can be solitary animals, but much more often 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 proved 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) first identified sponges as an independent type Sponges (Porifera).
In total, 5000 species of sponges are known. This is an ancient group of animals known from the Precambrian.
General characteristics of the type of sponges. Sponges combine the features of primitive multicellular animals with a specialization for an immobile lifestyle. The primitive organization of sponges is evidenced by such signs as the absence of tissues and organs, the high regenerative capacity 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 bear the traits of specialization for an immobile lifestyle. They have a skeleton that protects the body from mechanical damage and predators. The skeleton can be mineral, horny or mixed 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 of the type name - Porifera (rop - pores, fera - bearing). Through the pores, water enters the body with suspended food particles. With the flow of water through the body of sponges, all the functions of nutrition, respiration, excretion, and reproduction are passively carried out.
In the process of ontogenesis, a perversion (inversion) of the germ layers occurs, i.e., the primary outer layer of cells takes the position of the inner layer, and vice versa.
There are three classes of sponges: the class Lime sponges (Calcispongiae), the class Glass sponges (Hyalospongiae), the class Ordinary sponges (Demospongiae).
External and internal structure of sponges. Single sponges in the simplest case have the shape of a glass, for example Sycon (Fig. 70, 1). This form has a heteropolar axial symmetry. In the goblet sponge, the sole is distinguished, with which it attaches to the substrate, and at the upper pole - the mouth - the osculum.
Through the body of sponges, a constant flow of water is carried out: through the pores, water enters the sponge, 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 the axial symmetry is broken.
The sponge body wall consists of two layers of cells (Fig. 71): integumentary cells (pinacocytes) and an inner layer of flagellated collar cells (choanocytes), which perform the function of filtering water and phagocytosis. Choanocytes have a funnel-shaped collar around the flagellum. The collar is formed from linked microvilli. Between the layers of cells there is a gelatinous substance - mesoglea, in which individual cellular elements are located. These include stellate supporting cells (collentites), skeletal
Rice. 71. The 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. The arrows show the direction of water flow in the body of the sponge.
cells (sclerocytes), mobile amoeboid cells (amoebocytes) and undifferentiated cells - archeocytes, which can give rise to any other cells, including sex cells. Sometimes there are weakly contracting cells - myocytes. Among pinacocytes, special cells are distinguished - porocytes with a through pore. The porocyte is capable of contraction and can open and close the pore. The pores are scattered throughout the body of the sponge or form clusters.
There are three types of morphological structure of the sponges askon, sikon, leukon (Fig. 72). The simplest of them is ascon. Asconoid sponges are small single ones, in which water enters through the pores and pore channels penetrating the body wall into the atrial cavity lined with choanocytes, and then exits through the osculum. Seacon type sponges are larger, with thicker walls, in which there are flagellar chambers. The flow of water in sponges of the syconoid type occurs along the following path: pores, pore canals, flagellar chambers, atrial cavity, osculum. Unlike asconoid sponges, syconoid 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 syconoids is lined with pinacocytes. The most complex type of structure is the leukone. These are colonial sponges with numerous osculums. There are many skeletal elements in the thick layer of mesoglea. Stenka
Rice. 73. The shape of the needles in sponges (according to Dogel): A - uniaxial needle, B - triaxial, C - four-axial, D - multiaxial, D - complex triaxial needle or glass sponge florik, E - irregular needle
the body is penetrated by a network of canals connecting numerous flagellar chambers. The flow of water in the leuconoid sponge is carried out along the path: pores - pore canals - flagellar chambers - efferent canals - atrial cavity - osculum. Leuconoid sponges have the largest digestive surface.
The structure type of sponges does not reflect their systematic relationship. In different classes of sponges there are representatives with different morphological structures. This indicates parallel paths of evolution in different classes of sponges. The advantage of the complication of the structure of the sponges turned out to be that with an increase in the size of the body of the sponges, the digestive surface of the layer of choanocytes increased and the intensity of filtration increased. For example, a Leuconia sponge (leukon) 7 cm in size filters 22 liters of water per day.
Skeleton sponges internal and is formed in the mesoglea. The skeleton can be mineral (lime or silicon), horny or mixed - silicon-horn.
The mineral skeleton is represented by needles (spicules) of various shapes: 1-, 3-, 4- and 6-axes and 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 spongy filaments remain.
Examples of sponges with different skeleton compositions: leucandra (Leucandra) has a calcareous skeleton; glass sponge (Hyalonema) - silicon; badyaga sponge (Spongilla) - silicon-horny, and toilet sponge (Euspongia) - horny, or spongy.
Lime needles of sponges are calcite crystals with an admixture of other elements (Ba, Sr, Mn, Mg, etc.). Outside, the needles are covered with an organic shell.
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 needles are formed by several scleroblasts or intracellular syncytium with several nuclei.
Spongy fibers are formed extracellularly due to the release of fibrillar filaments by cells - spongiocytes. The spongy fibers cement the needles in the silicon-horn skeleton.
Horny and skeletal sponges are a secondary phenomenon.
Physiology of sponges. Lips are motionless. However, it is known that pore-bearing porocytes and sponge osculums can slowly narrow and expand due to contractions of myocyte cells and the cytoplasm of some other cells surrounding these holes. Motile cells include amoebocytes, which perform a transport function in the mesoglea. They carry food particles from choanocytes to other cells, remove excreta, and during the breeding season they carry sperm along the mesoglea to the eggs. Choanocyte flagella are in constant activity. Due 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 pseudopods, digest some of the food particles 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 body and form independent organisms, while in colonial sponges, budding leads to colony growth. Freshwater sponges badyagi (Spongilla) are capable of internal
Rice. 74. Gemmules of freshwater sponges (according to Rezvom): 1 - badyagi gemmul - Spongilla lacustris, 2 - Ephydatia blembingia gemmul. The section shows the cellular contents, a double spongy membrane with rows of microsclera, a pore
budding. At the same time, internal buds - gemmules (Fig. 74) are formed in the mesoglea. Gemmul formation usually begins in autumn before the death of the mother colony. At the same time, archeocytes form clusters in the mesoglea, around which sclerocytes form a double spongy sheath with silicon needles or complex skeletal elements - amphidisks.
In the spring, archeocytes emerge from the gemmula through a special time, which begin to divide. In the future, all types of sponge cells are formed from them. From the set of gemmules in the skeletal framework of the mother colony, a new one is formed - the daughter one. Gemmules also perform the function of settling, as they are carried by shadows. When fresh water bodies dry up, gemmules can be carried by wind to other water bodies. The formation of gemmules is the result of the adaptation of sponges to life in fresh waters.
Sexual reproduction has been described for calcareous and silicon-horn sponges. Sponges are usually hermaphroditic, rarely dioecious. Sex cells are formed in the mesoglea from undifferentiated cells - archeocytes. Cross fertilization. Spermatozoa from the mesoglea enter the atrial cavity, and out of it. With the flow of water, the spermatozoa fall out through the pores into the body of another sponge, and then penetrate into the mesoglea, where they merge with the eggs. 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 in different sponges.
In some calcareous sponges, for example, in Clathrina (Fig. 75, A), as a result of crushing the zygote, a coeloblastula larva is formed, consisting of cells of the same size with bundles. The coeloblastula enters the water, and then some of the 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 - the formation of a sponge with flagellated chambers. B - phases of the development of the sponge Leucosolenia: 1 - zygote, 2, 3 - uneven fragmentation of the embryo, 4 - formation of stomoblastula with micromeres and macromeres (flagellums of micromeres are turned inward), 5 - eversion (excurvation) of the stomoblastula through the phialopore, 6 - formation of amphiblastula and temporary invagination of macromeres into the blastocoel, 7 - restoration of the amphiblastula spherical shape and its release into the water, 8 - transformation of the settled larva into a sponge with inversion of the layers
They lose flagella, acquire an amoeboid form. This is how a two-layer parenchymula 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: flagellar cells sink inward, giving rise to choanocytes, and amoeboid cells come 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 silicon-horn sponges, development is more complicated and with the formation of an amphiblastula larva. So, in the calcareous sponge Leucoslenia (Fig. 75, B), as a result of uneven crushing of the egg, a single-layer embryo of the stomoblastula with a hole - fialopor is initially formed. Large cells are located along the edges of the fialopora, and the rest of the stomoblastula consists of small cells with flagella directed inside the embryonic cavity. Subsequently, the stomoblastula turns inside out through the phialopore, after which it closes. This process of eversion of the embryo is called excurvation. A single-layer spherical larva is formed - amphiblastula. One half of this sphere is formed by small flagellated cells - micromeres, and the other half - by large cells without flagella - macromeres. After excurvation, the amphiblastula experiences temporary gastrulation - the protrusion of macromeres inward. Before the larva enters the external environment, the macromeres protrude back, and it again acquires a spherical shape. Amphiblastulae float flagellar cells forward, then settle to the bottom and they begin secondary gastrulation. Only now flagellar cells protrude inside, 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 bed inversion 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 a diametrically opposite one. Compared with the development of the sponge Clathrina, Leucoslenia has a more advanced mode of gastrulation, which occurs not by immigration of individual cells, but by invagination of the cell sheet.
The inversion of layers in the embryogenesis of sponges indicates the functional plasticity of 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 features of the chemical state and structure of the skeleton.
Class Lime sponges (Calcispongiae, or Calcarea)
These are sea sponges with a calcareous skeleton. Skeletal needles can be triaxial, quadruple and uniaxial. Among calcareous sponges, there are single goblet or tubular forms, as well as colonial ones. Their dimensions do not exceed 7 cm in height. Representatives of this class include the goblet sponge Sycon and the colonial Leucandra (Fig. 70, 1).
Grade Glass Sponges
(Hyalospongiae, or
Hexaclinellida)
These are predominantly large, deep-sea marine forms with a silicon skeleton consisting of six-axis spines. Sometimes individual needles are reduced, and in some cases the needles are soldered together and form amphidisks or complex lattices (Fig. 76). Glass sponges have a beautiful openwork skeleton and are used as collectibles and souvenirs. For example, the sponge - the basket of Venus (Euplectella asper) in the form of an openwork cylinder, the glass sponge - hyalonema (Hyalonema) with a long tail rod of thick silicon needles is very much appreciated. The body of some representatives
Rice. 76. Deep-sea glass sponges on the left - Venus's basket Euplectella asper, on the right - Hyalonema sieboldi
Rice. 77. Silicon sponges: on the left - a cup of Neptune Poterion neptuni, on the right - a toilet sponge Spongia officinalis
glass sponges reaches about 1 m in length, and a bunch of needles, with which the sponge is fixed in soft ground, can be up to 3 m. Fishing for glass sponges is carried out mainly off the coast of Japan.
Class Ordinary sponges (Demospongiae)
The class under consideration includes the vast majority of modern types of sponges. They have a silicon skeleton combined with spongy filaments. But in some species, the silicon needles are reduced and only the spongy skeleton remains. Silicon needles - four-axis or one-axis.
Ordinary sponges are diverse in shape, size, color. In the surf zone, sponges usually take the form of outgrowths, carpets, and pillows. These are geodia sea sponges (Geodia) of spherical shape, sea oranges (Tethya), cork sponges (Subrites). At great depths, sponges can be branched or tubular, goblet-shaped. Among the beautiful sponges, the cup of Neptune (Poterion neptuni, Fig. 77) stands out. Commercial sponges include a toilet sponge (Spongia zimocca) with soft spongy. skeleton. The fishing of toilet sponges is developed in the Mediterranean, Red Seas, as well as in the Caribbean Sea, Indian Ocean. Off the coast of Florida and Japan created
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) that damage the calcareous shells of mollusks, including commercial species (oysters, mussels).
A group of freshwater sponges are 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). She settles on stones, snags, pieces of wood. Previously badyagu was used in medicine as a remedy for rheumatism, bruises.
Most sponges are active biofilters, freeing food from suspended organic and mineral particles. For example, a sponge badyaga the size of a finger per day filters 3 liters of water. Sponges are important in the biological treatment of marine and fresh waters. Recently, biologically active substances have been found in some sponges, which will find wide application in pharmacology.
Sponges that are sold in stores and used for washing dishes or cleaning the kitchen are not real. They are made of synthetic materials, although they are very similar to 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 trickles of water that entered through one hole and exited through another. But still, for many years, scientists still did not know what kind of animal it was. It was believed that these are tiny single-celled creatures that live together in one large colony.
We now know that sponges are the dried skeletons of marine animals belonging to the "porous" class. This is a fairly 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 not like those found in other animals. They are in the form of columns, each of which ends with a large "weir". 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). Waste is also thrown away together with waste water. This is why fresh sponges that still have water left 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 is a light jelly-like mass, which contains moving cells. They are likely involved in the processes of food digestion, respiration, and waste removal.
Sponges can have a different shape and color. In general, they are very diverse, the most valuable species of sponges can be found at great depths at a distance of 80–130 km from the coast.
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 that perform various functions, and intercellular substance.
The body wall of sponges is permeated with numerous pores and channels coming from them, communicating with the internal cavity. The cavities and canals are lined with flagellated collar cells. With few exceptions, sponges have complex mineral or organic skeletons. Fossil remains of sponges are already known from Proterozoic rocks.
Lime and glass sponges:
1 - Polymastia corticata; 2 - sea loaf sponge (Halichondria panicea); 3 - cup of Neptune (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 type is divided into four classes: calcareous sponges, silicon-horn or ordinary, glass or six-ray 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 needles.
As an example, consider the structure of a lime sponge. Its body is sac-like, its base is attached to the substrate, and the hole, or mouth, is turned upwards. The paragastric region of the body communicates with the external environment by numerous channels, beginning with external pores.
In the body of an adult sponge, there are two layers of cells - ecto- and endo-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 others, germ cells. The outer layer is formed by flat ectodermal cells, the inner layer is formed by collar cells - choanocytes, from the free end of which a long tick sticks out. Cells freely scattered in the mesoglea are divided into immobile - stellate, performing a supporting function (collencites), skeletal mobile (scleroblasts), engaged in the digestion of food (amoebocytes), reserve amoeboid, which can turn into any of the above types, and sexual. The ability of cellular elements to pass into each other indicates the absence of differentiated tissues.
According to the structure of the body wall and the canal system, as well as the location of the sections of the flagellar layer, three types of sponges are distinguished, the simplest of which is the ascon and the more complex ones, the sicon and leukon.
Various types of sponge structure and their channel system:
BUT - ascon; B - sikon; IN - leucon. The arrows show the flow of water in the body of the sponge.
The sponge skeleton is formed in the mesoglea. The mineral (calcareous or siliceous) skeleton consists of separate or soldered needles (spicules) that form inside scleroblast cells. The organic (spongin) skeleton is composed of a network of fibers that are similar in chemical composition to silk and are formed intercellularly.
Sponges are filtrate organisms. Through their body there is a continuous flow of water, caused by the action of collar cells, the flagella of which beat in one direction - towards the paragastric cavity. Collar cells capture food particles (bacteria, unicellular, etc.) from the water passing by them and swallow them. Part of the food is digested on the spot, part is transferred to amoebocytes. Filtered water is ejected from the paragastric cavity through the mouth.
Sponges reproduce both asexually (by budding) and sexually. Most sponges are hermaphrodites. Sex cells lie in the mesoglea. Spermatozoa enter the canals, are excreted through the mouth, penetrate into other sponges and fertilize their eggs. The zygote cleaves, resulting in a blastula. In non-calcareous and some calcareous sponges, the blastula consists of more or less identical flagellar cells (coeloblastula).
In the future, part of the cells, losing flagella, plunges inward, filling the cavity of the blastula, and as a result, a larva-parenchymula appears.
More often, sponges live in colonies resulting from incomplete budding. Only a few sponges are solitary. There are also secondary single organisms. Their importance in the life of reservoirs is very great. By filtering through their body a huge amount of water, they help to cleanse it of impurities from solid particles.
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Sponges are a type of aquatic predominantly marine immobile primitive animals. In terms of the complexity of their structure, they occupy an intermediate position 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, a person 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 \u200b\u200bhow animal sponges are arranged. Their distinctive feature is the porous structure of the body, capable of passing a large amount of water through itself.
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 interconnected, 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 and muscle cells.
The shape of the body of sponges is different: similar to a bowl, a tree, etc. At the same time, all sponges have a central cavity with a fairly large hole (mouth) through which water exits. The sponge sucks in water through smaller holes (tubules) in its body.
The figure above shows three options for the structure of the sponge aquifer system.
In the first case, water is sucked into a common large cavity through narrow side channels. In this common cavity, nutrients are filtered from the water (microorganisms, organic residues; some sponges are predators and are able to capture animals). Catching food and the flow of water is carried out by the cells depicted 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 the cells responsible for nutrition. The first variant of the structure of the body of a sponge is called ascon, second - Seacon, the third - leukone.
Cells shown in red are called choanocytes.
They have a cylindrical shape, a flagellum facing the chamber-cavity. They also have a so-called plasma 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 ascon's body. Integumentary cells are marked in yellow ( pinacocytes). They perform a protective function. Between choanocytes and pinacocytes there is a rather powerful layer mesohyl(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.
archeocytes(light green cell in the diagram) - are amoeba-like mobile undifferentiated cells that can turn into all others. When a sponge loses a body part, it is thanks to the division and differentiation of archeocytes that the process of regeneration occurs.
Also, archeocytes perform the function of transporting substances between cells (for example, from choanocytes to pinacocytes). There are also many other types of cells in the mesohyl (sex cells, nutrient-containing cells, collagen, etc.). Also in the mesochile there are needles that perform a supporting skeletal function, they allow the sponge to keep its shape. The needles have a crystalline structure.
Sponges reproduce both asexually and sexually. Asexual reproduction is carried out by budding.
Daughter individuals may remain attached to the parent. As a result, colonies are formed. During sexual reproduction, spermatozoa from one sponge enter the channels and chambers of another. Fertilization of eggs (oocytes) occurs. The resulting zygote begins to divide, a larva is formed, which leaves the mother's body with a current 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 settling in a new place, it twists so that the flagella turn inward, and the larva begins to grow, turning into a sponge.
SPONGE (Spongia, Porifera) - a type of multicellular invertebrate aquatic animals. G. is characterized by cellular differentiation with little intercellular coordination, as a result of which the individual cells of the body are practically independent of each other.
G.'s body consists of ento- and ectoderm and a gelatinous substance lying between them - mesoglia; muscle and nerve cells characteristic of higher animals are absent. G.'s skeleton consists of calcareous or silica formations of different size and shape - spicules, in some types of G. - from organic matter (spongin).
Water is constantly filtered through channels that run inside the body and are lined from the inside with a layer of ectodermal flagellar cells (choanocytes).
Various microorganisms (protozoa, bacteria, algae, etc.), as well as particles of detritus that enter the body with the flow of water, are captured by cells and digested in them.
Some of the freshwater G. (for example, bodyagi) 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 also cause significant harm.
In total there are approx. 5000 types 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 species of G. and several types of bodyag.
The practical value of sponges is small. Toilet, or Greek, G. 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 in folk medicine is used as a treatment. remedy for rheumatism, as well as a cosmetic.
D. N. Zasukhin.
Sponges are exclusively aquatic animals that lead a stationary lifestyle, like many plants.
They firmly establish themselves on some solid substrate, and do not leave their "familiar place" of their own free will. These are such primitive organisms that they have no 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". 
The rudimentary ability to respond to strong stimuli in them is associated with the contraction of myocytes or protoplasm of epithelial and mesogley cells, while each cell responds to irritation independently.
Experiments aimed at studying the ability of sponges to respond to external stimuli have shown that this reaction is extremely slow.
So, sponges living in shallow water are able to close the mouth (during low tide) in three minutes, and fully open it 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 prolegs in the thickness of the mesoglea.
The inability of sponges to move parts of their body would have a negative impact on their viability - after all, for a normal existence, sponges need a watercourse that brings food, gases through the channels to the cells of the body and carries away waste products. In stagnant water, sponges would not be able to develop and exist normally if it were not for choanocytes. These cells are located along the channels and chambers passing through the porous body of the sponge, and are equipped with movable flagella that are in constant motion.
It is the flagella of choanocytes that create the necessary flow of water through the body of the animal.
If a dye is injected into the body of an aquarium sponge with a syringe, then after a while a cloud of colored water will appear from the mouth.
Like all aquatic animals, sponges use oxygen dissolved in water for breathing.
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 cells of the mesoglea, located near the watercourse, capture oxygen, give off waste products. Because many of the cells in the mesoglea are mobile and the mesoglea itself is jelly-like, the cells in it mix slowly and most of them are able to take in food and remove waste.
A certain role in supplying cells with oxygen and removing carbon dioxide is played by microscopic algae that 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.
The watercourse contributes not only to gas exchange, but also to the cells of the sponges 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 a 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 are fed by organic microparticles that are in suspension in water - the remains of microscopic animals and plants, unicellular organisms.
The particles enter the canals and flagellar chambers with the help of the same choanocytes, then they are captured by mobile amoebocytes and spread throughout the mesoglea. At the same time, the amoebocytes release the pseudopod, envelop the particle, and draw it into the cell.
A vacuole appears in the pseudopod - a bubble 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 the nutrient particle is too large to be digested by one amoebocyte, a group of amoebocytes comes into play - they surround the particle from all sides and digest it together. The structure of choanocytes in some types 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, amoebocytes capture both organic matter and that which cannot be digested in the vacuole.
Undigested food residues and indigestible contents are released into the mesoglea and gradually move to the walls of the canals, from where they are expelled by choanocyte flagella into the external environment through the atrial cavity and mouth.
How long do sponges live?
Sponges are ancient primitive multicellular animals. They live in marine, less often fresh water bodies. They lead a fixed 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 silicic), horny (sponginous) or mixed (silicic-sponginous).
There are three types of sponge structure: ascon (asconoid), sicon (syconoid), leukon (leuconoid) (Fig. 1).
rice. one.
Different types of sponge structure:
1 - ascon, 2 - sicon, 3 - leucon.
The most simply organized sponges of the asconoid type are in the form of a bag, which is attached to the substrate with its base, and the mouth (osculum) is turned upwards.
The outer layer of the sac wall is formed by integumentary cells (pinacocytes), the inner layer is formed 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 forming spicules (needles of the internal skeleton). The entire body of the sponge is permeated with thin canals leading to the central atrial cavity. Continuous work of choanocyte flagella creates a water flow: pores → pore channels → atrial cavity → osculum.
The sponge feeds on those food particles that the water brings.
rice. 2. The structure of the 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 protrusions form, which look like pockets lined with flagellar cells (Fig. 2).
The flow of water in the syconoid sponge is carried out along the following path: pores → pore channels → flagellar pockets → atrial cavity → osculum.
The most complex type of sponge is the leukone.
Sponges of this type are characterized by a thick layer of mesoglea with many skeletal elements. The internal protrusions plunge deep into the mesoglea and take the form of flagellar chambers connected by efferent canals to the satria cavity. The atrial cavity in leuconoid sponges, as well as in syconoid sponges, is lined with pinacocytes.
Leukonoid sponges usually form colonies with many mouths on the surface: in the form of crusts, plates, clods, bushes. The flow of water in the leuconoid sponge is carried out 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 is carried out in the form of external budding, internal budding, fragmentation, the 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, the flagellar cells move inward, they become choanocytes, and the amoeboid cells come to the surface and turn into pinacocytes.
Development of the lime sponge (Clathrina sp.):
1 - zygote, 2 - uniform crushing, 3 - coeloblastula,
4 - paranchymula in water, 5 - settled paranchymula
with bed inversion, 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 animals turned inside out (Enantiozoa).
The larva of most sponges is a parenchymula, in structure it almost completely corresponds to the hypothetical "phagocytella" of I.I. Mechnikov.
In this regard, at present, the hypothesis of the origin of sponges from a phagocytella-like ancestor is considered the most reasonable.
Type Sponges are divided into classes: 1) Lime sponges, 2) Glass sponges, 3) Ordinary sponges.
Marine solitary or colonial sponges with a calcareous skeleton.
Skeletal needles can be three-, four- and uniaxial. The sicon belongs to this class (Fig. 2).
Marine deep-sea sponges with a silicon skeleton consisting of six-axis spines. In a number of species, the needles are soldered, forming amphidisks or complex lattices.
The skeletons of some species are very beautiful and are used as collectibles and souvenirs.
Representatives: basket of Venus (Fig. 4), hyalonema.
This class includes the vast majority of modern types of sponges.
The skeleton is silicon combined with spongy filaments. In some species, silicon needles are reduced, leaving only spongy filaments.
Silicon needles - four- or uniaxial. Representatives: toilet sponge (Fig. 5), Neptune's cup (Fig. 6), badyaga, living in fresh water.
rice. 4.
Basket of Venus
(Euplectella asper)
fig.5. toilet sponge
(Spongia officianalis)
rice. 6.
Neptune Cup
(Poterion neptuni)
Level A tasks
Choose one correct answer from the four given
A1. Sponges are characterized
Systematic sponges are based on
A3. The intestines are characterized
A5. body cavity
Level B assignments
Choose three correct answers from the six given
The following characteristic features of the lifestyle of sponges 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
IN 2. In the outer layer of the body of the hydra are 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, live birth and alternation of generations are characteristic
6) in the process of evolution they had a loss of the 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. Set the correspondence between classes and taps Mollusks and Echinoderms
CLASSES TYPES
A) sea lilies 1) Shellfish
B) starfish 2) Echinoderms
B) gastropods
D) sea urchins
D) bivalve
E) Ophiurs
G) Holothurians
H) Cephalopods
Establish a correspondence between some orders of insects and the type of their mouth apparatus.
INSECT ORDER MOUTH TYPE
A) cockroach 1) sucking
B) Orthoptera 2) gnawing
B) Coleoptera
D) Dragonflies
E) butterflies
Set the correct sequence of biological processes, phenomena, practical actions
B8. Establish the sequence of stages of butterfly development
1) adult insect
3) caterpillar
4) chrysalis
Set the sequence of events for the rosin of bees
Including about 10,000 known species living on Earth today. Members of this type of animal are calcareous sponges, ordinary sponges, 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 the marine environment, but a few species can be found in freshwater.
Sponges are primitive multicellular animals that do not have a digestive, circulatory or nervous system. They have no organs and the cells do not organize a well-defined structure.
There are three main classes of sponges. Glass sponges have a skeleton that is made up of brittle, glassy needles formed from silica. Ordinary sponges are often brightly colored and grow larger than other sponges. Ordinary sponges account for more than 90 percent of all modern types of sponges. Lime sponges are the only class of sponges that have spicules composed of calcium carbonate. Lime sponges are usually smaller than other members of the type.
The body of a sponge is like a bag, perforated with many small holes or pores. The walls of the body are made up of three layers:
Sponges feed by filtering water. They suck in water through pores located along the entire 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 retains water flowing through the central cavity into a hole in the top of the sponge called the osculum. As water passes through the collar cells, food is captured by the rings of tentacles. Further, food is digested in food or amoeboid cells in the middle layer of the wall.
The water flow also provides a constant supply of oxygen and removes nitrogenous waste. Water exits the sponge through a large hole in the top of the body called the osculum.
Sponges are divided into the following major taxonomic groups:
Sponges are ancient primitive multicellular animals. They live in marine, less often fresh water bodies. They lead a fixed 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 silicic), horny (sponginous) or mixed (silicic-sponginous).
There are three types of sponge structure: ascon (asconoid), sicon (syconoid), leukon (leuconoid) (Fig. 1).
rice. one.
1 - ascon, 2 - sicon, 3 - leucon.
The most simply organized sponges of the asconoid type are in the form of a bag, which is attached to the substrate with its base, and the mouth (osculum) is turned upwards.
The outer layer of the sac wall is formed by integumentary cells (pinacocytes), the inner layer is formed 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 forming spicules (needles of the internal skeleton). The entire body of the sponge is permeated with thin canals leading to the central atrial cavity. The continuous work of choanocyte flagella creates a water flow: pores → pore channels → atrial cavity → osculum. The sponge feeds on those food particles that the 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 protrusions form, which look like pockets lined with flagellar cells (Fig. 2). The flow of water in the syconoid sponge is carried out along the following path: pores → pore channels → flagellar pockets → atrial cavity → osculum.
The most complex type of sponge is the leukone. Sponges of this type are characterized by a thick layer of mesoglea with many skeletal elements. The internal protrusions plunge deep into the mesoglea and take the form of flagellar chambers connected by efferent canals to the satria cavity. The atrial cavity in leuconoid sponges, as well as in syconoid sponges, is lined with pinacocytes. Leukonoid sponges usually form colonies with many mouths on the surface: in the form of crusts, plates, clods, bushes. The flow of water in the leuconoid sponge is carried out 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 is carried out in the form of external budding, internal budding, fragmentation, the 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, the flagellar cells move inward, they become choanocytes, and the amoeboid cells come to the surface and turn into pinacocytes.
rice. 3.
1 - zygote, 2 - uniform crushing, 3 - coeloblastula,
4 - paranchymula in water, 5 - settled paranchymula
with bed inversion, 6 - young sponge.
Further, the larva 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 animals turned inside out (Enantiozoa).
The larva of most sponges is a parenchymula, in structure it almost completely corresponds to the hypothetical "phagocytella" of I.I. Mechnikov. In this regard, at present, the hypothesis of the origin of sponges from a phagocytella-like ancestor is considered the most reasonable.
Type Sponges are divided into classes: 1) Lime sponges, 2) Glass sponges, 3) Ordinary sponges.
Marine solitary or colonial sponges with a calcareous skeleton. Skeletal needles can be three-, four- and uniaxial. The sicon belongs to this class (Fig. 2).
Marine deep-sea sponges with a silicon skeleton consisting of six-axis spines. In a number of species, the needles are soldered, forming amphidisks or complex lattices.
