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Protozoa

Protozoa are a very diverse group of single-celled organisms, with more than 50,000

different types represented. The vast majority are microscopic, many measuring less than

1!00 mm, "ut some, such as the freshwater #pirostomun, may reach 0.1$ in %& mm' in

length, large enough to ena"le it to "e seen with the na(ed eye.

#cientists have discovered fossilized specimen of protozoa that measured 0.$) in %!0

mm' in diameter. *hatever the size, however, protozoans are well-(nown for their

diversity and the fact that they have evolved under so many different conditions.

+ne of the "asic reuirements of all protozoans is the presence of water, "ut within this

limitation, they may live in the sea, in rivers, la(es, stagnant ponds of freshwater, soil,

and in some decaying matters. any are solitary organisms, "ut some live in colonies

some are free-living, others are sessile and some species are even parasites of plants and

animals %including humans'. any protozoans form comple/, e/uisite shapes and their

"eauty is often greatly overloo(ed on account of their diminutive size.

The protozoan cell "ody is often "ounded "y a thin plia"le mem"rane, although some

sessile forms may have a toughened outer layer formed of cellulose, or even distinct

shells formed from a mi/ture of materials. ll the processes of life ta(e place within this

cell wall. The inside of the mem"rane is filled with a fluid-li(e material called cytoplasm

, in which a num"er of tiny organs float. The most important of these is the nucleus ,

which is essential for growth and reproduction. lso present are one or more contractile

vacuoles, which resem"le air "u""les, whose jo" it is to maintain the correct water

"alance of the cytoplasm and also to assist with food assimilation.

Protozoans living in salt water do not reuire contractile vacuoles as the concentration of

salts in the cytoplasm is similar to that of seawater and there is therefore no net loss or

gain of fluids. ood vacuoles develop whenever food is ingested and shrin( as digestion


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progresses. 2f too much water enters the cell, these vacuoles swell, move towards the

edge of the cell wall and release the water through a tiny pore in the mem"rane.

#ome protozoans contain the green pigment chlorophyll more commonly associated with

higher plants, and are a"le to manufacture their own foodstuffs in a similar manner to

plants. +thers feed "y engulfing small particles of plant or animal matter. To assist with

capturing prey, many protozoans have developed an a"ility to move. #ome, such as

3uglena and Trypanosoma are euipped with a single whip li(e flagella which, when

uic(ly moved "ac( and forth, pushes the "ody through the surrounding water "ody.

+ther protozoans %e.g., Paramecium' have developed large num"ers of tiny cilia around

the mem"rane the rhythmic "eat of these hairli(e structures propel the cell along and

also carry food, such as bacteria , towards the gullet. #till others are capa"le of changing

the shape of their cell wall. The moe"a, for e/ample, is capa"le of detecting chemicals

given off "y potential food particles such as diatoms , algae, "acteria or other protozoa.

s the cell wall has no definite shape, the cytoplasm can e/trude to form pseudopodia

%4ree( pseudes, false pous, foot' in various sizes and at any point of the cell surface.

s the moe"a approaches its prey, two pseudopodia e/tend out from the main cell and

encircle and engulf the food, which is then slowly digested.

6arious forms of reproduction have evolved in this group, one of the simplest involves a

splitting of the cell in a process (nown as "inary fission. 2n species li(e amoe"a, this

process ta(es place over a period of a"out one hour7 the nucleus divides and the two

sections drift apart to opposite ends of the cell. The cytoplasm also "egins to divide and

the cell changes shape to a dum"-"ell appearance. 3ventually the cell splits giving rise to

two identical daughter cells that then resume moving and feeding. They, in turn, can

divide further in this process (nown as ase/ual reproduction, where only one individual is

involved.

#ome species that normally reproduce ase/ually, may occasionally reproduce through

se/ual means, which involves the joining, or fusion, of the nuclei from two different

cells. 2n the case of paramecium , each individual has two nuclei7 a larger macronucleus


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that is responsi"le for growth, and a much smaller micronucleus that controls

reproduction. *hen paramecium reproduce "y se/ual means, two individuals join in the

region of the oral groove8a shallow groove in the cell mem"rane that opens to the

outside. *hen this has ta(en place, the macronuclei of each "egins to disintegrate, while

the micronucleus divides in four. Three of these then degenerate and the remaining

nucleus divides once again to produce two micronuclei that are genetically identical. The

two cells then e/change one of these nuclei that, upon reaching the other individual9s

micronucleus, fuse to form what is (nown as a zygote nucleus. #hortly afterwards, the

two cells separate "ut within each cell a num"er of other cellular and cytoplasmic

divisions will continue to ta(e place, eventually resulting in the production of four

daughter cells from each individual.

Protozoans have evolved to live under a great range of environmental conditions. *hen

these conditions are unfavora"le, such as when food is scarce, most species are a"le to

enter an inactive phase, where cells "ecome non-motile and secrete a surrounding cyst

that prevents desiccation and protects the cell from e/treme temperatures. The cysts may

also serve as a useful means of dispersal, with cells "eing "orne on the wind or on the feet

of animals. +nce the cyst reaches a more favora"le situation, the outer wall "rea(s down

and the cell resumes normal activity.

any species are of considera"le interest to scientists, not least "ecause of the medical

pro"lems that many cause. The tiny Plasmodium protozoan, the cause of malaria in

humans, is responsi"le for hundreds of millions of cases of illness each year, with many

deaths occurring in poor countries. This parasite is transferred from a malarial patient to a

healthy person "y the "ite of female mosuitoes of the genus nopheles. s the mosuito

feeds on a victim9s "lood the parasites pass from its salivary glands into the open wound.

rom there, they ma(e their way to the liver where they multiply and later enter directly

into red "lood cells. :ere they multiply even further, eventually causing the "lood cell to

"urst and release from ;-&; infectious "odies into the "lood plasma. mosuito feeding

on such a patient9s "lood may a"sor" some of these organisms, allowing the parasite to


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complete its life cycle and "egin the process all over again. The shoc( of the release of so

many parasites into the human "lood stream results in a series of chills and fevers8

typical symptoms of malaria. cute cases of malaria may continue for some days or even

wee(s, and may su"side if the "ody is a"le to develop immunity to the disease. a"esia, spread

"y tic(s, causes red water fever in cattle.

?ot all protozoans are parasites however, although this is "y far a more specialized life

style than that adopted "y free-living forms. #everal protozoans form a uniue,

nondestructive, relationship with other species, such as those found in the intestine ofwood-eating termites. @iving in the termites9 intestines the protozoans are provided with

free "oard and lodgings as they ingest the wood fi"ers for their own nutrition. 2n the

process of doing so, they also release proteins which can "e a"sor"ed "y the termite9s

digestive system, which is otherwise una"le to "rea( down the tough cellulose walls of

the wood fi"ers. Through this mutualistic relationship, the termites "enefit from a

nutritional source that they could otherwise not digest, while the protozoans receive a

safe home and steady supply of food.

See also moe"ic dysentery 3ntamoe"a histolytica 3pidemiology, trac(ing diseases

with technology *aste water treatment *ater uality

ஓரண ஓரணகறபபடபபனறன 50,000 கம மறபடட வ யனஒறற வசல உயரள ஒ

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ம படட கழ, உளளன. வபமபலனநய அத வசயலபதத பமன வபரய !"ளம (3மம"), #ல 0.17 அடய$ம, பலகற 1/200 மம"அளம, %னல # பனற !னன"ரSpirostomum பனற சல வ&ல பர ம.

''னள டடம 0.78 (20 மம") அளடபபற (ன ஓரண ப)ம&ளமதரப)பபடட. (னன அள*, (ன+ம, பரடடச பன,ததனமமறம அரள பல

படட !லமளன "- உன(ன உமய !னக அறயபபடட. அனத பரடடசஅ)பபட தளல ஒன !"ர ,னனலயல உளள, %னல#!த ரயற உளள, அரள%ள, .ரள, !னன"ர, ம, த கள&ள, டல -, மறம சல

சத! /ய&ளல #லம. பல தனத உயரன&ள உளளன, %னல சல லனளல -;சல மறறரள மபறற உளளன, ழம உளளன; மறம சல #ன&ள தர&ள மறம ( மனதரளஉடபட) ல&கள$டஒடள. பல பரடடச சலன, !ரததயன)&ள

அம த&ள அ-அ))வபரம அரளன சறய அள* லலல. சல மபறற )&ளல ஒ ர0ளளடன வள அகவசல1ல2,அலல வபடள ஒலயகம #! உனறன $ட

தனதமன கள .றபததயலம.%னல (னற1ம 3ரடடசன உயரணஅ)), ஒவமலலய ள! வகம ச* 4-பபட)ற.

-ன அனத வசயலபம #!த வசல 5ர !டவபம. ச* உளள சறய உப3ள பல மத!#தல க-ய,த1(ன ஒ தரம பனற வபள #பப,!ரபபபபட)கம.#!த ம ,யமனளரசச மறம #னபவபம அசயம

%கம , உளள. ம1ம தறபதயஅதன லஅக-ய,த1சரயன !"ர சம!லய பரமர உளள, ம1ம உ* 6"ரம உத ற கம-ள,

ஒததனறனஒன அலலஅதறக மறபடட 5&தத vacuoles, உளளன. க-ய,த1ல உப3ளன வசற* டல!"க ஒதத மறம !ர #-ப3 அலல

தர&ள %தயம (ன உளள (ன உப3 !"ரல ழம பரடடசள 5&தத vacuoles தயலல. உ* உடவட மறம வசரமனம

,னனற (ன5 பவதலலம உ* vacuoles உனறன.அதம த"ர வசல ந-ற (னறல,#!த vacuoles வப, வசல 5ர ளமபல !

!ரதத மறம ச* ஒ சறய ள7லம த"ர தல. சல பரடடச ம*ம வபஅத தர&ள வதடர3டய பசச !றம பசசயம வ)னறன, மறம தர&ள ஒ ஒதத யல த&ள உ*ப

உறபதத வசயய ,)0ம. மறறரள %ல அலலல&க /யம சறய ளள 4-!ளள 7லம உ*. #ரய பபறற உத*தற, பல பரடடச

!ரதத ஒ தறன உபபடட. பனற ப-&கடய உயர மறமTrypanosoma பனற சலர, ரல ,ன+ம பன+ம !ர! ப, 5றற0ளள !"ர

7லம உடலல ( #!ர-ள பனற ஒ ச*வபறறகம. மறற பரடடச %(.., Paramecium' ச* 5றற சறய பசர வபம (யல

உபபடட#!த hairli(e டடமப3ள தள )ப3 உ* க-ல !,உதரததறக ப8ரய பனற,அறயன உ! ம1ம உ* (த.#ன+ம சலர

வசல 5ர )ம மற தறன உளளன

.அம"ப

,(தடட

,பனற நபசளன

,பச, ப8ரய அலல மறற ஓரண சததயமன உ*ளள 7லம%9ப

வபபடட ரசயன&ள டற0ம தறன உளள. வசல 5ர (!த தடடடடமன )ல உளள(ன சடடபள2ததல வபயல அம வளயதள: ,)0ம

%ரம pseudes, தறன pous, ல' பலஅள*ளல அணமறபரபப1ளள (!த #டததல.அம"ப தன#ரய வ!&கமப,#ர வபயல ,ய வசல #! வளய !"ட) மறம 5றற ளத பனனர வம வசர #

உ*, ழ& னறன.


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#னபவபம பல தமன(ளயஒன #$றபபள* அறயபபம ஒ வசயல,ற வசல ஒ பளகம அட&கம, #!த கழல உபபடளளன.அம"ப

பனற #ன&ளல,#!த வசயல,ற பறற ஒ ம !ரம ஒ லததல!டவபற7 பரத, #ர பர*ள வசலலன (தர ,ன:க தரவசலனறன.க-ய,த1 ம1ம பரத வதட&கற மறம வசல ஒ;ம

ம தறறம )தத மறற. பனனர !ம மறம உ* ம"ம அ!த #ர ஒதத 9மள வசலள உதறக -வசய0ம #தயல வசல பரற.அரள,#தவயட), ஒர ஒ தனபபடட சமப!தபபடட அம!ளள பலலல#னபவபத, (னபபம #!த வசயலததல ம1ம பர ,)ய

வப பலல #னபவபம (ன சல #ன&ள, (பபத#ர வ வசலள #! ள சர!, அலல#*, உளளடய பலயல -,றள7ல,ம #னபவபம

வசயயலம. ளரசச வபப3 (ன ஒவபரய வப&, #னபவபம டபபதம ஒ ம சறய ந: paramecium -ல, ஒவ தனபபடட #ர ளஉளள.

Paramecium பலயல 7லம #னபவபம ப, #ர !பரள வளயதறகம (ன வசல ச* ய அலரச- ஒ மலடடமன பளளம பகதயல சர. #!த #டததல (த ப

ந!னக பரற ப, ஒவmacronuclei, சதயவதட&கற. பனனர #!த 7ன ச"ர-டய$டற மறம ம"த,ளள மரபணஒர மதரயன (ன #ர

நன தயர ம"ம பரற. #ர வசலள பனனர மறற தன!பரன நஅட0மம", உ ஒ#*பவபளஅறயபபற (னன அம (ன, #!த ளல

ஒனறல பரமற. அதன பனனர ரலய, #ர வசலள பரனறன%னலஒவ அணல பற வசல1லர மறம சடபள2ம பள*ள பல#தயல ஒவ தனபபடட #!

!னக சய உயரணள உறபதத ள, !ட வதடம. பரடடசள 5றச4-ல !லமள ஒவபரய அளலன"- - உபபடளளன.

#!த !லமள பனற உ* தடபபட ப, சதமறற #கம ப, வபமபலன #ன&ள வசலள அலலத !ம %, அ&க வசயலறற !லயல, உளளட*ம மறம உலரததல

தற மறம த"ர வபப!ல#! வசல பற(ன ஒ 5றற0ளள !"ரட) 5ர,)0ம. !"ரட)ள உயரண:க ற அலல ல&கள லல மயததனல வ,பரல ஒ பய+ளள -,றயவசயலபடலம. !"ரட) ஒ சதமன !லமஅட0ம ,ற,வளப3ற 5ர உடறமறம வசல சதரவசயலப ம"ம.

பல#ன&ள #லலகற!த.வனனல பல ரம (ன மத பரசசனள, ''னள சமனட) உளளன. சறய பள2ம)யம 3ரடடசன மனதரளல மலரய ரம, .-

!ளல !ழம பல மர&ள வட !ய -கள


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உளளன. மலரய பரடடச .றபம (ன அ-பபம சற!த அறயபபடட !யள ஒனறகம ப,

மறற சமம பர-*யத:க ஒ பரலனம1ம 3ரடடசன வதற .றபற.!moe"ic யறப3, (தடட, அம"ப=2டல) .றபற .; ஒ

வ)ய > > )7லம பர*ற%பபர ? 5"னம ச*கயர 3ரடடசன

#r$panosoma .றபற; ஒவதடர3டய #ன&ள சயல வதறக மறம மததய அவமரல உளள#ரதத ஒட !ய .றபற; %imeria ,யலள மறம - ஒரண

.றபற; மறம ஒ ஒரணஒட, உ7லம பர*ம, ல!ட சப3 !"ர யசசல

.றபற. #!த ழம )&ள வளயல ட ஒசறப3 - ப7லம #!த பம, அனத

பரடடச ஒடள, (ன+ம உளளன. பல பரடடச பனற மரம உணம ரயன (னற கடல பப பனற மறற #ன&ள, ஒதனபபடட, அ-ல, உற. அரள த&ள

வச!த;டடசசத மர#-ள உடவளள பனற ரயனளல கடலல -பரள பரடடச#லசம த&கதறக மறம த&கமடததல -&பபற. பயல, அரள

மர#-ள மயன வசல1ல2 5ரள உட! #லலவயனல ,)யலல#ரயன வசரமனஅமப3, உற'சபபற ,)0ம (!த 3ரட)ன தல. #!த பர2பர உற*ள7லம,

ரயன பரடடச ஒ பபபன "ட)ல உ* !லயன -&ல வபம பஅரள#லலவயனல, 6"ர ,)யலல (ன ஒ;டடசசத%தரம !னம.

ம1மamoe"ic யறப3 ப&ள; அம"ப=2டல); வத-லநடபம !யள ப3 !ய பரல; !"ர சசச -*; த"ர தர வப பலல #னபவபம (ன சல #ன&ள, (பபத #ர வ வசலள #! ள சர!,அலல #*, உளளடய பலயல

-,றள7ல,ம #னபவபம வசயயலம. ளரசச வபப3 (ன ஒ வபரயவப&,#னபவபம டபபதம ஒ ம சறய ந7 paramecium-ல, ஒவ தனபபடட #ர ள உளள. Paramecium பலயல 7லம

#னபவபம ப, #ர !பரள வளய தறகம (ன வசல ச* யஅலரச-ஒ மலடடமன பளளம பகதயல சர.#!த #டததல (த ப

ந !னக பரற ப, ஒவ macronuclei, சதய வதட&கற.பனனர #!த 7ன ச"ர-டய$டற மறம ம"த,ளள மரபணஒர

மதரயன (ன #ர நன தயர ம"ம பரற. #ர வசலள பனனர மறற தன!பரன ந அட0ம ம", உ ஒ#*பவபள

அறயபபற (னன அம (ன, #!த ளல ஒனறல பரமற.அதன பனனர ரலய, #ர வசலள பரனறன%னல ஒவ அணல பற

வசல1லர மறம சடபள2ம பள*ள பல #தயல ஒவ தனபபடட #! !னக சய உயரணள உறபதத ள, !ட வதடம.

பரடடசள 5றச4-ல !லமள ஒவபரய அளலன "- -உபபடளளன.#!த !லமள பனற உ* தடபபட ப, சதமறற

#கம ப, வபமபலன #ன&ள வசலள அலலத !ம %,அ&க வசயலறற !லயல, உளளட*ம மறம உலரததல தற மறம த"ர வபப!ல

#! வசல பற (ன ஒ 5றற0ளள !"ரட) 5ர ,)0ம. !"ரட)ள உயரண:க ற அலல ல&கள லல மயததனல வ, பரல

ஒ பய+ளள -,றய வசயலபடலம. !"ரட) ஒ சதமன !லமஅட0ம,ற, வளப3ற 5ர உடற மறம வசல சதரவசயலப ம"ம.

பல#ன&ள #லலகற!த .வனனல பல ரம (ன மத பரசசனள,''னள சமன ட) உளளன. சறய பள2ம)யம 3ரடடசன

மனதரளல மலரய ரம, .- !ளல !ழம பல மர&ள வட !ய -கள


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ஒட பரனம அன9பல2 வப வ5ள )7லம ஒ%ரயமன !பர ஒமலரய !யள #! மறறபபம. வ5 பதபபடட #ரதத உ (ன

ஒடள தற!த யம அதன உம-!"ர 5ரபபளல #!த டனறன.அ&க#!,அரள அரள வப, பனனர சப3 ரதத அணள !ர)ய ந-ய

அ&க லல"ரல த&ள - வசயய.#&அரள உடம மறம #ரதத

பள2மல ஒ ;-&; வதற உடலள #! #ரதத வசல #தனல,#ன+ம வப. பனற ஒ !யளயன #ரதத ஒ வ5 உ* ம"ம வசயல,ற அதன - 5-றச ,) மறம வதட& ஒட

அ+மதற,#!த உயரன&ள சல உற'ச #லம.களர மறம யசசல -மனயல மலரய அறகறள ஒ வதடரல மனத #ரதத ஓடடததல ,)*ளஒபலஒடள வளய" அதரசச. மலரய மயன -கள சல !டள அலல ர&ள வதடர!தகம, மறம உடல !ய (தரப3

சத உ ,)0ம (னறல 5)வதரயமல. ம"ள,)யமல அபப-தத, (ன+ம, வபனமறம மலரய #ன+ம வபப மடல&ளல மரம ஒ ,ய ரம உளள. சல ம!ள #பப, ளர!த மலரய பள2ம)யம பல

)&ளல #! மள ப உபபட னறன (னற1ம,

அறறல சல 1ன ம!ள$ட !ய (தரப3 உளளன. மலரய பரடடச .றபம (ன அ-பபம சற!த அறயபபடட !யள ஒனறகம ப, மறற சமம பர-* யத:க ஒ பரலன ம1ம

3ரடடசன வதற .றபற. moe"ic யறப3, (தடட,அம"ப =2டல) .றபற . ஒ வ)ய > > )7லம பர*ற%பபர

? 5"னம ச*கயர 3ரடடசன Trypanosoma .றபற ஒவதடர3டய #ன&ள சயல வதறக மறம மததயஅவமரல உளள #ரதத ஒட

!ய .றபற 3imeria,யலள மறம - ஒரண.றபற மறம ஒ ஒரணஒட, உ7லம பர*ம, ல!ட சப3 !"ர யசசல .றபற.

#!த ழம )&ள வளயல ட ஒ சறப3 - ப 7லம #!தபம,அனத பரடடச ஒடள, (ன+ம உளளன. பல

பரடடச பனற மரம உணம ரயன (னற கடல பப பனற மறற #ன&ள, ஒதனபபடட,அ-ல, உற.அரள த&ள வச!த ;டடசசத

மர#-ள உடவளள பனற ரயனளல கடலல -பரள பரடடச #லசம த&கதறக மறம த&கமடததல -&பபற. பயல,அரள மர

#-ள மயன வசல1ல2 5ரள உட! #லலவயனல ,)யலல # ரயன வசரமன அமப3, உற'சபபற,)0ம (!த 3ரட)ன தல.#!த

பர2பர உற*ள7லம, ரயன பரடடசஒ பபபன "ட)ல உ* !லயன-&ல வபம பஅரள #லலவயனல, 6"ர ,)யலல

(ன ஒ;டடசசத%தரம !னம. ம1ம amoe"ic யறப3 ப&ளஅம"ப=2டல) வத-லநடபம

!யள ப3 !ய பரல !"ர சசச -* த"ர தர


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