Characteristics of sporozoa, nutrition, reproduction

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Abraham McLaughlin

The sporozoa They are obligate parasitic organisms, both of vertebrates and invertebrates, and in certain cases they live inside the cells of their host. As they develop they cause the destruction of the cell in the living. It is a polyphyletic group.

The term sporozoan derives from the Greek root sporos which means "seed", referring to its ability to form infectious spores: highly resistant structures that can be transmitted from one host to another, or involving other means, such as water or by the bite of an infected invertebrate.

Source: By Photo Credit: Content Providers: CDC / Dr. Mae Melvin [Public domain], via Wikimedia Commons

It is quite a mixed bag. Pseudopods are rare, but if they exist they are used as feeding structures and not for locomotion. The reproduction of sporozoans and their life cycles are complex and involve more than one host.

Among the most prominent examples of this group - mainly due to their importance as pathogens - we can mention the genera: Plasmodium, Toxoplasma, Monocystis, among others.

Each species has a range of pH, temperature and amount of oxygen that varies according to the host. Therefore, it is difficult to create these conditions artificially to grow these organisms in the laboratory..

Article index

  • 1 Features
  • 2 Classification
  • 3 Nutrition
  • 4 Playback
    • 4.1 Life cycle of Plasmidium spp.
    • 4.2 Sporogonic cycle
    • 4.3 Schizogonic cycle
  • 5 References

Characteristics

Sporozoans are single-celled parasites that vary widely in morphology and structure of the individuals that make up the group. In addition, each stage of the life cycle corresponds to a specific form.

For example, we can find organisms as small as 2 to 3 microns and at another stage of the cycle it can measure from 50 to 100 microns. Adult forms lack means of locomotion.

Therefore, it is useful to describe only the vegetative form of the life cycle called the trophozoite. Typical sporozoans are round, egg-shaped, or elongated. They are surrounded by a film that covers the plasma membrane.

In the cytoplasm, we find all the typical elements of a eukaryotic cell, such as mitochondria, the Golgi apparatus, the endoplasmic reticulum, among others..

Similarly, there is a micropore and a posterior hole called the anal pore. It is necessary to mention the striking complexity of the apical complex, although the function of each element is not known with certainty..

Classification

The classification of these organisms as "sporozoans" is considered heterogeneous and polyphyletic. They are currently classified into four separate groups that only have their common lifestyle as obligate parasites and complex life cycles, characteristics that are not phylogenetically informative..

Sporozoan is not a taxonomically valid term. Four groups have the characteristics of a sporozoan: the apicomplexes, the haplosporidia, the microsporidia and myxosporidia..

The Phylum Apicomplexa belongs to the clade Alveolata and is characterized by the apical complex, a class of organelles associated with cell ends in some stages of development.

Cilia and flagella are absent in most members. Generally the term sporozoan is applied to this Phylum.

Nutrition

Most sporozoans feed through an absorption process and others can ingest food using the pores described above..

As they are obligate parasites, substances with nutritional value come from the fluids of the host organism. In the case of intracellular forms, food is composed of the fluids of the cell.

Reproduction

The life cycles of a typical sporozoan are complex, consisting of sexual and asexual phases. In addition, they can infect different hosts during one cycle..

They are divided by asexual reproduction processes, specifically by multiple fission. Where a stem cell divides and many daughter cells are identical to each other.

In a general way we can summarize the life cycle of a sporozoan in: a zygote gives rise to a sporozoite through a process of schizogony, this in turn produces a merozoite. The merozoite produces gametes that fuse into a zygote, closing the cycle.

Life cycle of Plasmidium spp.

Plasmidium sp. it is one of the representative organisms and the most studied among the sporozoans. It is the etiological agent of malaria (also known as malaria), a pathology with fatal consequences. Four species of this genus infect humans: P. falciparum, P. vivax, P. malariae Y P. ovale.

The cycle of Plasmidium sp. involves two hosts: an invertebrate of the genus Anopheles (it can infect several species of this genus of mosquitoes) and a vertebrate that can be a primate, either man or a monkey. The cycle is divided into two stages: sporogonic and schizogonic.

Sporogonic cycle

The sporogonic cycle takes place in the female invertebrate, which acquires the parasite through the ingestion of blood from a vertebrate infected by sexually differentiated parasites in microgametocytes and macrogametocytes..

Macrogametocytes mature in the gut of the mosquito and produce flagellate forms, the microgametes. Macrogametocytes give rise to macrogametes.

After fertilization, an elongated zygote with displacement capacity is formed that penetrates the stomach wall of the mosquito where it will form the oocysts.

Oocysts produce a large number of sporozoites, which spread through the body of the mosquito until they reach the salivary glands..

Schizoogonic cycle

The schizoogonic cycle begins with the vertebrate host. The sporozoites penetrate the skin by the bite of the infected mosquito. The parasites circulate throughout the bloodstream until they find the liver cells or hepatocytes. The cycle is in turn divided into pre-erythrocytic and erythrocytic stages.

Erythrocytes, also called red blood cells, are blood cells that contain hemoglobin inside them. Sporozoites divide within hepatocytes and form a schizont by multiple fission. The schizont matures in about twelve days and releases about 2,000 merozoites. Release occurs by the rupture of the merozoite.

In this step the erythrocytic stage begins. Merozoites invade red blood cells where they take on an irregular appearance, a shape called a trophozoite. Parasites feed on hemoglobin and produce hemozoin, a brown pigment, as a waste substance..

The trophozoite is divided by another multiple fission event. First, a schizont forms and after the red blood cell burst, the merozoites are released. The latter invade new cells every 72 hours, producing fever and chills..

References

  1. Audesirk, T., Audesirk, G., & Byers, B. E. (2003). Biology: Life on Earth. Pearson education.
  2. Beaver, P. C., Jung, R. C., Cupp, E. W., & Craig, C. F. (1984). Clinical parasitology . Lea & Febiger.
  3. Cruickshank, R. (1975). Medical microbiology: The practice of medical microbiology (Vol. 2). Churchill livingstone.
  4. Hickman, C. P., Roberts, L. S., Larson, A., Ober, W. C., & Garrison, C. (2001). Integrated principles of zoology. McGraw-Hill.
  5. Pumarola, A., Rodriguez-Torres, A., Garcia-Rodriguez, A. & Piedrola-Angulo, G. (1987). Microbiology and Medical Parasitology. Masson.
  6. Trager, W., & Jensen, J. B. (1976). Human malaria parasites in continuous culture. Science, 193(4254), 673-675.

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