MASTIGOPHORA (FLAGELLATES): CHARACTERISTICS, MORPHOLOGY, NUTRITION - BIOLOGY - 2024

Mastigophora or flagellates is a subphylum of protozoa that includes a large number of unicellular organisms of the most diverse. Its main characteristic is the presence of flagella in the body, which are useful, since they help it feed and move through the environment.

This is a group of living beings that has been the object of study for a long time, so its biological characteristics are very well known. Within this group are some protozoa that constitute well-recognized pathogens, such as Trypanosoma gambiense and Trypanosoma rhodesiense, among others. Sometimes the pathologies they cause can be fatal.

Source: By Various authors. Compilation by me., via Wikimedia Commons

The representative genera of this subphylum are the following: Trypanosoma, Trichomonas, Leishmania and Giardia. Many of them are pathogens, so hygiene measures should be practiced at all times to avoid contagion and subsequent disease.

General characteristics

When it comes to her lifestyle, she is diverse. There are species of flagellates that are forming colonies that can host more than 5 thousand individuals. On the contrary, there are others who lead a solitary and free life, while some others are fixed to the substrate, being then sedentary.

Similarly, some species of flagellates are considered highly pathogenic for humans, one of the most representative organisms being the causative agent of Chagas disease, Trypanosoma cruzi. Disease-causing flagellates are considered parasites of humans.

In its life cycle two stages can be observed:

• Trophozoite: they have a shape similar to a tear, have approximately 8 flagella and have two cell nuclei inside. They measure about 13 microns and have a large karyosome. It also has a deventous species at the front end.
• Cyst: they measure approximately 12 microns, have an oval shape and have a very resistant wall that protects it from the adverse conditions of the external environment. Likewise, it has between 2 and 4 cores.

Taxonomy

The taxonomic classification of the Mastigophora subphylum is as follows:

Domain: Eukarya

Kingdom: Protista

Phylum: Sarcomastigophora

Subphylum: Mastigophora

Morphology

Diagram of Euglena pointing out its parts. Taken and edited from commons.wikimedia.org

The members of this group are unicellular (formed by a single cell) of the eukaryotic type. This means that your cell has a cell membrane, a cytoplasm with organelles, and a nucleus surrounded by a membrane. In this nucleic acids (DNA and RNA) are contained.

Some of the flagellate species present inside plastids, which are cytoplasmic organelles in which some natural pigments are found, such as chlorophyll, among others.

Its body has a curved shape, which can be spherical or oval. The hallmark of this group of organisms is that they have a large number of flagella, which are extensions of the membrane that serve to move. Likewise, they are capable of extending regions of their body, forming pseudopods, which help them feed.

Among the cytoplasmic organelles that these organisms present is a primitive Golgi apparatus, called the parabasal body. Some of the genera that belong to this group lack mitochondria.

Additionally, like many protozoa, those of this subphylum have a single contractile vacuole that they use to maintain the water balance inside the cell.

Habitat

Mastigophora are found in a great diversity of habitats. Phytoflagellates mainly inhabit both marine and freshwater aquatic environments, where they live mainly in the water column. Some dinoflagellates have developed parasitic lifestyles in invertebrates or even fish.

Most zooflagellates have developed mutualistic or parasitic symbiotic relationships. Kinetoplastids are small, holozoic, saprozoic, or parasites. They normally live in stagnant waters.

The most medically important kinetoplastid species belong to the genus Trypanosoma. These species employ an intermediate host, which is primarily a blood-sucking invertebrate.

The definitive hosts are all vertebrates, including man. On the other hand, Trichonympha species, which have evolved as intestinal symbionts of termites and insects, benefit these organisms by supplying enzymes that digest cellulose. Important parasites are also included in this subclass.

Retortomonadins and Trichomonadins are all parasites. The former live as parasites of the digestive tract of vertebrates and invertebrates. The latter live in different tissues of their hosts.

Diplomonadians are also parasites. Oxymonadines and hypermastigines are endozoic. Oxymonadines can be parasites or mutualists of xylophagous insects, while hypermastigines, for their part, are mutualists of cockroaches and termites.

Breathing

Flagellated organisms do not have specialized organs to capture the oxygen that is circulating in the environment. Due to this, they must develop a simpler mechanism to be able to incorporate it inside and thus be able to use it.

The type of breathing that this type of organism displays is direct. This means that the oxygen passes through the membrane and enters the cell. This occurs by a passive transport process known as simple broadcast.

Once inside the cell, oxygen is used in numerous energy and metabolic processes. The carbon dioxide (CO ₂) that is generated is released from the cell, again through the cell membrane and through facilitated diffusion.

Reproduction

Because these are one of the most primitive groups of living things that exist, their reproduction is a fairly simple process. These types of individuals reproduce asexually, through a mechanism known as bipartition or binary fission.

In this process, from a parent two individuals are obtained exactly the same as the cell that originated them in the first place. Likewise, as it is an asexual reproduction process, it does not entail any type of genetic variability.

The first thing that must happen for the reproduction process to begin is for the cell's DNA to duplicate itself. You must make a complete copy of yourself. This must be so because when dividing, each copy of the DNA will go to the new descendants.

Once the genetic material has been copied or duplicated, each copy is located at opposite ends of the cell. Immediately, it begins to experience a division in the longitudinal plane. In this process, the cytoplasm and finally the cell membrane divide, giving rise to two cells.

Those two cells that originated, from the genetic point of view are going to be exactly the same as the progenitor cell.

Nutrition

These types of organisms are heterotrophs. This means that they do not synthesize their own nutrients, but instead feed on other living things or substances made by others. Flagellates usually feed on small algae, certain bacteria, and debris.

These organisms feed through a simple diffusion process or through a structure known as a cytostome. The latter is nothing more than a small opening through which the food particles will enter, which will later be phagocytosed.

Once the food has entered the cell, it comes into contact with the food vacuoles, in the center of which are a series of digestive enzymes whose function is to fragment the nutrients and transform them into simpler substances that can be used by the cells for their processes. vital.

Of course, as a product of the digestion process, certain substances remain that may be waste or could not be digested. Regardless of which is the case, that substance must be released from the cell because it does not fulfill any function within it.

The one involved in the elimination of digestion waste is the contractile vacuole, which helps to expel substances that are unnecessary for the cell.

Diseases

Red tide. Photo by: SteemKR. Taken and edited from: notitarde.com

Various diseases are caused by flagellated protists.

Dinoflagellates can flourish as "red tides." Red tides cause high fish mortality and can poison humans who eat shellfish that have ingested protozoa.

Poisoning occurs by dinoflagellate metabolites that accumulate in the food chain. These metabolites include saxitoxin and gonyatoxins, okadaic acid, brevitoxins, ciguatoxin, and domoic acid.

These metabolites produce amnesic, paralyzing, diarrheal and neurotoxic intoxication due to the ingestion of molluscs contaminated by them. They also produce ciguatera.

Sleeping sickness

Also called "human African trypanosomiasis", it is transmitted by the bite of an infected tsetse fly (Glossina sp.). The culprit is Trypanosoma rhodesiense, a kinetoplastid zooflagellate.

If it is not treated, it can be fatal. Symptoms include fever, swollen lymph nodes, headache, muscle and joint pain, irritability.

In advanced stages, it causes personality changes, alterations in the biological clock, confusion, speech disorders, seizures, and difficulty walking.

Chagas disease

Also known as Chagas disease, American trypanosomiasis or Chagas-Mazza disease, it is a disease transmitted by triatomine insects (chips).

It is caused by the flagellate protozoan Trypanosoma cruzi. The disease affects several wild vertebrates, from where it can be transmitted to humans.

The disease has three phases: acute, indeterminate and chronic. The latter can take up to a decade to appear. In the acute phase, a local skin nodule called a chagoma appears at the site of the bite by the transmitter.

If the sting occurred on the conjunctival mucous membrane, unilateral periorbital edema may develop, as well as conjunctivitis and preauricular lymphadenitis. This set of symptoms is known as Romagna.

The indeterminate phase is generally asymptomatic, but fever and anorexia, also lymphadenopathy, mild hepatosplenomegaly, and myocarditis may occur. In the chronic phase, the disease affects the nervous system, the digestive system and the heart.

Dementia, cardiomyopathy, and sometimes dilation of the digestive tract and weight loss can occur. Without treatment, Chagas disease can be fatal.

Leishmaniasis

Set of zoonotic diseases caused by mastigophores of the genus Leishmania. It is a disease that affects dogs and humans. Some wild animals such as hares, opossums and coatis are asymptomatic reservoirs of the parasite. It is transmitted to humans by the bite of infected female sandflies.

Leishmaniasis can be cutaneous or visceral. In the first, the parasite lodges in the skin. Between one and twelve weeks after the mosquito bite, an erythematous papule develops.

The papule grows, ulcerates and generates a crust of dry exudate. Lesions tend to heal spontaneously after months. In visceral leishmaniasis, inflammation of the liver and spleen occurs. Severe bloating, loss of body condition, malnutrition, and anemia also occur.

Trichomoniasis

Trichomonas vaginalis is a pathogenic Mastigophore belonging to the Trichomonadida order. It parasitizes the urogenital tract only in humans. This species can be found in the vagina and urethra of women, while in men it can be found in the urethra, prostate, and epididymis.

In women it produces vulvovaginitis after an incubation period that can last from 5 to 25 days. It manifests with leucorrhoea, vulvar itching and vaginal burning. If the infection reaches the urethra, urethritis may occur.

In man it almost always occurs asymptomatically, which is why it is considered a carrier. In cases of presenting symptoms, they are produced by urethritis, prostatitis or epididymitis. These infections cause burning when urinating, urethral discharge, as well as preputial edema.

References

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