REPRODUCTION IN PROTOZOA

Reproduction is the process by which living organism produce young ones of their own species.  Reproduction is defined as behavioral instinct of living organism to maintain the race.

In protozoa reproduction takes place by:-

1. Asexual method
2. Sexual method

1.       Asexual method of reproduction in protozoa:-

• Many Protozoa reproduces by Asexual method, in which single parent is involved.
• The development of new individuals without the fusion of male and female gametes.
• Asexual reproduction may be of following types-

1. Binary fission and multiple fission
2. Budding
3. Plasmotomy

 

BINARY FISSION IN PROTOZOA:- 

It is most common in protozoa. During binary fission animal body divides in such a place that two identical halves are produced.

 

Simple binary fission or orthodox type:-

This simple binary fission is found in irregular shaped organism like – amoeba. Plane of division is unknown or division is in any plane. Nucleus divides first than cytoplasm divides like mitosis.

 Transverse binary fission:-

Transverse binary fission is found in Paramecium (ciliates).

Plane of division is always transverse to the longitudinal axis of the body of organism. It takes place during favorable conditions; when food, temperature and water is suitable.

• Micro nucleus divides into two nuclei by process of mitosis.
• Mega or Macro nucleus divides by Amitosis.
• Micro and Macro nuclei moves towards opposite pole.
• Constriction appears in the middle.
• One contractile vacuole goes to one daughter paramecium, other is reformed.
• Parental oral groove, vestibule, cytopharynx goes to one daughter paramecium but in other daughter paramecia, new set of these structures are formed.
• Binary fission takes 30-120 minutes to complete the process.

 

Longitudinal binary fission:-

Longitudinal binary fission is found in certain ciliates and flagellates. e.g., Vorticella, Euglena.

In longitudinal binary fission, nucleus and cytoplasm divides in longitudinal plane.

Oblique binary fission:-

In this type of binary fission, organism divides by oblique plane. Oblique binary fission takes place in dianoflagellates.

 

MULTIPLE FISSION IN PROTOZOA :-

In multiple fission, the nucleus of the cell divides very rapidly into many nuclei. Each daughter nucleus gradually surrounded by little mass of cytoplasm and forming pseudopodia spores, as in Amoeba. In case of malarial parasite it forms schizont.

Multiple fission is found in most protozoans like – Amoeba, Plasmodium and monocysts etc. By the rupture of cell membrane, daughter nuclei with cytoplasm released in the environment (water or Blood) etc.

Each daughter schizont or pseudopodia spores forming gradually into young.

BUDDING IN PROTOZOA:-

• Asexual reproduction by budding takes place in many protozoa.

E.g., – Class :- Suctoria: vorticella, Ephalota

           Class :- Flagellata: Acinata

• By budding, one or more smaller individuals are formed from single parent body. Budding may be Exogenous or Endogenous.

 

IN EXOGENOUS BUDDING:- 

Buds develops as an out growth on the parent body, Which after sometime detached and leads free life.

 

IN ENDOGENOUS BUDDING:-

The buds are produced inside the parent’s body in special space called brood pouch or brood chamber. After sometime, bud detached from the parent body and leads free life.

 

PLASMOTOMY IN PROTOZOA:-

In certain multinucleate protozoa like OPALINA and PELOMYXA, the cytoplasm divides but nuclei don’t divide. Each daughter cell regains the normal number of nuclei by nuclear division.