CHAPTER 11CHAPTER 11PROTOZOANSPROTOZOANS

Protozoa are a diverse Protozoa are a diverse assemblage with mixed assemblage with mixed affinities.affinities.

a.a. They lack a cell wall.They lack a cell wall. b.b. They have at least one They have at least one

motile stage in the life motile stage in the life cycle.cycle.

c. Most ingest their food.c. Most ingest their food.

Biological ContributionsBiological Contributions 1.1. Protozoa have intracellular Protozoa have intracellular

specialization or organization of specialization 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 separate some colonial protozoa have separate somatic and reproductive zooids.somatic and reproductive zooids.

3.3. Asexual reproduction occurs by Asexual reproduction occurs by mitotic division. mitotic division.

4.4. Some have true sexual reproduction Some have true sexual reproduction with zygote formation.with zygote formation.

5.5. Responses to stimuli represent Responses to stimuli represent the simplest reflexes and inborn the simplest reflexes and inborn behaviors known.behaviors known.

6.6. Shelled protozoa have the Shelled protozoa have the simplest exoskeletons.simplest exoskeletons.

7.7. Basic enzymes systems support Basic 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 of Many have developed means of locomotionlocomotion

General FeaturesGeneral Features 1. A protozoan is a complete organisms in 1. A protozoan is a complete organisms in

which all life activities are carried on within which all life activities are carried on within the limits of a single plasma membrane.the limits of a single plasma membrane.

2. Phylogenetic studies show that protozoa 2. Phylogenetic studies show that protozoa do not form a monophyletic group.do not form a monophyletic group.

3. Over 64,000 species are named; half are 3. Over 64,000 species are named; half are fossils.fossils.

4. Although they are unicellular organisms, 4. Although they are unicellular organisms, protozoan cell organelles are highly protozoan cell organelles are highly specialized.specialized.

5. They are ecological diverse, widely 5. They are ecological diverse, widely dispersed, but many are limited to narrow dispersed, but many are limited to narrow environmental ranges.environmental ranges.

6.6. They can be fantastically numerous, They can be fantastically numerous, forming gigantic ocean soil deposits.forming gigantic ocean soil deposits.

7.7. About 10,000 are symbiotic in or on About 10,000 are symbiotic in or on animals or plants; some are human animals or plants; some are human disease agents.disease agents.

8. 8. Some are colonial with multicellular Some are colonial with multicellular stages but have noncolonial forms.stages but have noncolonial forms.

9.9. Protozoa have only one non-Protozoa have only one non-reproductive cell type and lack embryonic reproductive cell type and lack embryonic development; embryonic development is development; embryonic development is one of the criteria for metazoa. one of the criteria for metazoa.

Characteristics of Protozoan Characteristics of Protozoan PhylaPhyla

1.1. They are unicellular with some They 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 present All 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 are formed, No organs or tissues are formed,

but specialized organelles serve but specialized organelles serve many of these functionsmany of these functions..

6.6. They include free-living, They include free-living, mutualistic, commensal and parasitic mutualistic, commensal and parasitic forms.forms.

7.7. They move by pseudopodia, They move by pseudopodia, flagella, cilia and they can direct cell flagella, cilia and they can direct cell movements.movements.

8.8. Most are naked, but some have a Most are naked, but some have a simple endoskeleton or exoskeleton.simple endoskeleton or exoskeleton.

9.9. All types of nutrition are present: All types of nutrition are present: autotrophic, heterotrophic and autotrophic, heterotrophic and saprozoic. saprozoic.

10. They can be aquatic or terrestrial.10. They can be aquatic or terrestrial.

11.11. Reproduction is asexual by Reproduction is asexual by fission, budding or cysts; or sexual fission, budding or cysts; or sexual by conjugation or syngamy of by conjugation or syngamy of gametes.gametes.

Classification:Classification: Follows Hausmann and Follows Hausmann and Hulsmann (1996) and represents a major Hulsmann (1996) and represents a major departure from the Eleventh Edition:departure from the Eleventh Edition:Phylum ChlorophytaPhylum ChlorophytaPhylum RetortamonadaPhylum Retortamonada

Class DiplomonadeaClass DiplomonadeaOrder Order

DiplomonadidaDiplomonadidaPhylum AxostylataPhylum Axostylata

Class ParabasaleaClass ParabasaleaOrder Order

TrichomonadidaTrichomonadidaPhylum EuglenozoaPhylum Euglenozoa

Subphylum EuglenidaSubphylum EuglenidaClass EuglenoideaClass Euglenoidea

Subphylum KinetoplastaSubphylum KinetoplastaClass TrypanosomatideaClass Trypanosomatidea

A More Conventional Classification Presentation:A More Conventional Classification Presentation:

Phylum Apicomplexa (aka. SporozoaPhylum Apicomplexa (aka. Sporozoa

Class GregarineaClass Gregarinea

Class CoccideaClass Coccidea

Phylum Mastigophora (aka FlagellataPhylum Mastigophora (aka Flagellata

Dinoflagellata (Many times included with the Dinoflagellata (Many times included with the algal forms often called Phytomastigophora as algal forms often called Phytomastigophora as opposed to the animal like forms called opposed to the animal like forms called Zoomastigophora(includesTrypanosoma and Zoomastigophora(includesTrypanosoma and GiardiaGiardia

Members of Axostylata have a stiffening rod Members of Axostylata have a stiffening rod composed of microtubules, the composed of microtubules, the AxostyleAxostyle.. (Figure 11.11)(Figure 11.11)

Members of the Class Parabasalea have a Members of the Class Parabasalea have a parabasal bodyparabasal body,, which is a Golgi apparatus which is a Golgi apparatus connected by a fiber to one of the connected by a fiber to one of the kinetosomes.kinetosomes.

Although mitochondria are absent, members Although mitochondria are absent, members of Order Trichomonadida posses of Order Trichomonadida posses hydrogeneosomeshydrogeneosomes which are organelles which are organelles analogous to mitochondria but which produce analogous to mitochondria but which produce molecular hydrogen when oxygen is absent.molecular hydrogen when oxygen is absent.

Trichomonas vaginalisTrichomonas vaginalis infects the urogenital infects the urogenital tract of humans and is sexually transmitted.tract of humans and is sexually transmitted.

Representative TypesRepresentative TypesPhyla Retortamonada and AxostylataPhyla Retortamonada and Axostylata

Small groups but of importance to humans.Small groups but of importance to humans. May represent groups derived very early May represent groups derived very early

from an ancestral eukaryote before from an ancestral eukaryote before mitochondria and plastids were acquired mitochondria and plastids were acquired by symbiogenesis.by symbiogenesis.

Mitochondrial enzymes have been reported Mitochondrial enzymes have been reported in both groups so their absence of in both groups so their absence of mitochondria may be a secondary mitochondria may be a secondary derivation.derivation.

Retortamonds lack both mitochondria and Retortamonds lack both mitochondria and Golgi bodies (e.g., Golgi bodies (e.g., Giardia lambliaGiardia lamblia).).

Phylum SarcomastigophoraPhylum Sarcomastigophora

1.1. This includes two subgroups of This includes two subgroups of protozoa that move by either protozoa that move by either pseudopodia or flagella; however, some pseudopodia or flagella; however, some in each group use the method found in each group use the method found predominantly in the other group.predominantly in the other group.

2.2. Subphylum MastigophoraSubphylum Mastigophora: the : the Flagellated ProtozoaFlagellated Protozoa

This is divided into class This is divided into class Phytomastiophorea with chlorophyll Phytomastiophorea with chlorophyll and animal-like Zoomastigophorea and animal-like Zoomastigophorea without chlorophyll.without chlorophyll.

Phylum Sarcodina (the amoeba and Phylum Sarcodina (the amoeba and relativesrelatives

Some are naked and some have Some are naked and some have shellsshells

A. RadiolariaA. Radiolaria B. ForaminiferaB. Foraminifera In some classifications these are In some classifications these are

placed in a subphylum Actinopoda . placed in a subphylum Actinopoda . The other members of sarcodines are The other members of sarcodines are

put in Rhizopoda put in Rhizopoda

Subphylum KinetoplastaSubphylum Kinetoplasta a.a. Zooflagellates lack chromoplasts and have Zooflagellates lack chromoplasts and have

holozoic or saprozoic nutrition; most are holozoic or saprozoic nutrition; most are symbiotic. symbiotic.

b.b. Trypanosoma is an important genus of Trypanosoma is an important genus of protozoan parasites; some are not pathogenic.protozoan parasites; some are not pathogenic.

1)1) Trypanosoma brucei gambienseTrypanosoma brucei gambiense and and T. b. T. b. rhodesienserhodesiense cause African sleeping sickness in cause African sleeping sickness in humans.humans.

2)2) T. brucei bruceiT. brucei brucei causes a related disease causes a related disease in domestic animals.in domestic animals.

3)3) These trypanosomas are transmitted by These trypanosomas are transmitted by tsetse flies; natural reservoirs include antelope tsetse flies; natural reservoirs include antelope and other wild mammals. and other wild mammals.

4)4) Half of the 10,000 new cases each Half of the 10,000 new cases each year are fatal; the remainder may suffer year are fatal; the remainder may suffer brain damage. brain damage.

5)5) Trypanosoma cruziTrypanosoma cruzi causes Chagas causes Chagas disease in Central and South America; disease in Central and South America; this parasite is carried by a bug and this parasite is carried by a bug and causes nervous system problems.causes nervous system problems.

c.c. Leishmania Leishmania species cause visceral species cause visceral diseases in humans; they are transmitted diseases in humans; they are transmitted by sand flies.by sand flies.

d.d. Various species ofVarious species of Trichomonas Trichomonas live live in the cecum, colon, mouth and in the cecum, colon, mouth and urogenital tracts of humans. urogenital tracts of humans.

Subphylum SarcodinaSubphylum Sarcodinaa.a. Amoeba proteusAmoeba proteus in the superclass in the superclass Rhizopoda is most commonly studied.Rhizopoda is most commonly studied.b.b. They are freshwater but require a They are freshwater but require a substratum on which to crawl.substratum on which to crawl.c.c. The cell membrane encloses the The cell membrane encloses the ectoplasm and endoplasm.ectoplasm and endoplasm.d.d. The nucleus, contractile vacuole and The 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; food rotifers, etc. by phagocytosis; food vacuoles exist 15-30 hoursvacuoles exist 15-30 hours..

f.f. Reproduction is by binary fission using Reproduction is by binary fission using mitosis.mitosis.

g.g. Other rhizopoda include the huge Other rhizopoda include the huge Chaos Chaos carolinensecarolinense, , Amoeba radiosaAmoeba radiosa with slender with slender pseudopodia and entozoic ameba. pseudopodia and entozoic ameba.

h.h. Entamoeba histolyticaEntamoeba histolytica lives in the human lives in the human large intestine and attacks the intestinal wall large intestine and attacks the intestinal wall with enzymes, causing severe and often fatal with enzymes, causing severe and often fatal diarrhea.diarrhea.

i.i. Entamoeba coliEntamoeba coli in the intestine and in 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 Some rhizopods have a siliceous or chitinoid test for protection; pseudopodia chitinoid test for protection; pseudopodia project from openings.project from openings.

k.k. Foraminiferans are shelled rhizopods Foraminiferans are shelled rhizopods found mainly in oceans; some have found mainly in oceans; some have complex haploid and diploid cycles.complex haploid and diploid cycles.

l.l. Slime molds in class Eumycetozoa Slime molds in class Eumycetozoa live on forest detritus; they stream live on forest detritus; they stream together to form a pseudoplasmodium together to form a pseudoplasmodium with discrete cells or a multinucleate with discrete cells or a multinucleate plasmodium producing a fruiting body.plasmodium producing a fruiting body.

m.m. Radiolarians reproduce by binary Radiolarians reproduce by binary fission, budding and sporulation.fission, budding and sporulation.Role of Sarcodina in Building Earth Role of Sarcodina in Building Earth DepositsDeposits

a. Hard shells of foraminiferans a. Hard shells of foraminiferans and radiolarians have been and radiolarians have been preserved preserved since Precambrian times.since Precambrian times.

b. Abundant in the Cretaceous b. Abundant in the Cretaceous and and Tertiary periods, some Tertiary periods, some measured up measured up to 100 mm in to 100 mm in diameter!diameter!

c. One-third of the sea bottom c. One-third of the sea bottom ooze ooze in the Atlantic consists of in the Atlantic consists of GlobigerinaGlobigerina shells.shells.

d.d. Radiolarians have less soluble Radiolarians have less soluble siliceous shells and form the ooze in siliceous shells and form the ooze in Pacific and Indian oceans and fossil in Pacific and Indian oceans and fossil in Tertiary rocks of California.Tertiary rocks of California.

e.e. The White Cliffs of Dover are The White Cliffs of Dover are sedimentary sarcodine deposits that were sedimentary sarcodine deposits that were uplifted.uplifted.

f.f. Their use as indicators of rock ages is Their use as indicators of rock ages is important to oil geologists.important to oil geologists.

PseudopodiaPseudopodia (Figures 11.4, 11.5) (Figures 11.4, 11.5) a.a. This is chief means of locomotion in This is chief means of locomotion in

Sarcodina, many flagellates and ameboid cells Sarcodina, many flagellates and ameboid cells of many invertebrates and vertebrates.of many invertebrates and vertebrates.

b.b. LobopodiaLobopodia are large blunt extensions of are large blunt extensions of the cell body containing both endoplasm and the cell body containing both endoplasm and ectoplasm.ectoplasm.c.c. In the In the limaxlimax form, the whole body moves form, the whole body moves rather than sending out arms.rather than sending out arms.d.d. FilopodiaFilopodia are thin extensions containing are thin extensions containing only ectoplasm; these are seen in class Filosea. only ectoplasm; these are seen in class Filosea. e.e. ReticulopodiaReticulopodia repeatedly rejoin to form a repeatedly rejoin to form a netlike mesh.netlike mesh.

f.f. AxopodiaAxopodia occur in Actinopoda. occur in Actinopoda. (Figure 11.6)(Figure 11.6)

1)1) Axial rods of microtubules Axial rods of microtubules support these long thin support these long thin pseudopodia.pseudopodia.

2)2) They form a geometrical array, They form a geometrical array, which is the axonome of the which is the axonome of the

axopod.axopod.3)3) Addition and removal of Addition and removal of

microtubular material extends and microtubular material extends and retracts the axopod.retracts the axopod.

4)4) Cytoplasm flows away from the Cytoplasm flows away from the body on one side and toward the body on one side and toward the

body on the other.body on the other.

4.4.Superclass Actinopoda (Figure 11.17)Superclass Actinopoda (Figure 11.17)

a.a. Actinopoda consist of the freshwater class Actinopoda consist of the freshwater class Heliozoea and three marine classes of Heliozoea and three marine classes of radiolarians.radiolarians.

b.b. All have axopodia; and all, except All have axopodia; and all, except Heliozoea, have tests. Heliozoea, have tests.

c.c. Radiolarians are the oldest known Radiolarians are the oldest known protozoa; they are pelagic and live in shallow protozoa; they are pelagic and live in shallow water.water.

d.d. A central perforated capsule separates the A central perforated capsule separates the inner and outer cytoplasm.inner and outer cytoplasm.

e.e. The shell surface is fused with spines; The shell surface is fused with spines; cytoplasm around the capsule extends cytoplasm around the capsule extends axopodia to catch prey.axopodia to catch prey.

Phylum Apicomplexa (Superphylum Phylum Apicomplexa (Superphylum Alveolata) Alveolata)

1. All are endoparasites; hosts are in many 1. All are endoparasites; hosts are in many animal phyla.animal phyla.

2. An apical complex is a feature of this 2. An apical complex is a feature of this phylum; it is present only in certain phylum; it is present only in certain stages.stages.

3. Rhoptries and micronemes help it 3. Rhoptries and micronemes help it penetrate the host’s cells.penetrate the host’s cells.

4. Pseudopodia occur in some stages; 4. Pseudopodia occur in some stages; gametes may be flagellated and gametes may be flagellated and contractile fibrils may form waves to contractile fibrils may form waves to propel it through liquid.propel it through liquid.

5.5. The life cycle usually includes both sexual and The life cycle usually includes both sexual and asexual stages; an invertebrate may be an asexual stages; an invertebrate may be an intermediate host.intermediate host.

6. At some point, they form a spore (oocyst) that 6. At some point, they form a spore (oocyst) that is infective in the next host and protects the is infective in the next host and protects the sporozoansporozoan..

Class SporozoeaClass Sporozoeaa.a. Sporozoea is the most important class; it Sporozoea 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 little parasites of invertebrates but are of little economic import.economic import.

2)2) PiroplasmiaPiroplasmia includes some veterinary includes some veterinary parasites: parasites: Babesia bigeminaBabesia bigemina causes Texas causes Texas red-water fever in cattle.red-water fever in cattle.

3)3) CoccidiaCoccidia are important intracellular parasites are important intracellular parasites in both invertebrate and vertebrates.in both invertebrate and vertebrates.

b.b. Eimeria Eimeria is a genus (along with is a genus (along with IsosporaIsospora) that causes coccidiosis.) that causes coccidiosis.

1) 1) IsosporaIsospora infections are mild unless infections are mild unless the immune system is weak, as in AIDS the immune system is weak, as in AIDS patients.patients.

2)2) Eimeria tenelaEimeria tenela is often fatal to is often fatal to young fowl. young fowl.

3)3) Organisms undergo schizogony Organisms undergo schizogony in intestinal cells; the zygote forms an in intestinal cells; the zygote forms an oocyst that passes in the feces and oocyst that passes in the feces and releases eight sporozoites when ingested releases eight sporozoites when ingested by the next host.by the next host.

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

d.d. Plasmodium: The Malarial Organism Plasmodium: The Malarial Organism

1) 1) Malaria is the most important Malaria is the most important infectious disease of humans.infectious disease of humans.

2)2) Four species infect humans; each Four species infect humans; each produces different clinical symptoms.produces different clinical symptoms.

3)3) AnophelesAnopheles mosquitoes carry all mosquitoes carry all forms; the female injects theforms; the female injects the PlasmodiumPlasmodium in her saliva. in her saliva.

4)4) SporozoitesSporozoites penetrate liver cells penetrate liver cells and initiate schizogonyand initiate schizogony..