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Which algae do not have flagellar stages? Class Flagellates




Term protoctists proposed at the end of the 20th century. This kingdom includes eukaryotic, relatively simply structured organisms. Among them: mushroom-like organisms - chytridiomycotes, oomycotes, slime molds, as well as algae (formerly lower plants) - green, brown, diatoms and others.

The main features of representatives of this kingdom: they often live in an aquatic environment; unicellular, colonial or multicellular; the body is not divided into vegetative organs; vegetative, asexual and sexual reproduction; in ontogenesis (individual development of the organism) there are no embryonic stages; nutrition is autotrophic and heterotrophic.

The mushroom-like organisms discussed below ( chytridiomycotes, oomycotes, slime molds) share features with both colorless flagellates (animals) and colored algae. Until recently, these organisms were considered in the kingdom of fungi ( Fungi) in the section of lower mushrooms.

Mushroom-like protoctists - Myxobionta

Division Chytridiomycota(Chytridiomycota)

Fig. 10. 1. A - "Black leg" cabbage, appearance of the diseased plant (pathogen Olpidium brassicae), B - cabbage olpidium in the cells of the root collar of cabbage seedlings: 1 – zoosporangia, 2 – zoospores; 3 – bare protoplasts, 4 – resting spores.

Rice. 10. 2. A - potato cancer, appearance of the lesion; B - synchytrium endobioticum: 1 - zoospores, 2 - summer cyst in the epidermal cell, 3 - beginning of cyst germination, 4 - disintegration into separate sporangia, 5 - copulation, 6 - winter cyst, 7 - cyst germination.

Oomikota Department(Oomycota)

Rice. 10. 3. Potato mushroom (Phytophthora infestans): a, b – potato leaves and tubers affected by late blight; c – mycelium and sporangiophores on a potato leaf; d, e – release of zoospores from zoosporangium; f, g – zoospore and its germination; h, i – conidia and its germination.

Department of slime molds (myxomycota)(Myxomycota)

Rice. 10. 4.A – trichium (Trichia): 1 – appearance of sporulation, 2 – part of the capillitium (special threads in sporulation that contribute to the scattering of spores) and spores; B– leocarpus (Leocarpus): 1 – appearance of sporulation, 2 – part of the capillium and spores.

Vegetative body of slime mold – plasmodium(mucous, non-sheathed multinuclear protoplasm), having a variety of colors: pink, lemon yellow, red, purple, etc. Plasmodium moves slowly, like amoebas, absorbing and digesting bacteria, small fungi, particles of decaying plants and animals. Their sizes vary from a few millimeters to 1 m in diameter, but their weight is small - up to 20-30 g.

During the period of vegetative development, slime molds live in damp, dark places. They crawl into the light to form fruiting bodies, sporangia and etalia, in which haploid spores are formed. The latter germinate into zoospores in water, and into myxamoebas in a humid environment. After a certain period of development, zoospores or myxamoebas copulate in pairs, forming diploid myxamoebas, which, dividing and growing repeatedly, form plasmodium.

Seaweed - Thallobionta, or Algae

Seaweed- the oldest photosynthetic organisms on Earth, which created its oxygen atmosphere. Algae primarily live in aquatic environments. About 30 thousand species of algae are known. Most of them live freely in the water column ( phytoplankton), some are attached to the bottom of reservoirs or underwater objects, or simply lie on the bottom ( phytobenthos). Some algae live on the soil, in the soil or on tree trunks.

Algae are unicellular, colonial or multicellular, ranging in size from a few micrometers to 60-100 m with a very wide variety of body shapes.

Reproduction in algae is varied: vegetative, asexual and sexual.

Vegetative propagation is carried out by budding, cell division in two, fragments of filaments (in multicellular filamentous organisms), disintegration of colonies and “nodules” (Characerous algae).

Asexuality is accomplished by spores: motile (zoospores) or immobile (aplanospores). Spores are single-celled, formed in special organs - sporangia or inside vegetative cells.

Sexual reproduction is carried out by gametes, which are formed in special unicellular organs of sexual reproduction: oogonia (female gametangia) and antheridia (male gametangia). The essence of sexual reproduction is the fusion of gametes and the formation of a zygote. After a period of dormancy, the zygote germinates, forming zoospores or a new plant. In the development cycle of algae, the ratio of diploid and haploid phases is different. If meiosis occurs during the germination of the zygote, then the algae is haploid throughout its life, and the diploid phase is represented by the zygote. In some, reduction division occurs in gametangia before the formation of gametes, then the diploid phase predominates in their life cycle, and the haploid phase is represented only by gametes. This change of haploid and diploid generations is called a change of nuclear phases.

The forms of the sexual process are varied:

isogamy- fusion of morphologically identical mobile gametes;

heterogamy- fusion of germ cells that differ in size and (or) mobility (behavior);

oogamy- fusion of gametes that differ sharply in shape, size and behavior; female gamete is a large, immobile egg, male gamete is small, usually mobile - sperm;

conjugation- fusion of the contents of two vegetative cells, physiologically performing the functions of gametes (Fig. 10. 5).

Rice. 10.5. Forms of the sexual process in algae: 1 – isogamy, 2 – heterogamy, 3 – oogamy, 4 – conjugation.

Large algae are used as food, as feed for farm animals, and in medicine they serve as raw materials for the production of agar, alginates, and iodine. Some representatives are used in the process of biological wastewater treatment and as bioindicators of water pollution.

Depending on the biochemical characteristics (set of pigments, composition of the cell wall, type of reserve substances), the following divisions of algae are distinguished: Red (Crimson), Diatoms, Brown, Green.

Department Red algae(purple) - Rhodophycota

There are about 3800 species. These are mainly inhabitants of the seas; a small part is found in fresh water bodies and in the soil. Among the purple algae there are immobile unicellular algae, filamentous and lamellar. Sizes from a few centimeters to 1-2 m (porphyry). The thallus of red algae is highly dissected and has the appearance of branched multicellular filaments attached to the substrate with the help of rhizoids (Fig. 10. 6).

Rice. 10. 6.Red algae .

Chromatophores in the form of grains or plates contain pigments: red ( phycoerythrin), blue ( phycocyan), green ( chlorophyll).

Phycoerythrin predominates in deep-sea algae. It masks other pigments and gives a bright red color. Shallow-water forms have a bluish color, since phycocyanins predominate in them.

The product of photosynthesis is a polysaccharide - purple starch, deposited in the cytoplasm. Cell walls, in addition to cellulose, are impregnated with a large amount of pectin substances, which strongly mucus and swell, forming a soft or cartilaginous general framework in which cell protoplasts are immersed. Some scarlet walls are impregnated with calcium carbonate and magnesium.

Red algae reproduce asexually and sexually. Motile (flagellar) stages are completely absent during reproduction. During asexual reproduction, sporangia are formed containing 1-4 passive spores. Sexual process oogamous. Female genital organ - karpogon has an abdomen (expanded basal part), in which the egg and process are located - trichogyna. The male reproductive organ of the antheridium is a small, colorless cell that carries haploid germ cells - spermation. The latter, without flagella, are passively transported by water currents and adhere to the trichogyne. At the point of contact, the walls of the spermatium and trichogyne dissolve, the nucleus of the spermatium penetrates into the abdominal cavity of the carpogonum, and merges with the female nucleus. After fertilization, a zygote is formed, and then diploid carpospores. A diploid thallus develops from carpospores, on which haploid thallus are formed as a result of reduction division. tetraspores. On the haploid thallus developing from tetraspores, reproductive organs are formed again, and the cycle repeats.

Sporophytes and gametophytes have similar or different structures.

Bagryanka– the best agarwood plants(anfelcius – Ahnfeltia); having highly mucilaginous pectin-cellulose walls. Porphyra ( Porphyra) is used as food (its industrial cultivation is developed in Japan). In some countries, scarlet mushrooms are used as feed for farm animals.

Division Diatoms–Diatomophycota

There are more than 10,000 species, distributed in the plankton of seas, oceans and fresh waters, in the upper layers of soil, in hot springs, and in snow. These are unicellular and colonial organisms. The protoplast of cells is differentiated into cytoplasm, nucleus, and vacuoles. A reserve product of carbohydrate nature is chrysolamine. Chromatophores are large, lamellar or granular, yellowish-brown, contain chlorophylls, fucoxanthin and other xanthophylls (diatoms belong to the group of brown-colored algae). Instead of a cell wall, a thin bivalve shell consisting of silica is formed. The larger valve (epithecium) is placed on a smaller valve (hypotheca), like a lid on a box. Under the shell there is a pectin wall (Fig. 10. 7).

Rice. 10. 7.Pinnularia (Pinnularia): a - view of the shell from the valve, b - view of the shell from the girdle, c - view of the algae from the valve, d - successive stages of cell division.

According to the shape of the cells, all diatoms are divided into two groups: centric (radially symmetrical) - mainly planktonic algae of the seas and oceans and pennate (bilaterally symmetrical) - often freshwater benthic and ground algae.

Diatoms reproduce by longitudinal, most often vegetative cell division in two, followed by the completion of one flap of the silicon shell - the hypotheca. The sexual process is isogamy and oogamy.

Diatoms live in a diploid state (that is, the nuclei contain a double set of chromosomes), and only their gametes are haploid.

The role of diatoms in nature is great: they serve as the main food for a significant number of aquatic organisms (they have high nutritional value); take a primary part in sedimentation (a huge number of shells of dead diatoms form diatomaceous ooze at the bottom of reservoirs).

Department Brown algae–Fucophycota

Contains about 1,500 species, mainly growing in all seas. The size of these algae ranges from a few millimeters to 20-100 m. The thallus has the form of either branched mononuclear and multinuclear filaments, or it has a complex structure (it is, as it were, divided into stem-like and leaf-like parts and has the rudiments of primitive tissue - assimilation, storage, mechanical and conductive ) (Fig. 10. 8).

Rice. 10. 8. Brown algae .

The main pigments of brown algae are: chlorophylls A And With, carotene, xanthophyll. The latter pigment gives the algae a characteristic brown color.

The cell walls consist of two layers: the outer layer, containing alginic acid, and the inner layer, formed by a type of cellulose - algulose. The cells have one large nucleus, large vacuoles with cell sap and small vacuoles containing tannins, chromatophores in the form of disks or grains. Reserve substances are laminarin, mannitol and, in small quantities, fats.

Reproduction of brown algae: vegetative (parts of thalli), asexual (zoospores) and sexual (isogamy, heterogamy and oogamy).

The most famous genus of brown algae is kelp(Laminaria)(Fig. 10. 9).

Rice. 10. 9.Kelp (Laminaria): a – general appearance of the sporophyte; b – section of a multicellular thallus with zoosporangia; c – zoospores; d – male gametophyte with antheridia; e – female gametophyte with oogony.

Representatives of this genus (sugar kelp - Laminaria saccharina, kelp palmate - L. digitata, Japanese kelp – L. japonica) form entire plantations in the northern and Far Eastern seas (in places with constant water movement, near open shores). They are also known as sea kale. Their thallus is divided into rhizoids, “stem” and “leaf” parts. The internal structure of the thallus is quite complex; differentiation into primitive tissues is noticeable. The thallus is perennial, the plate is replaced annually.

The thallus described is a diploid sporophyte. On the surface of the leaf blade of the sporophyte, single-locular zoosporangia are formed in groups, containing numerous zoospores. Zoospores are haploid and physiologically unequal. When germinating, zoospores produce microscopic-sized gametophytes - growths in the form of branching threads consisting of a small number of cells.

Sexual reproductive organs are formed on the growths: female (oogonium) and male (antheridia). Antheridia are multicellular (a sign of a higher organization). In gametangia, one gamete is formed (egg and sperm, respectively). After fertilization, a new diploid sporophyte grows from the zygote without a dormant period.

Kelp is used: as food (dietary food rich in iodine); for the production of medicines (contain iodine and polysaccharides, iodine concentration is at least 0.1%); to obtain algin polysaccharide (used as jelly-forming substances in the confectionery industry, in the manufacture of varnishes and paints); for feed for farm animals; as a fertilizer (rich in potassium).

Green algae department–Chlorophycota

The largest department, which includes up to 20 thousand species. They live mainly in fresh waters and seas, some on snow, tree trunks and soil. Green algae have all types of thallus organization: unicellular, colonial, multicellular filamentous and lamellar (Fig. 10.10).

Rice. 10. 10. Green algae.

Green algae contain pigments - chlorophylls " A" And " V", carotenes and xanthophylls (the last two pigments do not mask chlorophyll, and therefore the algae are green in color). The reserve product is starch, which is deposited in the chromatophore around the pyrenoid. Chromatophores of various shapes: cup-shaped (Chlamydomonas, Chlorella), ribbon-shaped (Spirogyra). In the stroma of green algae chromatophores there is a light-sensitive eye - stigma. Cell walls usually contain cellulose and pectins. The endoplasmic reticulum is more developed than that of other algae. All types of reproduction and all types of sexual processes are represented.

Department representatives:

Genus Chlamydomonas(Chlamydomonas) from the class Volvoxaceae - includes about 500 of the most primitive species of the department of green algae. These include unicellular, round or pear-shaped, biflagellate, having a nucleus, cytoplasm, and a chromatophore with a pyrenoid; two pulsating vacuoles, a red eye that orients its movement under the influence of light; wall consisting of pectin substances and hemicellulose. Capable of photosynthesis, but can consume ready-made organic substances. Most often found in polluted water (puddles, ditches). Reproduces vegetatively, asexually and sexually. Asexual reproduction is carried out by dividing the mother cell into 2, 4, 8 parts, from which zoospores are formed, which then turn into small vegetative individuals. During sexual reproduction, gametes are formed; when they fuse, a zygote is formed, which overwinters, and in the spring it divides and forms young individuals.

Chlorella (Chlorella) from the Chlorococcal class - a very widespread algae that is found in plankton and benthos of various water bodies, in moist soil, on the bark of trees and is a common symbiont of lichens. Chlorella is a unicellular, spherical algae that lacks mobility (passively transported by water currents). Its protoplast contains a bell-shaped chromatophore with a cavity containing a nucleus. Reproduction is only asexual, producing four or eight immobile spores.

Genus Ulotrix(Ulothrix) from the Ulothrix class includes 25 species that prefer fresh and brackish, clean water bodies. Ulotrix is ​​a green multicellular filamentous algae. The thread is unbranched, up to 10 cm long. The lowest cell of the thread is elongated into a long, colorless rhizoid (foot), which attaches the algae to the substrate. The remaining cells are identical, each has one chromatophore with pyrenoids, a nucleus, and a thin, sometimes mucus-like, cellulose wall. Asexual reproduction is carried out by cell division into 2 or 4 four-flagellate zoospores, which emerge into the water, attach to underwater objects, divide and form an algae thread. During sexual reproduction (isogamy), small mobile gametes are formed, which enter the water and fuse in pairs. The resulting zygote is covered with a dense shell; under favorable conditions, it is divided into 4 flagellated spores, which, attaching to underwater objects, divide to form a thread of algae.

Ulva(Ulva) from the class Ulothrixaceae is widely distributed along the coast of the southern and northern seas. Its thallus is multicellular, lamellar; plates of two layers of cells. At the base, the plate narrows into a short petiole with a sole, with which it is attached to a solid substrate. The ulva plate can easily break off and continue to live in this state. There are no specialized reproductive organs. Potentially, each cell can become a sporangium in a diploid generation, or a gametangium in a haploid generation.

Spirogyra (Spirogyra) from the class Conjugates - a multicellular non-branching filamentous algae that forms the bulk of bright green mud in ponds. The cells contain one nucleus, a vacuole in the center, and ribbon-shaped, spirally twisted chromatophores in the near-wall layer of cytoplasm, along the midline of which there are pyrenoids surrounded by starch grains. Vegetative reproduction - by fragments of filaments, asexual reproduction - by immobile aplanospores, formed one in each cell. Sexual reproduction - conjugation: processes grow from the opposite cells of two adjacent filaments, which merge (the contents of one cell flow into another), forming a zygote; after a period of rest, the contents of the zygote are divided twice, forming 4 cells, 1 of which grows into a new individual.

Caulerpa(Caulerpa) from the class Siphonaceae - has a large thallus, covered with a thick membrane, no cellular partitions; the vacuole and wall cytoplasm with numerous nuclei are continuous. Externally, siphonaceae are similar to leafy plants. There is no asexual reproduction by zoospores; sexual reproduction occurs according to the type of isogamy.

Vaucheria(Vaucheria) from the Siphon class. This algae lives in moist soil, in fast-flowing and stagnant bodies of water. Some species of this genus prefer brackish water. The thallus of the voucheria is unicellular, multinucleate, in the form of thin green creeping threads. Chloroplasts are lens-shaped and spindle-shaped, without pyrenoids. The reserve substance is oil. Reproduction is by fragments of filaments, asexual - by multinucleated polyflagellate zoospores, aplanospores and cysts. The sexual process is oogamy.

Hara (Chara) from the class Charovaya - found in fresh and brackish water bodies (but does not tolerate strong salinity). These are large, up to 50 cm or more, multicellular algae that prefer clean water bodies enriched with calcium salts. In its appearance, hara resembles higher plants, in particular horsetails. The so-called stem is dissected into so-called nodes and internodes; “leaves”—whorls of short lateral branches—extend from the nodes, and are attached to the substrate by rhizoids. Chromatophores are small, disc-shaped. Vegetative reproduction is by nodules, there is no asexual reproduction, sexual reproduction is oogamy. The reproductive organs are multicellular. The genus Hara includes 40 species. Representatives of the Charovs are sometimes allocated to a special department, the Charovs ( rice. 10. 11).

Rice. 10. 11. Charovaya algae.

Plant taxonomy deals with the study and description of plant species and their distribution into groups based on the similarity of structure and family relationships between them, creating a classification.

The main taxonomic categories in the classification of plants are species, genus, family, order, class, division, kingdom. Sometimes intermediate taxonomic categories are used: subspecies, supergenus, subkingdom, superkingdom and others.

Table 1. Taxonomic categories and taxa using potatoes as an example:

Lower plants, or algae

General characteristics. Algae are a large group of photosynthetic, predominantly aquatic, photoautotrophic eukaryotic plants. Most algae are characterized by: mainly an aquatic habitat, but a large number of species are also found on land (on the soil surface, wet stones, tree bark, etc.).

Most algae are suspended in the water column or actively floating ( phytoplankton), some lead an attached lifestyle ( phytobenthos). Green algae live in the coastal zone at shallow depths, brown algae contain pigments that allow them to live at a depth of up to 50 m, and a set of photosynthetic pigments of red algae allows them to live at a depth of 100-200 m, and some representatives are found at a depth of up to 500 m.

The body of algae can be unicellular, colonial or multicellular. If it is a multicellular organism, then its body is not differentiated into organs and tissues and is called thallus, or thallus. In complexly organized algae, elementary differentiation of the body can be observed, imitating the organs of higher plants - rhizoids, stem-like and leaf-like formations appear.

Cell structure. The cells of most algae have a cell wall formed by cellulose and pectin (only in primitive motile unicellular and colonial algae; in zoospores and gametes, the cells are limited only by the plasmalemma); the cell wall is almost always covered with mucus. The protoplast of cells consists of cytoplasm, one or more nuclei and chromatophores (plastids) containing chlorophyll and other pigments; chromatophores contain special formations - pyrenoids- protein bodies around which starch accumulates, formed during photosynthesis. Vacuoles are usually well developed; sometimes (especially in motile cells) there are special contractile vacuoles; Most mobile algae have flagella and a light-sensitive formation - an eye, or stigma, thanks to which the algae have phototaxis(the ability to actively move the entire organism towards the light).

Reproduction is asexual and sexual, asexual reproduction carried out using zoospores (motile) or spores (immobile). Asexual reproduction can also be carried out using vegetative propagation by fragmentation of the thallus, cell division of unicellular algae, and in colonial algae - due to the collapse of colonies.

Sexual reproduction occurs through the formation of many specialized germ cells - gametes and their fusion (fertilization), which is a sexual process. As a result of the fusion, a zygote is formed, which is covered with a thick protective shell. After a period of rest (less often immediately), the zygote grows into a new individual, formed mainly by meiotic division (zygotic reduction). This completes sexual reproduction. The forms of the sexual process in algae are isogamy, heterogamy, oogamy. For some algae, the sexual process takes place in the form conjugation. In highly organized algae, gametes develop in special organs of sexual reproduction: eggs - in oogonia, spermatozoa - in antheridia. In diploid algae there is sporic reduction– meiosis occurs during the formation of zoospores from which they develop gametophytes. Gametophytes mitotically form gametes, and when a zygote is formed, a diploid algae is formed that forms spores - sporophyte. In haploid algae, spores and gametes can develop mitotically in the cells of the same individual.

Origin of algae usually associated with the absorption of cyanobacteria into a eukaryotic aerobic cell, which became chloroplasts. Recently, a hypothesis has emerged that explains why chloroplasts in different sections of algae differ sharply in structure and set of photosynthetic pigments - the ancestors of chloroplasts in different groups of algae may have had different photosynthetic bacteria. On the other hand, the same photosynthetic bacteria could be captured by different host organisms at different stages of evolutionary development. And the similarity of mitochondria in all eukaryotic organisms indicates that mitochondria originated from a single ancestor, closest to the modern aerobic non-sulfur purple bacterium, and the symbiosis of an anaerobic heterotrophic prokaryote and oxidizing bacteria developed before photosynthetic bacteria entered the symbiotic organism.

Red algae, or purple algae. One of the subkingdoms of the Plant kingdom. Among the purple algae there are both unicellular and multicellular filamentous and lamellar algae (Fig.). Of the 4,000 species, only 200 have adapted to life in fresh water bodies and on soil, the rest are inhabitants of the seas. The color of red algae is varied, it is determined by the different quantitative content of pigments: chlorophylls A And d, carotenoids and phycobillins: red (phycoerythrin) and blue (phycocyanin). Moreover, the color of algae is different at different depths; in shallow water they are yellow-green, then pink and at a depth of more than 50 m they become red. The maximum depth at which scarlet beetles have been found is 500 m, where they use the blue-violet wavelengths of sunlight. The shorter the wavelength, the greater its energy, so light waves with the shortest wavelength penetrate to the greatest depth. Moreover, to divers they appear black, they absorb all the light falling on them so effectively; they look red on the surface. Pigments are concentrated in chromatophores that look like grains or plates; there are no pyrenoids.

The cell wall is pectin-cellulose, capable of strong mucus formation, as a result of which in some algae the entire thallus acquires a slimy consistency. Many people may have calcium carbonate (CaCO 3) or magnesium (MgCO 3) deposited in their walls.

The product of assimilation is purple starch, similar in structure to glycogen. Unlike ordinary starch, when stained with iodine, it acquires a brown-red color.

There is an alternation of sexual (haploid,n) and asexual (diploid 2n) generations. Asexual reproduction of red algae is carried out using haploid non-flagellated spores, developing meiotically in sporangia (sporic reduction). Purple females are characterized by an oogamous sexual process.

Gametophytes develop from spores; gametophytes produce non-flagellated male and female gametes. Most scarlet plants are dioecious plants. A diploid sporophyte develops from the zygote. Gametophyte and sporophyte are indistinguishable in appearance. Vegetative propagation by parts of the thallus is typical only for low-organized scarlet plants.

Absence of flagellated forms- a characteristic feature of purple skin. It is assumed that scarlet beetles originated from eukaryotes that did not yet have flagella; on this basis, they are classified as a separate subkingdom.

Scarlet flowers are of great practical importance. Agar-agar is obtained from them, which is used in the confectionery and microbiological industries; many of them are raw materials for the production of glue. Iodine and bromine are obtained from the ash of scarlet plants. Some red algae are used to feed livestock. In Japan, China, the islands of Oceania and the USA, scarlet mushrooms are used as food. Purple considered a delicacy. red algae Chondrus used to produce carrageens - special polysaccharides that suppress the reproduction of the AIDS virus.

Department Brown algae. The department includes about 1500 species of multicellular, mostly macroscopic (up to 60-100 m) algae, leading attached ( benthic) Lifestyle. Most often they are found in shallow coastal waters of all seas and oceans, sometimes far from the coast (for example, in the Sargasso Sea).

Structure. The thalli of brown algae have the most complex structure among algae. Unicellular and colonial forms are absent. In highly organized cells, the thallus partially differentiates, forming tissue-like anatomical structures (for example, sieve tubes with oblique partitions). As a result of this, the formation of “stem” and “leaf” parts of the thallus occurs, performing heterogeneous functions. Algae are fixed in the substrate using rhizoids.

The cells of brown algae are mononuclear with numerous chromatophores that look like disks or grains. The brown color of algae is due to a mixture of pigments (chlorophyll, carotenoids, fucoxanthin). The main reserve substance is laminarin(a polysaccharide with bonds between glucose residues other than starch), deposited in the cytoplasm. The cell walls are heavily mucused. The mucus helps retain water and thus prevent dehydration, which is important for intertidal algae.

Reproduction sexual and asexual. The forms of the sexual process are different - isogamy, heterogamy, oogamy. There is an alternation of the asexual generation - the sporophyte and the sexual generation - the gametophyte. Sporophyte and gametophyte can be either the same or different in size and shape. Asexual reproduction occurs with the help of numerous biflagellate zoospores, meiotically formed in unicellular, less often multicellular zoosporangia of the sporophyte. On gametophytes ( n) oogonia and antheridia are formed, in which gametes are formed, and a sporophyte develops from the zygote. Vegetative propagation is carried out by parts of the thallus.

Kelp. Representatives of the kelp genus are known as “seaweed” (Fig.). They are widespread in the northern seas. A mature sporophyte of kelp is a diploid plant with a length of 0.5 to 6 or more meters.

The kelp thallus has one or more leaf-like plates located on a simple or branched stem-like structure attached to the substrate by rhizoids. The stem-like formation with rhizoids is perennial, and the blade dies every year and grows back in the spring.

Reproduction. Zoosporangia are formed on the surface of the plates, in which, as a result of meiotic division, haploid zoospores with two unequal flagella are formed. They germinate into microscopic filamentous gametophytes, on which reproductive organs are formed. The sexual process is oogamous. In oogonia and antheridia, one gamete is formed; after fertilization, a diploid sporophyte develops from the zygote without a resting period. Thus, in kelp there is an alternation of generations; the diploid sporophyte forms zoospores from which haploid gametophytes develop.

Typical representatives brown algae are kelp, macrocystis (its huge thallus reaches a length of 50-60 m), fucus, sargassum.

Meaning . Being autotrophs, algae are the main producers (i.e. producers) of organic substances in various bodies of water. In addition, during the process of photosynthesis they release oxygen, thereby creating favorable conditions for the life of not only aquatic, but also terrestrial organisms.

Algae play a huge role in human life: they are food for many commercial fish and other animals, they serve as additives in various nutritional mixtures, they are part of compound feeds, and some algae (for example, “sea kale”) are eaten. The cells of brown algae on top of the cellulose cell wall are covered with pectin, consisting of alginic acid or its salts; when mixed with water (in a ratio of 1/300), alginates form a viscous solution. Alginates are used in the food industry (for the production of marshmallows, marmalades), in perfumery (for the production of gels), in medicine (for the production of ointments), in the chemical industry (for the production of adhesives, varnishes). In the textile industry, they are used to make fade-resistant and waterproof fabrics. Seaweed is used to produce fertilizers, iodine, and bromine. Iodine was previously obtained exclusively from brown algae. Brown algae can serve as an indicator of the location of gold; they are able to accumulate it in the cells of the thallus.

Green algae department. The department unites about 13,000 species, this is the most extensive department among algae. A distinctive feature is the pure green color of the thalli, caused by the predominance of chlorophyll over other pigments. Distributed everywhere. Mostly green algae are inhabitants of fresh water bodies, but there are also marine species. Some live on land. There are species that enter into symbiotic relationships with some animals (sponges, coelenterates, tunicates) and fungi.

Structure . Green algae are represented by unicellular, colonial and multicellular forms. The cells have a dense cellulose-pectin shell and can be mononuclear or multinuclear. The cytoplasm contains chromatophores with pigments (mainly chlorophyll a and b). In addition to chlorophyll, cells contain carotenoids, xanthophylls and other pigments. Chloroplasts are similar to plastids of higher plants. The main storage substance accumulated in chloroplasts is starch.

Reproduction . Most green algae are haploid. Reduction of genetic material occurs after the formation of a zygote - zygotic reduction. But a regular alternation of sexual and asexual generations is also often observed.

Green algae are considered the ancestors of land plants: they have the same sets of photosynthetic pigments, the shell contains not only cellulose, but also pectin, a reserve substance is starch, reserve nutrients accumulate not in the cytoplasm (like other algae), but in plastids.

Genus Chlamydomonas. In translation - a single organism covered with ancient Greek clothing - chlamys. Single-celled algae that live mainly in shallow water bodies polluted with organic matter (Fig. 60). The Chlamydomonas cell has a round or oval shape, the front end is pointed in the form of a spout. It contains two flagella of equal size, with the help of which Chlamydomonas moves in water. The cell membrane is pectin-cellulose. In the center of the cell there is a cup-shaped chromatophore with a large pyrenoid. The nucleus is located in the recess of the chromatophore. At the anterior end of the cell there is a stigma and pulsating vacuoles.

Chlamydomonas reproduces both asexually and sexually. The haploid phase predominates in the life cycle. During asexual reproduction, Chlamydomonas loses its flagella, the contents of the cell are divided mitotically twice, and four daughter cells are formed under the shell of the mother cell. Each of them secretes a shell and forms flagella, turning into zoospores.

Under the influence of enzymes, the shell of the mother cell is destroyed, and they come out, grow to the size of the mother cell and also proceed to asexual reproduction (Fig. 61).

The sexual process in many species of Chlamydomonas occurs according to the type of isogamy. The cell contents divide to form 8 to 32 gametes, which resemble zoospores but are smaller in size. Cells with different sex signs merge. The resulting zygote becomes covered with a thick membrane and enters a period of rest. When favorable conditions occur, the contents of the zygospore are divided meiotically, and four haploid cells are formed, each of which becomes a new chlamydomonas.

In some species, the sexual process is carried out according to the type of heterogamy (both gametes are mobile, but the female gamete is larger than the male) or according to the type of oogamy (the female gamete is immobile).

Genus Chlorella. A single-celled algae that lives in fresh and salty water bodies, on moist soil, and rocks (Fig. 62). The cells look like green balls with a diameter of up to 15 microns. It has no flagella, ocelli or contractile vacuoles. The cells have a cup-shaped chromatophore with or without a pyrenoid and a small nucleus. Chlorella uses solar energy much more efficiently for photosynthesis. If terrestrial plants use about 1% of solar energy, then chlorella uses 10%. The sexual process for this alga is not known. Asexual reproduction occurs by mitotic division of the contents of the mother cell twice or three times. As a result of division, four or eight immobile spores are formed ( aplanospores). After the maternal membrane ruptures, the cells come out, increase in size and divide again.

Chlorella is interesting because its cells contain a large amount of nutrients - 50 complete proteins, fatty oils, carbohydrates, vitamins A, B, C and K, and even antibiotics (and it contains 2 times more vitamin C than lemon juice). Nowadays, you can buy chlorella in an online store, for example in this one https://elitnie-chai.ru/superfood/hlorella.html. It multiplies so intensively that the number of its cells increases a thousandfold per day.

Chlorella was the first algae that humans began to grow in culture. It was used as an experimental object to study some stages of photosynthesis. In some countries (USA, Japan, Israel), pilot plants for growing chlorella have been created and the possibility of using chlorella as a source of food for humans has been studied. The Japanese have learned to process chlorella into a white powder rich in proteins and vitamins. It can be added to flour for baking baked goods. In addition, chlorella is used as a source of cheap livestock feed and in biological wastewater treatment.

Class Ulotrix. Multicellular algae, the thallus of which is filamentous or lamellar. The most famous representatives belong to the genus Ulotrix and the genus Ulva. Non-branching threads of ulotrix, attaching to underwater objects - stones, piles, snags, etc., form green tufts. All cells (with the exception of the elongated colorless rhizoidal cell, with the help of which the algae attaches) have a similar structure. In the center of the cell there is a nucleus and a chromatophore, which has the shape of an open ring. The chromatophore contains several pyrenoids. The growth of the thread in length occurs due to cell division in the transverse direction. It grows in fast-flowing rivers and leads an attached lifestyle (Fig. 65).

Under favorable conditions, ulothrix reproduces by zoospores with four flagella. They are formed in even numbers (2, 4, 8 or more). Zoospores come in different sizes - large and small. The ability to actively move zoospores contributes to the dispersal of ulotrix.

The sexual process occurs according to the type of isogamy. Individual cells of the filament transform into gametangia, in which biflagellate gametes are formed. When gametes fuse, a four-flagellate zygote is formed. Then it discards its flagella and goes into a resting state.

Subsequently, the zygote divides reductionally, giving rise to four cells, each of which forms a new thread.

An important evolutionary line is associated with the transition from a filamentous thallus to a lamellar one. This is exactly the shape of the thallus in representatives of the genus Ulva (sea lettuce). Externally, the ulva resembles a thin green sheet of cellophane; its thallus up to 150 cm consists of two layers of cells. Ulva is characterized by alternation of generations, and the diploid sporophyte and haploid gametophytes do not differ in appearance. This alternation of generations is called isomorphic.

Genus Spirogyra. Green filamentous algae up to 8-10 cm long (Fig. 63). Numerous species of spirogyra live in fresh water bodies and in stagnant water. Clusters of Spirogyra filaments form mud. The threads are unbranched, formed by one row of cylindrical cells. There are no flagellar stages.

In the center of the cells there is a large nucleus. It is surrounded by cytoplasm, diverging in the form of strands from the center of the cell to the periphery. Here they connect with the wall layer of the cytoplasm. The strands penetrate a large vacuole. The cells contain ribbon-shaped, spiral-shaped chromatophores. They are located wall-to-wall on the inside of the shell. In different species of Spirogyra, the number of chromatophores ranges from 1 to 16. Large colorless pyrenoids are located in large numbers in the chromatophores. Outside, the algae is surrounded by a mucous sheath.
Fig... Ladder conjugation of Spirogyra

Algae grow in length by transverse cell division. Spirogyra reproduces asexually and sexually. Asexual reproduction is carried out by parts of the threads when they accidentally break.

The sexual process is carried out by conjugation (Fig. 64). Conjugation can be ladder or lateral. In ladder conjugation, two strands are parallel to each other. Adjacent cells form dome-shaped outgrowths that grow towards each other.

At the point of contact, the partitions separating the cells dissolve, and a channel is formed connecting both cells. The contents of one cell (male) are rounded and flow through the tube into another (female), and their contents (primarily the nuclei) merge. With lateral conjugation, fertilization occurs within one thread. In this case, the fusion of protoplasts of two adjacent cells is observed.

The zygote formed as a result of fertilization is surrounded by a thick cell wall and enters a period of rest. In spring, the zygote undergoes reduction division and forms four haploid nuclei. Three nuclei degenerate, and the fourth divides mitotically and gives rise to a new haploid thread. Thus, Spirogyra goes through its life cycle in the haploid phase; only its zygote is diploid.

Key terms and concepts

1. Plant taxonomy. 2. Phytoplankton, phytobenthos. 3. Thallus, thallus. 4. Phototaxis. 5. Crimson starch. 6. Pyrenoids. 7. Gametophyte and sporophyte of kelp. 8. Kelp. 9. Chlorella, chlamydomonas. 10. Aplanospores. 11. Ulotrix, ulva. 12 Isomorphic alternation of Ulva generations. 13. Spirogyra

Basic review questions

  1. The main taxonomic categories used in plant classification.
  2. Characteristics of scarlets.
  3. Characteristics of brown algae.
  4. The meaning of brown algae.
  5. Characteristics and representatives of green algae.
  6. Reproduction of Chlamydomonas, Chlorella.
  7. Reproduction of Ulothrix, Spirogyra.
  8. Reproduction of Ulva.

Unicellular, coenobial and colonial forms of algae with a monad (flagellate) body structure; these include almost all Euglenophyta, b. h. Pyrrophyta and Chrysophyta, separate classes. Xanthophyta and Chlorophyta.

  • - see N-antigens...

    Dictionary of microbiology

  • - a group of lower, mostly water districts. Unicellular or multicellular, solitary and colonial forms ranging in size from several. micrometers to tens of meters. In multicellular V. the thallus is often branched,...

    Agricultural Encyclopedic Dictionary

  • - lower plant organisms. V.'s body has a simple structure and is not divided, like in higher flowering plants, into roots, stems and leaves...

    Agricultural dictionary-reference book

  • - premium group water organisms that usually contain chlorophyll and produce organic. in the process of photosynthesis...

    Natural science. encyclopedic Dictionary

  • - a group of lower Slothaceous plants that have chlorophyll and are capable of photosynthesis. They are divided into 6 types: heteroflagellates, brown, red, green, diatoms, blue-green...

    Explanatory dictionary of soil science

  • - class of protozoa. Single-celled organisms that, at a certain stage of development, have whip-like devices for movement. Flagella give them sensitivity...

    Scientific and technical encyclopedic dictionary

  • - a vast and heterogeneous group of primitive, plant-like organisms...

    Collier's Encyclopedia

  • - unicellular, coenobial and colonial forms of algae with a monad body structure; these include almost all Euglenophyta, b. including Pyrrophyta and Chrysophyta, separate classes. Xanthophyta and Chlorophyta...

    Dictionary of botanical terms

  • - see rhizoplasts...

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    Large medical dictionary

  • - microscopic unicellular, single-flagellated autotrophic marine planktonic algae with an intracellular silica, usually hollow skeleton...

    Geological encyclopedia

  • - parts of the canalicular system of sponges, lined with cells with a tourniquet each, surrounded by a protoplasmic collar...

    Encyclopedic Dictionary of Brockhaus and Euphron

  • - flagellates, unicellular and colonial organisms that have flagella as organs of movement. Some groups of life, for example, euglenaceae, are classified by botanists as plants, and by zoologists as animals...

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  • - flagellate pl. A class of unicellular protozoa, characterized by the presence of flagella...

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"FLAGELLATE ALGAE" in books

author

From the book Animal World of Dagestan author Shakhmardanov Ziyaudin Abdulganievich

1.2. Type Sarcomastigophora, or Sarcoflagellates, Sarcodaceae and Flagellates (Sarcomastigophora)

From the book Animal World of Dagestan author Shakhmardanov Ziyaudin Abdulganievich

1.2. Type Sarcomastigophora, or Sarcoflagellates, Sarcodae and Flagellates (Sarcomastigophora) There are 18,000 species of them, they have pseudopods - non-permanent outgrowths of the cytoplasm or flagella, and sometimes both. The type has two classes: 1) Sarcodaceae

1.2.2. Class Flagellates (Mastigophora), or Flagellates, Flagellates

From the book Animal World of Dagestan author Shakhmardanov Ziyaudin Abdulganievich

1.2.2. Class Flagellates (Mastigophora), or Flagellates, Flagellates Flagellates (flagellates) include more than 6 thousand species of protozoa, unicellular and colonial organisms that live in the seas, fresh water bodies, in soil and in the organisms of multicellular animals. Their body shape

Seaweed

From the book Sushi and rolls at home author Kostina Daria

Seaweed

author Roza Volkova

Brown algae

From the book Seafood that Heals the Body author Roza Volkova

Seaweed

From the book Seafood that Heals the Body author Roza Volkova

Algae Lower plants Botanists usually divide all plants into higher and lower. In everyday life, we meet mainly with higher plants, that is, with those that have leaves, stems and roots. Higher plants include mosses, mosses, horsetails and ferns,

Seaweed

From the book Crossword Guide author Kolosova Svetlana

Seaweed

From the book The History of Our Deception, or How to Eat, What to Treat, How to Avoid Radiation in order to Stay Healthy author Mizun Yuri Gavrilovich

Algae Algae contains almost all vitamins and essential micro- and macroelements, such as iodine. It breaks down fatty elements, which are then easily removed from the body. Seaweed also removes toxins and strengthens the skin. In many seaweeds

According to their characteristics (color, structure, methods of reproduction, etc.), algae are divided into several types (divisions): green, blue-green, golden, diatoms, yellow-green, pyrrophytic, euglenic, red and brown algae.

Let's give a brief description of the types.

Green algae - Chlorophyta

Unicellular, colonial, multicellular and noncellular forms. Multicellular forms are represented mainly by filamentous algae. Some are distinguished by a complex internal structure, reminiscent of higher plants in appearance.

Algae are purely green in color, however, in addition to green chlorophyll, the chromatophores contain yellow pigments - carotene and xanthophyll. The cell membrane consists of fiber. Chromatophores with pyrenoids.

Reproduction is carried out by vegetative, asexual and sexual means. Vegetative propagation occurs by dividing the organism into parts. Asexual reproduction is carried out by motile zoospores with flagella of equal size (usually 2-4 of them) or aplaiospores - immobile spores.

With the help of zoospores, green algae not only reproduce, but also disperse. The sexual process of reproduction is varied. Representatives of green algae are Chlamydomonas, Spirogyra, Chlorella, Ulothrpx, Cladophora, Closterium, etc.

Blue-green algae - Cyanophyta

Unicellular, colonial and filamentous forms. Algae have blue-green, yellow-green, olive green and other types of colors. The color is explained by the presence of four pigments in blue-green algae: green chlorophyll, blue phycocyan, red phycoerythryp-pa and yellow carotene. These algae do not have a formed chromatophore and nucleus, flagellar stages and the sexual process are absent. Blue-green algae include: oscillatoria, nostoc, gleotrichia, anabena, etc.

Golden algae - Chrysophyta

Single-celled and colonial forms. They contain chlorophyll and phycochrysipus, which is why the color of representatives of this group of algae is golden or brownish-yellow. The cells are in some cases naked or covered with a poorly differentiated protoplasmic membrane; golden algae are found, the body of which is dressed in a shell or enclosed in a house.

Some forms are mobile and move with the help of flagella, while other forms are immobile in a vegetative state. They reproduce by division or zoospores.

Capable of forming cysts to withstand unfavorable conditions. The sexual process is very rare. Representatives of this type of algae are mallomonas, dinobrion, chrysameba, etc.

Diatoms - Bacillariophyta

Unicellular and colonial organisms with a silicified shell consisting of two halves called valves. Chromatophore I<ел-того или светло-бурого цвета от наличия в нем, кроме хлорофилла, бурого пигмента диатомина. Размножение осуществляется путем деления клеток на две, у некоторых диатомовых наблюдается образование двужгутиковых зооспор. Известен половой процесс. К диатомовым водорослям относятся пинну л я р ия, навикула, плевросигма, гомфонема, сиредра, мелозира и др.

Yellow-green, or heteroflagellate, algae - Xanthophyta, or Heterocontae

These include unicellular, colonial, filamentous and noncellular forms. These algae contain, in addition to chlorophyll, yellow pigments - xanthophyll and carotene; their color varies from light to dark yellow-green. Reproduction occurs by longitudinal cell division, zoospores (they are characterized by the presence of two flagella of unequal size and unequal structure), and autospores. The sexual process is known. Representative: botridium.

Pyrrophyte algae - Pyrrophyta

Unicellular and colonial forms. In addition to chlorophyll, algae contain the pigment pyrrophyll, which gives the algae a brown and brownish-yellow color. The cells are naked or covered with armored membranes. They reproduce by division, zoosiors, autosiors. They form cysts. Sexual reproduction is rare. Pyrrophyte algae include: peridinium, ceracium, etc.

Euglenophyta - Euglenophyta

Unicellular motile forms with one or two flagella, sometimes without them; the cells are bare, the role of the shell is played by the outer layer of protoplasm, sometimes the cell is located in the house. Most algae are green in color, sometimes light green due to the presence of xaptophylla. Reproduction occurs by longitudinal division, the sexual process is unknown. Representatives of euglena algae are euglena and facus.

Red algae, or purple algae, Rhodophyta

They live mainly in the seas, only a few live in fresh waters. These are multicellular algae, colored red.

(with different shades). The color of algae is associated with the presence in them, in addition to chlorophyll, of other pigments - phycoerythrin and phycocyan.

Asexual reproduction is carried out by aplano-spores. The sexual process is very complex and is characterized by the presence of male organs - antheridia and female organs - oogonia, or carpogones.

The representative is batrachospermum.

Brown algae, Phaeophyta

The name was given due to the yellow-brown color of the thallus, caused by the presence, in addition to green chlorophylls, of a large number of brown carotenoid pigments. Multicellular, predominantly macroscopic algae (the largest organism living in water is the brown algae macrocystis, which reaches a length of 60 m, growing by 45 cm per day).

Reproduction is vegetative, asexual and sexual. Gametes and zoospores bear two flagella on the side, different in length and morphology. Brown algae are widespread in all seas of the planet; they often form underwater forests, reaching their greatest development in the seas of temperate and subpolar latitudes, where they are the main source of organic matter in the coastal zone. In tropical latitudes, the largest accumulation of brown algae is in the Sargasso Sea. Representatives of only a few genera live in desalinated and fresh waters, for example, Pleurocladia, Streblonema, Lithoderma.

Flagellates are the oldest group of protozoa, lying at the root of the family tree of the animal world and connecting animals with the plant world. Back in the middle of the century before last, the famous Russian biologist L. S. Tsenkovsky (1822-1887) pointed out the absence of a sharp boundary between flagellated protozoa and unicellular algae. Indeed, some of the flagellates (euglenaceae and phytomonads) are rightfully classified as both the type of protozoa, i.e., animals, and the type of green algae, i.e., plants.

Class characteristics

One of the most important characters used in the classification of protozoa is the organelles of movement. In flagellates, these are flagella, or whips - thin cytoplasmic projections. They are usually located at the anterior end of the body and arise from special basal granules (basal body or kinetosome). The number of flagella in different species ranges from 1 to 8 or more. In some flagellates (Leishmania, trypanosomes), at the base of the flagellum, in addition, a special organelle is placed - the kinetoplast. In terms of its ultrastructure, it corresponds to a mitochondrion, but is distinguished by a high DNA content. It is believed that energy is generated in the kinetoplast for the movement of the flagellum, which performs a rotational movement and seems to be screwed into the water. In some representatives of the class, the flagellum runs along the body, connecting to it with a thin outgrowth of the cytoplasm. The mentioned outgrowth, or undulating membrane, makes wave-like movements and serves as an additional organelle of movement.

According to the method of nutrition (assimilation) they are divided into:

Reproduction is usually asexual, by longitudinal division into two parts. Many species also have a sexual process, during which the fusion of sexual forms occurs (copulation).

Numerous species of green flagellates (euglenaceae and phytomonas) live in stagnant freshwater bodies of water. At times they appear in such large quantities that the water turns green (water bloom).

Solitary free-living forms

A typical representative of solitary forms is green euglena (Euglena viridis). Its body shape is spindle-shaped, constant due to the compaction of the outer layer of protoplasm. In the cytoplasm, in the back of the body, there is a large spherical nucleus.

At the front end of the body of green euglena there is a thin flagellum, due to the rotation of which it moves. There is also a pulsating vacuole, its reservoir and several chromatophores containing chlorophyll, in which the synthesis of carbohydrates from carbon dioxide and water (photosynthesis) occurs in the light, i.e. autotrophic nutrition is noted. The products of photosynthesis are deposited in the form of a starch-like substance - paramyl. Euglena searches for illuminated places with the help of a light-sensitive eye - a photoreceptor, colored red, also located at the anterior end of the body.

Euglena can also feed holozoically, swallowing formed food particles. If the habitat is rich in dissolved organic substances, then they enter the euglena’s body by osmosis. Thus, in the structure and method of nutrition of euglena, a combination of the properties of an animal and plant organism is noted.

Maintaining a certain concentration of salts in the cytoplasm, i.e., osmotic pressure, is carried out by a special organelle - a pulsating, or contractile, vacuole located at the anterior end of the body. The pulsating vacuole periodically increases in volume. Having reached a certain size, it pours out the accumulated liquid through the reservoir and after some time begins to grow again. The fluid enters the vacuole through the afferent channels.

Euglena reproduces asexually, by longitudinal division of the body. First, the nucleus divides, the basal body and chromatophores double, and then the cytoplasm divides. The flagellum is discarded or transferred to one individual, and in another it is formed anew. Division in the longitudinal direction is one of the characteristic features of the flagellate class. Under unfavorable conditions, encystment occurs: the flagellum is retracted, the euglena is rounded and forms a dense shell. Encysted euglena can divide one or more times while remaining inside the membranes.

Different types of euglena are characteristic of water bodies with varying degrees of organic pollution, therefore, along with algae, they can serve as a criterion for the sanitary assessment of water supply sources.

Colonial forms

Colonial flagellates (Volvox, Pandorina, Eudorina, etc.) are considered as transitional forms from unicellular to multicellular organisms. The most simply structured colonies consist of 4-16 completely identical single-celled individuals connected together - zooids. Each zooid has a flagellum, an ocellus, chromatophores and a contractile vacuole.

A representative of the colonial species of flagellates, Volvox globator, forms large spherical colonies consisting of many thousands of vegetative zooids - small pear-shaped cells, each of which has two flagella. Ball diameter 1-2 mm. Its cavity is filled with a gelatinous substance. All Volvox cells (zooids) are connected to each other by thin protoplasmic bridges, which makes it possible to coordinate the movement of flagella. The colony moves in water thanks to the coordinated movement of the flagella of individual individuals.

In Volvox, a division of the function of colony cells is already observed. Thus, at one pole of the colony, with which it moves forward, there are cells with more developed light-sensitive ocelli, and in the lower part of the colony (where the ocelli are poorly developed) there are cells capable of division (reproductive cells, generative zooids), i.e. differentiation into somatic and sexual individuals is noted.

Volvox reproduction is carried out through special - generative - zooids. They move from the surface into the colonies and here, multiplying by division, form daughter colonies. After the death of the mother colony, the daughter colonies begin an independent life. In autumn, due to generative individuals, sexual forms are also formed: large immobile macrogametes (female reproductive zooids) and small microgametes equipped with two cords (male reproductive zooids). During the process of gametogenesis, individuals that transform into macrogametes do not divide and increase in size. Individuals that produce microgametes divide repeatedly and form a large number of small biflagellate individuals. Microgametes actively seek out immobile macrogametes and fuse with them, forming zygotes. Zygotes give rise to new colonies. The first two divisions of the zygote are meiotic. Consequently, in colonial flagellates only the zygote has a diploid set of chromosomes, all other stages of the life cycle are haploid.

Order Protomonadina Family Trypanosomatidae Genus Leishmania

Leishmania is the causative agent of leishmaniasis, a vector-borne disease with natural focality. Leishmania was discovered by the Russian doctor P. F. Borovsky in 1898. The most important are representatives of the genus Leishmania, which belongs to the Trypanosome family, the distinctive feature of which is the ability to form several morphologically different forms during the development cycle, depending on the conditions of existence. Changes in form occur in both invertebrate and vertebrate hosts.

The following morphological forms are distinguished:

  • trypanosomal form - characterized by a flattened ribbon-like body, in the center of which there is an oval nucleus. The flagellum begins behind the nucleus. The axial filament of the flagellum goes to the anterior end of the body, forming a well-developed undulating membrane. At the anterior end of the body it ends, and the flagellum protrudes forward, forming a long free end.
  • critidial form - the flagellum begins slightly anterior to the nucleus, moving forward, forming a short undulating membrane and a free end.
  • leptomonas form - the flagellum begins at the very edge of the anterior end of the body, the undulating membrane is absent, the free end of the flagellum is of considerable length.
  • leishmanial form - has a round shape and a large round nucleus. The rod-shaped kinetoplast is located at the anterior end of the body. The flagellum is either absent, or there is only its intracellular part; it does not extend beyond the body.
  • metacyclic form - similar to the critidial form, but lacks a free flagellum. (Fig. 1).

Flagellates of the genus Leishmania have two morphological forms - leptomonas and leishmanial (Fig. 2) or intracellular.

Leishmanias are divided into dermatotropic (localized in the skin) and viscerotropic types (localized in the internal organs).

The causative agent of visceral leishmaniasis (Leischmania donovani, L. infantum)

Localization. Cells of the liver, spleen, bone marrow, lymph nodes, reticuloendothelial cells of subcutaneous tissue.

. Visceral leishmaniasis is most common in India (pathogen L. donovani), found in the Mediterranean countries, Transcaucasia and Central Asia (pathogen L. infantum), where it is called kala-azar. In a number of countries in Asia, Africa and South America, leishmaniasis is also caused by other types of Leishmania.

. Leptomonas and leishmanial forms.

Recently, it was discovered that Leishmania is also found in the reticuloendothelial cells of the skin, which explains the method of infection of mosquitoes. The affected cells sometimes form a continuous layer or are concentrated near the sweat glands and blood vessels.

Pathogenic effect. There is an irregular, persistent fever. The spleen and liver gradually enlarge and can reach enormous sizes (Fig. 3). Exhaustion develops, the content of red blood cells in the blood decreases, and anemia occurs. The disease can be acute or take a chronic course (1-3 years). The mortality rate is very high. Mostly children get sick.

Prevention: personal - individual protection against mosquito bites; public - a set of measures to combat mosquitoes and rodents, the destruction of stray dogs and jackals sick with leishmaniasis. At the same time, it is necessary to carry out sanitary educational work and treatment of patients.

Pathogens of cutaneous leishmaniasis (Leishmania tropica)

Three subspecies of the dermatotropic species of Leishmania are known: L. tropica minor and L. tropica major (in the eastern hemisphere) and L. tropica mexicana (in the western hemisphere).

Geographical distribution. Widely distributed in a number of countries in Europe, Asia, America, and Africa. In Russia, cutaneous leishmaniasis caused by L. tropica (Borovsky's disease) has been eliminated, and that caused by L. major is found in Transcaucasia and Central Asia, especially in a number of regions of Turkmenistan.

Morphophysiological characteristics. Leptomonas and leishmanial forms are indistinguishable from the forms of viscerotropic leishmania.

Life cycle. Almost no different from the causative agent of visceral leishmaniasis. The source of infection is humans and wild animals (small rodents living in sandy semi-deserts and deserts - gerbils, gophers, hamsters, some types of rats and mice). Infection in animal reservoirs under natural conditions sometimes reaches 70%. The disease in animals also manifests itself in the form of skin ulcers. Mosquitoes serve as carriers. There is close contact between rodent reservoirs and mosquito vectors. A rodent's burrow is a permanent habitat and breeding place for mosquitoes, the infestation of which can reach 35%. The role of humans in the spread of cutaneous leishmaniasis is small, with the exception of some areas of the globe (India).

Pathogenic effect. With cutaneous leishmaniasis, round, long-term (about a year) non-healing ulcerations form on exposed parts of the body, mainly on the face. After healing, a disfiguring scar remains (Fig. 4). After an illness, immunity lasts for life.

Laboratory diagnostics. Microscopic examination of discharge from ulcers.

Prevention: personal - individual protection against mosquito bites; It is recommended to carry out preventive vaccinations of cutaneous leishmaniasis strains from animals on closed areas of the skin. Such vaccinations subsequently protect against the appearance of disfiguring ulcers and scars on the face and other open parts of the body. As a public prevention, mosquito and rodent control is carried out. In particular, they introduce chloropicrin into the burrows and plow up areas of land inhabited by gerbils in areas adjacent to the villages.

Genus Trypanosoma

Trypanosoma gambiense is the causative agent of trypanosomiasis - human African sleeping sickness.

Localization. In the human body and other vertebrates it lives in blood plasma, lymph, lymph nodes, cerebrospinal fluid, spinal cord and brain tissues.

Geographical distribution. Found in equatorial Africa. In foci of the disease, trypanosome is found in the blood of antelopes, which serve as its natural reservoir. The carrier is an African blood-sucking insect - the tsetse fly (Glossina palpal is). The disease occurs only in the area of ​​distribution of this fly.

Morphophysiological features. Size from 13 to 39 microns. The body is curved, flattened in one plane, narrowed at both ends, equipped with one flagellum and an undulating membrane. Feeds osmotically. Reproduction occurs asexually, by longitudinal division.

Life cycle. Trypanosomiasis caused by T. gambiense is a typical vector-borne disease with natural focality. The causative agent of trypanosomiasis develops with a change of hosts. The first part of the life cycle of trypanosomes takes place in the digestive tract of the tsetse fly (Glossina palpalis), outside of whose range trypanosomiasis (African sleeping sickness) does not occur, the second part - in the body of vertebrates (cattle and small cattle, pigs, dogs, some wild animals ), as well as humans. When a fly absorbs the blood of a sick person, trypanosomes enter its stomach. Here they reproduce and undergo a series of stages. The full development cycle is about 20 days. Flies, whose bodies contain trypanosomes of the invasive stage, can infect humans when they bite.

Pathogenic effect. A patient with trypanosomiasis experiences severe damage to the central nervous system: muscle weakness, exhaustion, mental depression, and drowsiness. The painful condition lasts 7-10 years and, if left untreated, ends in death.

Laboratory diagnostics. For laboratory diagnostics, blood, punctures of lymph nodes and cerebrospinal fluid are examined.

Prevention. Personal prevention comes down to taking medications that can protect against infection from a tsetse fly bite. Public prevention consists of eliminating the vector. For this purpose, the breeding places of flies - bushes near the home and along the banks of water bodies - are treated with insecticides or cut down.

Order Polymastigina

Intestinal Trichomonas (Trichomonas hominis). Causes intestinal trichomoniasis.

Localization. Colon.

Geographical distribution. Everywhere.

Morphophysiological characteristics. The body is oval in shape with a pointed outgrowth at the posterior end, with one vesicular nucleus. The length of the body is 5-15 µm, 4 free flagella extending from the anterior end, extending forward, and one directed backward, which is associated with the undulating membrane. The body is pierced in the middle by a supporting rod, ending in a pointed spike at the rear end of the body. The cell mouth is located near the nucleus. In the cytoplasm there are digestive vacuoles that serve to digest bacteria and intestinal contents swallowed by the cellular mouth. Osmotic nutrition is also possible - with liquid substances. Reproduction is asexual, by longitudinal division. The ability to form cysts is disputed.

Infection occurs through vegetables and fruits, dirty hands contaminated with feces containing Trichomonas, and unboiled water.

Pathogenic effect not proven, since intestinal Trichomonas is found in the intestines of healthy people and patients with intestinal diseases. There is an opinion that intestinal Trichomonas does not cause disease, but only accompanies pathological processes caused by other reasons.

Laboratory diagnostics. Microscopic examination of fecal smears, detection of vegetative forms in feces.

Prevention. Personal - washing hands before eating and after visiting the restroom, heat treatment of food and drinking water, thorough washing of vegetables and fruits eaten raw, protecting food and water from dust and from flies, which can be mechanical carriers of various pathogens . Public prevention consists of monitoring the sanitary condition of water supplies, food enterprises and grocery stores, public places, fighting flies, and disseminating hygienic knowledge.

Urogenital trichomonas (Trichomonas vaginalis)- the causative agent of urogenital trichomonas.

Localization. Genitourinary tract of men and women.

Geographical distribution. Everywhere.

Morphophysiological characteristics. Its structure is very similar to intestinal Trichomonas. Distinctive features are the large body size (length ranges from 7 to 30 microns). The body shape is most often pear-shaped, there are 4 flagella, an undulating membrane and a supporting rod ending in a spine.

Pathogenic effect. Causes inflammatory processes in the genital tract that are protracted. It is believed that the predisposing factor for the manifestation of pathogenicity is the presence of a certain type of bacteria in the genital tract.

In women, the vagina is initially affected, but subsequently the disease becomes multifocal. Acute cases are characterized by copious fluid discharge, itching and burning. In men, the disease is mostly asymptomatic.

Infection occurs through sexual contact, as well as through the use of bedding, linen, and sponges of the patient. Infection is possible during examination by a gynecologist through contaminated instruments and gloves.

Laboratory diagnostics. Microscopic examination of smears from the discharge of the genitourinary tract. The diagnosis is made based on the presence of vegetative forms in the patient’s secretions.

Prevention. Determined by the method of infection.

Giardia (Lamblia intestinalis). The disease causes giardiasis. This flagellate was discovered by Kharkov University professor D. F. Lambl in 1859.

Localization. Duodenum, can penetrate into the bile ducts for the second time.

Geographical distribution. Everywhere.

Laboratory diagnostics. Detection of cysts in feces or vegetative forms in the contents of the duodenum during probing.

Prevention. a) thermal treatment of food and drinking water; boiling kills Giardia cysts; b) thoroughly washing fruits, vegetables and other foods consumed raw; c) storing cooked food and drinking water in closed containers. It should be borne in mind that Giardia cysts can fall on food with dust and be carried onto it by flies; d) fight against flies. Flies visit sewage dumps, cesspools, they land on human feces, rotting food and, having soiled their bodies in feces, fly into a person’s home, where they land on food, dishes, and human skin; e) washing hands before eating and after using the restroom.