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Copyright © 2013 Pearson Education, Inc. Lectures prepared by Christine L. Case
© 2013 Pearson Education, Inc. Lectures prepared by Christine L. Case
Chapter 12
The Eukaryotes: Fungi, Algae, Protozoa, and
Helminths
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Fungi
12-1 List the defining characteristics of fungi. 12-2 Differentiate asexual from sexual reproduction,
and describe each of these processes in fungi. 12-3 List the defining characteristics of the four phyla
of fungi described in this chapter. 12-4 Identify two beneficial and two harmful effects of
fungi.
Learning Objectives
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Kingdom Fungi
Nutritional Type Chemoheterotroph
Multicellularity All, except yeasts
Cellular Arrangement Unicellular, filamentous, fleshy
Food Acquisition Method Absorptive
Characteristic Features Sexual and asexual spores
Mycology: the study of fungi
Fungi
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Table 12.1 Selected Features of Fungi and Bacteria Compared.
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Vegetative Growth
Molds The fungal thallus consists of hyphae; a mass of hyphae
is a mycelium Unicellular fungi Fission yeasts divide symmetrically Budding yeasts divide asymmetrically
Dimorphism Pathogenic dimorphic fungi are yeastlike at 37°C
and moldlike at 25°C
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Figure 12.2 Characteristics of fungal hyphae.
Septum
Cell wall
Pore Nuclei
Septate hypha Coenocytic hypha Growth of a hypha from a spore
Spore
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Figure 12.3a Aerial and vegetative hyphae.
Aerial hyphae
Aspergillus niger
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Figure 12.4 A budding yeast.
Parent cell
Bud
Bud scar
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Figure 12.5 Fungal dimorphism.
Yeastlike growth Moldlike growth
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Figure 12.6a Representative asexual spores.
Conidia
Conidiophore
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Figure 12.6b Representative asexual spores.
Arthrospores
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Figure 12.6c Representative asexual spores.
Pseudohypha
Blastoconidia
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Figure 12.6d Representative asexual spores.
Chlamydoconidium
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Figure 12.6e Representative asexual spores.
Sporangiospores
Sporangiophore
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Sexual Reproduction
Three phases: Plasmogamy: haploid donor cell nucleus (+) penetrates
cytoplasm of recipient cell (−) Karyogamy: + and − nuclei fuse Meiosis: diploid nucleus produces haploid nuclei
(sexual spores)
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Sexual Spores
Zygospore: fusion of haploid cells produces one zygospore
Ascospore: formed in a sac (ascus) Basidiospore: formed externally on a pedestal
(basidium)
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Medically Important Phyla of Fungi
Zygomycota Microsporidia Ascomycota Anamorphs
Basidiomycota
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Zygomycota
Conjugation fungi Coenocytic Produce sporangiospores and zygospores Rhizopus, Mucor (opportunistic, systemic mycoses)
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Figure 12.7 The life cycle of Rhizopus, a zygomycete.
Sporangiospore
Spore germinates to produce hyphae.
Vegetative mycelium grows. Sporangium
Sporangiophore
Sporangium bursts to release spores.
Aerial hypha produces a sporangium.
Gametes form at tip of hypha.
Sporangiospores
Spore germinates to produce hyphae.
Spores are released from sporangium.
Zygote produces a sporangium.
Karyogamy and meiosis.
Zygosporangium containing zygospore
Zygospore forms.
Plasmogamy.
Sexual reproduction
Asexual reproduction
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Microsporidia
No hyphae No mitochondria Intracellular parasites Encephalitozoon intestinalis
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Figure 12.8 The life cycle of Encephalitozoon, a microsporidian.
Asexual reproduction
Cytoplasm breaks up around nuclei to form spores.
Cytoplasm grows, and nuclei reproduce.
New spores are released.
Spores are ingested or inhaled.
Vacuole Mature spores
Cytoplasm and nucleus enter.
Host cell
Spore injects tube into host cell.
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Ascomycota
Sac fungi Septate Teleomorphic fungi Produce sexual and asexual spores
Ascospores and frequently conidiospores Aspergillus (opportunistic, systemic mycosis) Blastomyces dermatitidis, Histoplasma capsulatum
(systemic mycoses) Microsporum, Trichophyton (cutaneous mycoses)
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Figure 12.9 The life cycle of Talaromyces, an ascomycete.
Vegetative mycelium grows.
Sexual reproduction Asexual
reproduction
Conidium germinates to produce hyphae.
Ascospore germinates to produce hyphae.
Conidia are released from conidiophore.
Hypha produces conidiophore.
Conidia
Conidiophore
Ascus opens to release ascospores.
Meiosis then mitosis.
Karyogamy.
Plasmogamy.
Ascospore
– +
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Anamorphs
Produce asexual spores only rRNA sequencing places most in Ascomycota; a few are
Basidiomycota Penicillium Sporothrix (subcutaneous mycosis) Stachybotrys, Coccidioides, Pneumocystis (systemic
mycoses) Candida albicans (cutaneous mycoses)
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Basidiomycota
Club fungi Septate Produce basidiospores and sometimes
conidiospores Cryptococcus neoformans (systemic mycosis)
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Figure 12.10 A generalized life cycle of a basidiomycete.
Sexual reproduction
Asexual reproduction
Basidiospore germinates to produce hyphae.
Plasmogamy.
Vegetative Mycelium grows.
Fruiting structure (“mushroom”) develops.
Basidiospores are formed by meiosis.
Basidiospores mature.
Basidiospores are discharged.
Fragment grows to produce new mycelium.
Hyphal fragment breaks off vegetative mycelium.
– +
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Economic Effects of Fungi
Saccharomyces cerevisiae: bread, wine, HBV vaccine
Trichoderma: cellulase Taxomyces: taxol Entomophaga: biocontrol Coniothyrium minitans: kills fungi Paecilomyces: kills termites
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Fungal Diseases (Mycoses)
Systemic mycoses: deep within body Subcutaneous mycoses: beneath the skin Cutaneous mycoses: affect hair, skin, and nails Superficial mycoses: localized, e.g., hair shafts Opportunistic mycoses: caused by normal
microbiota or environmental fungi
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Check Your Understanding Assume you isolated a single-celled organism that
has a cell wall. How would you determine that it is a fungus and not a bacterium? 12-1
Contrast the mechanism of conidiospore and ascospore formation. 12-2
List the asexual and sexual spores made by Zygomycetes, Ascomycetes, and Basidiomycetes. 12-3
Why are microsporidia classified as fungi? 12-4 Are yeasts beneficial or harmful? 12-4
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Lichens
12-5 List the distinguishing characteristics of lichens, and describe their nutritional needs.
12-6 Describe the roles of the fungus and the alga in a lichen.
Learning Objectives
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Lichens
Mutualistic combination of an alga (or cyanobacterium) and fungus
Alga produces and secretes carbohydrates; fungus provides holdfast
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Figure 12.11a Lichens.
Three types of lichens
Fruticose
Foliose
Crustose
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Figure 12.11b Lichens.
Lichen thallus
Fungus Alga
Cortex
Algal layer
Fungal hyphae
Cortex
Rhizine
Medulla
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Economic Effects of Lichens
Dyes Antimicrobial (Usnea) Litmus
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Check Your Understanding What is the role of lichens in nature? 12-5 What is the role of the fungus in a lichen? 12-6
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Algae
12-7 List the defining characteristics of algae. 12-8 List the outstanding characteristics of the five
phyla of algae discussed in this chapter. 12-9 Identify two beneficial and two harmful effects of
algae.
Learning Objectives
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Kingdom Protista
Nutritional Type Photoautotroph
Multicellularity Some
Cellular Arrangement Unicellular, colonial, filamentous, tissues
Food Acquisition Method Diffusion
Characteristic Features Pigments
Algae
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Figure 12.12a Algae and their habitats.
Red 𝛌𝛌
Orange 𝛌𝛌
Yellow 𝛌𝛌
Violet 𝛌𝛌
Blue 𝛌𝛌 Red algae
Multicellular green algae
Brown algae
Unicellular green algae, diatoms, dinoflagellates
Sublittoral zone
Littoral zone
Green algae, cyanobacteria, euglenoids
LAND SURFACE
Algal habitats
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Figure 12.12 Algae and their habitats.
Pneumatocyst Blade
Brown alga (Macrocystis)
Stipe
Red alga (Microcladia)
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Figure 12.13a Green algae.
Multicellular green alga (Ulva)
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Figure 12.14a Diatoms.
Eunotia, a freshwater diatom that grows in acidic water
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Figure 12.15 Peridinium, a dinoflagellate.
Flagellum
Flagellum
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Produce male and female hyphae.
Figure 12.16 Oomycotes.
Sexual reproduction
Asexual reproduction
Male antheridial hyphae grow around female oogonium and insert their nuclei into the oogonium.
Zygotes are released.
Zygote germinates.
Vegetative hyphae grow on organic matter.
Hyphae produce sporangia.
On a suitable substrate, zoospore germinates to produce hyphae.
Motile zoospores swim from the sporangium.
Zoospore
Oogonium
Antheridial hypha
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Phaeophyta
Brown algae (kelp) Cellulose and alginic acid cell walls Multicellular Chlorophyll a and c, xanthophylls Store carbohydrates Harvested for algin
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Rhodophyta
Red algae Cellulose cell walls Most are multicellular Chlorophyll a and d, phycobiliproteins Store glucose polymer Harvested for agar and carrageenan
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Chlorophyta
Green algae Cellulose cell walls Unicellular or multicellular Chlorophyll a and b Store glucose polymer Gave rise to plants
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Figure 12.13b Green algae.
Life cycle of a unicellular green alga (Chlamydomonas)
Zygote formation
Fertilization
Meiosis
Growth
Nucleus
Chloroplast
Gamete formation
Cell wall
Stored starch
Eyespot
Flagella
Mitosis
Sexual reproduction
Asexual reproduction
Growth
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Diatoms
Pectin and silica cell walls Unicellular Chlorophyll a and c, carotene, xanthophylls Store oil Fossilized diatoms formed oil Produce domoic acid
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Figure 12.14 Diatoms.
Asexual reproduction of a diatom
Eunotia, a freshwater diatom that grows in acidic water
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Dinoflagellates
Cellulose in plasma membrane Unicellular Chlorophyll a and c, carotene, xanthins Store starch Some are symbionts in marine animals Neurotoxins cause paralytic shellfish poisoning
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Figure 12.15 Peridinium, a dinoflagellate.
Flagellum
Flagellum
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Oomycota
Cellulose cell walls Multicellular Chemoheterotrophic Produce zoospores Decomposers and plant parasites Phytophthora infestans responsible for Irish potato blight P. cinnamoni infects Eucalyptus P. ramorum causes “sudden oak death”
Water molds
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Produce male and female hyphae.
Figure 12.16 Oomycotes.
Sexual reproduction
Asexual reproduction
Male antheridial hyphae grow around female oogonium and insert their nuclei into the oogonium.
Zygotes are released.
Zygote germinates.
Vegetative hyphae grow on organic matter.
Hyphae produce sporangia.
On a suitable substrate, zoospore germinates to produce hyphae.
Motile zoospores swim from the sporangium.
Zoospore
Oogonium
Antheridial hypha
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Check Your Understanding How do algae differ from bacteria? From fungi?
12-7 List the cell wall composition and diseases caused
by the following algae: diatoms, dinoflagellates, oomycotes. 12-8, 12-9
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Protozoa
12-10 List the defining characteristics of protozoa. 12-11 Describe the outstanding characteristics of the
seven phyla of protozoa discussed in this chapter, and give an example of each.
12-12 Differentiate an intermediate host from a definitive host.
Learning Objectives
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Kingdom Various
Nutritional Type Chemoheterotroph
Multicellularity None
Cellular Arrangement Unicellular
Food Acquisition Method Absorptive; ingestive
Characteristic Features Motility; some form cysts
Protozoa
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Characteristics of Protozoa
Vegetative form is a trophozoite Asexual reproduction is by fission, budding, or
schizogony Sexual reproduction by conjugation Some produce cysts
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Medically Important Phyla of Protozoa
Diplomonads Parabasalids Euglenozoa Amebae Apicomplexa Dinoflagellates Ciliates
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Diplomonads
No mitochondria Multiple flagella Giardia lamblia
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Figure 12.18 Members of the super kingdom Excavata.
Giardia trophozoites. Giardia cyst.
Cyst
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Parabasalids
No mitochondria Multiple flagella No cyst Trichomonas vaginalis
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Figure 12.18d Members of the super kingdom Excavata.
Trichomonas vaginalis.
Axostyle Undulating membrane
Flagella
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Euglenozoa
Move by flagella Euglenoids Photoautotrophs
Hemoflagellates Trypanosoma spp.
− Sleeping sickness −Chagas’ disease
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Figure 12.18e Members of the super kingdom Excavata.
Euglena.
Chloroplasts
Eye spot
Flagella
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Figure 23.23 Trypanosoma cruzi, the cause of Chagas’ disease (American trypanosomiasis).
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Amebae
Move by pseudopods Entamoeba Acanthamoeba
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Figure 12.19 Amebae.
Pseudopods
Nucleus
Food vacuole
Amoeba proteus
Entamoeba histolytica
Nucleus
Red blood cells
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Apicomplexa
Nonmotile Intracellular parasites Complex life cycles Plasmodium Babesia Cryptosporidium Cyclospora
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Figure 12.20 The life cycle of Plasmodium vivax, the apicomplexan that causes malaria. Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human.
Sporozoites undergo schizogony in liver cell; merozoites are produced.
Merozoites released into bloodstream from liver may infect new red blood cells.
Merozoite develops into ring stage in red blood cell.
Intermediate host Ring stage grows and
divides, producing merozoites.
Merozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes.
Another mosquito bites infected human and ingests gametocytes.
In mosquito’s digestive tract, gametocytes unite to form zygote.
Resulting sporozoites migrate to salivary glands of mosquito.
Sexual reproduction
Asexual reproduction
Female gametocyte
Male gametocyte
Zygote
Male
Gametocytes
Female
Sporozoites in salivary gland
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Chapter 12, unnumbered figure A, page 357.
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Chapter 12, unnumbered figure B, page 357.
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Figure 23.24 The life cycle of Toxoplasma gondii, the cause of toxoplasmosis.
If a pregnant woman accidentally ingests oocysts (contacted when changing a cat litter box), prenatal infection of the fetus may occur.
If humans eat undercooked meat containing tissue cysts, they may become infected.
Definitive host
Tachyzoites Bradyzoites in tissue cyst Sporocysts
Sporozoite
Intermediate hosts
Mature oocyst (10–13 μm x 9–11 μm)
Sporogony
Immature cyst
Immature oocyst is shed in cat feces.
Mature oocysts develop by sporogony and contain two sporocysts, each with four infective sporozoites.
Oocysts can infect many hosts, including mice, domestic animals, and humans, via ingestion.
Sporozoites from ingested oocysts invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites.
Cat ingests bradyzoites in tissue cysts of animals, usually mice.
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Figure 12.15 Peridinium, a dinoflagellate.
Flagellum
Flagellum
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Figure 27.13 A red tide.
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Ciliates
Move by cilia Complex cells Balantidium coli is the only human parasite
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Figure 12.21 Ciliates.
Pellicle Cytostome
Contractile vacuole Macronucleus Micronucleus Anal pore
Cilia
Food vacuoles
Cilia
Cytostome
Paramecium
Vorticella
Stalk
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Figure 12.17 Conjugation in the ciliate protozoan Paramecium.
Macronucleus
Micronucleus
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Check Your Understanding Identify three differences between protozoa and
animals. 12-10 Do protozoa have mitochondria? 12-11 Where does Plasmodium undergo sexual
reproduction? 12-12
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Slime Molds
12-13 Compare and contrast cellular slime molds and plasmodial slime molds.
Learning Objective
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Figure 12.22 The generalized life cycle of a cellular slime mold.
Spore is released.
Cells in spore cap form spores.
Fruiting body with spore cap forms.
Slug stops migrating and begins to form stalk in differentiation stage.
Sheath forms to create migration stage (slug) (0.5 mm).
Ameba germinates from spore.
Stalk (1 mm)
Spore
Nucleus
Spore caps
cAMP
cAMP
cAMP
Amebae aggregate.
Amebae move toward cAMP signal given off by one ameba.
Ameba reproduces.
Asexual reproduction
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Figure 12.23 The life cycle of a plasmodial slime mold.
Plasmodium grows, distributing nutrients by cytoplasmic streaming.
Haploid gametes fuse, producing zygote.
Gamete germinates from spore.
Spores are released.
Nuclei in spores go through meiosis, forming gametes.
Multinucleate plasmodium forms.
Zygote develops by nuclear division and cell growth.
Plasmodium separates into groups of protoplasm.
Each group forms sporangia on stalks.
Spores develop in sporangia.
Sexual reproduction
Asexual reproduction
Channel of cytoplasmic streaming
Sporangia
Stalk
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Check Your Understanding Why are slime molds classified with amebae and not
fungi? 12-13
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Helminths
12-14 List the distinguishing characteristics of parasitic helminths.
12-15 Provide a rationale for the elaborate life cycle of parasitic worms.
Learning Objectives
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Kingdom Animalia
Nutritional Type Chemoheterotroph
Multicellularity All
Cellular Arrangement Tissues and organs
Food Acquisition Method Ingestive; absorptive
Characteristic Features Elaborate life cycles
Helminths
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Helminths (Parasitic Worms)
Kingdom: Animalia Phylum: Platyhelminthes (flatworms)
−Class: trematodes (flukes) −Class: cestodes (tapeworms)
Phylum: Nematoda (roundworms)
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Characteristics of Helminths
Reduced digestive system Reduced nervous system Reduced locomotion Complex reproduction
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Life Cycle of Helminths
Monoecious (hermaphroditic) Male and female reproductive systems in one animal
Dioecious Separate male and female
Egg → larva(e) → adult
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Check Your Understanding Why are the drugs used to treat parasitic helminths
often toxic to the host? 12-14 Of what value is the complicated life cycle of
parasitic helminths? 12-15
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12-16 List the characteristics of the two classes of parasitic platyhelminths, and give an example of each.
12-17 Describe a parasitic infection in which humans serve as a definitive host, as an intermediate host, and as both.
12-18 List the characteristics of parasitic nematodes, and give an example of infective eggs and infective larvae.
12-19 Compare and contrast platyhelminths and nematodes.
Helminths
Learning Objectives
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Figure 12.25 Flukes.
Oral sucker
Intestine
Ventral sucker Testis
Ovary
Fluke anatomy Clonorchis sinensis
Oral sucker
Ovary Intestine Testes
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(b) Life cycle of Schistosoma, cause of schistosomiasis.
Figure 23.28 Schistosomiasis.
Free-swimming cercariae penetrate human skin, losing tail.
Intermediate host
Cercariae are released from the snail.
Cercariae travel through circulatory system to intestinal blood vessels, where they mature into adults.
Adult female flukes lay eggs.
(a) Male and female schistosomes. The female lives in a groove on the ventral (lower) surface of the male schistosome (“split-body”), is continuously fertilized, and continuously lays eggs. The sucker is used by the male to attach to the host.
Eggs reach body of water after being excreted in human feces or urine.
Cercaria (0.33 mm)
Cercaria (0.13 mm)
Definitive host
Female (size: 15–20 mm)
Eggs
Male
Adult flukes
Egg (0.15 mm)
Miracidium (0.2 mm)
Male
Mouth Sucker Female Mouth
Eggs hatch into free-swimming larvae (miracidia).
Miracidium reproduces in snail, forming several cercariae.
Miracidium penetrates snail.
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Figure 12.26 The life cycle of the lung fluke, Paragonimus, spp.
Cercaria
Redia
Cercaria (0.5 mm long)
Intermediate host
Cercaria leaves snail and enters crayfish.
Metacercaria (0.25–0.5 mm)
In crayfish, cercaria encysts to produce metacercaria.
Infected crayfish is eaten by human, and metacercaria develops into adult fluke.
Definitive host
Free-swimming miracidium enters snail.
Intermediate host
Miracidium (0.8 mm long)
Miracidium develops in egg and hatches from egg.
Eggs reach water after being excreted in feces.
Adult fluke (7.5–12 mm long)
Eggs
Inside snail, miracidium develops into redia, which reproduces asexually to produce rediae; several cercariae develop within redia.
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1 Hermaphroditic adult fluke releases eggs into human lung.
Sexual reproduction
Asexual reproduction
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Hooks
Sucker
Scolex
Sucker
Genital pore Ovary
Mature proglottid will disintegrate and release eggs
Figure 12.27 General anatomy of an adult tapeworm.
Neck
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Humans as Definitive Hosts
Definitive Host Taenia saginata
Cysticerci in beef muscle
Intermediate Host
Echinococcus granulosus
Adult in dog
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Scolex
Definitive host eats intermediate host, ingesting cysts.
Figure 12.28 The life cycle of the tapeworm, Echinococcus, spp.
Definitive host
Adult tapeworm
Scoleces from cyst attach to intestine and grow into adults.
Adult tapeworm releases eggs.
Egg (30–38 µm)
Hydatid cyst
Larvae develop into hydatid cysts.
Brood capsule Scolex
Larva Eggs hatch, and larvae migrate to liver or lungs.
Intermediate host ingests eggs.
Intermediate host
Human intermediate host ingests eggs. Dead end.
Intermediate host
Sexual reproduction
Asexual reproduction
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© 2013 Pearson Education, Inc. Adult pinworm
Figure 12.29a The pinworm Enterobius vermicularis.
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Figure 12.30 The heartworm Dirofilaria immitis.
Heartworm
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Adult pinworm
Figure 12.29 The pinworm Enterobius vermicularis.
Mouth
Intestine
Ovary
Genital pore
Anus
Female (8–13 mm long)
Mouth
Intestine
Genital pore
Anus
Spicules
Male (2–5 mm long)
Larva
Egg (55 μm long)
Pinworm egg
Testis
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Figure 25.26 The life cycle of Trichinella spiralis, the causative agent of trichinellosis.
Ingested cysts develop into Trichinella spiralis adults in the pig’s intestinal wall.
Garbage, including undercooked or raw pork
Meanwhile, other animals eat infected meat that has been dumped.
Capsule
Adult worms produce larvae that encyst in the pig’s muscles.
Section of encysted T. spiralis
Human eats undercooked pork containing cysts that are infective to humans or animals that ingest it.
Trichinellosis in humans; ingested cysts develop into T. spiralis adults. Adults produce larvae that encyst in muscles.
T. spiralis adult
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Figure 25.23 An Ancylostoma hookworm attached to intestinal mucosa.
Hookworm
Intestinal mucosa
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Check Your Understanding Differentiate Paragonimus and Taenia. 12-16 What is the definitive host for Enterobius?
12-17 What stage of Dirofilaria immitis is infectious
for dogs and cats? 12-18 You find a parasitic worm in a baby’s diapers.
How would you know whether it’s a Taenia or a Necator? 12-19
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12-20 Define arthropod vector. 12-21 Differentiate a tick from a mosquito, and name
a disease transmitted by each.
Arthropods as Vectors
Learning Objectives
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Arthropods as Vectors
May transmit diseases (vectors) Kingdom: Animalia Phylum: Arthropoda (exoskeleton, jointed legs)
−Class: Insecta (6 legs) − Lice, fleas, mosquitoes
−Class: Arachnida (8 legs) −Mites and ticks
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Arthropods as Vectors
Mechanical transmission Biological transmission Microbe multiplies in vector
Definitive host Microbe’s sexual reproduction takes place in vector
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Figure 12.31 Mosquito.
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Figure 12.32 Tick.
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Insert Fig 12.33
Figure 12.33 Arthropod vectors.
2.5 mm
2.5 mm
Rat flea Human louse Deer fly Kissing bug
1 cm
2 cm
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Check Your Understanding Vectors can be divided into three major types,
according to roles they play for the parasite. List the three types and a disease transmitted by each. 12-20
Assume you see an arthropod on your arm. How will you determine whether it is a tick or a flea? 12-21