Asexual reproduction of sponges. Sponge type. Structural features and classes of sponges. Internal structure of representatives
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-ray sponges, or glass sponges (Hexactinellida, Hyalospongia).
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 of the animal kingdom, numbering about 8,000 species.
There are three classes:
- Limestone - have a calcareous skeleton;
- Glass - have a silicon skeleton;
- Ordinary - have a silicon skeleton with spongin filaments (the spongin protein holds the parts of the skeleton together).
Rice. 1. Sponge colony.
General characteristics of sponges are given in the table.
|
Sign |
Description |
|
Lifestyle |
Attached. They form colonies. There are single representatives |
|
Habitats |
Fresh and salt water bodies in different climatic zones |
|
Can reach 1 meter in height |
|
|
Heterotrophic. They are filter feeders. Internal flagella create a current of water that penetrates into the body. Organic particles, plankton, and detritus deposited on the walls are absorbed by cells |
|
|
Reproduction |
Sexual or asexual. During sexual reproduction, they lay eggs or form larvae. There are hermaphrodites. When asexual, they form buds or reproduce by fragmentation |
|
Lifespan |
Depending on the species, they can live from several months to several hundred years. |
|
Natural enemies |
Turtles, fish, gastropods, starfish. Poison and needles are used for protection |
|
Relationships |
They can form symbiosis with algae, fungi, ciliated worms, mollusks, crustaceans, fish and other aquatic inhabitants |
The main representatives of sponges are Neptune's cup, badyaga, Venus's basket, and the luminous sponge of Clion.
Rice. 2. Kliona.
Structure
Despite the fact that these are symmetrical animals with all the signs of a living organism, they are conventionally classified 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, sponges look like bags attached to the substrate with a sole. The walls of the sponge form the atrial cavity. The external opening is called the orifice (osculum).
There are two layers , between which there is a jelly-like substance - mesoglea:
- ectoderm - the outer layer formed by pinacocytes - flat cells resembling epithelium;
- endoderm - the inner layer formed by choanocytes - cells resembling funnels with flagella.
Mesoglea contains:
- mobile amoebocytes that digest food and regenerate the body;
- germ cells;
- supporting cells containing spicules - silicon, limestone or horny needles.
Rice. 3. The structure of sponges.
Sponge cells are formed from undifferentiated cells - archaeocytes.
Physiology
Despite the lack of organ systems, sponges are capable of feeding, respiration, reproduction, and excretion. The receipt of oxygen, food and the release of carbon dioxide and other metabolic products occurs due to the flow of water inward, which is created by vibrations of the flagella.
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Fertilization occurs in the same way during sexual reproduction. The flow of water absorbs the sperm of one sponge, which fertilizes the eggs in the body of the other sponge. As a result, larvae are formed that come out. Some species produce eggs. They attach to the substrate and, as they grow, transform into an adult.
Every five seconds, a volume of water equal to the internal volume of its body passes through the sponge. Water enters through the pores and leaves through the mouth.
Meaning
For humans, the importance of sponges lies in the use of their hard skeleton for industrial, medical and aesthetic purposes. The ground skeleton was used as an abrasive and for cleaning. Soft-skeleton sponges were used to filter water.
Currently, dried and crushed badyaga is used in folk medicine to treat bruises and rheumatism.
In nature, sponges are natural water purifiers. Their disappearance leads to pollution of the reservoir.
What have we learned?
From a report for a 7th grade biology lesson, we learned about the features of the lifestyle, structure, significance, 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, obtaining food, oxygen and germ cells from it for fertilization. Metabolic products, sperm and fertilized cells or larvae enter the water. Thanks to rapid regeneration, they are able to reproduce by fragmentation.
Test on the topic
Evaluation of the report
Average rating: 4.4. Total ratings received: 279.
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 what is 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 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. 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.
The development of sponges dates back to antiquity; they are believed to be the oldest animals on the globe. Sponges arose (according to scientists) approximately one billion two hundred million years ago. And today these amazing animals inhabit the vastness of the World Ocean. And in this article we will talk not only about their development, but also about how sponges reproduce.Sponges: reproduction and lifestyle
Sponges are invertebrate animals that lead a predominantly marine (aquatic) lifestyle. There are a number of species that live in fresh water bodies. They lead an almost motionless life, attached to the bottom of the reservoir.
At the same time, their primitive nervous system (very primitive) practically does not react to external stimuli. Most often, sponges lead a colonial lifestyle (but there are exceptions).
The development of sponges has led to them being classified into four classes. Classification is made based on the structure of the skeleton.
Classification of sponges:
common sponges - the skeleton is formed by uniaxial flint needles;
calcareous sponges - the skeleton of sponges with three and four rayed needles, made of calcareous calcium:
coral sponges - the skeleton consists of a mass of basalt (maybe aragonite or calcite);
glass sponges - the skeleton consists of silicon (six-rayed stars).
Reproduction of sponges by budding
Sponges reproduce in several ways. So one of the ways is budding, a bud swells on the surface of the sponge, in which a new life is formed. As the kidney grows, it separates from the mother’s body, after which it independently attaches to the bottom next to the mother’s body.
A daughter individual may simply be a section of the mother cell (a separated section, so to speak). This budding is mainly characteristic of calcareous sponges, although it is also observed in some glass species.
If the formation of buds occurs at the ends of the needles, then the formation of a series of buds connected to each other is possible. In this case, the connection with the mother is weak.
Sexual reproduction of sponges
Sponges can also reproduce sexually. Among the colonies there are dioecious individuals, and there are also hermaphrodite sponges. To date, the reproduction of calcareous, four-rayed and siliceous species has been studied in most detail.
It should be noted that there is no external difference between males and females. Sex cells form in the mesoglea of the sponge. This is where the eggs mature and their sperm form.
Considering that sponges are filtrates (pumping water through themselves), spermatozoa are picked up by the current of water and through channels, they can either go outside or enter the flagellar chambers of neighboring sponges. Provided that mature eggs are located in the flagellar chambers, they are transported to the mature eggs with the help of amoebocytes.
Fertilization of the egg, followed by its fragmentation (with the formation of a “larva”), occurs in the mother’s body. Although there are some types of four-rayed sponges, in which the eggs are hatched outside, where sponge development occurs.
The sponge larva looks like either a ball or a three-dimensional oval, the size of which can reach one millimeter. The surface of the larva is strewn with flagella; they, constantly contracting, give the larva acceleration, and it moves.
Free “swimming” can last up to three days, after which it either attaches to the substrate or dies. The larva (swimming) has the following structure: internal mass (large granular cells), outside the cells are covered with a layer of flagellar cells (cylindrical).
The larva has two layers and is called parenchymula. The cause is improper (uneven) crushing of the egg. The first stages of egg cleavage lead to the formation of cells of various sizes. The so-called micromeres and macromeres.
Micromeres quickly divide and envelop larger macromeres, thus achieving a two-layer parenchyma. Some sponges have vesicle-shaped larvae (mostly calcareous species).
The vesicle shell consists of only one layer of cells with flagella. Such a larva is called coelobastula. Coming out of the mother’s body, some of the cells cast off their flagella and plunge into the larva. This is how the development of the sponge begins.
Such transformations lead to the fact that the larva turns into a parenchtmula.
When reproducing, sponges have two larval forms: parenchymula and amphiblastula. Being in the water for some time (swimming), the larva settles to the bottom, and it is there that it is consolidated, followed by the formation and development of a sponge.
Asexual reproduction of sponges
Rarely, but it does occur, asexual reproduction of sponges. Such reproduction of sponges represents the separation of a site from the body (the magnitude can be very different). Next, the separated area develops into a full-fledged sponge organism.
Under unfavorable conditions, sponge reproduction can occur with the help of reduction bodies. When normal living conditions are restored, the reduction bodies reproduce new sponges.
Now you know how sponges reproduce. These articles will introduce you to these ancient animals in more detail:
The following articles will tell you about other interesting representatives of invertebrates:
Sponges(Spongia) is a type of invertebrate animal. Sponges probably descend from colonial collared flagellated protozoans, forming a blind branch at the base of the phylogenetic tree of metazoans.
Sponges arose in the Precambrian (about 1 billion 200 million years ago!, i.e. these are very ancient organisms), and reached their greatest prosperity in the Mesozoic.
Sponges are predominantly marine organisms, but not many are freshwater. Outwardly, sponges are even difficult to mistake for animals. They sit completely motionless, attached to the substrate, and do not react in any way to irritation. Sponges are often colonial organisms, but solitary ones are also found. The sponges feel hard and tough to the touch. Freshwater sponges are gray or greenish, but sea sponges are often brightly colored. Color depends on the presence of pigment cells. Many sponges have a specific unpleasant taste and smell, so they are not edible and no one touches them.
Sponges have an extremely primitive organization. Their body doesn't have any symmetry, it formless. Inside the goblet or sac-shaped body (from a few mm to 1.5 m or more in height) of a typical sponge there is paragastric cavity opening at the top wellhead hole. Sponges do not have real organs and tissues, but their body consists of a variety of cellular elements. On the surface of the body there are flat cells - pinacocytes, from the inside the paragastric cavity is lined with flagellated collar cells, or choanocytes. Between the layer of pinacocytes and the layer of choanocytes lies a structureless substance - mesoglea, containing amebocytes, collencytes, scleroblasts and other cells. On the surface of the sponge's body there are many since then, leading to channels piercing the walls of the body. Depending on the degree of development of the canal system, the localization of choanocytes and the flagellar chambers formed by them, 3 types of sponge structure are distinguished: ascon, sicon And lacon.
Almost all sponges have skeleton, formed by flint or limestone needles In horny sponges, the skeleton consists of the protein substance spongin.
The life activity of sponges is associated with continuous by straining through the body of water, which, thanks to the beating of the flagella of many choanocytes, enters the pores and, having passed through a system of canals, flagellar chambers and the paragastric cavity, comes out through the mouth. Food particles (detritus, protozoa, diatoms, bacteria, etc.) enter the sponge with water and metabolic products are removed. Food is captured by choanocytes and canal wall cells.
Most sponges are hermaphrodites. A ciliated larva develops from the egg - parenchymula, or amphiblastula, which comes out, floats, then settles to the bottom and turns into a young sponge. During metamorphosis, a process characteristic only of sponges is observed, the so-called perversions germinal leaflets, in which the cells of the outer layer migrate inward, and the cells of the inner layer end up on the surface. In addition, sponges have widespread budding and education gemmulus- types of asexual reproduction.
All sponges, as mentioned earlier, are aquatic, predominantly marine colonial, less often solitary animals leading a sedentary lifestyle. They are found from the coastal zone and almost to the maximum depths of the ocean; they are most diverse and numerous on the shelf (shelf is a flat, not deep zone of the seabed). Over 300 species live in the northern and Far Eastern seas of our country, about 30 species in the Black Sea, and 1 species of sponge in the Caspian Sea. In total, about 2,500 species have been described to date.
Sponge type is divided into 4 classes. The classification of sponges is based on their skeletal structure.
Class 1. Ordinary sponges(Demospongiae). In these sponges, the skeleton is formed by uniaxial or four-rayed flint spines. Channel system of leukonoid type. Usually colonial, less often solitary forms, predominantly marine forms. This most numerous class of modern sponges is represented by 2 orders: Siliceous and Quadruped sponges.
In Silica sponges, the skeleton consists of flint uniaxial needles and organic matter - spongin or spongin fibers alone, forming a reticulate, less often tree-branched, support of the body. These are mainly colonial forms, having the appearance of cortical or cushion-shaped fouling, unevenly grown lumps, plates or various kinds of tubular, funnel-shaped, stalk-like, bushy and other formations, up to 0.5 m or more in height. Siliceous horn sponges include those known to us Badyagi and several types Toilet sponges. Toilet sponges are used for toilet, medical and technical purposes. The fishery for these sponges is developed in the Mediterranean and Red Seas, off the coast of the island. Madagascar, Philippines, in the Gulf of Mexico and the Caribbean Sea. The most valued is the so-called Greek sponge(Euspongia officinalis).
Four-rayed sponges have a spherical, ovoid, goblet-shaped, cushion-shaped body, usually up to 0.5 m in height. The skeleton is formed by flint, usually four-rayed (hence the name) or their derivatives - uniaxial needles located radially in the body. Also colonial, less often solitary forms. They live mainly to a depth of 400 m. The family of four-ray sponges belongs to Drilling jaws, or Clions. These sponges are capable of making passages inside any calcareous substrate, leaving round holes with a diameter of about 1 mm on its surface. It is believed that the drilling mechanism is due to the simultaneous action of carbon dioxide released by the surface cells of the drilling sponges and the contractile forces of these cells. About 20 species, mainly in the shallow waters of warm seas. In our country there are 3 species, in the Japanese, Black, White and Barents Seas. These sponges are dangerous pests of oyster jars.
Class 2. Lime sponges(Calcispongiae). The skeleton of these sponges is formed by three-, four-beam and uniaxial needles made of calcium carbonate. The body is often barrel-shaped or tube-shaped. The only class of sponges that includes sponges that have all 3 types of channel systems. Calcareous sponges are small solitary (up to 7 cm high) or colonial organisms. Over 100 species, distributed exclusively in seas of temperate latitudes, mainly in shallow waters. Representatives Sicon, Sikandra, Leucandra, Ascetta.
Class 3. Coral sponges(Sclerospongiae). Colonial sponges. The width of the colonies is up to 1 m, height - 0.5 m. Known from the Mesozoic. The skeleton consists of a basal mass of aragonite or calcite and flint uniaxial needles. Living tissue only covers the surface of coral sponges with a thin layer (about 1-2 mm thick). Canal system of leukonoid type. A total of 10 species live in shallow water among the coral reefs of the West Indies, the western parts of the Pacific and Indian Oceans, in the Mediterranean Sea and off the island. Madeira.
Class 4. Glass sponges, or Six-beam sponges (Hyalospongia, or Hexactinellida). Known since the Cambrian. They were most diverse and numerous in the Cretaceous period of the Mesozoic era. Skeleton made of flint six-rayed needles (or their derivatives) with rays lying in three mutually perpendicular planes. Mostly single, bag-shaped, tubular, goblet-shaped or barrel-shaped, up to 1.5 m high. About 500 species. Oceanic organisms that usually live at depths of over 100 m. Glass sponges are very beautiful and are used as decorations. For example, a sponge basket of Venus, Euplectella, Hyalonema.
