Protozoa I

Protozoans

Over 50,000 known 45 phyla (more than metazoa!) species

Relationship to Other Organisms

  Two Kingdoms – Arististotle, Linnaeus  Plants  Metaphyta  Protophyta  Animals  Metazoa  Protozoa Lots of problems with this scheme

Relationship to Other Organisms

  3 kingdoms of Haeckle/Darwin  Plants  Animals  Protists  Took care of the little stuff seen with the early microscopes Still has problems

Relationship to Other Organisms

 Copeland’s Four-Kingdom System (1938)  Kingdom Monera.  Kingdom Protoctista or Protista (priority?).    Protozoa Red and brown algae Fungi  Kingdom Plantae   Green algae Fungi  Kingdom Animalia

Relationship to Other Organisms

  Whittaker – 1960’s  Added Kingdom Fungi 5 Kingdoms  Kingdom Animalia  Kingdom Plantae  Kingdom Fungi  Kingdom Protista Eukaryotes  Kingdom Monera - Prokaryotes

Kingdoms and Domains

 Carl Woese - U. of Illinois (1970’s present)  Studied gene sequences of bacteria, archaea, and eukaryotes  Found major fundamental differences

Relationship to Other Organisms

 Carl Woese – late 1970’s  Archaea NOT Archaebacteria  Biochemistry is different from bacteria  More closely related to animals than they are to bacteria  Briefly had six kingdoms with Archaea and Eubacteria replacing the Monera  Changed to three domains    Eubacteria Archaea Eukarya Prokaryotes

3 Domains of Life 6 Kingdoms of Life

Relationship to Other Organisms

 Protista or Protoctista  Some algae (red, most green algae are not included)  Protozoa   Traditionally classified based on how they move: amoebae, flagellates, ciliates, sporozoans Has changed recently to also contain:  Some slime molds  Aquatic “molds”  “Protists” are now distributed among all kingdoms.” pg 37 incorrect. No prokaryotic protists!

Old system classified by locomotion

 Ciliophora (=Ciliata, ciliates) a clade Hypotrichs, holotrichs, heterotrichs, suctorians  Apicomplexa- (=Sporozoa) a likely clade Gregarina, Coccidia – includes many important parasites  Mastigophora (=flagellates) a functional group Excavates, Kinetoplastids, Parabasalids, Choanoflagellates, Dinoflagellates (some are important parasites)  Sarcodina (=amoebas) a functional group Amoebozoa, Foraminifera, Actinopoda (Radiolaria, Heliozoa) (many are important geologically)

Protozoan Phylogeny

 Problem  Protozoa is a polyphyletic group  Multiple ancestors rather than a single ancestral protozoan  Aim is to establish monophyletic groups that have a single ancestor

Protozoan Phylogeny

 Reclassification based on  Life History  Ultrastructure  Biochemistry  Molecular data including DNA sequencing  Most trees are being constructed based on molecular data   May or may not be the “best” way to go Dissenting camps: role of lateral gene transfer, choice of genes for sequencing, convergent evolution, etc.

Relationship to Other Organisms

  Protista – still used as teaching tool.

 Grades 7-12?

 Undergrad intro bio (with reservations) We will not discuss Protists !

 Instead, note the following schemes:  First - breakdown of what used to be protists.

 Second - taxonomic relationships of organisms covered in P. Ch 3 (pg 38).

 Only cover those in text and/or lab

Eukaryote classification is in flux

 The major clades are not yet sorted out – but there is rapid progress  Based on cell structural features, there are about 60 different named eukaryote taxa according to Patterson (Tree of Life)  These have been sorted into 8 clades based on molecular & structural data by Baldauf 2003 (Science 300:1703)

8 major eukaryote clades (mainly from Baldouf 2003)

1.

2.

3.

4.

 Opisthokonts includes animals, fungi Single basal flagellum on reproductive cells, flat mitochondrial cristae (most eukaryotes have tubular ones).  Plants includes land plants, green algae, red algae Plastids with just two outer membranes (primary plastids).  Heterokonts includes brown algae, golden algae, diatoms, water molds Unique flagellum decorated with hollow tripartite hairs (stramenopiles) and, usually, a second plain one. Plastids have 4 membranes (secondary).

 Cercozoa includes foraminifera (& radiolaria?) Amoebae with filose pseudopodia, often living within tests.

5.

6.

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8.

 Amoebozoa includes lobose amoebae, most slime molds Mostly naked amoebae (lacking tests), often with lobose pseudopodia.  Alveolates includes ciliates, dinoflagellates, apicomplexans Have systems of cortical alveoli directly beneath their plasma membranes  Discicristates includes many flagellates, some slime molds Have discoid mitochondrial cristae  Amitochondrial excavates includes parabasalids, diplomonads Most have an excavated ventral feeding groove, and all lack mitochondria.

Defining Characteristics of “Protozoa”

   1674 Antonie van Leeuwenhoeke Nearly ubiquitous –wherever there is water  Soil  Water  On/in plants and animals Life styles  Free-living  Symbioses   Mutualists Parasites

Antonie van Leeuwenhoeke

Things that animals do (and protozoa too)        Move (at some stage in the life cycle) Obtain food and digest it Obtain oxygen Maintain water and salt balance Remove metabolic wastes Reproduce Sense and react to the environment

Defining Characteristics of “Protozoa”

   General characteristics highly variable  Size, morphology, ultrastructure  Nutritional mode, physiology  Behavior, life history Importance  Disease agents  Model organisms in biological research Most are probably unknown  82,000 known species  ½ of these are fossils (shelled forms)

Defining Characteristics of “Protozoa”

 Importance  Disease agents  Model organisms     Ecology Genetics Physiology Development

Defining Characteristics of “Protozoa”

     Eukaryotic Unicellular  Mostly small 5-250 μm (0.5 μm – 7 mm)  Multicellularity in a few but this is a derived character No collagen or chitin in cell walls Heterotrophic  Ancestral state is non-photosynthetic  Photosynthesis in a few groups is a derived character Most are motile (except Apicomplexa)

Protist Bauplan - On Being Unicellular

 Strategies and constraints of a

Unicellular Bauplan

 Size limitations  Body structure  Excretion  Gas exchange  Support and locomotion  Nutrition  Reproduction  Activity and sensitivity

On Being Unicellular

   Protozoa vs metazoa Protozoa are unicellular  Thought to be simplest form of life  BUT … Protozoa are not simple!

 A protozoan is more complex than any single metazoan cell  Very complex internal structure  Specialized organelles take the place of organs in metazoans

Halteria

Stylonychia

Size limitations

 Surface area to volume ratio  SA increases as radius squared  V increases as radius cubed  As cell becomes larger, diffusion becomes more and more difficult (~1 mm limit)  Need to have lots of complex projections etc. to increase SA

Body Structure

 Cytoplasm has two regions 

Ectoplasm

 Next to cell membrane  Clear, stiff, gelatinous 

Endoplasm

 Inner portion   More fluid in nature http://www.youtube.com/watch?v=85D GyFzxvy8&feature=player_detailpage

Body Structure

  Only one plasma membrane  Everything is inside that membrane  Structure is identical to the plasma membrane of all other multicellular organisms  High SA/V for protist cells Membrane has fluid mosaic structure  Lipids and proteins can move about laterally within the membrane

Membrane has fluid mosaic structure

Body Structure

 Internal structures  Cytoskeleton  Shape  Rigidity

Cytoskeleton Myonemes

Cytopharynx Macronucleus 250 µm Cytopharynx Cirri

Body Structure

 Outer coverings - give shape/support/protection 

Pellicle

  Interlocking strips of protein below plasma membrane in Euglenids Gives cell shape and stability while permitting flexibility

Eugloid movement =

metaboly

Body Structure

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Lorica

 Vase-shaped protective shell

Body Structure

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Test

 External “shell”  Usually many parts  Plates are below plasma membrane (cellulose plates in dinoflagellates, various materials in testate amoebas)  CaCO 3 foraminiferans  Silica in radiolarians

Body Structure

 The usual eukaryotic organelles  May be more than one macronucleus   Runs everyday activities of cell May be one or more micronuclei  Used for sexual reproduction  Some are anaerobes     Most have no mitochondria or cytochromes, and have an incomplete TCA cycle (tricarboxylic acid cycle) Some contain hydrogenosomes-small membrane delimited organelles containing a unique electron transfer system that uses protons as terminal electron acceptors to form molecular hydrogen Trichonympha lives in the gut of termites Giardia is an intestinal parasite

Mitochondria clockwise Paramecium Cryptomonad Euglena

Body Structure

    Some protozoa are anaerobes.

  Trichonympha Giardia lives in the gut of termites is an intestinal parasite Most have no mitochondria or cytochromes, and have an incomplete TCA cycle (tricarboxylic acid cycle).

Some contain hydrogenosomes-small membrane delimited organelles containing a unique electron transfer system that uses protons as terminal electron acceptors to form molecular hydrogen.

Some have symbiotic aerobic bacteria that do the job of TCA cycle for the host.

Body Structure

 Defense against predation  Change shape to become harder to eat.

 Euplotes predator detects presence of  Chemically   Physically Euplotes swells in middle and becomes too big for Lembadion to swallow

Body Structure

 Special organelles  Contractile vacuoles  Osmoregulation in freshwater species

Contractile Vacuole Osmoregulation in FW

Contractile Vacuole Osmotic Regulation

Body Structure

 Special organelles  Trichocysts  Defense, prey capture

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Gas Exchange

No circulatory system  All transport is by diffusion  Plasma membrane must remain moist for gases to diffuse  Restricts protozoa to moist habitats