Morphology of Leishmania donovani | Diagram

In this article, we will learn the morphology or structure of Leishmania donovani. Leishmania donovani is a parasite that causes Visceral Leishmaniasis in humans. It has a characteristic elongated, thin, and spindle-shaped morphology, with a length of around 20-30 μm and a width of 2-5 μm. The parasite has an anterior flagellum, a single nucleus, and a large kinetoplast that contains its DNA.

Diagram

Morphology of Leishmania donovani

1. Shape and Size

• • • The Leishmania genus occurs in two forms or stages; leishmanial and leptomonad.
    • The leishmanial form is present in the vertebrate (man) and the leptomonad form is present in the invertebrate(sandfly) hosts.

a) Leishmanial or amastigote form

• • • • • It occurs in the vertebrate host or man.
        • It is present intracellularly in blood cells or reticulo-endothelial cells of the host.
        • It is microscopic and rounded.
        • It has a nucleus, blepharoplast, and kinetoplast.
        • It has no free flagellum.
        • It measures 2µ to 4µ in diameter.

b) Leptomonad or promastigote form

• • • • • It occurs in the invertebrate host or sandfly.
        • It is found in the midgut of the host.
        • It is elongated, slender, and spindle-shaped.
        • It has a large nucleus, blepharoplast, and kinetoplast.
        • It also has a long free flagellum.
        • A fully formed leptomonad measures 15-20µ in length and 1-2µ in width.

2. Cell Membrane

• • • The whole body is covered externally by firm covering or pellicle.
    • It is thin, delicate, and elastic.
    • It gives a definite shape to the body.

3. Flagellum

• • • Leishmania bears only one flagellum. That’s why they are called uniflagellate.
    • In the leptomonad form, the flagellum is long and free.
    • The flagellum arises from the basal body or blepharoplast.
    • The blepharoplast or basal body is situated near the anterior end of the body.
    • In the leishmanial form, there is no free flagellum or the flagellum is greatly reduced.

4. Cytoplasm

• • • Underneath the pellicle, the cytoplasm is present. That means the cytoplasm is covered by the pellicle.
    • It is colorless.
    • It is not differentiated into ectoplasm and endoplasm.
    • The blepharoplast, kinetoplast, rhizoplast, Golgi body, mitochondrion, vacuole and nucleus are present in the cytoplasm.

5. Nucleus

• • • A single large nucleus is present eccentrically or in the center of the body.
    • It is spherical in shape.
    • It is vesicular and with a distinct central karyosome or nucleolus.
    • It is covered by a double unit membrane with pores and measures about 1µ in diameter.

Frequently Asked Questions

Ques 1: What are the two forms of Leishmania donovani?

Ans 1: Leishmanial or amastigote forms and leptomonad or promastigote form.

 

Ques 2: Do Leishmania have flagella?

Ans 2: The leptomonad form has a flagellum but the leishmanial form doesn’t have any flagella. It uses its flagellum to move.

 

Ques 3: What is the thread-like structure in Leishmania?

Ans 3: Flagellum.

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