ProtozoaProtozoa are unicellular (or colonial) organisms that do not constitute a natural group, in fact a group traditionally used in scientific classification, but currently considered devoid of sys ...

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Protozoa

Protozoa are unicellular (or colonial) organisms that do not constitute a natural group, in fact a group traditionally used in scientific classification, but currently considered devoid of systematic phylogenetic value such as polyphyletic. Predation arises with protozoa, which are divided into several Phyla:

A system is being constructed on a molecular and ultrastructural basis.

Rhizopoda

Rhizopoda are distinguished based on the the absence of cilia and flagella and the presence of PSEUDOPODI. These structures allow the cell the characteristic of amoeboid movement, the ingestion of particles or prey, the partial digestion and the extrusion of waste. The amoeboid movement is due to the ability to form pseudopods linked to the presence of actin microfilaments. Sarcodines are heterotrophs and take organic material from the surrounding environment through pinocytosis and phagocytosis. They can ingest organic matter from anywhere on the cell membrane, and are mostly predators. The size of the food vacuoles varies according to the substance ingested, they move in the cytoplasm and can melt. All categories of digestive enzymes including cellulases are known. The vacuoles that contain the material that is not digested are expelled from any portion of the cell surface. As for support, the sarcodines have a cellular membrane depending on the species of a tunic and skeletal structure. The forms without coating are without symmetry but the others have a symmetry determined by the shape of the shell (spherical, radiated or bilateral). The skeletons can be composed of environmental material that is cemented or more often secreted by the cells themselves and, in this case, the skeleton can be:

Organic: chitin (polymer of N-acetyl-glucosamine).
Inorganic: calcium carbonate (foraminifera); siliceous (radiolaria) compounds.
Reproduction occurs mainly through binary splitting; multiple splitting occurs in Entamoeba histolytica, foraminifera and radiolarians. Sexual reproduction, for now only described in foraminifera, has very complex cycles including hologram and often alternation of sexual and asexual phases.

Mastigophore

Mastigophores are present, at least at some stage in their life cycle, in one or many scourges. They are unicellular or colonial organisms, some sessile, which can be autotrophic and heterotrophic (Phytomastigophorea and Zoomastigophorea). They are considered the first type of eukaryotic life to appear on earth; to date, about 9,000 ubiquitous species are known in aquatic environments. The flagellum that characterises them is made up of microtubules and microfilaments that allow movement and is a common structure in many eukaryotic cells with a similar structure. Flagellates maintain their shape because the membrane is covered with a film composed of spiral protein strips. Many are covered with rigid external tunics secreted by the cell itself composed of various substances including cellulose and silica according to the groups. Many are autotrophs but heterotrophs feed on diffusion and active transport. They present a specialised area for absorption which is the cytostome. Many mastigophores are endosymbionts and cause serious diseases as well as for humans such as leishmaniasis or trypanosomiasis. Some are parasites of the digestive tract of various animals, of the urogenital tract or intratissutal. Most of them reproduce mostly by white split.

Ciliophoran or Ciliates

Ciliophoran or Ciliates owe their name to the presence of eyelashes for locomotion and creating food currents. They are protozoa that are free life or diners. They have a precise shape because the cell membrane is covered with a film. They have two nuclei: macronucleus and micronucleus. Only the micronucleus has a reproductive function, which synthesizes DNA and is diploid. The cilia differ from the flagella for a different length (less than 15mm) and a different beat. They are very complex and their classification is based on this group. The ciliature is distinguished in oral and somatic. Oral ciliature is organized around the cytostome, to convey water and organic particles. In somatic ciliature the cilia are arranged in pairs in regular rows whose function is movement. The ciliates are all heterotrophs, which feed on debris or bacteria as both sessile and floating filter feeders, and are a great variety of food strategies. Many ciliates are called OLOZOICI, or swallowed because they devour other protozoa or rotifer predators of other protists, which are also killed by using trichocysts and/or toxic-cysts. Others are indicated as Suttons, not eyelash visualizations but tentacles with hooking organs for the prey that is sucked by the tentacle. Others are called vortexes, they are in fact sessile forms such as Vorticella and are nourished thanks to peristomal cilia, which is a flow of water that transports food particles to the cytostome.

 Apicomplexa

Apicomplexa are all endosymbionts. Penetration into the host cell takes place thanks to the presence in the apical complex merozoite and sporozoite stages, hence the name of the group. Apicomplexa do not have movement organs. The flight flows in a sliding movement on the substrate, and is characteristic of many apicomplexa. Toxoplasma shows the ability to crawl traces rich in glycoproteins on the substrate. The absence of a flag and apparent changes in the cell surface are noted.

 

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