Volvocine Line

Evolution of Multicellularity in flagellated green algae

Chlamydomonas

Volvox

see also

Volvocine Evolution

notes

Protozoan Biodiversity

A guide to the major groups Species seen in lab are marked with a

Bauplan for protozoa

  Small size (high SA:V) because of limitations imposed on by diffusion; allows for efficient nutrient assimilation (in photoautrotrophs and mixotrophs), excretion, and gas exchange Locomotion provided by pseudopodia, cilia or flagella

Bauplan for protozoa

 Feeding/nutrition:  Photoautotrophs  Heterotrophs  Pinocytosis (cell drinking dissolved nutrients)     Osmotroph - rely on uptake of small organic molecules Phagocytosis (cells eating solid particles) Use food vacuoles for intracellular digestion Some such as those with fixed shapes, may have  Cytostome (“cell mouth”) and  Cytoproct (“cell anus”)  Mixotrophs - heterotrophs or photoautotrophs

Bauplan for protozoa

 Very sensitive to external stimuli, but do not have a nervous system; some may have sensory cilia  May respond to   Light Mechanical stimuli   Chemical gradients Temperature gradients;  Reproduction varies: sexual or asexual (binary fission, multiple fission, budding)

Supergroups

        Excavata: feeding groove, phagotrophy Euglenozoa: flagella, Euglena mitochondria Archaeplastida: algae Alveolata: alveoli Stramenopila: very diverse, straw-like hairs on flagella Rhizaria: plankton, pseudopodia Amoebozoa: pseudopodia, slime molds Opisthokonta: single posterior flagellum

Phylogeny

Supergroup Excavata

 Related to some of Earth’s earliest eukaryotes  Named for a feeding groove “excavated” into the cells of many representatives  Food particles are taken into cells by phagotrophy  Endocytosis and evolutionary basis for endosymbiosis

Supergroup Excavata

Jakoba libera

 Flagellated protozoans • Single-celled heterotrophs with flagella • Unwalled cells, pellicle retains shape

Zooflagellates

Excavata (clade?)

 Primitive flagellates with multiple flagella & feeding groove  Lack Golgi apparatus, mitochondria lacking in some, highly modefied in others  Some important human parasites    Giardia Trichomonas Trypanosoma

Excavata

,

continued

 Giardia and some other excavates lack mitochondria.

 This condition may be primitive or derived.

 Two separate haploid nuclei – look like big eyes!

 Other excavates (e.g. complete mitochondrial genome known closest to bacterial genome - therefore primitive.

Jakoba ) have the most  Mitochondrial genome of other eukaryotes is greatly reduced by gene transfer to cell nucleus

Excavata -

(excavate - feeding groove that terminates in a cytostome on the cell surface, usually associated with a posteriorly-directed flagellum; not present in all excavate taxa)  Diplomonadida  Giardia  Parabasala   Trichomonads Trichomonas vaginalis Trichonymphs Trichonympha spp  Euglenozoa  Trypanosomes Trypanosoma spp

Diplomonadida and Parabasala

   Group that lacks mitochondria Evolved before eukaryotes acquired mitochondria  But recent evidence may suggest that these groups actually lost their mitochondria Multiple flagella

Diplomonadida* and Parabasala**

   Giardia lamblia* Trichonympha* Trichomonas vaginalis**

Giardia intestinalis (lamblia

)

Giardia intestinalis

Giardiasis

• Water in wilderness areas is often contaminated with cysts from animal feces.

• Cysts hatch in intestines and release trophozoites.

• Always boil and/or treat water before drinking.

• Print out full size slide of life cycle of parasite.

Giardiasis

 Clinical Features:  Disease varies from asymptomatic to severe diarrhea and malabsorption.

 Acute giardiasis develops after an incubation period of 1 to 14 days (average of 7 days) and usually lasts 1 to 3 weeks.

 Symptoms include diarrhea, abdominal pain, bloating, nausea, and vomiting.

 In chronic giardiasis the symptoms are recurrent and malabsorption and debilitation may occur.

Flagellates

Parabasalids

     Multiple flagella (hypermastigote) Parabasal bodies modified Golgi apparatus Lack mitochondria All are symbiotes in animals Examples: Trichonympha, Trichomonas

Trichonympha

Trichonymphs

 Trichonymphs (phylum Axostylata) are excavates with hundreds of flagella  They live in the guts of wood-eating termites and cockroaches  Feed on wood particles consumed by the host insect  They rely on endosymbiotic bacteria to digest cellulose  So insect gets the energy and carbon from bacterial metabolism – a long trip from wood!

Parabasalids

Termite symbiotes

    Guts of termites, wood roaches, other wood-eating insects.

Digestion of cellulose ecologically critical function.

Acquisition at hatching and molting.

Mutualism  Mutualistic bacteria inside Trichonympha al. digest the wood .

et

Trichonympha

Eastern termite: Reticulitermes flavipes

12 symbiotic flagellates found in the gut (Yamin, M. A. 1979. Sociobiology, 4: 3-119) 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Dinenympha fimbriata Dinenympha gracilis Holomastigotes elongatum Microjoenia fallax Monocercomonas sp.

Personympha major Personympha vertens Spironympha kofoidi Spirotrichonympha flagellata Spirotrichonympha sp.

Trichomonas trypanoides Trichonympha agilis 7.

12.

2.

Joseph Leidy 1823-1891 Prominent American biologist- Univ. of Pennsylvania. Vertebrate paleontology, parasitology, other fields

Trichonympha

Termite gut symbionts

Streblomastix Trichonympha

Parabasalids

Trichomonads

• Commensal or parasitic flagellates with axostyle and parabasal body •

Trichomonas vaginalis

(far right) in human urogenital tract.

Trichomonas vaginalis

  Trichomoniasis = STD Clinical Features:  Trichomonas vaginalis infection in women is frequently symptomatic.

 Vaginitis with a purulent discharge is the prominent symptom, and can be accompanied by vulvar and cervical lesions, abdominal pain, dysuria and dyspareunia.

 The incubation period is 5 to 28 days.

 In men, the infection is frequently asymptomatic; occasionally, urethritis, epididymitis, and prostatitis can occur.

Trichomonas vaginalis

Euglenids

Phylum Euglenozoa

Today’s euglenids are a modern rep resentative of an ancient line of life, so different from other protists that some biologists have suggested placing them in a kingdom of their own.

Supergroup Euglenozoa

    Supergroup of flagellates named for

Euglena

Disk-shaped mitochondrial cristae Euglenoids have unique interlocking protein strips beneath plasma membrane  Pellicle Can crawl through mud – euglenoid movement or metaboly

Euglenozoa

Discicristates Discicristates

Euglenozoa

 Most euglenoids live in freshwater  Some have chloroplasts that arose by secondary endosymbiosis from a green alga  Contractile vacuoles expel excess water

Euglenozoa

 Kinetoplastids unusually large mass of DNA (kinetoplast) have an  Trypansosoma brucei  Most are parasites  Have a single giant mitochondrion   Biting insects are vectors Example: Trypanosomes

Flagellates

Kinetoplastida

 Possess “kinetoplast” region of mitochondrion    Flagellum adheres to cell via “membrane” Includes important parasites of man and domestic animals: Trypanosoma, Leishmania Digenetic life cycle (two hosts)  vertebrate  Gut of blood-feeding insect (vector)

Trypanosomes (Kinetoplastids)

 Trypanosomes (also in phylum Euglenozoa) are colorless, mostly pathogenic parasites  They reproduce asexually by mitosis  Kinetoplast – contains extranuclear DNA  Trypanosoma brucei ( gambiense

African sleeping sickness

) causes  T. cruzi causes Chagas’ disease of Central and South America and now potentially in the U.S.

Tsetse fly Tsetse Fly Vectors of trypanosome diseases Trypanosomes in blood smear Kissing bug

25 µm Red blood cells Trypanosome with undulating membrane Flagellum

Figure 5.27

Trypanosoma cruzi

Chagas disease

    Trypanosomiasis

T. cruzi

life cycle

Transmitted to man via feces of bug Intracellular reproduces asexually, forming pseudocysts.

Return to bloodstream and picked up by bug with blood meal.

Do not show antigenic variation.

Triatomine refers to the subfamily Triatominae of the family Reduviidae

  

Chagas’ Disease

Clinical Features:

A local lesion can appear at the site of inoculation. The acute phase is usually asymptomatic, but can present with manifestations that include fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, neurological disorders, & myocarditis.

Most acute cases resolve over a period of 2 to 3 months into an asymptomatic chronic stage. The symptomatic chronic stage may not occur for years or even decades after initial infection. Its manifestations include cardiomyopathy; pathologies of the digestive tract such as megaesophagus and megacolon; and weight loss. Chronic Chagas disease and its complications can be fatal. Charles Darwin may have contracted this disease in Chile during his voyage on the H.M.S. Beagle, which resulted in his infirmity in later life.

Trypanosomiasis

American trypanosomiasis ( Chagas disease )

     Trypanosoma cruzi 16-18 million persons are infected 100 million are at risk 50,000 deaths annually leading cause of heart disease in South and Central America

T. cruzi

insect host:

Triatoma

(Order Hemiptera)

Kinetoplastida

Trypanosoma

   T. rhodesiense and T. gambiense cause African sleeping sickness in man.

T. brucei causes nagana in ungulates (hoofed mammals). Insect host: tse-tse flies, Glossina

Trypanosomiasis

African sleeping sickness

     Often fatal if untreated.

Anemia, fever, edema due to swollen lymph nodes.

Neurological symptoms dementia, lethargy, paralysis. Controlled in past decades by anti-tse-tse programs- now increasing again.

300,000 cases/year

African Sleeping Sickness

     Bite reaction Parasitemia  Attacks of fever which starts 2-3 weeks after the bite CNS stage  Changes in character and personality Terminal stage is marked by wasting and emaciation Death results from coma, intercurrent infection or cardiac failure

African trypanosomes

Quick-change artists - antigenic variation

    Fluctuating parasite number- antigenically distinct forms.

VSG (variant surface glycoprotein) coats cell surface.

Cells switch between different versions of VSG.

Shed VSG causes problems VSG

Kinetoplastida

Leishmania

• vector: biting sandflies,

Phlebotomus

(O. Diptera) • Zoonosis= mainly parasite of animals that also infects man • reservoir hosts- various mammals- rodents, carnivores (including dogs)

Leishmaniasis

• Intracellular - infects macrophages in mammal hosts.

• Visceral leishmaniasis suppresses immune response by destroying macrophages in lymph nodes, liver and spleen • Cutaneous leishmaniasis causes skin ulcers.

• 1.5-2 million clinical cases/year- estimate 12 million infected.

Euglenids

 Cell surface covered by pellicle  Protein strips  Unique among eukaryotes  Consists of the plasma membrane, a series of proteinaceous strips underneath the plasma membrane, and groups of microtubules associated with each strip.   Species with longitudinal strips have rigid cells; no metaboly Species with spirally placed strips are flexible; have metaboly

Euglenids

    Photosynthetic species  Store paramylon starch in single pyrenoid  Have photosensitive eyespot or stigma, that helps orient towards light Heterotrophic species can either absorb nutrients from water or may feed on bacteria Two flagella  Long one has mastigonemes and is used for motility  Second short flagella is not used for swimming No sexual reproduction ever reported

Euglena

Paramylon starch around pyrenoid

Contractile vacuole paramylon

Euglena gracilis

Click here for movie of metaboly in Euglena

Euglena acus

On slide

Peranema

Anatomy similar to Euglena without the chloroplasts and pyrenoids.

Peranema - notice the pellicle

Peranema

 Peranema is a predator, capturing and engulfing smaller euglenids. Two rods, located in the mouth area, are used to hold prey during engulfment.

 In the euglenid line, as in most other flagellated protists, individuals divide longitudinally.  Division begins with duplication of the basal body at the base of the flagellum creating a cell with two flagella that then splits right down the middle.

Alveolata

 Dinoflagellates, apicomplexans, and ciliates  All contain membrane bounded cavities (alveoli)

Supergroup Alveolata

 All alveolates have tiny sacs ( alveoli ) beneath the plasma membrane  All single-celled 

Examples:

 Ciliates, dinoflagellates, and apicomplexans

Alveolates

 Group characteristics  Sacs (alveoli) lie immediately below the cell surface.

 Have tubular inner membranes (cristae) in their mitochondria (Tubies).  Three major taxa with very different adaptive strategies    Dinoflagellates (Mostly) parasitic apicomplexa; non-motile Ciliates.

Supergroup Alveolata

   Ciliophora  Ciliates – conjugation Dinozoa   Dinoflagellates – some photosynthetic, others not Important in nearshore oceans Apicomplexa   Medically important parasites Plasmodium *Named for saclike membranous vesicle (alveoli) present in cell periphery*

Dinoflagellates

Subphylum Dinozoa Dinoflagellata =

Dinoflagellates

     Often classed with algae Cell complexity  Single cells or chains of cells.

How are their cells organized?   Mesokaryotes – permanently condensed chromosomes Mitotic spindle located outside of the nucleus (which remains intact during mitosis) What pigments do they possess?  Chlorophyll a, Chlorophyll c and Peridinin.

What storage product is made?  Starch and oils.

Dinoflagellates

 Cell wall features?

 Most dinoflagellates are encased in plates of armor.

 Thick cellulose plates encased in vesicles beneath the cell membrane  Some are “naked” and lack these plates  2 flagella present.  One trails behind   One lies in groove around center of cell Cell spins slowly like a top as it swims

Gonyaulax:

an armoured dinoflagellate. Cell wall is subdivided into multiple polygonal vesicles filled with relatively thick cellulose plates

Ceratium

A “naked” dinoflagellate. Cell wall does not have thickened cellulose armour plates.

Note:

Armored

dinoflagellate.

Know

: cingulum, sulcus, hypotheca, epitheca, flagella

Dinoflagellates

Dinoflagellates

 Some have elaborate eyespots called ocelli, which have a pigmented portion and a lens-like refractive portion.  Some have trichocysts, which are ejectile organelles similar to the nematocysts in Cnidarians.  What other group of protists has these?

Ceratium

Ceratium

Note: nuclei with permanently condensed chromosomes

 

Dinoflagellates

Mature dinoflagellates are haploid (1n)  Dikaryotic nuclei – 2 haploid nuclei  permanently condensed chromosomes Reproduction  Mostly asexual  Reproduce by fission  A few can reproduce sexually   Gametes formed by mitosis (not meiosis) because the cells are already haploid.

Gametes (1n) are motile  Zygotes (2n) formed by fusion of gametes also motile

Dinoflagellates

  Ecology  90% are marine  10% freshwater  About 50% are photosynthetic; the rest are heterotrophs (parasites) Photosynthetic dinoflagellates are second only to diatoms as primary producers in coastal waters.  May be free-living or symbiotic   Zooxanthellae - symbionts of cnidarians and others vital to the growth and survival of coral reefs

Zooxanthellae

  Dinoflagellate endosymbionts of animals and protozoa Coral reef builders

Zooxanthellae

 Symbiotic dinoflagellates found in many marine invertebrates  Genus

Symbiodinium

 Sponges, corals, jellyfish, Tridacnid clams and flatworms  Also found within protists, such as ciliates, foraminiferans, and colonial radiolarians.

Zooxanthellae

Zooxanthellae

   Endosymbionts of animals and protozoa In coral polyps zooxanthellae are found in the second layer of cells below the epidermis; one algal cell per animal cell. Important components of reef building corals*  Provide them with nutrients  Remove waste  Contribute to the production of calcium carbonate skeletons * More about this when we study Cnidarians

Zooxanthellae

 Mutualism  Host organism ingests the dinoflagellate and incorporate it into its own tissues without harming it.  Dinoflagellate divides repeatedly, and begins to manufacture carbohydrates which are provided to the host.  Many corals get all their food from the zooxanthellae; build reefs much faster with the dinoflagellates present in their tissues.

Zooxanthellae

Zooxanthellae

 Recall observations on zooxanthellae in tissues of

Aiptasia

anemones from S219 aquarium 

Cassiopeia

jellyfish (aquarium) also have zooxanthellae and typically rest upside down in shallow mangrove beds.

 This provides maximum sun exposure for symbionts  Jellyfish also feeds on passing zooplankton  Blue structures are vesicular appendages that hold zooxanthellae

Aiptasia anemone with zooxanthellae

The upper layer of the Acropora sp. is the epidermis. The lower layer is the gastrodermis. Within the cells are round to oval golden spheres. These are the zooxanthellae.

Cassiopeia, the Upside-Down Jelly or Mangrove Jelly (Figure 7), generally lies on upside-down on the substrate where it tends its internal garden of zooxanthellae, which give it a greenish color. While there, the bell margins pulsate creating a current across the oral surface where plankton and other particles are subdued by nematocysts and caught in a gelatinous coating. The captured particles are carried to the mouth or to other secondary mouths that occur on the oral arms. These are animals of warm, shallow water of the West Indies, the Pacific, and the Indian Oceans.

Coral Bleaching = loss of zooxanthellae

Causes – discussed with Cnidarians

Bioluminescent Dinoflagellates

Bioluminescence

 Some dinoflagellates are capable of producing light - bioluminescence  Molecules made by the organism produce light in a chemical reaction.  Luciferin and luciferase  Same reaction that occurs in fireflies

Health Issues

 Many dinoflagellates produce neurotoxins  Poisons that injure the nerves of marine life that feed on the dinoflagellates  May cause massive kills of fish and shellfish, as well as other forms of marine life.

 If animals containing these toxins are eaten by humans, the result may be illness or even death.  Neurotoxins affect muscle function, preventing normal transmission of electrochemical messages from the nerves to the muscles by interfering with the movement of sodium ions through the cellular membranes

Health Issues

 These toxins in the water can blow inland in sea spray and cause temporary health problems for people who live near the coast.  The toxin from that an aspirin sized tablet of the poison could kill 35 people; it is one of the strongest known poisons Gonyaulax catenella is so toxic

Neurotoxins

   Saxitoxin - most common dinoflagellate toxin  100,000 times more potent than cocaine  Found in North American shellfish from Alaska to Mexico, and from Newfoundland to Florida Brevitoxin  Causes fish kills  May also cause poisoning in humans when it accumulates in the tissues of shellfish Red Tides  Population explosions of dinoflagellates that can color the water red.

 Shellfish contain high levels of toxins during these times

Boat Gonyaulax and views of red tides A red tide results from a population explosion of dinoflagellates (an algal bloom). Cell densities are so high that they turn the water a red color.

Bioluminescent Red Tide

Noctiluca

Neurotoxins

  Humans may be poisoned:  By eating contaminated fish - Ciguatera  Or by eating shellfish, such as clams or mussels paralytic shellfish poisoning or PSP. Poisoning is serious but not usually fatal.  Lethal concentrations lead to death from respiratory failure and cardiac arrest within twelve hours of consumption  Old rule of thumb was that shellfish should only be eaten during months with an "R" in them, and not during May to August. Summer brings runoff of nutrients and blooms of dinoflagellates. NOT VERY RELIABLE !

Noctiluca - a bioluminescent marine dinoflagellate; also causes red tides. Can feed heterotrophically by using its longer posterior flagellum to capture prey.

Pfiesteria piscicida

Note the long flagella Ulcers on fish caused (?) by Pfiesteria

Pfiesteria

and some of its relatives cause death in fish and respiratory and neurological complications in humans