Mastigophora or Flagellates

Flagellate protozoa are divided into two groups: phytoflagellates, which usually contain chlorophyll and are photosynthetic and which are usually studied together with algae, and zooflagellates which do not have chlorophyll and carry out their nutrition in a heterotrophic manner. All components of the class have one or more scourges.

Source: Flagellated Protozoa: Radiolaria Berkshire Community College Bioscience Image Library

Flagellates are also called Mastigophores (mastix = flagellum; phoros = bear, ter) and have an internal structure similar to that of the flagella of cells in other eukaryotes. They correspond to modified and elongated centrioles, and differ from the flagella of prokaryotes, which are made up of proteins alone.

The reproduction of flagellates is, in most cases, asexual by binary, longitudinal division.
Flagellates can be free-living, some move freely in the water, using flagella, while others live attached to the substrate by a peduncle, using the flagellum only to capture food. Some flagellates have a “collar” around the base of the flagellum and are therefore called choanoflagellates. There are colonial choanoflagellates that form colonies fixed to the substrate by a stalk and those that form free colonies, immersed in a gelatinous matrix.

Parasitic Scourges of Man

Among these, the genera Trichomonas, Giardia, Leishmania and Trypanosoma stand out, as they are very common. Trichomonas vaginalis is a parasite of the female and male genital system, producing an infection called trichomoniasis. Its transmission occurs through sexual contact or, uncommonly, through the use of unsanitary toilets.

Giardia lamblia (or G. intestinalis) parasitizes the intestine and can cause dysentery, called giardiasis. Transmission occurs through ingestion of contaminated food or water. It settles in the jejunum-ileum and can often settle in the gallbladder, making treatment much more difficult. Basic sanitation care is the main resource in preventing giardiasis.

In Brazil, one of the most important parasitosis is Chagas disease, caused by Trypanosoma cruzi. Chagas disease (named after Carlos Chagas, a Brazilian researcher who studied and discovered the disease cycle) is extremely serious and has no cure. It is estimated that in South America alone, approximately 7 million people suffer from this disease, which is usually called “mega disease” (large), because it causes hypertrophy and flaccidity in the affected region (megacolon, megaesophagus, etc.). ). Chagas disease presents a certain selectivity for the cardiac musculature and, as a consequence, dysfunctions that can lead to death, although sometimes in the long term.

Source: Triatoma infestans or the “Kissing Bug”, “Assassin Bug”, or “Cone-Nose Bug”, is a vector for Chagas’ Disease. Chagas Disease is caused by the parasitic protozoan Trypanosoma cruzi and is transmitted while the insect vector from the family Reduviidae, subfamily Triatominae, is blood-feeding on a human host. Photo Credit: Content Providers(s): CDC/World Health Organization

The etiologic agent of the disease is T. cruzi and the vector is a hematophagous insect of the triatomid group, popularly known as barber or chupanza (Triatoma infestans, Panstrongylus megistus and other species). Therefore, in the life cycle of Trypanosoma there are two hosts: the man (or other mammal) and the barber. The most efficient way to eradicate Chagas disease is to eliminate the vector (barber). Figure 6b shows a schematic of the life cycle of T. cruzi.

Other important species in this group are Trypanosoma gambiensis and Trypanosoma rhodesiense transmitted by the tsetse fly and etiological agents of African sleeping sickness. Trypanosoma equiperdum, for example, only infects horses, being transmitted sexually.


Hoorman, J. J. (2011). The role of soil protozoa and nematodes. Fact Sheet: Agriculture and Natural Resources.(Smith KL), The Ohio State University Extension, Colombus, Ohio.

Anderson, O. Roger. “The Flagellates (Phylum: Sarcomastigophora; Subphylum: Mastigophora).” In Comparative Protozoology, pp. 16-34. Springer, Berlin, Heidelberg, 1988.

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