Protozoan Groups

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Chapter 11
Protozoan Groups
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Outline

• Intro
• Defining protozoan groups
• Form and function
• locomotion
• cells
• nutrition
• excretion and osmoregulation
• reproduction
• encystment and excystment
• Major protozoan taxa
• Phylogeny and adaptive radiation

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Intro

• 1st evidence of life 3.5 BYA (prokaryotes)
• Eukaryotes arise from prokaryotes via
  symbiogeneis
• mitochondria, chloroplasts

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Intro

• Protozoans
• zoa animal-like (no CW, motile stage in life)
• defining characteristic eukaryotic and single
  cell (acellular/unicellular)
• widespread, 64,000 sp. named, 250,000 sp.?
• contributions
• ? intracellular specialization w/ organelles
  (division of
  labor w/i cell)
• division of labor btwn cells
• asexual and sexual reproduction
• simple reflexes/instincts (respond to stimuli)
• some have exoskeletons
• means of nutrition (autotrophic, saprozoic,
  holozoic)
• some symbiotic
• mutualistic, commensalistic, parasitic
• enzyme systems
• locomotion (sessile, free swimming)

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How Protozoan Groups Are Defined

• Protista plant- and animal-like single-celled
  organisms
• protozoa animal-like single-celled organisms
• feeding behavior used as distinction
• plant-like autotrophic
• animal-like heterotrophic
• phagocytosis infolding/invagination of PM
  around food particle
• phagotrophs (holozoic feeders) eat visible
  particles
• osmotrophs (saprozoic feeders) consume soluble
  food
• but autotrophic protozoans can be phago- and
  osmotrophs too
• some can change depending on environment
  (opportunistic)
• they dont conform!

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How Protozoan Groups Are Defined

• means of locomotion used to separate
• lack locomotor structure - C. Sporozoa
• flagellates use flagella (few, long)
• ciliates use cilia (many, short)
• amebas use psuedopodia (mvmt of cytoplasm)
• naked or covered PM w/ test (shell of
  siliceous/chitinous material)

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How Protozoan Groups Are Defined

• 7 phyla
• P. Chlorophyta (uni-/multicellular algae) (e.g.
  Volvox)
• P. Retortamonada (e.g. Giardia)
• P. Axostylata (e.g. Trichomonas)
• P. Euglenozoa (e.g. Euglena)
• P. Retortamonada (e.g. Giardia)
• P. Apicomplexa (sporozoans) (e.g.
  Cryptosproidium, Plasmodium)
• P. Ciliophora (ciliates) (e.g. Paramecium)
• P. Dinoflagellata (flagellates)

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How Protozoan Groups Are Defined

• Characteristics of protozoans
• unicellular, some colonial, multicellular stages
• microscopic, some larger
• all symmetries, variable shape
• no germ layer
• specialized organelles, no organs/tissues, single
  or multiple nuclei
• free-living, mutualistic, commensalistic,
  parasitic
• pseudopodia, flagella, cilia, sessile
• naked, some simple endo- or exoskeleton
• autotrophic, heterotrophic, saprozoic
• aquatic, terrestrial, free-living, symbiotic
• asexual or sexual reproduction

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Form and Function

• Locomotion
• cilia and flagella
• 92 tube of microtubules axoneme
• covered by membrane
• kinetosome (a.k.a. basal body) 9 triplets
  of
  microtubules base of cilia/flagella,
  anchor to
  body
• also used in feeding, R, food handling,
  reproduction,
  excretion, osmoregulation
• sliding microtubule hypothesis
• cleavage of ATP results in arms of
  dynein (motor
  protein) walking
  along adjacent microtubule
• sliding relative to adjacent pair
  spokes btwn
  central pair and
  doublets bending

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Form and Function

• pseudopodia
• extensions of cytoplasm
• endoplasm granular
• ectoplasm transparent
• extension of ectoplasm hyaline cap
• types
• lobopodia blunt tip
• filipodia thin, sharp pointed
• rhizopodia branched filaments
• reticulopodia branched filaments that rejoin
• axopodia thin, pointed w/ central filament of
  microtubles

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Form and Function

• Functional components of cells
• nucleus w/ nucleoli
• mitochondria w/ DNA
• cells that lack mitochondria have hydrogenosomes
• evolved from mitochondria, func. w/o O2
• Golgi apparatus (a.k.a. dictyosome)
• plastids
• some chloroplasts
• extrusomes extrude stuff
• contractile vacuoles protozoan vacuole that
  takes up and releases water to outside of cell,
  func. osmoregulation/excretion

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Form and Function

• Nutrition
• holozoic feeders infolding/invagination of PM
  around food particle (phagocytosis)
• food particle pinched off into membrane-bound
  phagosome (food vacuole)
• lysosomes w/ digestive enzymes fuse w/ phagosome
• waste released by vacuole fusing w/ PM
  (exocytosis)
• saprozoic feeders consume soluble food via
  direct transport across PM (pinocytosis)
• facilitated transport, active transport, diffusion

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Form and Function

• Reproduction
• asexual via fission
• binary fission 2 identical cells
  
  produced
• budding progeny cell smaller than parent, grows
  to maturity
• multiple fission (schizogony) multiple
  individuals simultaneously produced
• sporogony union of gametes prior schizogony
• sexual
• some undergo meiosis just prior gamete formation
  (gametic meiosis)
• others undergo meiosis just after fertilization
  (zygotic meiosis)
• thus live mostly n state
• others undergo alteration of n and 2n
  (intermediary meiosis)
• like plants
• syngamy fertilization by anothers gamete
• autogamy fertilization by your own gamete
• conjugation exchange gametic nuclei btwn paired
  organisms

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Form and Function

• Encystment and excystment
• survive harsh conditions by forming cysts
  (encystment)
• cyst dormant form w/ resistant external
  coverings and metabolic shutdown
• parasites
• triggered by adverse conditions (temp., food,
  drought, O2, pH)
• return from cyst (excystment) in favorable
  conditions