules; in some species of G. - from organic matter (spongin).

Through channels passing inside the body and lined from the inside with a layer of ectodermal flagellar cells (choanocytes), water is continuously filtered.

Various microorganisms (protozoa, bacteria, algae, etc.), as well as particles of detritus that enter the body with the flow of water, are captured by the cells and digested in them.

Some of the freshwater hydrocarbons (for example, trampoline) play an important role in the natural purification of water bodies, but at the same time, settling in various hydraulic structures and clogging them, they can cause significant harm.

In total there are approx. 5000 species of G.; in the northern and Far Eastern seas within the USSR lives approx.

300 species, in the Black Sea - approx. 30, in the Caspian - 1 species. Freshwater G. in the USSR are represented by Baikal G. species and several species of thistle.

The practical value of sponges is small. The toilet, or Greek, fish serves as an object of fishing in the Mediterranean and some other seas; It is sometimes used in dried and purified form in surgery instead of cotton wool. Dried bodyaga is used in folk medicine as a treatment. a remedy for rheumatism, and also as a cosmetic product.

D. N. Zasukhin.

Biology and lifestyle of sponges

Sponges are exclusively aquatic animals that lead a sedentary lifestyle, like many plants.

They firmly settle on some solid substrate and do not leave their “home” of their own free will. These are such primitive organisms that they do not have the ability to move independently on the ground or in the water column.

The immobile lifestyle of sponges is due to the fact that sponges do not have an organized muscular and nervous system, since the cells that make up their body are differentiated and are not able to act “collectively”.
Their rudimentary abilities to respond to strong irritants are associated with the contraction of myocytes or protoplasm of epithelial and mesoglea cells, with each cell responding to irritation independently.

Experiments aimed at studying the ability of sponges to respond to external stimuli have shown that this reaction is extremely slow.

Thus, sponges living in shallow water are able to close the mouth (during low tide) in three minutes, and open completely in 7-10 minutes.

In addition to the ability to contract, some sponge cells (in particular, amoebocytes) are able to move slowly with the help of pseudopodia and pseudopods in the thickness of the mesoglea.

The inability of sponges to move parts of their body would negatively affect their viability - after all, for normal existence, sponges need a watercourse that brings food, gases and carries away waste products through channels to the body cells. In stagnant water, sponges would not be able to develop and exist normally if not for choanocytes. These cells are located along channels and chambers passing through the porous body of the sponge, and are equipped with motile flagella that are in constant motion.

Sponges - description, types, characteristics, nutrition, examples and classification

It is the flagella of choanocytes that create the necessary flow of water through the animal’s body.
If you inject dye into the body of an aquarium sponge with a syringe, then after a while a cloud of colored water will appear from the mouth.

Breathing sponges

Like all aquatic animals, sponges use oxygen dissolved in water to breathe.

As a result of oxidative processes, sponges release carbon dioxide, which must be removed from the cells into the external environment. Gas exchange occurs during the flow of water through the channels and flagellar chambers, while the mesoglea cells, located near the watercourse, capture oxygen and release waste products. Since many mesoglea cells are motile, and the mesoglea itself has a jelly-like appearance, the cells in it are slowly mixed, and most of them are able to receive nutrition and remove waste.

A certain role in supplying cells with oxygen and removing carbon dioxide is played by microscopic algae, which enter the channels and pores of sponges with water and live there for some time. In this case, a symbiotic relationship is observed between sponges and phytoalgae.

Nutrition and secretions of sponges

The water flow contributes not only to gas exchange, but also to the sponge cells receiving nutrients and mineral salts necessary for normal life.

Since the cells of sponges are differentiated, there is no need to talk about the existence of any, even rudimentary, digestive system in these animals. Each cell of the body independently extracts everything necessary from the water, and releases everything unnecessary into the water. We can say that the level of physiology of sponges in this respect resembles the physiology of unicellular organisms.

Sponges feed on organic microparticles suspended in water - the remains of microscopic animals and plants, single-celled organisms.

The particles enter the canals and flagellar chambers with the help of the same choanocytes, then are captured by mobile amoebocytes and spread throughout the mesoglea. In this case, the amebocytes release a pseudopod, embrace the particle and draw it into the cell.

A vacuole appears in the pseudopod - a vesicle filled with a medium capable of dissolving and digesting organic matter. The particle dissolves, and grains of a fat-like substance appear on the surface of the vacuole.

If a nutrient particle is too large for one amebocyte to digest, a group of amebocytes comes into play - they surround the particle on all sides and digest it together. The structure of choanocytes in some species of sponges allows them to also take part in the digestion of food.

Sponges pass through their pores, channels and flagellar chambers everything that is contained in the water, including inedible particles. At the same time, amebocytes capture both organic matter and what cannot be digested in the vacuole.

Undigested food remains and indigestible contents are secreted into the mesoglea and gradually move to the walls of the canals, from where they are expelled into the external environment by the flagella of choanocytes through the atrial cavity and orifice.

How long do sponges live?

Type of Sponge (Porifera, or Spongia)

Structure and classes of sponges

Sponges are ancient primitive multicellular animals. They live in marine and less often fresh water bodies. They lead a stationary, attached lifestyle. They are filter feeders. Most species form colonies. They do not have tissues or organs. Almost all sponges have an internal skeleton. The skeleton is formed in the mesoglea and can be mineral (calcareous or silicon), horny (spongin) or mixed (silicon-spongin).

There are three types of sponge structure: ascon (asconoid), sicon (syconoid), leukon (leuconoid) (Fig. 1).

rice. 1.

Different types of sponge structure:
1 - ascon, 2 - sicon, 3 - leukon.

The most simply organized sponges of the asconoid type have the shape of a bag, which is attached at the base to the substrate, and with the mouth (osculum) facing upward.

The outer layer of the sac wall is formed by integumentary cells (pinacocytes), the inner layer by collar flagellar cells (choanocytes).

Choanocytes perform the function of water filtration and phagocytosis.

Between the outer and inner layers there is a structureless mass - mesoglea, in which there are numerous cells, including those that form spicules (needles of the internal skeleton). The entire body of the sponge is penetrated by thin canals leading to the central atrial cavity. The continuous work of choanocyte flagella creates a flow of water: pores → pore canals → atrial cavity → osculum.

The sponge feeds on the food particles that water brings.

rice. 2. Structure of Sycon (Sycon sp.):
1 - skeletal needles surrounding the mouth, 2 - atrial cavity,
3 - pinacocyte, 4 - choanocyte, 5 - stellate supporting cell,
6 - spicule, 7 - pore, 8 - amebocyte.

In sponges of the syconoid type, the mesoglea thickens and internal invaginations form, which look like pockets lined with flagellar cells (Fig. 2).

The flow of water in the syconoid sponge occurs along the following path: pores → pore canals → flagellar pockets → atrial cavity → osculum.

The most complex type of sponge is leucon.

Sponges of this type are characterized by a thick layer of mesoglea with many skeletal elements. The internal invaginations plunge deep into the mesoglea and take the form of flagellar chambers connected by efferent canals through the satrial cavity. The atrial cavity in leukonoid sponges, like in syconoid sponges, is lined with pinacocytes.

Leuconoid sponges usually form colonies with many mouths on the surface: in the form of crusts, plates, lumps, bushes. The flow of water in the leuconoid sponge occurs along the following path: pores → pore canals → flagellar chambers → efferent canals → atrial cavity → osculum.

Sponges have a very high ability to regenerate.

They reproduce asexually and sexually.

Asexual reproduction occurs in the form of external budding, internal budding, fragmentation, formation of gemmules, etc. During sexual reproduction, a blastula develops from a fertilized egg, consisting of a single layer of cells with flagella (Fig. 3).

Then some of the cells migrate inward and turn into amoeboid cells. After the larva settles to the bottom, flagellar cells move inward, they become choanocytes, and amoeboid cells come to the surface and turn into pinacocytes.

Development of the lime sponge (Clathrina sp.):
1 - zygote, 2 - uniform fragmentation, 3 - coeloblastula,
4 - parenchymula in water, 5 - settled parenchymula
with inversion of layers, 6 - young sponge.

That is, the primary ectoderm (small flagellar cells) takes the place of the endoderm, and the endoderm takes the place of the ectoderm: the germ layers change places. On this basis, zoologists call sponges inside-out animals (Enantiozoa).

The larva of most sponges is a parenchymula, whose structure almost completely corresponds to the hypothetical “phagocytella” of I.I. Mechnikov.

In this regard, the hypothesis of the origin of sponges from a phagocytella-like ancestor is currently considered the most reasonable.

The type of sponge is divided into classes: 1) Lime sponges, 2) Glass sponges, 3) Ordinary sponges.

Class Calcareous sponges (Calcispongiae, or Calcarea)

Marine solitary or colonial sponges with a calcareous skeleton.

Skeletal spines can be three-, four-, or uniaxial. Sicon belongs to this class (Fig. 2).

Class Glass sponges (Hyalospongia, or Hexactinellida)

Marine deep-sea sponges with a silicon skeleton consisting of six-axial spines. In a number of species, the needles are soldered together, forming amphidisks or complex lattices.

The skeletons of some species are very beautiful and are used as collectible objects and souvenirs.

Representatives: basket of Venus (Fig. 4), hyalonema.

Class Common sponges (Demospongiae)

The vast majority of modern sponge species belong to this class.

The skeleton is made of silicon in combination with spongine threads. In some species, silicon spines are reduced, leaving only spongine filaments.

Silicon needles are four- or single-axis. Representatives: toilet sponge (Fig. 5), Neptune's cup (Fig. 6), badyaga, living in fresh water bodies.

rice. 4.

Basket of Venus
(Euplectella asper)
Fig.5. Toilet sponge
(Spongia officianalis)
rice. 6.

Neptune Cup
(Poterion neptuni)

Training tasks. Invertebrates

Level A assignments

Choose one correct answer from the four proposed

A1. Characteristic of a sponge

Systematic sponges are based on

A3. Characteristic of the intestines

A5. Body cavity

Level B assignments

Choose three correct answers out of six given

The following characteristic features of the sponge lifestyle are known:

3) depending on the conditions, sponges of the same species may differ in body shape

4) all sponges live in both sea and fresh water

6) sponges live for several thousand years

AT 2. The outer layer of the hydra's body contains cells

2) stinging

4) nervous

5) intermediate

1) they have special suction cups or hooks

4) during reproduction, a large number of eggs are formed, viviparity and alternation of generations are characteristic

6) in the process of evolution they lost their nervous system

AT 4. The mantle cavity of mollusks is a cavity

1) into which the anal, genital and excretory openings open

4) in which the respiratory and chemical sense organs are located

5) between the mantle and the body of the mollusk

Match the contents of the first and second columns

AT 5. Establish a correspondence between the classes and tapas Mollusks and Echinoderms

CLASSES TYPES

A) sea lilies 1) Molluscs

B) starfish 2) Echinoderms

B) Gastropods

D) sea urchins

D) bivalve

E) Brittle stars

G) Holothurians

H) Cephalopods

Establish a correspondence between some orders of insects and the type of their oral apparatus.

ORDER OF INSECTS TYPE OF ORAL APPARATUS

A) Cockroaches 1) sucking

B) orthoptera 2) gnawing

B) Coleoptera

D) Dragonflies

E) Butterflies

Establish the correct sequence of biological processes, phenomena, practical actions

Q8. Establish the sequence of stages of butterfly development

1)adult insect

3) caterpillar

4) doll

Establish the sequence of events when bees are born

Sponges, those sold in stores and used for washing dishes or cleaning the kitchen are not real. They are made of synthetic materials, although they closely resemble a real sponge and are easy to use.

But real sponges appear in the sea, not in a chemical laboratory. For a long time, many were sure that they knew everything about sponges. It was believed to be a plant until a man named Robert Grant proved in 1825 that sponges were once animals!

He examined the sponges in the water through a microscope. And I saw streams of water that entered through some holes and came out through others. But still, for many years, scientists still did not know what kind of animal this was. They were believed to be tiny single-celled creatures that live together in one large colony.

We now know that sponges are the dried skeletons of marine animals that belong to the “porous” class. This is quite a significant group of animals. And although sponges are one of the lowest forms in the animal kingdom, their structure is quite complex.

Their top layer consists of flat cells, somewhat reminiscent of a ladder. The channels formed by these cells are unlike those found in other animals. They are shaped like columns, each of which ends in a large “spill”. These weirs suck water into the sponge and then release it. In this way, sponges obtain oxygen and food (millions of tiny organisms that are absorbed along with water). The waste is also disposed of along with waste water. This is why fresh sponges that still have water in them smell bad. But it should be noted that this protects the sponges, because the smell discourages other animals from eating them!

In the center of the sponge there is a light jelly-like mass containing moving cells. They are likely involved in food digestion, respiration, and waste removal.

Sponges can have different shapes and colors. In general, they are very diverse; the most valuable types of sponges can be found at great depths at a distance of 80–130 km from the coast.

Structure and classes of sponges

Sponges are ancient primitive multicellular animals. They live in marine and less often fresh water bodies. They lead a stationary, attached lifestyle. They are filter feeders. Most species form colonies. They do not have tissues or organs. Almost all sponges have an internal skeleton. The skeleton is formed in the mesoglea and can be mineral (calcareous or silicon), horny (spongin) or mixed (silicon-spongin).

There are three types of sponge structure: ascon (asconoid), sicon (syconoid), leukon (leuconoid) (Fig. 1).

rice. 1.
1 - ascon, 2 - sicon, 3 - leukon.

The most simply organized sponges of the asconoid type have the shape of a bag, which is attached at the base to the substrate, and with the mouth (osculum) facing upward.

The outer layer of the sac wall is formed by integumentary cells (pinacocytes), the inner layer by collar flagellar cells (choanocytes). Choanocytes perform the function of water filtration and phagocytosis.

Between the outer and inner layers there is a structureless mass - mesoglea, in which there are numerous cells, including those that form spicules (needles of the internal skeleton). The entire body of the sponge is penetrated by thin canals leading to the central atrial cavity. The continuous work of choanocyte flagella creates a flow of water: pores → pore canals → atrial cavity → osculum. The sponge feeds on the food particles that water brings.

rice. 2.
1 - skeletal needles surrounding the mouth, 2 - atrial cavity,
3 - pinacocyte, 4 - choanocyte, 5 - stellate supporting cell,
6 - spicule, 7 - pore, 8 - amebocyte.

In sponges of the syconoid type, the mesoglea thickens and internal invaginations form, which look like pockets lined with flagellar cells (Fig. 2). The flow of water in the syconoid sponge occurs along the following path: pores → pore canals → flagellar pockets → atrial cavity → osculum.

The most complex type of sponge is leucon. Sponges of this type are characterized by a thick layer of mesoglea with many skeletal elements. The internal invaginations plunge deep into the mesoglea and take the form of flagellar chambers connected by efferent canals through the satrial cavity. The atrial cavity in leukonoid sponges, like in syconoid sponges, is lined with pinacocytes. Leuconoid sponges usually form colonies with many mouths on the surface: in the form of crusts, plates, lumps, bushes. The flow of water in the leuconoid sponge occurs along the following path: pores → pore canals → flagellar chambers → efferent canals → atrial cavity → osculum.

Sponges have a very high ability to regenerate.

They reproduce asexually and sexually. Asexual reproduction occurs in the form of external budding, internal budding, fragmentation, formation of gemmules, etc. During sexual reproduction, a blastula develops from a fertilized egg, consisting of a single layer of cells with flagella (Fig. 3). Then some of the cells migrate inward and turn into amoeboid cells. After the larva settles to the bottom, flagellar cells move inward, they become choanocytes, and amoeboid cells come to the surface and turn into pinacocytes.

rice. 3.
1 - zygote, 2 - uniform fragmentation, 3 - coeloblastula,
4 - parenchymula in water, 5 - settled parenchymula
with inversion of layers, 6 - young sponge.

The larva then turns into a young sponge. That is, the primary ectoderm (small flagellar cells) takes the place of the endoderm, and the endoderm takes the place of the ectoderm: the germ layers change places. On this basis, zoologists call sponges inside-out animals (Enantiozoa).

The larva of most sponges is a parenchymula, whose structure almost completely corresponds to the hypothetical “phagocytella” of I.I. Mechnikov. In this regard, the hypothesis of the origin of sponges from a phagocytella-like ancestor is currently considered the most reasonable.

The type of sponge is divided into classes: 1) Lime sponges, 2) Glass sponges, 3) Ordinary sponges.

Class Calcareous sponges (Calcispongiae, or Calcarea)

Marine solitary or colonial sponges with a calcareous skeleton. Skeletal spines can be three-, four-, or uniaxial. Sicon belongs to this class (Fig. 2).

Class Glass sponges (Hyalospongia, or Hexactinellida)

Marine deep-sea sponges with a silicon skeleton consisting of six-axial spines. In a number of species, the needles are soldered together, forming amphidisks or complex lattices.