Classification of Protozoa

Classification

A phylum protozoon is a large and varied group and poses a number of problems in its classification. Protozoa are one-celled animals found worldwide in most habitats. Most species are free-living, but all higher animals are infected with one or more species of protozoa. Infections range from asymptomatic to life-threatening, depending on the species and strain of the parasite and the resistance of the host. The Protozoa are considered to be a subkingdom of the kingdom Protista, although in the classical system they were placed in the kingdom Animalia. More than 50,000 species have been described, most of which are free-living organisms; protozoa are found in almost every possible habitat. The fossil record in the form of shells in sedimentary rocks shows that protozoa were present in the Precambrian era. On the basis of light and electron microscopic morphology, the protozoa are currently classified into six phyla. Most species causing human disease are members of the phyla Sacromastigophora and Apicomplexa.In some systems of biological classification, the protozoa are a diverse group of unicellular eukaryoticorganisms. Historically,protozoawere defined as single-celled organisms with animal-like behaviors, such as motilityand predation. The group was regarded as the zoological counterpart to the "protophyta", which were considered to be plant-like, as they are capable of photosynthesis. The termsprotozoaandprotozoansare also used informally to designate single-celled, non-photosynthetic, protists, such as ciliates, amobaeand flagellates. The convectional scgeme followed by Hyman (1940), Hickman (1961) and Storer (1965) etc recognizes 2 sub – phyla on the basis of organs of locomotion and 5 classes, briefly outlined as follows:

Sub – phylum A: Plasmodroma

Locomotoey organelles are flagella, pseudopodia or none.

Class 1: Mastigophora, move by one to many flagella.

Class 2: Sarcodina, move and capture food by pseudopodia.

Class 3: Sporozoa, no locomotory organs.

Sub o- phylum B: Ciliophora

Cilia or sucking tentacles throughout or at certain stages.

Class 4: Ciliata, move by cilia throughout life

Class 5: Suctoria, move by cilia as young and by tentacles as adult

The following classification of protozoa is based in the scheme given by the committee on taxonomy and taxonomy problems of the society of protozoologists and mainly proposed by B.kM. Honigberg and others (1964). It divides protozoa first into 4 subphyla.

1. Sacromastigiosphora
2. Sporozoa
3. Cnidospora
4. Ciliophora

Sub – phylum 1: SARCOMASTIGOPOHORA

Locomotory organelles pseudopodia or flagella both. Nuclei of one kind (monomorphic).

Super class A: Mastigophora (= flagellate)

• Locomotor organelles flagella.
• Nutrition autotrophic or heterotrophic both.

Class 1: Phytomastogophoerea (Phytoflagellate)

• Chlorophyll-bearing chromatophores present
• Nutrition mainly holophytic
• Flagella 1 or 2, sometimes more

Order 1: Chrysomonadida

e.g. Chrys amoeba, synura, ochromonas, Ddinobryon

Order 2: Crytomonadida

e.g. Chilomonas, cryptomonas

Order 3: Euglendia

e.g. Euglena, peranema, phacus, copromonas

Order 4: Volvocida (=phytomonadida)

e.g. Chalamydomonas, volvox

Order 5: Chloromonadida

e.g. Vacularies, Coelomonas, gonyostomum

Order 6: Dinoflagellida

e.g. Noctilluca, ceratium

Super class 2: Zoomastigopohera (Zooflagellata)

• Chlorophyll or chromatophores absent. Mostly parasitic
• Nutrition holozoic or saprozoic
• Flagella one to many

Order 1: Rhizomastigida

e.g. Mastigamoeba , Dimorpha

Order 2:kinetoplastida

E.g.Bedo, Leishmania, Trypanosoma

Order 3: Choanoflagellida

E.g. Proterospongia

Order 4: Diplomonadida

E.g.Hexamita, Giardia

Order 5:Hypermastigida

E.g. Lophomonas, Trychonympha

Superclass B: Opalinata

• Entire body covered by cilia-like flagella
• Nuclei 2 to many , monomorphic
• Reproduction by Sym metrogenic binary fission or by syngamy of isogametes.
• Parasitic mainly in frogs and toads

E.g. Opalina, Zelleriea

Superclass C: Sarcodina(=Rhizopoda)

• Body mostly amoeboid without definite pellicle. Some with skeletons of some kind
• Locomotion by pseudopodia
• Nutrition holozoic or saprozoic

Class 1: Rhizopodea

Pseudopodia as lobopodian, filopodia or reticulopodia without axial filaments.

Subclass(a): Lobosia

Pseudopodia as lobopodia

Order 1: Amoebida

E.g. Amoeba, Entamoeba, Pelomyxa

Order 2: Arcellinda(Teatacida)

E.g. Arcella, Difflugia, Euglypha

Subclass (b): Filosa

Pseudopodia as filopodia. Naked or with a shell with single apertures

E.g. Allogromia, Penardia (naked)

Subclass (c): Granuloreticulosia

Pseudopodia delicate granular reticulopodia

Order: Foraminiferida

E.g. Globigerina, Elphidium (=Polystromella)

Class 2: Actinopodea

Pseudopodia mainly axopodia with axial filaments radiating from a spherical body.

Subclass (a): Heliozoa

E.g. Actinophrys, Actinosphaerium

Subclass (b): Radiolaria

E.g.Collozoum, Thalassicola

Subclass (c):Acantharia

E.g. Acanthometra

Subclass (d): Proteomyxidia

E.g. Vampirella, Pseudopora

Class 3: Piroplasmea

Small parasites in red blood cells of vertebrates.

E.g. Babesia (formerly included withSporozoa but its species don’t produce spores)

Sub-phylumII: Sporozoa

Locomotion organelles absent.Spores usually present. Exclusivelyendoparasites.

Class 1: Telosporea

Spores without polar capsules and filaments naked or encysted.

Subclass (a): Gregarinia

E.g. Monocystis, Gregorian

Subclass (b): Coceidia

E.g. Eimeria, Isospora, Plasmodium

Class 2:Toxoplasma

Spores absent. Only asexual reproduction.

E.g. Toxoplasma

Class 3: Haplospore

Spores cases present. Only asexual reproduction.

E.g. Ichthyosoridium

Sub-phylum III: Conidiospore

Spores with polar filaments present.

Class 1: Myxosporidia

• Spores large developed from several nuclei
• Spores with two or three valves
• Parasites mostly in fishes

E.g. Myxidium, Myxobolus, Ceratomyxa

Sub-phylum IV:Ciliophora

The presence of cilia as Locomotor and feeding organelles at some stage in the life cycle. Nuclei of 2 kinds (dimorphic).

Class: Ciliate

• Locomotororganells numerous hair-like cilia, present throughout life.
• Definite mouth (cytostome) and gullet present except in a few parasitic forms. Anal apertures (cytosine) permanent.
• Mostly two kinds of nuclei, large macronucleus, and smaller micronucleus.

Subclass (a): Holotricha

• Body cilia simple and uniform.
• Buccal cilia mostly absent.

Order 1:Gymnostomatida

E.g. Coleps, Didinum, Prorodon, Dileptus

Order 2: Trichostomatida

E.g. Balantidium, Colpoda

Order 3: Cgonotrichida

E.g. Spirochona, Lobochona

Order 4: Apostomatida

E.g. Hyalophysa

Order 5: Astomatida

E.g. Anoplophyrya, Maupasella

Order 6: Hymenostomatida

E.g. Colpidium, Paramecium

Subclass (b): Peritricha

• Adult without body cilia.
• Apical end with Buccal cilia.

Order: Peritrichida

E.g. Vorticella, Carchesium

Subclass (c): Suctoria

• Sessile and stalked body.
• Young and cilia, adult with suctorial tentacles

Order: Suctorida

E.g. Acineta, Ephelota, Podophyra

Subclass (d): Spirotrichia

• Reduces body cilia
• Buccal cilia well marked

Order 1: Heterotrichida

Body cilia short. Uniform or absent.

E.g. Stentor, Bursaria, Spirostomum

Order 2: Oligotrichida

Body cilia reduced or absent. Buccal membranes conspicuous.

E.g. Strombidium, Halteria

Order 3: Hypotrichida

Dorso– ventrally flattened. Fused cilia forming ventral cirri.

E.g. Euplotes, Stylonchia

Reference.

Aggarwal Sarita. A Text Book of Biolog,New Delhi.: Madhuban Educational Books, 2011.

Bhamrah, H.S., and Kavita, Juneja. A Text Book of Invertebrates, New Delhi: Anmol Publications Pvt Ltd, 2011.

Jordan E.L. and P. S., Verma. Invertebrate Zoology, New Delhi,: S. Chand and Company Pvt. Ltd., 2011.

Kotpal, R. L.,Modern Text Book of Zoology: Invertebrates, New Delhi, India: Rastogi Publications,2011.

http://www.parasitesinhumans.org/