General characters of protozoa.and classification - Theory

General Characters of Protozoa.

    Dr. Vidhin Kamble, Dept. of Zoology 

“Protozoans are microscopic unicellular or acellular organisms. They are either solitary  or colonial. Protozoans are the organism without tissue and organs. They reproduce sexually as well as sexually. They bears one or more nuclei.” 

In 1671 protozoans were first discovered by Antony Von Leeuwenhoek. Van Siebold (1845) identified protozoans as single cellular organisms. The name protozoa (Greek meaning -protos-first; zoan-animal) is given by Goldfuss in 1818. 

This phylum is divided into two subphyla on the basis of locomotary organs. Most accepted classification of protozoa is given by BM Honigberg and others based on the scheme given by the committee on Taxonomy and Taxonomic problems of the society of Protozoologists divides this phyla into 4 subphyla.

The phylum protozoa is classified in four subphyla.

1.     Subphylum                   -        Sarcomastigophora

2.     Subphylum                   -        Sporozoa

3.     Subphylum                   -        Chidophora         

4.     Subphylum                   -        Cilliophora

Subphylum- Sarcomastigophora             

1.     The locomotory organs are  flagella or pseudopodia or both.

2.     Presence of monomorphic nuclei. (Single nucleus).

3.     Reproduction is sexual as well as asexual.

4.     Sexual reproduction by syngamy or no spore formation.

5.     Asexual reproduction by transverse binary fission or multiple fission.

6.     This subphylum is further divided in to 3 super classes:

1.     Super class      -  Mastigophora (Flagellata)

2.     Super class      -  Opalinata

3.     Super class      - Sarcodina 

Super class : Mastigophora (Gr. Mastix=whip; phoros=bearing) (Flagellata)

1.     The locomotary organs  are whip like flagella or pseudopodia

2.     Nutrition is holozoic,  autotropic or heterotropic or both

3.     The body is surrounded with firm pellicle.

4.     Presence of single nucleus (Monomorphic)

5.     Reproduction is sexually or asexually.

6.     Sexual reproduction by syngamy or no spore formation.

7.     Asexual reproduction by binary fission of multiple fission. 

8.     It includes 2 classes as follows.

Super class : Mastigophora (Flagellata) -Class 1- Phytomastigophora

                                                                     Class 2- Zoo mastigophora   

   Class 1: Phytomastigophora (Gr. Phyton=plant; Mastix=whip; phoros=bearing)

1.     They are aquatic fresh water or marine organisms.

2.     The body is covered by pellicle.

3.     In cytoplasm chromatephores with chlorophyll is present.

4.     They are plant like flagellate with or without chloroplast.

5.     The locomotory organelles are flagella.

6.     Presence of 1 to 2 flagella.

7.     Holophytic nutrition like plant by photosynthesis.

8.     Sexual reproduction is syngamy.

9.     Asexual reproduction by longitudinal binary fission.

10.             Some form are small solitary or colonial.

11.            In this organism the reserve food is starch or paramylon.

Ex: Euglena, Ceratium, Noctiluca

Class 2: Zoomastigophora (Gr. Zoon=animal; Mastix=whip; phoros=bearing)

1.     These organisms do not have chloroplast and leucoplast in cytoplasm.
2.     In these organism chromoplast is absent.
3.    The nutrition is holozoic or saprozoic. 
4.   One to many flagella are present.     These are free living.
5.    Most of organisms are parasitic.
6.   The reserved food is glycogen.
7.   Some forms are parasitic present in reproductive path of man and some other vertebrates.
8.   They are symbionts or parasite in gut of wood eating insects.                                      Ex: Leishmania, Trypanosoma, Trichomonas, Trichonympha Giardia

Superclass 2: Opalinata

1.    

1.  These organisms live as commensals or parasites in the gut of anurans.
2. The body is uniformly covered by  oblique rows of cilia-like flagella.
3.   Organisms may have 2 or many nuclei are monomorphic.
4. Contractile vacuoles are absent.
5. Reproduction is  by sexual or asexual.
6. Sexual reproduction is takes place by fusion of flagellated ansinogametes. (anisogamy).
7.   Asexual reproduction takes place by binary fission.

Ex: Opalina, Zelleriella

Superclass 3: Sarcodina (Gr. Sarcode=fleshy)

1.  The locomotion is brought about by pseudopodia.
2.    Pseudopodia may be short and blunt or delicate and long.
3.     The body is amoeboid without definite pellicle.
4.   Cytoplasm is differentiated into outer ectoplasm and inner endoplasm.
5.   These are uninucleated (single nucleus).
6.    Presence of contractile vacuole except marine forms.
7. Asexual reproduction by binary fission.
8.   Sexual reproduction by gamet formation. 
9. The nutrition is holozoic or saprozoic. 

This super class is further divided into 3 classes:

1.     Class1- Rhizopodea

2.     Class 2-  Piroplasmea

3.     Class 3- Actinopodea

      Class 1: Rhizopodea (Gr. Zoon=animal; Mastix=whip; phoros=bearing)
1.    These animals are free living.
2.    Some are parasites
3.    These are naked
4.    In formanifera the body is covered with calcareous shell.

Ex: Amoeba, Entamoeba hystolytica, Elphidium, Arcella, Actinophyrys 

Class 2: Piroplasmea
1.    These animals are rounded or rod shaped or amoeboid.
2.    The animals in Piroplamea are parasite in red blood cells of vertebrates.
3.    Spore are absent. 

              Ex: Babesia

Class 3: Actinopodea (Gr. Actis=ray; podos=foot)
1.    Some forms are found in fresh water  and some are exclusively  marine forms.
2.    These are floating and sessile forms.
3.     The locomotory organelles are delicate in the form of axopodia.
4.    Reproduction is sexual as well as asexual.
5.    Body is rounded with siliceous spicules or shells.
6.   

        Ex: Collozoum, Acanthometra, Actinophrys,

SUBPHYLUM II: SPOROZOA (Gr.
1.    The animals of this subphylum are exclusively endoparasites.
2.    Locomotory organelles are absent.
3.    Some time pseudopodia are present used only for ingestion of food.
4.    Nutrition is saprozoic but some time they are holozoic.
5.    The life cycle is complicated and complete into tow reproductive phases i.e. asexual or sczogony and sexual or syngamy.
6.    The infective stage is sporozoites formed in syngamy hence called sporozoa.
 
      This subphylum includes 3 classes:
 
     Class 1: Telosporea
Class 2: Toxoplasmea
Class 3: Haplosporea

Class 1: Telosporea
1.     They are parasites of vertebrates and invertebrates in epithelial cells and blood cells.
2.     They are gut parasites of vertebrates.
3.    Pseudopodia are absent.
4.    Locomotion is by gliding.
5.    Body is covered with pellicle.
6.    Single nucleus is present in adult trophozoites.
7.    Nutrition is sporozoic.
8.    Sexual reproduction is by isogamy or anisogamy.
.
Ex: Plasmodium, Monocyctis, Eimera,

Class 2: Toxoplasmea

 
1.    They are parasites in vertebrates.
2.    Reproduction is only asexual and by transverse binary fission.
3.    Spore formation do not takes place.
4.    These are without pseudopodia or flagellum.
5.    Cyst formed having many sporozoites.

Ex: Toxoplasma, Sarcocystis.

       Class 3: Haplosporea 

1.      The spores are present. The spores are amoeboid.
2.     Pseudopodia are present.
3.      Reproduction is only sexual. 
4.      They are parasites of annelids and fishes. 
5.     Spores are absent but In some form they are present in cyst.

            Ex: Haplosporidium, Ichthyosporidium 

  SUBPHYLUM III: CNIDOSPORA (Gr. Knide=nettle; spora=seed)
1.    The animals belonging to this subphylum are parasitic.
2.    Locomotory organelles are absent.
3.    Spores are present throughout life and are with one or more polar filaments.
4.    Trophozoits with one or more nuclei.
5.    One or more trophozoits are formed from zygote without sporogony.
6.    This subphylum includes 2 classes:

Class 1: Myxosporidea
1.    These are parasites of fishes.
2.    The spores are large and develop from several nuclei encloses two to three valves.
3.    Spores are with 1 to 4 filaments.
4.    The shape of trophozoit is amoeboid.
Ex: Myxobolus

Class 2: Microsporidea
1.    Spores are small and developed from only one nucleus.
2.    Spores have single valve.
3.    These are generally intracellular parasites of arthropods.
4.    Polar capsule with single polar filament.
Ex: Nosema bombycis

SUBPHYLUM IV: CILIOPHORA (La. Cilium=eye lid with lashes; phoros=bearing)
1.    Ciliophorans are complex protozoans with a definite form and size. 
2.    The locomotory organelle are cilia.
3.    They are mixotrophic or heterotrophic in nutrition.
4.    Cilia also help in feeding at some stage of the life cycle.
5.    Presence of two nuclei. i.e. dimorphic.
6.    On the basis of size they are called as macronucleus and micronucleus.
7.    Macronucleus is vegetative and micronucleus is reproductive and diploid.
8.    They have cytostome (Mouth), cytopharynx, gullet, and anal aperture  called cytopyge (temporary).
9.    It reproduces sexually as well as asexually.
10.    Asexual reproduction takes place by transvers binary fission.
11.    Sexual reproduction takes place by conjugation, autogamy and cytogamy.
12.    Contractile vacuoles are osmoregulatary organ.
13.    Only one class is included in this subphylum:

Class 1: Ciliatea
1.    They are free living in freshwater or in marine water parasite.
2.    They are colonial and sedmentary. Some are sessile.
3.    Body is bounded by pellicle. 
4.    The locomotory organelles are numerous hair-like cilia.
5.    Cilia are distributed all over the body are present during whole or a part of life cycle.
6.    Nutrition is holozoic.
7.    Cytostome and cytopharynx often present.
8.    Presence of one or more contractile vacuoles.
9.    The nucleus is dimorphic including both macro nucleus and micronucleus.
10.    Reproduction is sexual as well as asexual.
11.    Asexual reproduction is by transverse binary fission.
12.    No free gametes formation during sexual reproduction.
13.    Sexual reproduction by conjugation and autogamy.Ex: Paramoecium, Vorticella, Balatidium coli, Nytotherus