1. Protozoa are a diverse assemblage of unicellular eukaryotes that lack cell walls and have at least one motile life stage. They include free-living, mutualistic, commensal, and parasitic forms that reproduce asexually through mitosis or sexually through conjugation/syngamy. 2. Important protozoan phyla include Euglenozoa, which includes the disease-causing trypanosomes, and Axostylata, which have a stiffening rod. Sarcodina, including the amoeba Amoeba proteus, move using pseudopods and feed through phagocytosis. Foraminifera and radiolarians have shells and have

1. CHAPTER 11CHAPTER 11
PROTOZOANSPROTOZOANS

2. Protozoa are a diverseProtozoa are a diverse
assemblage with mixedassemblage with mixed
affinities.affinities.
 a.a. They lack a cell wall.They lack a cell wall.
 b.b. They have at leastThey have at least
one motile stage in theone motile stage in the
life cycle.life cycle.
 c. Most ingest theirc. Most ingest their
food.food.

3.  Biological ContributionsBiological Contributions
 1.1. Protozoa have intracellularProtozoa have intracellular
specialization or organization ofspecialization or organization of
organelles in cells.organelles in cells.
 2.2. Cells may have distinct functions;Cells may have distinct functions;
some colonial protozoa have separatesome colonial protozoa have separate
somatic and reproductive zooids.somatic and reproductive zooids.
 3.3. Asexual reproduction occurs byAsexual reproduction occurs by
mitotic division.mitotic division.
 4.4. Some have true sexualSome have true sexual
reproduction with zygote formation.reproduction with zygote formation.

4.  5.5. Responses to stimuli representResponses to stimuli represent
the simplest reflexes and inbornthe simplest reflexes and inborn
behaviors known.behaviors known.
 6.6. Shelled protozoa have theShelled protozoa have the
simplest exoskeletons.simplest exoskeletons.
 7.7. Basic enzymes systems supportBasic enzymes systems support
all types of nutrition: autotrophic,all types of nutrition: autotrophic,
saprozoic and holozoic.saprozoic and holozoic.
 8.8. Many have developed means ofMany have developed means of
locomotionlocomotion

5.  General FeaturesGeneral Features
 1. A protozoan is a complete organisms1. A protozoan is a complete organisms
in which all life activities are carried onin which all life activities are carried on
within the limits of a single plasmawithin the limits of a single plasma
membrane.membrane.
 2. Phylogenetic studies show that2. Phylogenetic studies show that
protozoa do not form a monophyleticprotozoa do not form a monophyletic
group.group.
 3. Over 64,000 species are named; half3. Over 64,000 species are named; half
are fossils.are fossils.
 4. Although they are unicellular4. Although they are unicellular
organisms, protozoan cell organelles areorganisms, protozoan cell organelles are
highly specialized.highly specialized.
 5. They are ecological diverse, widely5. They are ecological diverse, widely
dispersed, but many are limited to narrowdispersed, but many are limited to narrow
environmental ranges.environmental ranges.

6.  6.6. They can be fantasticallyThey can be fantastically
numerous, forming gigantic ocean soilnumerous, forming gigantic ocean soil
deposits.deposits.
 7.7. About 10,000 are symbiotic in or onAbout 10,000 are symbiotic in or on
animals or plants; some are humananimals or plants; some are human
disease agents.disease agents.
 8.8. Some are colonial withSome are colonial with
multicellular stages but havemulticellular stages but have
noncolonial forms.noncolonial forms.
 9.9. Protozoa have only one non-Protozoa have only one non-
reproductive cell type and lackreproductive cell type and lack
embryonic development; embryonicembryonic development; embryonic
development is one of the criteria fordevelopment is one of the criteria for

7.  Characteristics of ProtozoanCharacteristics of Protozoan
PhylaPhyla
 1.1. They are unicellular with someThey are unicellular with some
colonial and multicellular stages.colonial and multicellular stages.
 2.2. Most are microscopic.Most are microscopic.
 3.3. All symmetries are presentAll symmetries are present
within members of the group.within members of the group.
 4.4. No germ layers are present.No germ layers are present.
 5.5. No organs or tissues areNo organs or tissues are
formed, but specialized organellesformed, but specialized organelles
serve many of these functionsserve many of these functions..

8.  6.6. They include free-living,They include free-living,
mutualistic, commensal andmutualistic, commensal and
parasitic forms.parasitic forms.
 7.7. They move by pseudopodia,They move by pseudopodia,
flagella, cilia and they can directflagella, cilia and they can direct
cell movements.cell movements.
 8.8. Most are naked, but some haveMost are naked, but some have
a simple endoskeleton ora simple endoskeleton or
exoskeleton.exoskeleton.

9. 9.9. All types of nutrition areAll types of nutrition are
present: autotrophic,present: autotrophic,
heterotrophic and saprozoic.heterotrophic and saprozoic.
10. They can be aquatic or10. They can be aquatic or
terrestrial.terrestrial.
11.11. Reproduction is asexual byReproduction is asexual by
fission, budding or cysts; orfission, budding or cysts; or
sexual by conjugation or syngamysexual by conjugation or syngamy
of gametes.of gametes.

10. Classification:Classification: Follows Hausmann andFollows Hausmann and
Hulsmann (1996) and represents a majorHulsmann (1996) and represents a major
departure from the Eleventh Edition:departure from the Eleventh Edition:
Phylum ChlorophytaPhylum Chlorophyta
Phylum RetortamonadaPhylum Retortamonada
Class DiplomonadeaClass Diplomonadea
Order DiplomonadidaOrder Diplomonadida
Phylum AxostylataPhylum Axostylata
Class ParabasaleaClass Parabasalea
Order TrichomonadidaOrder Trichomonadida
Phylum EuglenozoaPhylum Euglenozoa
Subphylum EuglenidaSubphylum Euglenida
Class EuglenoideaClass Euglenoidea
Subphylum KinetoplastaSubphylum Kinetoplasta
Class TrypanosomatideaClass Trypanosomatidea

11. A More Conventional ClassificationA More Conventional Classification
Presentation:Presentation:
Phylum Apicomplexa (aka. SporozoaPhylum Apicomplexa (aka. Sporozoa
Class GregarineaClass Gregarinea
Class CoccideaClass Coccidea
Phylum Mastigophora (aka FlagellataPhylum Mastigophora (aka Flagellata
Dinoflagellata (Many times includedDinoflagellata (Many times included
with the algal forms often calledwith the algal forms often called
Phytomastigophora as opposed toPhytomastigophora as opposed to
the animal like forms calledthe animal like forms called
Zoomastigophora(includesTrypanosoZoomastigophora(includesTrypanoso
ma and Giardiama and Giardia

12. 
Members of Axostylata have a stiffeningMembers of Axostylata have a stiffening
rod composed of microtubules, therod composed of microtubules, the
AxostyleAxostyle.. (Figure 11.11)(Figure 11.11)

Members of the Class Parabasalea have aMembers of the Class Parabasalea have a
parabasal bodyparabasal body ,, which is a Golgiwhich is a Golgi
apparatus connected by a fiber to one ofapparatus connected by a fiber to one of
the kinetosomes.the kinetosomes.

Although mitochondria are absent,Although mitochondria are absent,
members of Order Trichomonadida possesmembers of Order Trichomonadida posses
hydrogeneosomeshydrogeneosomes which are organelleswhich are organelles
analogous to mitochondria but whichanalogous to mitochondria but which
produce molecular hydrogen when oxygenproduce molecular hydrogen when oxygen
is absent.is absent.

Trichomonas vaginalisTrichomonas vaginalis infects theinfects the
urogenital tract of humans and is sexuallyurogenital tract of humans and is sexually
transmitted.transmitted.

13. Representative TypesRepresentative Types
Phyla Retortamonada andPhyla Retortamonada and
AxostylataAxostylata

Small groups but of importance toSmall groups but of importance to
humans.humans.

May represent groups derived very earlyMay represent groups derived very early
from an ancestral eukaryote beforefrom an ancestral eukaryote before
mitochondria and plastids weremitochondria and plastids were
acquired by symbiogenesis.acquired by symbiogenesis.

Mitochondrial enzymes have beenMitochondrial enzymes have been
reported in both groups so theirreported in both groups so their
absence of mitochondria may be aabsence of mitochondria may be a
secondary derivation.secondary derivation.

Retortamonds lack both mitochondriaRetortamonds lack both mitochondria
and Golgi bodies (e.g.,and Golgi bodies (e.g., Giardia lambliaGiardia lamblia).).

14. Phylum SarcomastigophoraPhylum Sarcomastigophora
1.1. This includes two subgroups ofThis includes two subgroups of
protozoa that move by eitherprotozoa that move by either
pseudopodia or flagella; however,pseudopodia or flagella; however,
some in each group use the methodsome in each group use the method
found predominantly in the otherfound predominantly in the other
group.group.
2.2. Subphylum MastigophoraSubphylum Mastigophora : the: the
Flagellated ProtozoaFlagellated Protozoa
This is divided into classThis is divided into class
Phytomastiophorea with chlorophyllPhytomastiophorea with chlorophyll
and animal-like Zoomastigophoreaand animal-like Zoomastigophorea
without chlorophyll.without chlorophyll.

15.  Phylum Sarcodina (the amoebaPhylum Sarcodina (the amoeba
and relativesand relatives
 Some are naked and some haveSome are naked and some have
shellsshells
 A. RadiolariaA. Radiolaria
 B. ForaminiferaB. Foraminifera
 In some classifications these areIn some classifications these are
placed in a subphylumplaced in a subphylum
Actinopoda .Actinopoda .
 The other members of sarcodinesThe other members of sarcodines
are put in Rhizopodaare put in Rhizopoda

18. Subphylum KinetoplastaSubphylum Kinetoplasta
 a.a. Zooflagellates lack chromoplasts andZooflagellates lack chromoplasts and
have holozoic or saprozoic nutrition; mosthave holozoic or saprozoic nutrition; most
are symbiotic.are symbiotic.
 b.b. Trypanosoma is an important genus ofTrypanosoma is an important genus of
protozoan parasites; some are notprotozoan parasites; some are not
pathogenic.pathogenic.
 1)1) Trypanosoma brucei gambienseTrypanosoma brucei gambiense andand T. b.T. b.
rhodesienserhodesiense cause African sleepingcause African sleeping
sickness in humans.sickness in humans.
 2)2) T. brucei bruceiT. brucei brucei causes a related diseasecauses a related disease
in domestic animals.in domestic animals.
 3)3) These trypanosomas are transmitted byThese trypanosomas are transmitted by
tsetse flies; natural reservoirs includetsetse flies; natural reservoirs include
antelope and other wild mammals.antelope and other wild mammals.

20.  4)4) Half of the 10,000 new cases each yearHalf of the 10,000 new cases each year
are fatal; the remainder may suffer brainare fatal; the remainder may suffer brain
damage.damage.
 5)5) Trypanosoma cruziTrypanosoma cruzi causes Chagascauses Chagas
disease in Central and South America; thisdisease in Central and South America; this
parasite is carried by a bug and causesparasite is carried by a bug and causes
nervous system problems.nervous system problems.
 c.c. LeishmaniaLeishmania species cause visceralspecies cause visceral
diseases in humans; they are transmitted bydiseases in humans; they are transmitted by
sand flies.sand flies.
 d.d. Various species ofVarious species of TrichomonasTrichomonas live inlive in
the cecum, colon, mouth and urogenitalthe cecum, colon, mouth and urogenital
tracts of humans.tracts of humans.

24. Subphylum SarcodinaSubphylum Sarcodina
a.a. Amoeba proteusAmoeba proteus in the superclassin the superclass
Rhizopoda is most commonly studied.Rhizopoda is most commonly studied.
b.b. They are freshwater but require aThey are freshwater but require a
substratum on which to crawl.substratum on which to crawl.
c.c. The cell membrane encloses theThe cell membrane encloses the
ectoplasm and endoplasm.ectoplasm and endoplasm.
d.d. The nucleus, contractile vacuole andThe nucleus, contractile vacuole and
vesicles can be seen by microscope.vesicles can be seen by microscope.
e.e. Ameba feed on algae, protozoa,Ameba feed on algae, protozoa,
rotifers, etc. by phagocytosis; foodrotifers, etc. by phagocytosis; food
vacuoles exist 15-30 hoursvacuoles exist 15-30 hours..

26.  f.f. Reproduction is by binary fission usingReproduction is by binary fission using
mitosis.mitosis.
 g.g. Other rhizopoda include the hugeOther rhizopoda include the huge ChaosChaos
carolinensecarolinense,, Amoeba radiosaAmoeba radiosa with slenderwith slender
pseudopodia and entozoic ameba.pseudopodia and entozoic ameba.
 h.h. Entamoeba histolyticaEntamoeba histolytica lives in the humanlives in the human
large intestine and attacks the intestinal walllarge intestine and attacks the intestinal wall
with enzymes, causing severe and often fatalwith enzymes, causing severe and often fatal
diarrhea.diarrhea.
 i.i. Entamoeba coliEntamoeba coli in the intestine andin the intestine and E.E.
gingivalisgingivalis in the mouth are not disease agents.in the mouth are not disease agents.
 j.j. Some rhizopods have a siliceous or chitinoidSome rhizopods have a siliceous or chitinoid
test for protection; pseudopodia project fromtest for protection; pseudopodia project from
openings.openings.

29. k.k. Foraminiferans are shelledForaminiferans are shelled
rhizopods found mainly in oceans;rhizopods found mainly in oceans;
some have complex haploid andsome have complex haploid and
diploid cycles.diploid cycles.
l.l. Slime molds in class EumycetozoaSlime molds in class Eumycetozoa
live on forest detritus; they streamlive on forest detritus; they stream
together to form a pseudoplasmodiumtogether to form a pseudoplasmodium
with discrete cells or a multinucleatewith discrete cells or a multinucleate
plasmodium producing a fruiting body.plasmodium producing a fruiting body.

31. m.m. Radiolarians reproduce by binaryRadiolarians reproduce by binary
fission, budding and sporulation.fission, budding and sporulation.
Role of Sarcodina in Building EarthRole of Sarcodina in Building Earth
DepositsDeposits
a. Hard shells of foraminiferansa. Hard shells of foraminiferans
and radiolarians have beenand radiolarians have been
preserved since Precambrian times.preserved since Precambrian times.
b. Abundant in the Cretaceousb. Abundant in the Cretaceous
and Tertiary periods, someand Tertiary periods, some
measured up to 100 mm inmeasured up to 100 mm in diameter!diameter!
c. One-third of the sea bottomc. One-third of the sea bottom
ooze in the Atlantic consists ofooze in the Atlantic consists of

32. d.d. Radiolarians have less solubleRadiolarians have less soluble
siliceous shells and form the ooze insiliceous shells and form the ooze in
Pacific and Indian oceans and fossil inPacific and Indian oceans and fossil in
Tertiary rocks of California.Tertiary rocks of California.
e.e. The White Cliffs of Dover areThe White Cliffs of Dover are
sedimentary sarcodine deposits thatsedimentary sarcodine deposits that
were uplifted.were uplifted.
f.f. Their use as indicators of rock agesTheir use as indicators of rock ages
is important to oil geologists.is important to oil geologists.

33. PseudopodiaPseudopodia (Figures 11.4, 11.5)(Figures 11.4, 11.5)
a.a. This is chief means of locomotion inThis is chief means of locomotion in
Sarcodina, many flagellates and ameboidSarcodina, many flagellates and ameboid
cells of many invertebrates and vertebrates.cells of many invertebrates and vertebrates.
b.b. LobopodiaLobopodia are large blunt extensions ofare large blunt extensions of
the cell body containing both endoplasmthe cell body containing both endoplasm
and ectoplasm.and ectoplasm.
c.c. In theIn the limaxlimax form, the whole body movesform, the whole body moves
rather than sending out arms.rather than sending out arms.
d.d. FilopodiaFilopodia are thin extensions containingare thin extensions containing
only ectoplasm; these are seen in classonly ectoplasm; these are seen in class
Filosea.Filosea.
e.e. ReticulopodiaReticulopodia repeatedly rejoin to formrepeatedly rejoin to form
a netlike mesh.a netlike mesh.

34. f.f. AxopodiaAxopodia occur in Actinopoda.occur in Actinopoda.
(Figure 11.6)(Figure 11.6)
1)1) Axial rods of microtubulesAxial rods of microtubules supportsupport
these long thinthese long thin pseudopodia.pseudopodia.
2)2) They form a geometrical array,They form a geometrical array, whichwhich
is the axonome of theis the axonome of the axopod.axopod.
3)3) Addition and removal ofAddition and removal of microtubularmicrotubular
material extends andmaterial extends and retracts theretracts the
axopod.axopod.
4)4) Cytoplasm flows away from theCytoplasm flows away from the bodybody
on one side and toward theon one side and toward the body onbody on
the other.the other.

35. 4.4. Superclass Actinopoda (Figure 11.17)Superclass Actinopoda (Figure 11.17)
a.a. Actinopoda consist of the freshwater classActinopoda consist of the freshwater class
Heliozoea and three marine classes of radiolarians.Heliozoea and three marine classes of radiolarians.
b.b. All have axopodia; and all, except Heliozoea,All have axopodia; and all, except Heliozoea,
have tests.have tests.
c.c. Radiolarians are the oldest known protozoa;Radiolarians are the oldest known protozoa;
they are pelagic and live in shallow water.they are pelagic and live in shallow water.
d.d. A central perforated capsule separates the innerA central perforated capsule separates the inner
and outer cytoplasm.and outer cytoplasm.
e.e. The shell surface is fused with spines;The shell surface is fused with spines;
cytoplasm around the capsule extends axopodia tocytoplasm around the capsule extends axopodia to
catch prey.catch prey.

41. Phylum Apicomplexa (SuperphylumPhylum Apicomplexa (Superphylum
Alveolata)Alveolata)
1. All are endoparasites; hosts are in many1. All are endoparasites; hosts are in many
animal phyla.animal phyla.
2. An apical complex is a feature of this2. An apical complex is a feature of this
phylum; it is present only in certain stages.phylum; it is present only in certain stages.
3. Rhoptries and micronemes help it penetrate3. Rhoptries and micronemes help it penetrate
the host’s cells.the host’s cells.
4. Pseudopodia occur in some stages; gametes4. Pseudopodia occur in some stages; gametes
may be flagellated and contractile fibrils maymay be flagellated and contractile fibrils may
form waves to propel it through liquid.form waves to propel it through liquid.

42. 5.5. The life cycle usually includes both sexual andThe life cycle usually includes both sexual and
asexual stages; an invertebrate may be anasexual stages; an invertebrate may be an
intermediate host.intermediate host.
6. At some point, they form a spore (oocyst) that is6. At some point, they form a spore (oocyst) that is
infective in the next host and protects theinfective in the next host and protects the
sporozoansporozoan..
Class SporozoeaClass Sporozoea
a.a. Sporozoea is the most important class; itSporozoea is the most important class; it
contains three subclasses.contains three subclasses.
1)1) GregariniaGregarinia, or gregarines, are common, or gregarines, are common
parasites of invertebrates but are of littleparasites of invertebrates but are of little
economic import.economic import.
2)2) PiroplasmiaPiroplasmia includes some veterinaryincludes some veterinary
parasites:parasites: Babesia bigeminaBabesia bigemina causes Texas red-causes Texas red-
water fever in cattle.water fever in cattle.
3)3) CoccidiaCoccidia are important intracellular parasitesare important intracellular parasites
in both invertebrate and vertebrates.in both invertebrate and vertebrates.

43. b.b. EimeriaEimeria is a genus (along withis a genus (along with
IsosporaIsospora) that causes coccidiosis.) that causes coccidiosis.
1)1) IsosporaIsospora infections are mild unlessinfections are mild unless
the immune system is weak, as in AIDSthe immune system is weak, as in AIDS
patients.patients.
2)2) Eimeria tenelaEimeria tenela is often fatal to youngis often fatal to young
fowl.fowl.
3)3) Organisms undergo schizogony inOrganisms undergo schizogony in
intestinal cells; the zygote forms anintestinal cells; the zygote forms an
oocyst that passes in the feces andoocyst that passes in the feces and
releases eight sporozoites when ingestedreleases eight sporozoites when ingested
by the next host.by the next host.

44. c.c. Toxoplasma gondiiToxoplasma gondii is a parasite of cats.is a parasite of cats.
1)1) Rodents, cattle, sheep, birds and humansRodents, cattle, sheep, birds and humans
can ingest sporozoites.can ingest sporozoites.
2)2) They cross the intestine and asexuallyThey cross the intestine and asexually
reproduce in tissues.reproduce in tissues.
3)3) As the host builds immunity, the zoitesAs the host builds immunity, the zoites
enclose in tough tissue cysts calledenclose in tough tissue cysts called
bradyzoites.bradyzoites.
4)4) Up to half of the U.S. population carriesUp to half of the U.S. population carries
tissue cysts from eating undercooked meat.tissue cysts from eating undercooked meat.
5)5) Toxoplasmosis is a serious threat duringToxoplasmosis is a serious threat during
pregnancy; 2% of the cases of mentalpregnancy; 2% of the cases of mental
retardation may be due to congenitalretardation may be due to congenital
toxoplasmosistoxoplasmosis..

45. d.d. Plasmodium: The Malarial OrganismPlasmodium: The Malarial Organism
1)1) Malaria is the most importantMalaria is the most important
infectious disease of humans.infectious disease of humans.
2)2) Four species infect humans; eachFour species infect humans; each
produces different clinical symptoms.produces different clinical symptoms.
3)3) AnophelesAnopheles mosquitoes carry allmosquitoes carry all
forms; the female injects theforms; the female injects the
PlasmodiumPlasmodium in her saliva.in her saliva.
4)4) SporozoitesSporozoites penetrate liver cellspenetrate liver cells
and initiate schizogonyand initiate schizogony..