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Home , Amoeba (genus), Archaeplastida, Excavata, Golden algae, Protista taxonomy, Pseudopodia

2/10/15

PROTISTA

The paraphyletic, non- fungi, non-, non- Eucarya + Even MORE new words to remember!

Key Points

• Origin of via symbiosis • Origin of classification based on functional (ecological) traits • Current classification based on phylogenetic principles • Alternation of generations prominent

General

1. Eukaryotes are mostly unicellular. 2. Mixed history of classification: “Protista” an informal term of convenience for non-fungal, non-plant, non-animal eukaryotes. 3. From to giant , arranged functionally.

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Functional arrangements

a. Animal-like heterotrophic : . b. Absorptive or -like protists: Pseudopodians. c. Plant-like photosynthetic protists: d. All of these groups are polyphyletic

Protists are…

1. …the earliest Eukaryotes a. True nucleus b. Cytoplasmic c. ~2.2 bya 2. …always associated with water, dampness, or body fluids a. Plankton, parasitic

Protists are…

3. …aerobic (almost all) and have mitochondria for cellular respiration. 4. …photoautotrophs, chemoheterotrophs, or both (mixotrophs). a. Note NO photoheterotrophs nor chemoautotrophs.

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Protists are…

5. …motile: most have flagella or cilia or at some stage. 6. …asexual or truly sexual (true and )

flagella

The Origin of Eukaryotes “How to make a ” • About 2.5 bya prokaryotes had diversified into many types. • But the small size and limited of prokaryotes constrained their . • So how did Eukaryotes become possible?

The Origin of Eukaryotes “How to make a Eukaryote” • Eukaryotic : true nucleus, cytoplasmic organelles – Membrane-enclosed structures with specialized function – Some with own genome (mitochondria, ) • This compartmentalization allowed the evolution of larger cells. But how?

3 2/10/15 evolution of nucleus Ancestral Archaean &

Endosymbiosis

• A sequence of events in which specialized prokaryotes live within Aerobic α-proteobacterium larger prokaryotes in è symbiotic relationship. • Some became Cyanobacterium mitochondria and some è chloroplasts. • Both were important in an increasingly aerobic world. Eukaryotic chemoheterotroph

Eukaryotic photoautotroph

Endosymbiosis evolution of nucleus Ancestral Archaean & • Model supported by similarity in structure and RNA between certain prokaryotes and corresponding eukaryote Aerobic organelles. α-proteobacterium è mitochondrion • By alternative genetic code (DNA sequence translation to amino acids). Cyanobacterium è chloroplast • Mitochondria: α- are relatives. • (chloroplast and some non-photosynthetic): Eukaryotic are chemoheterotroph

relatives. Eukaryotic photoautotroph

Diplomonads Euglenozoans

Protist Diversity

Diatoms

Brown algae

• Note that the vast majority “SAR” of eukaryotic diversity is Apicomplexans ‘protistan’ and unicellular. Forams Rhizarians • Is “Protista” monophyletic, Cercozoans paraphyletic, or Radiolarians polyphyletic? Chlorophytes • How does this phylogeny Charophytes indicate that the difference Land Amoebozoans

between paraphyletic and Slime polyphyletic is fuzzy? Tubulinids Entamoebas Unikonta Nucleariids Fungi

Animals

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Diplomonads Excavata Parabasalids Euglenozoans

Protist Diversity Stramenopiles

Diatoms Golden algae

Brown algae

Protozoans “SAR” clade

Alveolates Dinoflagellates • Excavata Apicomplexans I. Alveolata Ciliates Forams Rhizarians II. Opisthokonts (not Cercozoans covered now) Radiolarians Archaeplastida Red algae Green Algal Protists algae Chlorophytes IV. Stramenopiles Charophytes Land plants V. Archaeplastids Amoebozoans Slime molds Pseudopodians Tubulinids Entamoebas Unikonta Nucleariids VI. Rhizarians Opisthokonts Fungi VII. Amoebozoans Choanoflagellates

Diplomonads Excavata Parabasalids Euglenozoans

Protist Diversity Stramenopiles

Diatoms Golden algae

Brown algae

Protozoans “SAR” clade

Alveolates Dinoflagellates • Excavata Apicomplexans I. Alveolata Ciliates Forams Rhizarians II. Opisthokonts (not Cercozoans covered now) Radiolarians Archaeplastida Red algae Green Algal Protists algae Chlorophytes IV. Stramenopiles Charophytes Land plants V. Archaeplastids Amoebozoans Slime molds Pseudopodians Tubulinids Entamoebas VI. Rhizarians Unikonta Nucleariids Opisthokonts VII. Amoebozoans Fungi Choanoflagellates

Animals

Diplomonads Excavata Parabasalids Euglenozoans

Protist Diversity Stramenopiles

Diatoms Golden algae

Brown algae

Protozoans “SAR” clade

Alveolates Dinoflagellates • Excavata Apicomplexans I. Alveolata Ciliates Forams Rhizarians II. Opisthokonts (not Cercozoans covered now) Radiolarians Archaeplastida Red algae Green Algal Protists algae Chlorophytes IV. Stramenopiles Charophytes Land plants V. Archaeplastids Amoebozoans Slime molds Pseudopodians Tubulinids Entamoebas VI. Rhizarians Unikonta Nucleariids Opisthokonts VII. Amoebozoans Fungi Choanoflagellates

Animals

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Excavata

• Diplomonads • Parabasalids • Euglenozoans

Excavata: Parasites • Often anaerobic • What eukaryotic feature could be modified?

Giardia can be a severe intestinal parasite

Excavata: Parasites • Diplomonads: • Small, simple mitochondria () – Not involved in cellular respiration – Involved in maturation of iron-sulfur • Two separate nuclei – Function unclear, NOT duplicated can be a severe intestinal parasite

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Excavata: Parasites

• Parabasilids with reduced mitochondria: – Responsible for some anaerobic metabolism • Anaerobic, flagellated protozoa • Include vaginalis, the most common protistan STD

Excavata: Euglenozoans

• All characterized by spiral, crystalline rod inside flagella. • Kinetoplastids: – including – Kinetoplastid: housing extraneous DNA • : – Often mixotrophs – Photosynthesize in light – Heterotrophic via in dark

Alveolata

• What is its sister-clade? • Members of the probably can photosynthesize because of the secondary endosymbiosis of a red alga. • Characterized by small, membrane-bound cavities, alveoli Likely originated by secondary endosymbiosis

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Figure 28.2

Plastid

Dinoflagellates

Secondary endosymbiosis Membranes Apicomplexans are represented as dark lines in Red alga the cell. Cyanobacterium 1 2 3

Primary endosymbiosis Stramenopiles

Heterotrophic Secondary endosymbiosis eukaryote One of these membranes was lost in red and green algal Euglenids descendants. Secondary endosymbiosis Green alga

Chlorarachniophytes

Alveolata: Dinoflagellates • Marine & freshwater – photosynthetic (~50%) phytoplankton – Some predators – Some parasitic on fish • Most unicellular • “armor” and paired flagella produce spinning movement. • Explosive population blooms result in red tides.

Alveolata: Dinoflagellates

• Zooxanthellae: – Important mutualists with corals (also jellyfish, clams, sea slugs, and other protists). • Obligate mutualism for many coral: – provide carbohydrates via , get protection. • Coral bleaching: – Death or expulsion of zooxanthellae leads to death of corals.

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Alveolata: Apicomplexans

• Parasites of animals • Release tiny infectious cells (sporozoites) that have specialized ability to penetrate into host cells and tissues. • Complex history – Sexual & Asexual – Often multiple hosts – E.g. , mosquitoes, and humans

Alveolata: Ciliates • Move and feed by cilia. • Very diverse group with complex cells. – Manage to be aggressive predators and unicellular • Two types of nuclei: and micronuclei (convert back and forth). • via mitosis and . • via meiosis and conjugation

Diplomonads Excavata Algal Protists Parabasalids Euglenozoans Stramenopiles • Single-celled, colonial, or truly Diatoms multicellular (“”) Golden algae Brown algae “SAR” clade

• Freshwater or marine Alveolates Dinoflagellates • Important in aquatic food webs Apicomplexans • All have a (the primary Ciliates Forams pigment) Rhizarians Cercozoans

– Accessory pigments: Radiolarians – Carotenoids: yellow-orange Archaeplastida – Xanthophylls: brownish Red algae Green algae Chlorophytes – : red and blue Charophytes • Account for 1/2 of global Land plants photosynthetic production Amoebozoans Slime molds • Various life cycles, but Tubulinids alternation of generations is Entamoebas Unikonta key Nucleariids Opisthokonts Fungi Choanoflagellates

Animals

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Stramenopila • Sister-clade to Alveolates • Hair-like projections on flagellae • Photoautotrophs – Chloroplasts derived from eukaryotic symbiont (recall 2’ endosymbiosis) • have lost chloroplasts and are heterotrophic

Stramenopila: Diatoms (Bacillariophyta) • Olive-brown or yellow – What pigments are responsible for these?

Stramenopila: Diatoms (Bacillariophyta) • Olive-brown or yellow – Xanthophylls & carotenoids • Freshwater & marine • Distinctive cell structure based on silica wall matrix. • Excellent index fossils. • Form massive sediments.

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Stramenopila: Brown algae (Phaeophyta) • Carotenoids; xanthophylls • Why do so many marine photosynthesizers use auxiliary pigments? • Marine, multicellular. • Common in cool coastal water. • Some giant (100m) have fastest linear growth of any (60m/ season); e.g. Macrocystis, giant bladder kelp.

Stramenopila: Brown algae (Phaeophyta) • Truly multicellular , independently derived separate specialization: – Holdfast: rootlike anchor – Stipe: stemlike structure – Blades: leaflike structure where majority of photosynthesis occurs • True alternation of generations

Alternation of Generations

• Life cycles in which both haploid and diploid stages are multicellular. • Also evolved independently in plants and fungi. • Divided into haploid generation and diploid generation

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Stramenopila: Oomycetes

• Water molds, white rusts, mildews • Heterotrophs, lack chloroplasts • Important in organic decomposition in aquatic environments • Some (especially mildews) harmful plant pathogens. – Potato blight Phytophthora infestans

Archaeplastids (the non-plant ones) • Rhodophyta (Red Algae) • (Green Algae)

Archaeplastids: Red Algae (Rhodophyta)

• (not all red, red to black). • Multicellular, most marine (some fresh). • Abundant in warm coastal tropics. • Some in very deep water (ca 250m). • No flagellated stages in life cycle. • Chloroplasts from primary cyanobacteria symbiont.

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Archaeplastids: Green Algae (Chlorophyta)

• 7,000 species, most diverse Protista after diatoms. • Shared common ancestry with plants. • Like red algae, chloroplasts from primary cyanobacteria symbiont. – Synapomorphy of Archaeplastids • Mostly unicellular • Mostly

Chlamydomonas, a single-cellular freshwater green alga

Green algae life histories

• But have quite a diversity in life history • Can inhabit damp . • Can live symbiotically with protozoa, , fungi • Note that lichens can also be associations between fungi and cyanobacteria or brown algae or yellow- green algae (a we didn’t cover)

Green algae life histories

• Larger size and greater complexity evolved by three different mechanisms: 1. formation (e.g. in pond scum) 2. True multicellularity, complete with alternation of generations (e.g. the sea lettuce, Ulva) 3. Supercellularity: repeated division of nuclei with no cytoplasmic division, similar to fungal hyphae or slime molds (e.g. in Caulerpa)

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Diplomonads Excavata Parabasalids Euglenozoans

Pseudopodians Stramenopiles

Diatoms Golden algae

Brown algae

• Eukaryotes with “SAR” clade Pseudopodia that move Alveolates Dinoflagellates Apicomplexans and feed by cellular Ciliates Forams extensions. Rhizarians Cercozoans • Pseudopodia is a generic Radiolarians Archaeplastida term for extensions that Red algae Green can bulge from any portion algae Chlorophytes Charophytes of the cell. Land plants Amoebozoans

• Much like “wing”, this Slime molds does not indicate Tubulinids Entamoebas Unikonta homology. Nucleariids Opisthokonts Fungi Choanoflagellates

Animals

Rhizarians

• Originally united by DNA sequence data. • Pseudopodia are threadlike.

Rhizaria: Foraminiferans “Forams” • All marine, primarily in sand, attached to algae, or occur as plankton. • Encased in multichambered, coiled, snail-like shells (tests) made of (CaCO3) – More than 90% of known diversity are from fossils

– Deposition of CaCO3 tests creates and chalks. • can be uninucleate or and extends through tests as pseudopodia. • Some tests >5cm in diameter.

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Rhizaria: • “ray feet” or axopodia: numerous slender pseudopodia reinforced by . • Used for flotation and feeding: food sticks to axopods, engulfed and transported by cytoplasm • Important component of plankton: – Heliozoans in freshwater – Radiolarians in marine • Shells of silica often deposited in sediments

Amoebozoans • “-like foot” • Pseudopodia are lobe- or tube-shaped • Simple, naked, or shelled • Unflagellated cells that move via pseudopodia and feed by surrounding and engulfing food (phagocytosis) • Sister group of lineages including fungi and animals

Amoebozoans : Gymnamoebas & Entamoebas • More typical . • Gymnamoeba: – Free-living heterotrophs on or detritus. • Entamoebas: – All parasitic; – No meiosis, reproduce using various asexual modes – Include histolytica, responsible for amoebic

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Amoebozoans: Slime Molds (Mycetozoans) • Superficially resemble fungi • In cellular organization and reproduction are obviously amoebozoans.

Plasmodial slime molds (Myxomycota) • All heterotrophs, often brightly colored. • Feeding stage is a large amoeboid mass called the plasmodium (!). – Not multicellular, but multinucleated. – Via the process of coenocytosis: repeated division of nuclei without cytoplasmic division.

Plasmodial slime molds: “Alternation of generations”

Environmental stress

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Cellular slime molds (Acrasiomycota) • Aggregates of individual cells that keep their identity while feeding. • Haploid. • NOT coenocytic. • Reproduce asexually with fruiting bodies. • Reproduce sexually as giant cell (grows via consuming other haploid amoebas). • Probable inspiration for scene from Terminator 3

Comparative Biology & Cellular Slime molds • Researchers at UCSD studying , a cellular slime , found that two used to guide the amoeba to food sources are also used used to guide human white blood cells to the sites of infections.

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