The Golden Algae Department (photos, characteristics and descriptions of individual species you will find in this article) is known, perhaps, mainly only to biologists. Nevertheless, its representatives play a very important role in nature. Golden algae is one of the oldest groups of algae. Their ancestors were primary amoeba-like organisms. Golden algae are similar to yellow-green, diatoms and partially brown algae in terms of the set of pigments, the presence of silicon in the cell membranes, and the composition of the reserve substances. There is reason to believe that they are the ancestors of diatoms. However, this assumption cannot be considered fully proven.
Department of Golden Algae: General Description
Plants of interest to us are distinguished by significant morphological diversity. Golden algae (their photo is presented above) are both unicellular and multicellular, colonial. In addition, among the golden algae there is a very peculiar representative. His multi-core thallus is a bare plasmodium. Thus, golden algae are very diverse.
The cell structure of these organisms is characterized by the presence of a different number of flagella. Their number depends on the species. Usually there are two of them, but it should be noted that some types of golden algae have three flagella. The third, motionless, is located between two mobile. It is called a gantoneme and is characterized by expansion at the end. The function of the gantonema is that the cell with its help is attached to the substrate.
Coloring
Golden algae is a department that includes mainly microscopic species. Their chloroplasts are usually golden yellow. Of the pigments, chlorophyll A should be noted. In addition, chlorophyll E was found, as well as many carotenoids, including carotene and a number of xanthophylls, mainly golden fucoxanthin. The color of the representatives of the department we are interested in can have different shades, depending on the predominance of one or another of these pigments. It can be from greenish brown and greenish yellow to pure golden yellow.
Value and Propagation
Golden algae, whose species are numerous, are phototrophic organisms. Their significance lies mainly in the creation of primary products in water bodies. In addition, they participate in the food chain of various aquatic organisms, including fish, golden algae. Their species improves the gas regime of various reservoirs where they grow. They also form sapropel deposits.
The Golden Algae Division is characterized by the multiplication of its representatives by simple cell division, as well as by the breakdown of multicellular thallus or colonies into separate parts. Scientists also know the sexual process, which is a typical autogamy, hologamiya or isogamy. As a result of the reproduction process, endogenous siliceous cysts appear, differing on such a basis as the nature of the sculptural character of their shell. These cysts perform an important function - they help algae survive adverse conditions.
Golden algae distribution
Golden algae are distributed around the world. However, most often they grow in temperate latitudes. These plants live mainly in clean fresh waters. Golden algae is especially characteristic of sphagnum bogs with acidic waters. A small number of these organisms live in salt lakes and seas. In polluted waters, they are much less common. As for soils, only a few of their species live in them.
The Golden Algae department includes representatives of several classes. Below we briefly describe some of them.
Class Chrysocapsic
Its representatives are distinguished by the presence of a complex thallus, which is represented by a mucous structure. Chrysocapsicum include colonial forms, motionless, passively floating or attached. The cells of these organisms have neither flagella nor superficial protrusions. They are combined into a single whole by the common mucus of the colonies, usually located in its peripheral layers, however, they can also be in the central part.
Class Chrysotrich
This class includes golden algae having a lamellar, filamentous and multifilament structure. All of these organisms are multicellular, typically benthic, attached. Tall is represented by branched or simple, single or multiple rows of threads, disc-shaped parenchymal plates or bushes. They are not immersed in the common mucus.
This class combines freshwater forms, less often marine and brackish water forms. Chrysotrich are the most highly organized group of organisms among all golden algae. Its representatives are similar in appearance to the Ulotrix species belonging to the Green Algae division, as well as to the heterotrix species belonging to the Yellow-Green algae division. Some representatives of chrysotrichs resemble some of the most simply arranged brown algae.
Class Chrysosphere
This class includes golden algae, whose body structure is coccoid. The cells of these organisms are coated with a cellulose membrane. Harnesses and rhizopodia in representatives of this class are completely absent. These plants are unicellular, motionless. Less common are colonial forms, which are clusters of cells loosely connected to each other and not immersed in the common mucus. They do not form plates or threads during propagation.
Class Chrysophicia
This class combines golden algae having various types of thallus organization. It is his device that is the basis by which the following orders are distinguished in this class: rhizochrysidal (having a rhizopodial structure), chrysomonadal (mopad forms), chrysocapsal (palmeloid forms), pheotamnial (filamentous), and also chrysospheric (coccoid forms). We invite you to get acquainted with the individual orders of this class.
Chrysomonadal (otherwise - chromulinal)
This is the most extensive order combining golden algae having a monadic structure, both colonial and unicellular. The systematics of chrysomonads is based on the structure and number of flagella. Of particular importance is the nature of their cell integument. There are single and double flagellated forms. Previously it was believed that the first ones were more primitive, initial. However, an electron microscope helped scientists find that the supposedly single-flagged forms have a second small lateral flagellum. Researchers have suggested that bivalve chrysomonads with heteromorphic and heterocont flagella could be the starting ones, and single-flagged forms appeared as a result of subsequent reduction of the short tourniquet.
As for the cell integument of representatives of chrysomonadal, they are different. There are naked forms, dressed exclusively with a plasmalemma. Cells of other species are enclosed in special cellulose houses. On top of the plasmalemma of the third is a cover consisting of silicified scales.
With the help of cell division, the process of propagation of chrysomonads is carried out. Some species also have a sexual process.
It should be noted that chrysomonads are mainly freshwater organisms. Most often they live in clear waters. Chrysomonads are usually found in the cold season, in late autumn and early spring. Some organisms live under the ice in the winter. However, as scientists have found out, the temperature of the water is not so important for them. It has only indirect meaning. The chemistry of water is a decisive factor. It changes throughout the year: in the cold season, more nitrogen and iron are contained in water as a result of the absence of other vegetation. Most chrysomonads live in plankton. They have special devices for planktonic lifestyle. Some representatives of chrysomonads color the water brown, causing it to "bloom."
We invite you to get acquainted with the Ochromonad family, which belongs to this class.
Ochromonad family
We continue to review the Golden Algae department. Representatives of the Ochromonad family are various naked forms. Their cells are covered only with a cytoplasmic membrane having one or two flagella (unequal).
Rod Ochromonas
Algae of this genus usually live in freshwater neuston or plankton. Less commonly, they are found in brackish water bodies. This genus is represented by single golden-colored cells having two heteromorphic and heterocont flagella. Ohromonas is a naked cell, clad on the outside with only a cytoplasmic membrane. The cytoskeleton, consisting of microtubules located peripherally, supports its drop-shaped form. In the center of such a cell there is a cell nucleus. It is surrounded by a nuclear membrane consisting of two membranes.
Lamellar chromatophores (two of them) are enclosed in the expansion that exists between the membranes of the nuclear membrane. Their ultrastructure is typical of the department to which they belong. A large vacuole together with chrysolaminarin is located in the back of this cell. Mitochondria are scattered in the cytoplasm, the Golgi apparatus is located in front of such a cell. Flagella extend from its front end. There are two of them, they are not the same in length.
G. Buck studied the origin of mastigonemes and the fine structure of Ochromonas danica (golden algae). Photos with names help to visualize certain types of organisms. In the photo above - algae Ochromonas danica. This type is convenient for determining what the dynamics of development of mastigonemas are. The fact is that its cells have one interesting feature - they easily lose their flagella, and then form them again. This allows you to explore the material at various stages of regeneration of their flagellar apparatus.
Rod Mallomonas
Its representatives usually live in freshwater plankton. This genus is most abundant in terms of species. The cells of its representatives are different in shape. They are covered with scales with bristles or silicified scales. Mallomonas caudata (pictured above) is one of the largest species among representatives of this genus. For him, the ultrastructure of the contents of the bristles, flakes and contents of the cell, as well as the mechanism of their formation, release and subsequent deposition of them on the surface of the cell, are described in detail. However, there are still relatively few studies of this kind.
Briefly tell about the flagella of such a representative of the Mallomonas genus as M. caudata. He has two of them, but one is distinguishable only in an optical microscope. This flagellum has a normal structure. It carries 2 rows of hairy mastigones. In a light microscope, the second flagellum, which protrudes a short distance from the cell, is indistinguishable. A cover of scales hides it.
Sinur clan
This genus is characterized by ellipsoidal or spherical colonies consisting of pear-shaped cells. In the center of the colony, they are joined by the rear ends, sometimes very long. From the cytoplasmic membrane outside the cells are dressed with silica scales. These scales are located spirally, they overlap each other imbued. The ultrastructure and shape of these flakes, like that of malomonas, are of great taxonomic importance. For example, in a representative such as S. sphagnicola (pictured above), the basal lamina seen on a cross-section is flat, that is, it has the same thickness. Small perforations permeate it. An apical thickened margin is present at the anterior margin. The basal margin is bent. It surrounds the basal plate, forming a kind of staple in this golden seaweed. Its representatives have a hollow spike, bent outward. It is attached at some distance from the front edge of the plate. The time is at its base.
As for other representatives of such a department as Golden Algae, the structure of their scales is somewhat more complicated. This applies, in particular, to S. petersonii. On top of the finely perforated basal lamina in this species there is a medial crest (hollow). It is apical, blunt or pointed. Its end may extend beyond the frontal edge of the scale, thus simulating a spike. A large pore is located in the medial ridge, in front of it. The basal end of this flake is bent horseshoe-shaped. He hangs over her body. The posterior and anterior scales, which cover the cell body, have transverse ribs that extend from the medial crest. In addition to transverse, median also have longitudinal ribs. On the cell, the flake does not lie flat, but is apparently attached only to the opposite end of the spike. In S. sphagnicola (in the photo above), body scale profiles can also be found in cytoplasmic vesicles, mainly located near the outer surface of the chloroplast, although they can also be observed between it and vesicles with chrysolaminarin.
Coc-colitophoride group
Golden algae, the species and names of which we study, are numerous. Among them, a special group stands out - coc-colitophoride. Its representatives have their own characteristics. Their pelicula is surrounded on the outside with an additional layer of coccoliths (the so-called rounded calcareous bodies). They are located in the mucus secreted by the protoplast.
Haptophytic class
This class is distinguished primarily by the structure of monad cells that have a haptoneme, in addition to flagella. This class includes three orders. Consider one of them.
Primitive order
It is usually characterized by two isomorphic and isocont flagella, as well as a long haptoneme. The surface of the cells outside the plasmalemma is covered by non-mineralized organic flakes or coccolithic bodies (calcareous), which together form the coccosphere around the cell.
One of the families of this order is Prymnesiaceae. Both in fresh waters and in the seas, the genus Chrysochromulin related to it is represented. Oval or spherical cells with two smooth flagella of equal length, as well as a haptoneme, are covered outside the cytoplasmic membrane with non-mineralized organic scales. The latter are usually of two types. They vary either in shape or in size.
For example, Chrysochromulina birgeri has two types of scales that cover her body. They differ only in size. These flakes consist of oval plates, the pattern of which is represented by radial ridges. There are also two central protrusions, presented in the form of horns. The cell surface of other species is covered with scales, which morphologically differ more or less sharply. For example, the flat, rounded inner flakes of Ch. cyanophora have thin concentric ridges. They overlap each other, forming a case around the cell. Usually they are hidden by numerous cylindrical scales located outside.
Ch. Also has two kinds of flakes. megacyiindra are cylinders and plates. The cylinders are distributed fairly evenly throughout the cell. Each of them is attached to its basal plate with a lower end. The sides of these cylinders almost touch each other. Under them there are flat scales with rims, forming many layers.
Three types of flakes are observed in Ch. chiton. Their location is characteristic: six large ones without a rim are around one, large and with a rim. The gaps between them fill the smallest scales.
In conclusion, we briefly consider another family.
Kokkolitoforidovye family
It mainly includes marine species. An exception is hymenomonas, a freshwater genus. Monad cells of this family have two identical flagella. The haptoneme is usually noticeable quite well. Nevertheless, in a number of coccolithophorids, it appears to be reduced. For example, it is not observed in N. coronate.
Cells of this family do not differ in structure from other haptophytic cells. They have a nucleus, as well as chloroplasts, which are surrounded by the endoplasmic reticulum. They contain trithylakoid lamellae, with no shingles lamella. In the cell there is also a pyrenoid. Paired thylakoids cross it. Mitochondria, the Golgi apparatus , etc. are also present. As for the cell cover, it is located outside the cytoplasmic membrane. Kokkolity - flakes saturated with carbonate, of which it consists. Coccoliths together form a coccosphere around the cell. Some forms have organic non-mineralized flakes besides them.
Kokkolity and writing chalk
The origin of writing chalk, familiar to all of us, is very interesting. , , . , . 10 . , . , 95% . . , .
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