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Home , Amoebozoa, Excavata

9/29/14

Outline BIOSC 041 v General characteristics of v Our understanding of the relationships among groups continues to change rapidly! PROTISTS! v One hypothesis divides all (including protists) Reference: Chapter 28 into four supergroups: § § “SAR” § § Unikonta v Roles in Ecological Communities § Producers § Consumers § Parasites & pathogens

Diplomonads Excavata The Protists exhibit more structural and functional What is a Protist?

Euglenozoans diversity than any other group of eukaryotes § Everything that is not Stramenopiles something else Diatoms Golden § Include unicellular, colonial, and multicellular taxa § But definitely not an Brown algae

“SAR” clade “SAR” v The one-time of Apicomplexans

Protista has been abandoned

Forams v Protists are now recognized as Rhizarians Cercozoans

polyphyletic Radiolarians

§ Some lineages of protists Archaeplastida Green recognized as kingdoms algae Chlorophytes v Protist remains the informal Charophytes Land

name for highlighted taxa Amoebozoans v Slime molds “” are animal-like Tubulinids Entamoebas

protists Unikonta

Nucleariids Fungi

Choanoflagellates

Animals

Most protists are unicellular, and small… …but there are many exceptions…

v Single-celled protists can be very complex, as all biological v Galatheammina (Xenophyophore) functions are carried out by organelles in each individual v Benthic (deep sea) protozoan, ~10 cm in diameter cell v Single-celled(!!) § Most range in size from <1-200 µm § “ruffled” surface increases surface area for gas/nutrient exchange

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v The Protists also include colonial and multicellular taxa- Nutritional and reproductive diversity particularly algae v Algae are considered protists because they don’t meet the v Nutrition complex tissue criteria of true plants § Photoautotrophs § Range in size from 100’s um to 100’s meters (giant kelp) § Contain chloroplasts

§ Obtain energy from the sun and carbon from CO2 § Heterotrophs § Obtain both energy and carbon from organic molecules, absorbed from the environment or through ingestion of other organisms § Mixotrophs § Combine and heterotrophic nutrition v Reproduction § Sexual, asexual, or both!

Figure 28.2 Endosymbiosis in Eukaryotic Evolution Plastid v Protists owe their diversity to endosymbiosis- a engulfs another cell, which becomes an Dinoflagellates endosymbiont and then an organelle in the host cell Secondary § Review: endosymbiosis Membranes Apicomplexans are represented as dark lines in § Mitochondria evolved by endosymbiosis of an aerobic Red alga the cell. heterotrophic bacterium Cyanobacterium 1 2 3 § Chloroplasts evolved by endosymbiosis of Primary photosynthetic cyanobacterium endosymbiosis Stramenopiles v The plastid-bearing protists evolved into red and Heterotrophic Secondary Plastid endosymbiosis One of these (DNA of plastid genes in red algae and green algae closely membranes was lost in red and resemble DNA of ) green algal descendants. v During eukaryotic evolution, red and green algae also Secondary endosymbiosis underwent secondary endosymbiosis, in which they were Green alga

ingested by a heterotrophic eukaryote Chlorarachniophytes

Five Supergroups of Excavata Supergroup #1: Excavates Eukaryotes Parabasalids Euglenozoans Stramenopiles

Diatoms v Include protists with modified mitochondria and protists Golden algae v Our understanding of the with unique flagella Brown algae

“SAR” clade “SAR”

relationships among protist Alveolates Dinoflagellates v The clade Excavata is characterized by its cytoskeleton groups continues to change Apicomplexans Ciliates v Some members have a feeding groove

rapidly Forams Rhizarians Cercozoans v This diverse group includes v One hypothesis divides all Radiolarians § Diplomonads eukaryotes (including protists) Archaeplastida Red algae § Parabasalids Green algae into four supergroups Chlorophytes Diplomonads Excavata Charophytes § Euglenozoans Land plants Parabasalids

Amoebozoans

Slime molds Euglenozoans Tubulinids Entamoebas Unikonta SAR clade Nucleariids Opisthokonts Fungi Archaeplastida

Choanoflagellates Unikonta

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Excavata: Diplomonads and Parabasalids Parabasalids v These two groups lack plastids, have modified mitochondria, and most live in anaerobic environments v Have reduced mitochondria called v Diplomonads that generate some energy anaerobically § Have modified mitochondria called v Include vaginalis, the pathogen that § Derive energy from anaerobic biochemical pathways causes a type of vaginal infection in human females § Have two equal-sized nuclei and multiple flagella § Are often parasites, for example, intestinalis (also known as Giardia lamblia)

Euglenozoans - Kinetoplastids v Euglenozoa is a diverse clade that includes predatory v Kinetoplastids are distinguished from other protozoa by the heterotrophs, photosynthetic autotrophs, and parasites - a single containing an organized mass of DNA (kDNA) that comprises several copies of the v Distinguishing feature mitochondrial § A spiral or crystalline rod of unknown function inside v Include free-living consumers of prokaryotes in freshwater, their flagella marine, and moist terrestrial ecosystems v This clade includes the v Also include some pathogens § Kinetoplastids § , which causes sleeping sickness in humans § Euglenids § Another pathogenic trypanosome causes Chagas’ disease

More about trypanosomes Euglenozoa - Euglenids v Trypanosomes evade immune responses by switching surface v Euglenids have one or two flagella that emerge from a proteins pocket at one end of the cell v A cell produces millions of copies of a single protein v Some species can be both autotrophic and heterotrophic v The new generation produces millions of copies of a different protein v These frequent changes prevent the host from developing immunity

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Supergroup #2: SAR clade Alveolata v A highly diverse group of protists defined by DNA similarities v Members of the clade Alveolata have membrane-bounded v The “SAR” clade is a diverse monophyletic supergroup sacs (alveoli) just under the plasma membrane named for the first letters of its three major Stramenopiles, Alveolates, and Rhizarians v The function of the alveoli is unknown v The alveolates include v This group is the most controversial of the four supergroups (sometimes split to give 5 subgroups) § Dinoflagellates v Stramenopiles covered in Biosc 42 § Apicomplexans § Ciliates Excavata Diatoms Golden algae Stramenopiles Brown algae SAR clade SAR Dinoflagellates Apicomplexans Alveolates Ciliates Forams Cercozoans Rhizarians Radiolarians Archaeplastida Unikonta

Dinoflagellates Apicomplexans

v Dinoflagellates have two flagella and each cell is reinforced v Apicomplexans are parasites of animals, and some cause by cellulose plates serious human diseases v They are abundant components of both marine and freshwater phytoplankton § No movement, no free-living forms (obligate parasites) v They are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs § Complex intracellular structures and lifecycles (spread through host as v Toxic “red tides” are caused by blooms infectious cells called sporozoites) § One end, the apex, contains a complex of organelles specialized to penetrate host cells and tissues § Most have sexual and asexual stages that require two or more host species for completion

Figure 28.10-3 More about Apicomplexans Inside mosquito Inside human Merozoite Sporozoites (n) v Responsible for some of the most

serious human disease – Malaria Liver (), Toxoplasmosis cell v Plasmodium requires both Oocyst Apex

mosquitoes and humans to Merozoite Red blood 0.5 µm complete its cycle (n) cell Zygote v ~900,000 people die each year (2n) Red blood cells from malaria v Efforts are ongoing to develop

malaria vaccines FERTILIZATION

Gametes Gametocytes Key (n) Haploid (n) Diploid (2n)

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Figure 28.11 Ciliates Contractile Oral groove

Cell mouth Cilia v Ciliates, a large varied group of protists, are named for their 50 µm use of cilia to move and feed Food § Paramecium caudatum is a good example of a (a) Feeding, waste removal, and water balance v Have large macronuclei and Key Conjugation small micronuclei Asexual MEIOSIS reproduction v Genetic Variation § Exchange of haploid Haploid Diploid micronucleus Compatible micronucleus micronuclei via sexual mates The original Diploid conjugation macronucleus micronucleus disintegrates. v Reproduction MICRONUCLEAR § Asexual- binary fission FUSION

(b) Conjugation and reproduction

Rhizarians Radiolarians v called radiolarians have tests fused v DNA evidence supports as a monophyletic clade (so it into one delicate piece, usually made of silica sometimes is split from SAR into its own supergroup) v v Rhizaria includes some groups of (“testate Radiolarians use their to engulf ameobas”= with shells), including radiolarians, forams, and through cercozoans v The pseudopodia of radiolarians radiate from the v Amoebas are protists that move and feed by pseudopodia, central body extensions of the cell surface v Rhizarian amoebas differ from amoebas in other clades by having threadlike pseudopodia

Forams Cercozoans

v Foraminiferans, or forams, are named for porous, generally multichambered shells, called tests v Cercozoans include most amoeboid and flagellated

§ Organic material hardened with CaCO3 protists with threadlike pseudopodia v Pseudopodia extend through the pores in the v They are common in marine, freshwater, and soil v Foram tests in marine sediments form an extensive fossil ecosystems record v Most are heteroptrophs, including parasites and v Many forams have endosymbiotic algae predators

Imbricatea

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Supergroup #3: Archaeplastida 20 cm Supergroup 4: Unikonts

v Includes animals, fungi, and some protists (that are closely v Covered in detail in Biosc 42 related to fungi and animals) v Includes red algae, green algae, and v This group includes two clades: the amoebozoans and the land plants opisthokonts (animals, fungi, and related protists) v The root of the eukaryotic tree remains controversial v It is unclear whether unikonts separated from other Excavata Dulse (Palmaria palmata) eukaryotes relatively early or late SAR clade

Archaeplastida 2 cm Red algae Excavata SAR clade Chlorophytes Green algae Archaeplastida Charophytes Slime molds

Tubulinids Unikonta Land plants Entamoebas Unikonta Nucleariids Fungi

Choanoflagellates (a) Ulva, sea lettuce Animals

Amoebozoans Slime Molds

v Slime molds (mycetozoans) once thought to be fungi v Amoebozoans are that have lobe- or tube- shaped, rather than threadlike, pseudopodia- and no v Molecular systematics places slime molds in the clade shell v Two types: v They include slime molds, tubulinids, and entamoebas § Plasmodial (no cell membranes, but many nuclei) § Cellular (cell membranes present) § Give clues to evolution of multicellularity

Plasmodial Slime Molds Plasmodial Slime Molds v Many species of plasmodial slime molds are brightly v At one point in the life cycle, plasmodial slime molds form a pigmented, usually yellow or orange mass called a plasmodium (not to be confused with malarial Plasmodium) v The plasmodium is not multicellular v It is undivided by plasma membranes but contains many diploid nuclei v Extends pseudopodia through decomposing material, engulfing food by phagocytosis

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Cellular Slime Molds Tubulinids v Cellular slime molds form multicellular aggregates in which cells are separated by their membranes v Have lobe or tube-shaped pseudopodia. Typical “amoeboid” movement v Cells feed individually, but can aggregate to form a fruiting body v Common unicellular amoebozoans in soil as well as Spores FERTILIZATION freshwater and marine environments (n) Emerging amoeba v Most are heterotrophic and actively seek and consume (n) Zygote SEXUAL (2n) Solitary REPRODUCTION and other protists 600 µm amoebas (n) MEIOSIS Amoebas (n) Fruiting ASEXUAL bodies REPRODUCTION (n) Aggregated amoebas

Migrating aggregate 200 µm

Key Haploid (n) Diploid (2n)

Entamoebas Opisthokonts v Entamoebas are parasites of vertebrates and some v Opisthokonts include animals, fungi, and several invertebrates groups of protists v histolytica causes amebic , the § Nucleariids (amoeba more similar to fungi) third-leading cause of human due to eukaryotic § Choanoflagellates parasites

Excavata SAR clade Archaeplastida Slime molds

Tubulinids Unikonta Entamoebas Nucleariids Fungi

Choanoflagellates Animals

Protists play key roles in ecological communities Photosynthetic Protists

v Many protists are important producers that obtain energy v Protists are found in diverse environments from the sun § Aquatic, marine and terrestrial v In aquatic environments, photosynthetic protists and prokaryotes (cyanobacteria) are the main producers v Protists are found in all trophic levels v In aquatic environments, photosynthetic protists are limited § Producer (photoautotrophs) by nutrients § Various types of consumer (heterotrophs feeding § Primarily N and/or P, sometimes Fe on photoautotrophs or other heterotrophs) v These populations can explode (bloom) when limiting § Parasites (including human pathogens) nutrients are added § Detritovore § Important in recycling nutrients

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Symbiotic Protists Parasitic Protists

v Plasmodium causes malaria v Some protist symbionts benefit their hosts § Dinoflagellates v Pfiesteria shumwayae is a (zooxanthellae) dinoflagellate that causes photosynthesize to provide fish kills food for coral polyps that build reefs § Wood-digesting protists digest cellulose in the gut v Phytophthora ramorum of termites causes sudden oak death

A Protist as Ecosystem Engineer? Global warming and phytoplankton

v Galatheammina (Xenophyophore- giant unicellular organism) v Phytoplankton form the basis for marine and aquatic food v Can form very dense populations on undersea plains webs (most phytoplankton are protists) v Stirs up sediment and creates structure with slime secretions v Biomass of photosynthetic protists has declined as sea surface § Creates habitat for other bottom-dwelling organisms temperature has increased § Populations of crustaceans and worms much higher v If sea surface temperature continues to warm due to global where Galatheammina is present warming, this could have large effects on § Plays key role in circulating C & N back into the water § Marine ecosystems column § Fishery yields § The global carbon cycle

Figure 28.UN06 Eukaryote Key Morphological Supergroup Major Groups Characteristics Specific Examples

Excavata Diplomonads and Modified mitochondria Giardia, parabasalids Trichomonas

Euglenozoans Spiral or crystalline rod in- Trypanosoma, Kinetoplastids side flagella Euglenids

“SAR” Clade Stramenopiles Hairy and smooth flagella Phytophthora, Diatoms Laminaria Golden algae Brown algae

Alveolates Membrane-enclosed sacs Pfiesteria, Dinoflagellates (alveoli) beneath plasma Plasmodium, membrane Paramecium Apicomplexans Ciliates

Rhizarians Amoebas with threadlike Globigerina Radiolarians pseudopodia Forams Cercozoans

Archaeplastida Red algae Phycoerythrin (photosyn- Porphyra thetic pigment)

Green algae -type chloroplasts Chlamydomonas, Ulva

Land plants (See Chapters 29 and 30.) , ferns, , flowering plants

Unikonta Amoebozoans Amoebas with lobe- Amoeba, Slime molds shaped or tube-shaped pseudopodia Tubulinids Entamoebas Opisthokonts (Highly variable; see Choanoflagellates, Chapters 31–34.) nucleariids, animals, fungi

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