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. Jakoba) have the most
complete mitochondrial genome known closest to bacterial genome - therefore
primitive.
 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
Trichomonas vaginalis
 Trichonymphs Trichonympha spp
 Trichomonads

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 bodiesmodified 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 celluloseecologically critical
function.
Acquisition at
hatching and molting.
Mutualism
 Mutualistic
bacteria
inside Trichonympha et
al. digest the wood.
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 representative 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 have an
unusually large mass of DNA
(kinetoplast)
 Trypansosoma
 Most
brucei
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) causes
African sleeping sickness

T. cruzi causes Chagas’ disease of Central and
South America and now potentially in the U.S.
Tsetse fly
Kissing bug
Tsetse Fly
Vectors of trypanosome
diseases
Trypanosomes in blood
smear
Red blood
cells
Trypanosome
with undulating
membrane
Flagellum
25 µm
Trypanosoma cruzi
Chagas disease
Figure 5.27
Trypanosomiasis
T. cruzi life cycle




Transmitted to man
via feces of bug
Intracellularreproduces 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 symptomsdementia, 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
 Have
(alveoli) lie immediately below the cell surface.
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

Dinozoa
– conjugation
 Dinoflagellates – some photosynthetic,
 Important in nearshore oceans

others not
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
2
are “naked” and lack these plates
flagella present.
One trails behind
 One lies in groove around center of cell
 Cell spins slowly like a top as it swims

Ceratium
Gonyaulax: an armoured
dinoflagellate. Cell wall is
subdivided into multiple polygonal
vesicles filled with relatively thick
cellulose plates
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
meiosis

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 Gonyaulax catenella is so toxic
that an aspirin sized tablet of the poison could
kill 35 people; it is one of the strongest known
poisons
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