The development cycle of malarial plasmodia
The malarial plasmodium belongs to the simplest microorganisms of the Protista kingdom, the Sporozoa class, the haemosporidia order, the Plasmodium genus.
The types of Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum and Plasmodium ovale malarial plasmodia are dangerous for humans, as they are the cause of malaria. The type of Plasmodium ovale malarial plasmodia is more rare, and it can only be picked up in the African or Asian tropics.
The cycle of malarial plasmodium development: from a mosquito to a human
The cycle of malarial plasmodium development is divided into two practical equal parts, each of which passes in the body of either a mosquito or a human. Let's start with the moment when the sporozoites of the malarious plasmodium penetrate the human body.
Getting into the blood, sporozoite very quickly find themselves in the liver tissue and already here begin asexual reproduction (schizogony), turning into merozoites. These hungry young plasmodia penetrate the red blood cells (erythrocytes) and, while absorbing hemoglobin, continue to asexually multiply in the asexual way. At this stage, the structure of the malarial plasmodium is a cell no larger than 2 μm in size with protoplasm and nucleus, their shape is round or oval (similar to amoeba).
Then the merozoites, destroying the erythrocytes, emerge from them and take the form of rings, and in their protoplasm cavities form - digestive vacuoles, which accumulate nutrients and excrete the products of vital activity: so plasmodia toxins enter the bloodstream of a person.
At this stage, the development of the malarial plasmodium occurs "on schedule" - every 48 hours, and just at the same frequency in a person infected with malaria, attacks of fever with chills and very high fever occur.
Erythrocytic schizogony is cyclically repeated and continues until the amount of merozoites reaches the desired level. And then the cycle of development of malarial plasmodium enters the next stage, and gametocytes are formed by sex cells.
The cycle of malarial plasmodium development: from human to mosquito
To begin sexual reproduction of malarial plasmodium (sporogony), it is necessary to change the host and get into the stomach of the anopheles mosquito. By this time gametocytes are ready for separation into microgametocytes and macrogamethocytes.
And as soon as the mosquito bites the person, sick with malaria, with sucked-up blood, the gametocytes "migrate" to their main host. Here, microgametocytes are transformed into male reproductive cells of plasmodium, and macrogamethocytes into female reproductive cells. Each species of these reproductive cells has a single (haploid) chromosome set. What happens next is easy to guess, and as a result of the merging of gametes of the opposite sex, diploid cells with a complete set of chromosomes - zygotes of malarial plasmodium, having an elongated shape, are obtained.
Zygotes of malarial plasmodia are very mobile and, not mildly, meet between the cells of the muscular wall of the insect stomach, are fixed there and form sporocysts - round cells-incubators covered with a membrane (created, among other things, from mosquito tissues). This cycle of malarial plasmodium development in the mosquito is one of the last. During sporocyst growth, cell mitosis continues under their membrane, and hundreds of sporozoites are formed in each (the structure of which was described above).
There comes a time when the shell is torn, and all these sporozoites are just inside the body of the insect. They have to get closer to the "exit", and mobile sporozoites with this task are doing well, getting into the right place - in the salivary glands of the Anopheles mosquito.