Animal-Like Protists: The
ProtozoaChapter 10
Protists• Zoologists recognize between 7-45 Phlya of Protists
• This group is Polyphyletic- traced to separate ancestors
• Some are plant-like• Some are animal-like
Figure 11.01
Protozoa:• Are complete organisms in which all life activities are carried on within a single plasma membrane.
• Unicellular• Eukaryotic
Maintaining Homeostasis
Maintaining Homeostasis
• Cytoplasm has 2 regions–Ectoplasm- just beneath pellicle, clear and firm
–Endoplasm- granular and fluid, inner cytoplasm
See figure 8.3
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Fig. 8.3
W. D. Russell-Hunter, A Life of Invertebrates, © 1979.
Protozoan Protist
Maintaining Homeostasis
• Freshwater protozoa must regulate water because of osmosis.
• Contractile vacuoles or water expulsion vacuoles- remove excess water
Maintaining Homeostasis
• Cytopharynx- ingest food in a specialized region(analogous mouth)
• Food vacuoles-digest and transport food
• Cytopyge- specialized region to release waste
Maintaining Homeostasis
• Large surface area to volume ratio
–Gas exchange of oxygen and carbon dioxide
–Excretion of nitrogenous by products
–All happens by diffusion
Reproduction• Both asexual and sexual reproduction can occur.
• But most do mainly asexual.
Types of Asexual Reproduction
• Binary fission•Mitosis produces 2 new nuclei•Cytoplasm divides (cytokinesis)
»Longitudinal or transverse.•2 new organisms that are identical.
Binary Fissionhttp://protist.i.hosei.ac.jp/PDB/PCD1502/animation/DividingAmoeba.html
One is the loneliest number. . .
Unless you can do
OK now you do it!
Binary fission
Types of Asexual Reproduction• Budding
•New individuals arise from outgrowths of existing ones.
•Offspring may either detach from the parent or remain joined forming colonies.
Types of Asexual Reproduction
• Multiple fission or schizogony•Large number of daughter cells from the division of a single protozoan
•Many multiple mitotic nuclear divisions
•Cytoplasm divides, multiple new cells
Multiple fission or schizogony
Symbiotic Lifestyle
• Many protozoa have symbiotic lifestyles.
• Symbiosis- intimate association between two organisms.
• Three types: parasitism, commensalism, mutualism
Symbiotic Lifestyle
• Parasitism- one organism lives in or on a second organism, called a host
Parasitism• Definitive host-sexual stages of the parasite
• Intermediate host-when sexual stages produce offspring, enter this host, reproduce asexually.
• Many protozoa are parasites
Symbiotic Lifestyle
• Commensalism- one organism benefits and second is neither benefited or harmed.
Symbiotic Lifestyle
• Mutualism-both organisms benefit.
Taxonomy• Protozoologists: zoologists who specialize in the study of protozoa
• Found out that Protista Kingdom to diverse to put into one Kingdom
• Many protist phylum have been elevated to kingdom status
4 Major Categories of
Protozoa• Flagellated Protozoa• Amoeboid Protozoa• The Coccidea• The Ciliates
Flagellated Protozoa• Possess one to many flagella used for locomotion.
• Produce whip-like or helical movements
• Push or pulls protozoan through aquatic medium
Flagellated Protozoa
• Both Flagella and Cilia ( both used for locomotion) share a common ultrastructure.
Flagellated Protozoa
• 9 doublets (pairs) of microtubules arranged in a ring
• In center of the ring 2 single microtubules.
• Anchored in the cell by a basal body (centriole)
Flagellated Protozoa
The 9 + 2 arrangement
Flagellated Protozoa
• Many phyla represented• All possess pellicle for shape
• Two major groups:
Phytoflagellated
Zooflagellated
Phytoflagellate
• Possess chlorophyll• Produce large portion of food in marine food webs
• Oxygen in aquatic habitats come from them
Phytoflagellate
Dinoflagellates (dino= whirling)Marine and freshwater phytoplanktonTransverse groove 1-2 flagella-makes them whirl or spinOne trailing flagella pushes organism forward
Phytoflagellate
Dinoflagellates (dino= whirling)
PhytoflagellateDinoflagellates (dino= whirling)
Blooms (explosive population growth) can cause “red tide”Blooms appear brownish red or pinkish orange b/c of presence of carotenoidsToxins produced by some can cause massive kills of invertebrates and fish
This massive “red tide” of the dinoflagellate Noctiluca stretched for more than 20 miles along the southern California coast. Non-toxic blooms such as these can cause extensive mortalities of plants and animals in shallow waters when the bloom biomass decays, stripping oxygen from the water. (P. Franks)
Phytoflagellate
Dinoflagellates
Some can be bioluminescentOrganisms feed on them, the light attracts fishes that eat those predators
On the island of Vieques off the coast of Puerto Rico, Mosquito
Bay’s dinoflagellates
Making angel’s wings by sweeping her arms, Mosquito Bay tour guide Sharon Grasso lights up the surfaceof the water
Kayaking on the bay on the bay
Phytoflagellate
EuglenaFreshwater protozoa
ChloroplastIf cultured in dark feed by absorption and lose green color
PhytoflagellateEuglena
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Fig. 8.7
Structure of Euglena
Subphylum Mastigophora
(cl. Phytomastigophora)
Zooflagellate• Lack chloroplast• Heterotrophic• Some are parasites of humans
Zooflagellate
Trypanosomes bruceiParasite that causes African sleeping sickness
ZooflagellateTrypanosomes brucei
Tsetse flies are the intermediate hosts
Trypanosomes brucei life cycleTsetse fly bites an infected human
Trypanosomes multiply asexually in gut of flyTrypanosomes migrate to salivary glands transform thru number of body formsTsetse fly bites human, parasite in blood and multiplies asexually and transform thru number of body forms again
Trypanosomes brucei life cycle
• In human, parasite can live in blood, lymph, spleen, central nervous system, and cerebrospinal fluid
• If the parasite travels to the central nervous system this causes mental dullness, lack of coordination, “sleepiness”.
Trypanosomes brucei life cycle
ZooflagellateTrypanosomes cruziParasite that causes Chagas disease
Carlos Chagas
ZooflagellateTrypanosomes cruziKissing bugs are the intermediate hosts
ZooflagellateTrypanosomes cruziare shed in the feces of the bug and are inoculated into the human host by scratching infected feces into skin abrasions usually caused by the bug in the process of feeding (blood-sucking).
The feeding Kissing Bug
Amoeboid Protozoa• Move by Pseudopodia- temporary cell extensions usually of the ectoplasm and endoplasm for feeding and moving
PseudopodiaTypes:1. Lobopodia: broad extensions used for
locomotion and engulfing food2. Filopodia: provide constant two-way
streaming that delivers food in a conveyor belt fashion
3. Reticulopodia: similar to filopodia, except they extend out and form net-like series of extensions
4. Axopodia: thin, filamentous and supported by a central axis of microtubules
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Fig. 8.10
Variations in Pseudopodia
Pseudopodia
Amoeboid ProtozoaMost familiar amoebozoans are Rhizopodans
Naked- no test (shell)Live in shallow
freshwater
The AMOEBA
Amoeboid ProtozoaFeed on other protists
and bacteria by Phagocytosis
Phagocytosis
Amoeboid Protozoa
Binary fission occurs
Amoeboid Protozoa
Entamoeba histolyticaCauses dysentery in humansInflammation of lower intestinal tractDebilitating diarrheaNeeds no intermediate host
The CoccideaPhylum Apicomplexa All parasitesNo cilia or flagella (except in reproductive stages)Apical Complex for penetrating host cells
The Coccidea
Phylum ApicomplexaLife cycles typically asexual (schizogony, sporogony) some sexual (gametogony) phases
APICOMPLEXA
The CoccideaPlasmodium
Causes malaria (4 different species)Has devastated mores armies than has actual combatOver 100 million humans annually contract the disease, 2 million die each year
Plasmodium Life cycle
Involves vertebrate (us) and mosquito host
Life cycle of malaria
Plasmodium has two hosts: mosquitoes and humans.
Sexual reproduction takes place in the mosquito and the parasite is transmitted to humans when the mosquito takes a blood meal
Life cycle of malaria: humans
• The mosquito injects Plasmodium into a human in the form of sporozoites.
• The sporozoites first invade liver cells and asexually reproduce to produce huge numbers of merozoites which spread to red blood cells where more merozoites are produced through more asexual reproduction.
•
Life cycle of malaria: humans
• Some parasites transform into sexually reproducing gametocytes and these if ingested by a mosquito continue the cycle.
Life cycle of malaria: mosquitoes
• Gametocytes ingested by a mosquito combine in the mosquito’s stomach to produce zygotes.
• These zygotes develop into motile elongated ookinites.
Life cycle of malaria: mosquitoes
• The ookinites invade the mosquito’s midgut wall where they ultimately produce sporozoites, which make their way to the salivary glands where they can be injected into a new human host.
Malaria – Life cycle
Malaria caused by Plasmodium
The Coccidea
CryptosporidiumCauses chronic diarrhea and the only known protozoan to resist chlorinationTransmitted through water, food, animal-to-human and human-to-human contact
The Coccidea
Cryptosporidium
The CoccideaToxoplasma
Cat only host with sexual stage – sheds from intestinal tractMode of transmission : fecal oral from cat or oral (raw meat)
Toxoplasma
Once infection occurs most develop an effective immunityIf a woman is infected near time of pregnancy or during, congenital toxoplasmosis may develop in the fetusMajor cause of stillbirths and spontaneous abortions
The Ciliates• Complex protozoan • Fresh and marine
environments• All have 9 +2 cilia for
locomotion and generation of feeding currents
Locomotion: cilia Cilia are generally similar to flagella
but are much shorter, more numerous and widely distributed over the surface of the organism
Trichocysts: used for protection, rodlike or oval structures that can be discharged and stuck to predators
Trichocysts
Phylum Ciliophora:
Other Characteristics:1. Relatively rigid pellicle and
more or less fixed shape2. Distinct cytostome (mouth)
structure3. Dimorphic nuclei, typically
larger macronuclei and one more smaller micronuclei
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Fig. 8.17b
Ciliate (Paramecium)
Ciliophora
Nutrition:
• some ciliates possess an oral groove
• cilia sweep food particles down this groove toward the cytopharynx where a food vacuole forms
• some ciliates even possess a cytopyge which is used to remove waste from the organism
Genetic Control and Reproduction
One Macronucleus- regulates daily metabolic activites
One or more Micronuclei- genetic reserve of the cell
Genetic Control and Reproduction
Can reproduce asexually by transverse binary fission or budding
Or some can reproduce sexually by conjugation
Conjugation:1. Random contact brings individuals of
opposite mating types together (called conjugants)
2. Meiosis results in four haploid pronuclei3. Three pronuclei and the macronucleus
degenerate. Mitosis and mutual exchange of pronuclei is followed by fusion of the pronuclei.
4. Conjugants separate. Nuclear divisions that restore nuclear characteristics of species follow. Cytoplasmic divisions may accompany these events
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Fig. 8.21
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Conjugation in Paramecium
Symbiotic Ciliates
Some are mutualistic by inhabiting the rumen of many hoofed animals
Balantidium coli is a parasitic ciliate that lives in the large intestine of humans, pigs, and other mammals.
EOC Figure
The End