Asexual Reproduction in Unicellular Organisms > Multiple Fission

When a single organism divides into many daughter cells by forming multiple nuclei followed by cytoplasmic division, it is called multiple fission.

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The mode of asexual reproduction in which a single parent organism divides to produce many daughter organisms at the same time is called multiple fission.

When an Amoeba forms a protective covering around itself during adverse conditions and stops movement, it is called a cyst.

The process by which Amoeba withdraws its pseudopodia and forms a hard, protective, three-layered cyst around its body during unfavourable conditions is called encystation.

The small daughter cells formed when each daughter nucleus produced during multiple fission in Amoeba gets surrounded by a small amount of cytoplasm are called amoebulae or pseudopodiospores.

The type of multiple fission in which the parent Amoeba forms a cyst and releases many daughter individuals on return of favourable conditions is called sporulation.

The process of multiple fission occurring in the oocyst of Plasmodium inside the mosquito is called sporogony.

The daughter individuals formed as a result of sporogony in Plasmodium are called sporozoites.

The end products of multiple fission that are enclosed in a hard, resistant covering are called spores.

Amoeba:

In Amoeba, multiple fission usually takes place under unfavourable environmental conditions. The organism protects itself by forming a resistant covering and completes reproduction inside it.

1. When conditions become unfavourable, Amoeba withdraws its pseudopodia.
2. It secretes a three-layered chitinous covering around itself called a cyst.
3. This protective process is called encystation.
4. Inside the cyst, the nucleus divides repeatedly to form many daughter nuclei.
5. A small amount of cytoplasm collects around each nucleus.
6. Many tiny daughter cells called amoebulae or pseudopodiospores are formed.
7. When favourable conditions return, the cyst wall ruptures.
8. The amoebulae are released, and each grows into an adult Amoeba.

Amoeba: stages in multiple fission

Plasmodium:

In Plasmodium, multiple fissions occur during different stages of its life cycle. The process produces different forms depending on the site of reproduction.

1. Schizogony: Schizogony occurs in the liver cells and red blood cells of humans. During this process, the parasite undergoes multiple fission and produces many merozoites.
2. Sporogony: Sporogony occurs in the oocyst present in the body of the female Anopheles mosquito. During this stage, multiple fissions produce sporozoites.

• In multiple fission, a single parent divides into many daughter cells at once by first forming multiple nuclei, followed by cytoplasmic division around each.
• In Amoeba, under unfavourable conditions, it withdraws its pseudopodia and secretes a three-layered chitinous cyst around itself - a process called encystation.
• Inside the cyst, the nucleus divides repeatedly into many daughter nuclei, each gathering a little cytoplasm to form tiny daughter cells called amoebulae (pseudopodiospores), which are released as adults when favourable conditions return.
• In Plasmodium, schizogony occurs in the human liver and red blood cells, producing many merozoites by multiple fission.
• In Plasmodium, sporogony occurs in the oocyst inside the female Anopheles mosquito, where multiple fission produces sporozoites.