Sponges are so unlike other multicellular animals that for a long time they were considered representatives of a special group of "zoophytes", that is, animal-plants. Indeed, they lead an attached lifestyle, are unable to make active movements, they lack a nervous system and sensory organs. In addition, some of their representatives may have a green color, since algae settle in their cells.

About 9 thousand species of these amazing creatures are known, distributed in the seas and fresh waters.

For the first time, the structure and vital processes of sponges were studied in detail by R. E. Grant, who proposed the scientific name of this group of animals.

Structural features of sponges. Among the sponges there are single forms, but most species form colonies, the size of which can reach 2 m. Colonies of sponges in their shape can resemble bushes, cortical growths, lumps, etc., overgrowing various surfaces. The color is also varied - yellow, brown, white, red, purple or green.

There is evidence that giant sponges live on the surface of containers with spent nuclear fuel buried on the seabed.

Found in fresh water different kinds badyag. Their colonies often form around submerged objects. In stagnant water bodies, they have the shape of a bush, in flowing water bodies they look like cortical fouling. The color of the colony is gray or dirty green.

The body of a goblet-shaped sponge (Fig. 58, 1). With their lower part, animals are attached to underwater objects. With the help of special video filming, it was established that some sponges can move due to amoeboid cells. But even the fastest of them do not cover a distance of more than 1 mm per day.

At the opposite - upper - end of the body of the sponge is a hole. But it's not a mouth. If rubbed dry ink is poured into an aquarium with sponges, then its particles will first go to the body of the sponge, then through the tubules in the walls of the body they will get inside and, in the end, will be removed through the hole at the upper end of the body.

Thus, this hole does not serve to absorb food, but to remove water from the body with its undigested residues.

The body of a sponge is made up of cells of different types. But they do not form tissues. Each cell functions independently.

outer layer the bodies of sponges form cells that resemble the cells of the integumentary epithelium of other multicellular animals. Among the cells of the outer layer, there are those that have a pore. These pores begin a system of tubules penetrating the walls of the body. The openings of these tubules are surrounded by cells capable of contracting and closing them. The tubules conduct water with food particles to the internal cavity. This cavity is usually lined with special cells with flagella, the base of which is surrounded by a membranous collar. (Fig. 58, 2). Such cells form the inner layer. In many sponges, they are located inside the walls of the body, forming flagellar chambers. The work of the flagella ensures the movement of water through the system of tubules and the internal cavity.

Between the outer and inner layers of cells is intercellular substance, in which are located different types cells. Some of them form internal skeleton of sponges.

Another cell type amoeboid. These cells, with the help of false legs, capture food particles that are digested in their digestive vacuoles. Moving along the body of the sponge, amoeboid cells distribute nutrients. material from the site

In large vacuoles of special cells of many species of sponges that live at shallow depths with sufficient illumination, special types of cyanobacteria settle. These prokaryotes can make up to 50% of the cell mass of the sponge itself. They supply oxygen and synthesized organic substances, and receive from animals the carbon dioxide necessary for photosynthesis and protection from enemies.

The structure of sponges is characterized by the following features:

• they do not have real tissues, but only cells of different types;
• the body is goblet, usually fixedly attached to underwater objects;
• in the walls of the body there is a system of tubules, inside there is a cavity that communicates with environment a hole at the top of the body;
• the movement of water through the body of sponges is provided by collar cells with flagella;
• in the walls of the body there is a skeleton of inorganic or organic substances;

On this page, material on the topics:

• Structural features of the sponge type

• Type of sponge abstract

• Features of the internal structure of the sponge cell

• Between the outer and inner layers of cells in the body of sponges is

• Infusoria slipper features of the structure and life processes

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The first multicellular organisms on Earth were sponges leading an attached lifestyle. However, some scientists classify them as complex colonies of protozoa.

general description

Sponges are a separate phylum in the animal kingdom with about 8,000 species.
There are three classes:

• Lime - have a calcareous skeleton;
• glass - have a silicon skeleton;
• Ordinary - have a silicon skeleton with spongin filaments (spongin protein holds parts of the skeleton together).

Rice. 1. Colony of sponges.

general characteristics sponges is given in the table.

The main representatives of sponges are the cup of Neptune, the badyaga, the basket of Venus, the luminous sponge of klion.

Rice. 2. Klion.

Structure

Despite the fact that these are symmetrical animals with all the signs of a living organism, they are conditionally referred to as multicellular organisms, because. they do not have specific tissues and organs.

The structure of sponges is primitive, limited to two layers of cells permeated with pores and a skeleton. Visually, the sponges look like bags attached to the substrate with a sole. The walls of the sponge form the atrial cavity. The outer opening is called the mouth (osculum).

• ectoderm - outer layer formed by pinacocytes - flat cells resembling epithelium;
• endoderm - the inner layer formed by choanocytes - cells resembling funnels with flagella.

The mesoglea contains:

• mobile amoebocytes that digest food and regenerate the body;
• sex cells;
• supporting cells containing spicules - silicon, limestone or horn needles.

Rice. 3. Structure of sponges.

Sponge cells are formed from undifferentiated cells - archeocytes.

Physiology

Despite the absence of organ systems, sponges are capable of nutrition, respiration, reproduction, and excretion. The receipt of oxygen, food and the release of carbon dioxide and other metabolic products occurs due to the inward flow of water, which is created by oscillations of the flagella.

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In the same way, fertilization occurs during sexual reproduction. With the flow of water, the spermatozoa of one sponge are absorbed, which fertilize the eggs in the body of another sponge. As a result, larvae are formed that come out. Some species produce eggs. They attach to the substrate and as they grow, they turn into an adult.

Every five seconds, a volume of water passes through the sponge equal to the internal volume of its body. Water enters through the pores, exits through the mouth.

Meaning

For humans, the meaning of sponges lies in the use of a solid skeleton for industrial, medical and aesthetic purposes. The ground skeleton was used as an abrasive and for washing. Soft-skeletal sponges were used to filter water.

Currently, dried and crushed badyaga is used in folk medicine for the treatment of bruises and rheumatism.

In nature, sponges are natural water purifiers. Their disappearance leads to water pollution.

What have we learned?

From the report for the 7th grade biology lesson, we learned about the features of the lifestyle, structure, meaning, nutrition, and reproduction of sponges. These are primitive multicellular animals that lead an attached lifestyle and are formed by two layers of cells. They filter water, getting food, oxygen and germ cells from it for fertilization. Metabolic products, spermatozoa and fertilized cells or larvae enter the water. Due to rapid regeneration, they are able to reproduce by fragmentation.

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Sponge type (Porifera, from Latin porus - it's time, ferre - to carry). This type includes primitive multicellular animals leading a sedentary lifestyle, attached to solid substrates in water. Approximately 5,000 species are known, most of them marine.

The body is radially symmetrical and, in principle, consists of a central (paragastric) cavity surrounded by a two-layer wall. Water enters through the pores in the wall into this cavity, and from there it goes out through a wide mouth - at its upper end; however, in some sponges, the mouth is reduced or absent, which leads to an increase in the flow of water through the pores. Its movement is due to the beating of the flagella, which are supplied with cells lining the channels in the walls. Food, oxygen, sex products and waste products of metabolism are carried by this almost external water.

Appearance

The appearance of the sponge is very characteristic. In addition to the branched form, Baikal sponges can be crusty, spherical, mushroom-shaped (the type of Svarchevskaya papiration has the form of small whitish graceful “caps”, 1-4 cm in diameter). Sponge sizes vary widely: from 1-2 cm in diameter to flat shapes and up to 1 m tall in trees. All Baikal sponges are stronger and tougher than badyagi. The tissue of the sponge is very dense and elastic, it is torn with some effort. All sponges, both freshwater and marine, are characterized by a peculiar pungent and unpleasant odor.

Almost all freshwater sponges grown in the light are bright green in color. It depends on the symbiotic unicellular zoochlorella algae that live in their body. Sponges grown at depth or in the shade do not have a green color. Such sponges can be off-white, brown, bluish or reddish in color. Sometimes only part of the colony is green. Various species growing in the coastal zone of Lake Baikal differ in shades of green.

Internal structure of sponges

Examining the sponge, cutting it, we do not find in it any organs visible to the naked eye, but we see only a rough to the touch substance, riddled with voids and channels. When studying a sponge under a microscope at low magnifications, two elements can be distinguished in it: the skeleton and the parenchyma. The skeleton consists of silicon needles or spicules glued together in bundles with a transparent substance - spongin. The bundles of spicules form a more or less regular network or spatial lattice in the body of the sponge. The shape of the spicules and the architectonics of the skeleton, i.e. the location of the spicule bundles are of diagnostic value and are characteristic of each species. Spicules with rounded ends are called strongyls, spicules with pointed ends are called oxi. Unlike badyags, Baikal sponges have a very strong skeleton, because their spicules are soldered with a large amount of spongin.

The skeleton penetrates the soft mucous substance - the parenchyma and serves as its support. The parenchyma consists of mesoglea and cellular elements scattered in it, for which mesoglea plays the same role as blood plasma for blood cells. The sponge contains several types of cells. Outside, the sponge is covered with dermal cells. The internal cavities, the so-called flagellar chambers, are lined with choanocytes that have a constantly moving long cord. Silicoblasts and spongioblasts are involved in the formation of silicon spicules. Amebocytes are located in the mesoglea and have the potential to produce all other cellular elements, including the gonads. Nerve cells in sponges are absent, respectively, there is no irritability.

The cavities that permeate the entire body of the sponge form the most important, so-called irrigation system, which is divided into two parts - the inlet and outlet. The adductor system begins with numerous pores on the surface of the sponge and branches into adductor channels and cavities. The channels of the efferent system, gradually merging with each other into larger ducts, also approach the surface of the sponge and flow into the ocular openings or osculums. Thin walls everywhere separate the inlet system of channels from the outlet system similar to it, and nowhere is there a direct connection between them. Such communication occurs only in the flagellar chambers.

The movement of the cords in the flagellar chambers represents the engine that creates a continuous flow of water through the entire body of the sponge. The harnesses make constant helical movements. Thus, each of the countless chambers acts as a pump. Their combined efforts make water enter the pores, pass through the entire complex system channels and ejected through the ocular holes.

The vital activity of sponges

The sedentary lifestyle of sponges makes them look like plants. However, some of their cellular elements have amazing mobility. The speed of movement of some cells varies from 0.6 to 3.5 microns per minute (1 micron \u003d 1/1000 mm - approx. site). If a piece of a living sponge is rubbed through a fine sieve and a few drops of such pomace are stirred in a small amount of water, then under a microscope one can see a mass of living cells that move, releasing pseudopodia. Silicoblasts, which take part in the construction of silicon spicules, which are formed inside the mother cell, are especially mobile.

First, an axial filament appears, to which silicoblasts approach and deposit layers of silica on its surface until the spicule reaches the required thickness. The finished spicule is then moved into the mesoglea by other cells, which put it in its proper place in the skeletal bundle. Gluing it to the bundle is the task of spongioblasts that secrete spongin.

Sponges feed on particles suspended in water. Water, passing through the pores, enters the flagellar chambers, where small particles are captured by choanocytes, and then thrown into the mesoglea, where they are reabsorbed by other cells - amoebocytes, which digest them and carry nutrients throughout the body. Sponges lack selectivity and capture both nutrients and non-nutrients. The sponge is gradually freed from inedible particles, removing them through the osculums. Thus, substances suspended in water serve as food for sponges, if the size of the particles allows them to pass through the pores. But the amount of suspended solid food is not enough to feed sponges, and organic substances dissolved in water are an additional source. Along with the flow of water, oxygen enters the body of the sponge.

Sponge breeding

All sponges are dioecious. Some individuals produce only eggs, others spermatozoa, although outwardly male and female individuals do not differ in any way. Spermatozoa penetrate through the pores along with the water current inside the females and fertilize the eggs. The formation of the larva takes place inside the mother's body. When the larva matures, it leaves it and becomes free-swimming for a while. Rotating, the larva swims briskly in search of a suitable substrate.

Attachment of the larva usually occurs within the first 12 hours after leaving the mother's body, but sometimes it can be delayed up to two days. The settled larva flattens out, turning into a small whitish spot, in which very soon you can recognize a small sponge. During the development of a sponge from an egg to a free-swimming larva, there is a complete resemblance to the embryonic development of other animals. But the metamorphosis of the larva, which begins after its attachment, is a process characteristic of all sponges, which distinguishes them from all other multicellular animals. The germ layers change places, for this reason sponges are called animals "turned inside out".

All freshwater sponges, except Baikal, also have a process of asexual reproduction, the result of which is the formation of gemmules. These are dormant stages designed to preserve the species during unfavorable seasons (cold or dry). Spongyllid gemmules also perform the function of settling in other water bodies, where they can be brought by wind, water birds, or in another way. Gemmules remain viable for several years, are able to tolerate freezing and drying out.

A very important difference between endemic Baikal sponges and cosmopolitan spongyllids is their lack of ability to reproduce with the formation of gemmules. The constancy of the temperature regime of the deep-water lake contributed to the disappearance of this stage from their development cycle. Interestingly, some cosmopolitan spongyllids living in Baikal have also lost the ability to form gemmules.

The biological significance of sponges

Being active biofilter feeders and due to their mass distribution in Baikal, sponges form an important link in the lake's ecosystem and play a significant role in its hydrobiological regime. The role of sponges is determined by their participation in trophic chains, since they are the most important consumers of zoo- and phytoplankton that develop in the thickness of coastal waters, as well as silicon necessary for the construction of the skeleton.

Ecology and practical importance of sponges

Sponges reach the greatest species diversity in the tropical and subtropical zones of the World Ocean, although there are many of them in arctic and subarctic waters. Most sponges are inhabitants of shallow depths (up to 500 m). The number of deep-sea sponges is small, although they were found at the bottom of the deepest abyssal depressions (up to 11 km). Sponges settle mainly on stony soils, which is associated with the way they feed. A large number of
silt particles clog the channel system of the sponges and make their existence impossible. Only a few species live on muddy soils. In these cases, have
they usually have one or more giant spicules that stick into the silt and raise the sponge above its surface (for example, species of genera
Hyalostylus from Hyalonema). Sponges that live in the intertidal zone (on the littoral), where they are exposed to the action of the surf, look like growths,
pads, crusts, etc. In most deep-sea sponges, the skeleton is flint - strong, but fragile, in shallow-water sponges - massive or elastic
(horny lips). By filtering huge amounts of water through the body, sponges are powerful biofilters. By this they contribute to the purification of water from mechanical and organic pollution.

Sponges often cohabit with other organisms, and in some cases this cohabitation has the character of simple commensalism (lodging), in others it takes on the character of a mutually beneficial symbiosis. Thus, colonies of sea sponges serve as a place of settlement a large number different organisms - annelids, crustaceans, serpentine (echinoderms), etc. In turn, sponges often settle on other, including mobile, animals, for example, on the shell of crabs, shells of gastropods, etc. Some, especially freshwater sponges, are characterized by intracellular symbiosis with unicellular green algae (zoochlorella), which serve as an additional source of oxygen. With excessive development, algae are partially digested by sponge cells.

Drilling sponges (genus Cliona) represent a peculiar ecological group. Settling on a calcareous substrate (mollusk shells, coral colonies,
calcareous rocks, etc.), they form passages in it that open outwards with small holes. Outgrowths of the body of the sponge protrude through these openings,
bearing osculums. The mechanism of action of drilling sponges on the substrate is still unclear. In the dissolution of lime, apparently, an essential role is played by the carbon dioxide released by the sponge.

The practical value of sponges is small. AT southern countries there is a trade of toilet sponges with a horn skeleton, used for washing and various technical purposes. They are caught in the Mediterranean and Red Seas, the Gulf of Mexico, the Caribbean Sea, the Indian Ocean, off the coast of Australia.
There is also a fishery for glass sponges (mainly Eupectella) used as ornaments and souvenirs off the coast of Japan.

Classification

Sponge type classification is based on the composition and structure of the skeleton. There are three classes.

Class I. Lime sponges (Calcarea, or Calcispongia)

The skeleton is composed of carbonic lime needles, which can be four-, three-, or one-axle. Exclusively marine, mostly shallow-water small sponges. They can be built according to the asconoid, syconoid or leuconoid type. Typical representatives are the genera Leusolenia, Sycon‚ Leuconia.

Class II. Glass sponges (Hyalospongia)

Marine mainly deep-sea sponges up to 50 cm high. The body is tubular, bag-shaped, sometimes in the form of a glass. Almost exclusively solitary forms of the syconoid type. The flint needles that make up the skeleton are extremely diverse, triaxial at the base. Often soldered at the ends, forming lattices of varying complexity. A characteristic feature of glass sponges is the weak development of mesoglea and the fusion of cellular elements into syncytial structures. Typical genus Euplectella. In some species of this genus, the body is cylindrical, up to 1 m in height; the needles at the base, sticking into the ground, reach 3 m in length.

Class III. Ordinary sponges (Demospongia)

Most modern sponges belong to this class. The skeleton is flint, spongy, or a combination of both. This includes a detachment of four-beam sponges (Tetraxonia), the skeleton of which is composed of four-axis needles with an admixture of uniaxial ones. Characteristic representatives: spherical large geodia (Geodia), brightly colored orange-red sea oranges (Tethya), lumpy bright cork sponges (family Suberitidae), boring sponges (family Clionidae) and many others. The second detachment of the Demospongia class is the silicon-horned sponges (Cornacuspongia). The skeleton includes spongin as the only component of the skeleton or in various proportions with flint needles. This includes toilet sponges, a few representatives of freshwater sponges - badyag from the family. Spongillidae, endemic Baikal sponges of the family. Lubomirskiidae.

The body of sponges with a height of 1.5 mm to 1 m consists of a two-layer porous wall surrounding the central cavity. Between the layers of the wall is gelatinous mesoglea, which contains cells of various kinds. Sponges lead a motionless lifestyle, attaching their base to the substrate. Only the mouth and pores are able to narrow slightly. Under the action of flagellated cells - choanocytes, lining the inner surface of the sponges, water with suspended food particles is pumped through the pores into the inner cavity. Here, various organic substances, as well as bacteria and plankton, are captured by choanocytes. Metabolic products go out with water through a wide mouth. Some sponges pump through themselves up to one and a half tons of water per day.

Most sponges are hermaphrodites. Reproduction is sexual and asexual. The kidneys that form on the body, as a rule, do not separate from the mother's body, which leads to the appearance of colonies of the most bizarre shape. In the sexual process, the sperm fertilizes the egg; a larva emerges from the egg, swimming in the water for some time, and then attaching itself to the bottom. Most sponges live from a few weeks to two years; horse sponge can live up to 50 years or more. Sponges have a very well-developed ability to regenerate tissues: even if a sponge is cut into pieces, a new sponge will grow from each piece after a while.

The sponge skeleton develops in the mesoglea. It consists of the fibrillar protein collagen or the organic matter of spongin and millions of microscopic needles (spicules) formed by silica or lime carbonate. The structure of the skeleton serves as the main feature of the classification of sponges. About 5000 species of sponges, found mainly in the seas from the surface to a depth of 8 km, are divided into three classes: lime sponges(calcium carbonate skeleton) ordinary sponges(skeleton of one- or four-axis silica needles, less often of spongin), glass or six-beam jaws(silica skeleton of six-axis needles). More than 95% of all species belong to ordinary sponges.

Limestone sponges have been known since the Precambrian, glass sponges from the Devonian. At present, most researchers, following Ivan Mechnikov, consider a hypothetical animal, phagocytella, as the ancestor of sponges. This is evidenced by the structure of the larvae of sponges, close to the most archaic animals from the sub-kingdom of phagocytella-like -

Sponges are aquatic sessile multicellular animals. There are no real tissues and organs. Nervous system they lack. 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.

About 5 thousand species of sponges have been described, most of them live in the seas (Fig. 16). The type is divided into four classes: calcareous sponges (Calcarea), silicon-horn or ordinary sponges (Demospongia), glass or six-ray sponges (Hexactinellida, or Hyalospongia) and coral sponges (Sclerospongia). 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 siliceous uniaxial needles.

As an example, consider the structure of a lime sponge. Its body is saccular, its base is attached to the substrate, and its opening, 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 endoderm, 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 flagellum sticks out. Cells freely scattered in the mesoglea are divided into immobile stellate cells that perform a supporting function (collencites), skeletal mobile cells (scleroblasts) that digest food (amoebocytes), reserve amoeboid cells, which can turn into any of the above types, and sex cells. 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 (Fig. 14).

Rice. 14. Various types of structure of sponges and their channel system:

A - ascon; B - sicon; B - leukone. 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 similar in chemical composition to silk and 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 passing water 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 other sponges and fertilize their eggs. The zygote cleaves, resulting in a blastula. The second germ layer (phagocytoblast) is formed by immigration or invagination. 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 parenchymal larva appears.

Among sponge blastulas there are so-called amphiblastulae, in which the animal hemisphere consists of small flagellar cells, and the vegetative hemisphere consists of large cells without flagella, but filled with yolk. Amphiblastulae perform gastrulation in the body of the mother sponge: the cells of the vegetative hemisphere protrude into the blastocoel. However, when the larva enters the water, the endodermal cells again turn outward (degastrulation), returning to the state of amphiblastula. After that, the amphiblastula settles with its aboral pole to the bottom, its ectodermal flagellar cells protrude inward, while the endodermal ones remain outside. This phenomenon is called perversion of the germ layers. It also occurs in another case, when the parenchymal larva settles on the substrate. Then its ectodermal cells crawl inside, where they form collar-flagellar chambers. The endoderm overlies the ectoderm. The mouth is formed on the vegetative pole, which is turned upwards.

More often, sponges live in colonies resulting from incomplete budding. Only a few sponges are solitary, secondary solitary organisms are also found (Fig. 15). 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.

Rice. 15. Colonial and secondary single sponges:

1 - a colony of goblet sponges with well-separated zooids (Sy-con ciliatum); 2 - amorphous multi-mouthed sponge (Mycale ochotensis); 3 - 5 - cormus-like sponges - an intermediate form between a multi-mouth individual and a petite colony (Geodia phlegraei, Chondrocladia gigantea, Phakellia cribrosa); 6, 7 - secondary single sponges (Tentorium semisuberites, Polymastia hemisphaericum)

Table 11

Comparative characteristics of the main classes of sponges

Rice. 16. Lime and glass sponges:

1 - Polymastia corticata; 2 - sea loaf sponge (Halichondria panicea); 3 - bowl of Neptune (Poterion neptuni); 4 - Baikal sponge (Lubomirskia baikalensis);

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