Division: Chlorophyta
(green algae)
Chlorophyte Diversity
5 classes:
Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophyceae
Part II
Land plants
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Ulvophyceae
Class Ulvophyceae:
Microtubule Roots: cruciate
Basal Bodies: counter- clockwise
1.
How flagella are attached/constructed:
•
basal bodies orientation = counterclockwise
•
microtubule roots = cruciate
Flagella
Basal Bodies
2.
Cell covering:
•
scales vs. cell wall = wall (scales in some reproductive unicells)
3.
How cells actually divide:
•
spindle = closed
•
microtubule organization = phragmoplast
•
division by = furrow
Microtubule roots
Cell
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Ulvophyceans have diverse morphologies
Class Ulvophyceae:
Mostly marine macroalgae, some freshwater also
 Haplontic, diplontic or alternation of generations
 No hypnozygotes
Orders to know:
unbranched filament
branched filament
• Ulotrichales
• Ulvales (split off from ‘Ulotrichales’)
• Cladophorales
• Caulerpales (used to be ‘Codiales/Bryopsidales’)
• Dasycladales
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Division: Chlorophyta
Class: Ulvophyceae Trebouxiophyceae
parenchymatous
coenocytic/ siphonous
Order Ulotrichales –e.g.Ulothrix
Haplontic with codiolum phase
1N thallus,
the zygote is the only diploid stage
Life -Cycle
of the Ulotrichales
Haplontic
-Codiolum phase- cell wall is from 2n zygote with n spores inside
e.g. Ulothrix
Chlorophyceae Prasinophyceae
syngamy
Order: Ulotrichales Ulvales
Cladophorales
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Caulerpales
Dasycladales
• Spores have scales,
not true cell walls
1N gametes
2N
zygote
meiosis
occurs
in zygote
- Unicells, filaments, blades; uninucleate or multinucleate cells
- Simple, haplontic life histories; all with an attached Codiolum stage
formed by zygote; zygote undergoes meiosis, producing flagellated
meiospores
1N gametophytes
1N
codiolum
stage
• Cell wall of zygote
(2N) stays intact to
contain new
meiospores (N)
Focal genera: Ulothrix
1N zoospores
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Order Ulvales e.g. Ulva
Division: Chlorophyta
Class: Ulvophyceae Trebouxiophyceae
Order:
Ulotrichales
Ulvales
Isomorphic Alternation of Generations: organism having
a separate multicellular diploid sporophyte and haploid
gametophyte stage, sporophyte & gametophyte are
same sizes
Chlorophyceae Prasinophyceae
Cladophorales
Caulerpales
Dasycladales
- Uninucleate cells with a single parietal chloroplast
- Parenchymatous thallus; mono- or distromatic, sheets or tubes
- All cells can reproduce (holocarpic reproduction)
- Isomorphic alternation of generations
Focal genera: Ulva
“sea lettuce”
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Division: Chlorophyta
Class: Ulvophyceae Trebouxiophyceae
Order:
Ulotrichales
Ulvales
Ulva spp
• Distromatic
• Blade-like
• Often ephemeral in
intertidal
• Fast growing, tasty
to herbivores
Ulva intestinalis =
• Monostromati c
• Tubular
• Euryhaline- Tolerates
freshwater, often occurs
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near seeps
Chlorophyceae Prasinophyceae
Cladophorales
Caulerpales
Dasycladales
- Large, multinucleate cells, connected end to end with cross walls
- Chloroplasts  reticulate or multiple discoid arrayed in reticulate network
- Isomorphic alternation of generations
Focal genera:
Cladophora, Chaetomorpha, Dictyosphaeria,
Valonia
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Order Cladophorales
e.g. Cladophora
Isomorphic Alternation of Generations: organism having
a separate multicellular diploid sporophyte and haploid
gametophyte stage, sporophyte & gametophyte are
same sizes
-Japanese Cladophora spp: “marimo balls” or tribbles
• Size: up to 30 cm
•A folktale in which the hearts of a young couple who drown in the
lake turn into Cladophora balls
• Meditation – watch balls rising and falling
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California Cladophorales
Cladophora
- “Pin cushion” alga
- Branched filamentous
- Harbors inverts  Nutrients
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• Protected species - three day festival – to promote conservation
Tropical Cladophorales
Chaetomorpha
Dictyosphaeria
- Unbranched filaments
- Modified basal cell w/rhizoidal
extensions
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Ventricaria
- Opportunistic: “Ulva of the
-Made up of single central cell (big)
tropics”
and lots of lateral cells (small)
- Can outcompete corals when there
has been overfishing or storm
disturbance
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Division: Chlorophyta
Class: Ulvophyceae Trebouxiophyceae
Order Caulerpales
Chlorophyceae Prasinophyceae
Focal genera:
Order:
Ulotrichales
Ulvales
Cladophorales
Caulerpales
Dasycladales
- Coencocytic, siphonous thallus construction
- Lots of variability in form (uniaxial, multiaxial, etc.)
- Mostly biflagellate anisogamous reproduction; various life histories
Codium “dead man’s fingers”
Halimeda
Caulerpa
- Some calcified: major component of tropical sands  remains of
coralline greens form a layer >50 m thick at Great Barrier Reef
- Synchronous spawning in tropics
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Morphology
Morphology
Uniaxial and multiaxial construction
Coenocytic/siphonous construction:
= Multinucleate, no division of
cytoplasm with cell walls
“clotting compounds” to quickly
repair wounds
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Bryopsis
Codium “ dead man’s fingers”
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Order Caulerpales:e.g.Codi um
Diplontic: 2N thallus, the gametes are
the only haploid stage
Codium fragile
Morphology
Utricles
Codium fragile
Gametangium
Utricles-peripheral portions of the siphons maybe inflated &
aggregated to form coherent outer surface gametangium
(reproductive structure) originate from them
*Codium the size of an apple =
~30 km of siphons
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Codium and scallop interaction on East Coast
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Codium invasion on the East Coast
Alternative Stable State:
Membranipora , invasive bryozoan, epiphyte on and
causes mortality of native Laminaria,
• Attach and grow on
scallops
• Weigh them down and
prevent escape from
predators
Openings in Laminaria saccharina canopy favor
establishment of…
• Cast adrift in heavy storms
• Results in high mortality
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…Codium fragile  invasive alga which suppresses
recruitment of Laminaria sporophytes.
Levin et al. 2002
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Halimeda
Holocarpic reproduction in many tropical members of O. Caulerpales
- Thousands of individuals spawn synchronously
- Water visibility drops to ~ 1m downstream from reef, but disperses
within half an hour
- Empty thallus disintegrates, often within hours
- Anisogamous, dioecious= separate sexes
- Entire thallus turns into gametes
- Gametes migrate to surface overnight
- In some species:
gametes positively phototaxic
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zygotes are negatively phototaxic
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Tropical siphonous greens, timing of growth, and herbivory
-Gamete release is synchronous and
species and gender-specific
- New segments not fully calcified, but heavily defended chemically
- Major cue is amount of blue light
(time from sunrise)
- Chloroplasts stay in older segments until minutes before sunrise
- Contrasts highly with other marine
species that use lunar, tidal,
temperature cues to spawn
from Clifton, 1997
- New tissue put on at night (why?)
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- Increase in calcification = decrease in chemical defenses
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Synergy between calcification and secondary metabolites as
defenses against herbivores
Caulerpa invasion
- Calcification: CaCO4 precipitated from water column, incorporated into
cell wall of siphons, especially utricles
(decalcify Halimeda, just a mass of enormous siphons)
- Both chemical and structural defense common in tropical spp
- Temporal interplay during growth and development
- Old vs. young segments within an individual
- Old vs. young individuals
- Mark Hay’s work: true synergist effects in deterring urchins
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Morphology
• Native in Australia (but non-native strains have made it back there)
• 1st introduced as a non-native in Mediterranean (1984)
• In 2002 introduced at 2 sites in S.California (Carlsbad, Huntington Harbor)
• Genetics reveal invasive strain different from native strain
• Grows faster, larger, asexual reproduction, and resistant to cold temps
• Listed as one of the top 100 invasive species on earth
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Kleptoplastids
Caulerpa = uniaxial, but with trabeculae for support
trabeculae = ingrowth of wall material
(Sacoglossan opistobranchs as petty theives)
Siphons form rhizoidal holdfast, too
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Division: Chlorophyta
Class: Ulvophyceae
- Sacoglossan radula adapted to
host alga (length of tooth ~
thickness of siphon)
- Common in siphonous greens
- Pierce and suck out insides
- Stolen chloroplasts can last up
to a month or so – why not
longer?
Order:
Trebouxiophyceae Chlorophyceae Prasinophyceae
Ulotrichales
Ulvales
cladophorales
Caulerpales
Dasycladales
- Extensive fossil record, group is 500 my old with 11 extant genera
- Tropical, shallow water spp
- Unicellular thalli with one nucleus and radial symmetry
Celebrity genus: Acetabularia
Elysia
“mermaid’s wine glass”
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1930’s - Hammerling’s experiments with Acetabularia
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