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Home , Cellularization, Choanoflagellate, Didinium, Phylum, Protista taxonomy, Vorticella

SEM of Protista and the Origin of Metazoans

Goals: Introduction Review characteristics of single I. body plan A. S.A./Volume Constraint Explore the limitations of B. Reynolds number as a single cell II. Important Protista Learn some of the ways in which protists are important A. In food webs B. Agents of disease Evaluate evidence for the origin of from ancestors

III. Origin of Metazoans Evidence for colonial origin and metazoan ancestors (Based on Textbook Chapter 3)

Protista Defy Tidy Definition: Body plan characterized by: - >10 phyla, believed by some that they should be A. Unicellularity (most) classified as Kingdoms B. Small Size (< 5-250 µm)

- Among them are the C. Lacking Systems ancestors of multicell (including a ) including animals. Each individual is a cell that is functionally more versatile than any single cell from a multicell

Means of locomotion and associated structures are no longer Most Common TYPES of Protista: considered key characters in establishing the phylongeny (evolutionary relatedness) of Protista. ( Ciliophora): externally ciliated

Sarcodinids: 4 phyla of amoeboid types Paramecium (, foramenifera, radiozoans, heliozoans) Ciliates

foramenifera : several phyla of flagella-bearing Euglenoid types, including many photosynthetic forms and Some important parasitic forms

Spore-Formers: Phylum and other very important parasitic forms Amoeboid Flagellated

1 Kingdom Picture of the Day Giant Phylogeny is Complicated/Unresolved - Eats crustaceans -important Notodendrodes antarctikus predator

Alveolate Amoeboid Flagellated - Makes a sand case; selects grains Protozoa of only certain sizes from Protozoa Protozoa 1 sediments….. Central to discussion Inch about intelligence PH CILIOPHORA (2.5 cm) - Charles Darwin had this to say: GRANULORETICULOSA trypanosomes - (ciliates) (foramenifera) euglinids "The case of the three of RADIOZOA protozoan (I forget the names) which DINOZOA trichomonads apparently select differently sized () (radiolarians) grains of sand, etc., is almost the most Giardia APICOMPLEXA ACANTHARIA wonderful fact I ever heard of. One cannot believe that they have mental (coccidians (actinarians) power enough to do so… “ e.g. ) (heliozoans)

See pie chart ad taxonomic detail on pg 75 http://kabinetofcuriosities.blogspot.com/2010/02/tree- foraminifera.html

SOFI Comments… Kingdom Protozoa Too much phylogeny and ! This is not necessarily Phylogeny is Complicated/Unresolved interesting to students.

I never knew what we had to learn and what he thought was just cool to Amoeboid Flagellated know Protozoa Protozoa Protozoa

I will not need to know most of the things i learned, but i did learn things other than what i knew before. It was hard for me to get PH CILIOPHORA EUGLENOZOA interested and excited, but the teacher was GRANULORETICULOSA trypanosomes (ciliates) (foramenifera) euglinids This was one of my harder classes this semester. The tests were quite RADIOZOA DINOZOA trichomonads difficult and I really had to study to do well on them. (dinoflagellates) (radiolarians) Giardia APICOMPLEXA ACANTHARIA The grading is very fair. I really appreciate classes where if you put in (coccidians (actinarians) the effort you can do well and the professor doesn't try to trick you e.g. Plasmodium) with weird questions etc. on tests. It's fair that everything on the HELIOZOA tests we have gone over in , it's just the students job to decide if (heliozoans) they want to study it or not. I wish more of my classes were like this. See pie chart ad taxonomic detail on pg 75

Protista and the Origin of Metazoans I. Protistan Body Plan is Characterized by

Introduction -- Primarily unicellular I. Body Plan -- Small, 5 -300 µm A. S.A./Volume Constraint -- Lack organs B. Reynolds number (Lack a nervous system) II. Important Protists A. In food webs B. Agents of disease What constraints does the small unicellular body plan impose on the biology of protistans? III. Origin of Metazoans Evidence for colonial origin and metazoan ancestors

2 S.A./Vol relationship imposes a limit on cell size As a cell increases in size, exchange with the environment Some Amebas becomes more difficult partly solve 1 this problem Inch L Surface Area ~ L2 (2.5 cm) Volume ~ L3

Therefore S.A./V declines L as L increases

Cytoplasmic streaming provides continuous mixing or circulation of the cytosol

Small Size also affects scaling of physical forces Re = velocity x length of the organism Viscocity of Medium

Balance of inertia and drag When Re is high, drag is relatively negligible on a moving organism (example, Re is 30,000 for a dragonfly in flight)

Depends on the size and velocity of the organism When Re is low, drag forces dominate movement and on the viscocity of the medium. (example, Re for a protist could be <0.1)

Expressed as Reynolds Number (Re) Re = velocity x length of the organism In what way would low Reynolds Viscocity of Medium numbers affect the ecology of protists? Re = vel x L Vis

Re = velocity x length of the organism Viscocity of Medium

What is life like at Low Reynolds numbers?? -- no inertia -- force of gravity balanced by viscocity -- yet ciliates travel 2 mm per sec. (8 body lengths) -- feeding also affected

Vorticella feeding

3 Re = vel x L I. Protistan Body Plan is Characterized by Vis -- Primarily unicellular -- Small, 5 -300 µm Viscous forces can -- Lack organs also be important in (Lack a nervous system) air but the medium is not very dense what conditions will What constraints does the small unicellular produce a low Re??? body plan impose on the biology of protistans?

Midge

Anterior are the Food functional equivalents of vacuole organs.

Oral nuclei groove Organelles not generally found in metazoans Cyto- - contractile vacuoles stome - - toxicysts Fig 3.19 contractile Posterior http://www.youtube.com/watch?v=hSFJ- Paramecium Feeding vacuole Contraction spnn6c&NR=1

II. Importance of Protozoa Spasmin filaments

The spasmoneme is a biological A. Major role in ecosystems as decomposers, food source for spring . Contraction is metazoans completed in 2 ms at speeds up to 8 cm/sec and is triggered B. Responsible for a large number of human ailments, including by Ca++ activated interactions malaria, dysentery, sleeping sickness along the length of the supramolecular structure. The reaction does not require ATP C. Provided biologists with outstanding material for genetic, physiological and other studies.

4 Chagas’ Disease Trypanosoma cruzi Protista and the Origin of Metazoans (American trypanosome) Introduction Vector is a biting bug; parasite infects I. Body Plan bug through feces A. S.A./Volume Constraint Affects the nervous system and the ; can be fatal B. Reynolds number Child with Acute infection II. Important Protists A. In food webs B. Agents of disease

III. Origin of Metazoans Evidence for colonial origin and metazoan ancestors

Metazoa arose from Protozoa sometime before the 1200-600 mya What is a “metazoan”??

Which protozoan group was the ancestor?? Eukaryotic and multicellular

By what process was first metazoan formed?? Cell differentiation and coordination;

more than a colony or aggregation of cells Are metazoans Monophyletic or Polyphyletic??

Layers of cells organized into “tissues” What were the first Metazoans like??

Embryonic development; CAN WE EVER REALLY KNOW??

3 Phyla are Possible Candidates as Basal Group of all Animals Symbiotic Hypothesis Theoretically 3 ways in which a multicellular Colonial Hypothesis organism could evolve from a protist. Cnidarians Cellularization Hypothesis

Sponges

Flatworms

5 Cellularization

Strengths: Paramecium- are similar Weaknesses: no evidence of “compartmentalization” Strengths: Origin of from prokaryotes :flatworms with complex embryology Weakness: Genetic obstacles to . How :What about , ?? do they integrate into a reproducing organism?

Stained Paramecium showing multiple ”inclusions”

Macronucleus (Haeckle’s favorite)

Blastea

Gastrea

Strengths: models exist (Volvox, choanoflag.) : parallels embryology Weaknesses: ???

Similarities of ( cells) and (protozoan)

Choanoflagellates live as solitary and colonial forms

6 Model organization

Eudorina

Opisthokonts share: Pandorina uniflagellate (reproductive) stages with at the posterior Mitochondria with flattened, plate-like cristae Volvox

Genetic Evidence (18S r-DNA) Based on sequence analyses of 5 proteins Monosiga has 86% sequence with animals.

Mol. Biol. Evol. 23: 93-106 2006

Conclusions on Metazoan Origin

Evidence best supports the colonial theory

Choanoflagellate group is most likely ancestor; Evidence includes cell structure and genetic similarities

a. Phylogeny based on protein comparisons Idea that metazoans are monophyletic is supported

b-d. choanoflagellate cells bear a single Flagellum and an apical collar of - filled microvilli (bracket, c). D. an overlay of b- (reen), polymerized actin (red) and DNA (blue) localization reveals the position of the flagellum within the collar of microvilli.

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