heterokontophyta i 4

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• Midterm in one week (Tuesday, 4/27)

• Format:• Definitions• Short Answer• Ps/I Curve• Dichotomous key• Life History• A couple of matching sections• Short Essays

Dichotomous Key: Cannot use names of groups, instead characteristics

Example: Chlamydomonas, Dictyota, Halimeda

Has Chlorophyll CDictyota

No Chloropyll c

Forms palmelloid stageChlamydomonas

No palmelloid stageHalimeda

Kingdom: UnikontsPhylum: MolluscaClass:Gastropoda

clade: Heterobranchiainformal group: Opisthobranchia

clade Cephalaspideaclade Thecosomataclade Gymnosomataclade Aplysiomorphagroup Acochlidiaceaclade Sacoglossaclade Umbraculidaclade Nudipleuraclade Nudibranchia

Division: HeterokontophytaOr

(Ochrophyta, Chromophyta, Phaeophyta)

~ 1,500 species99% marine

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Brief history of photosynthetic organisms on earth

3.45 bya = Cyanobacteria appear and introduce photosynthesis

1.5 bya = first Eukaryotes appeared (nuclear envelope and ER thought to come from invagination of plasma membrane)

0.9 bya = first multicellular algae (Rhodophyta - Red algae)

800 mya = earliest Chlorophyta (Green algae)

400-500 mya = plants on land – derived from Charophyceae

250 mya = earliest Heterokontophyta (Brown algae)

100 mya = earliest seagrasses (angiosperms)

Adapted from Sadava 2007

Chromalvaeolates

Plantae

Excavates

Rhizaria

Unikonts

SpirochetesChlamydiasCyanobacteriaProteobacteria

ApicomplexansDinoflagellatesCliates

Heterokontophyta

DiatomsOomycetesHaptophytes

Glaucophytes

Rhodophyta

ChlorophytesLand PlantsCharophytes

DiplomonadsParabasalids

HeteroloboseansEuglenidsKinetoplastids

CercozoansForaminiferans

Radiolarians

FungiChoanoflagellatesAnimals

Loboseans

Slime moldsSlime molds

Bacteria

Archaea

Eukaryotes

Heterokontophyta Characteristics:1) Pigments?

2) Chloroplast structure?

3) Storage product?

4) Flagella?2

Division: Heterokontophyta

Many classes, mostly unicellular or colony of unicells:• class: Chrysophyceae• class: Synurophyceae• class: Dictyochophyceae• class: Pelagophyceae• class: Raphidophyceae• class: Xanthophyceae• class: Eustigmatophyceae• class: Tribophyceae• class: Phaeothamniophyceae• class: Phaeophyceae***

*** We will focus on marine macroalgae

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Hierarchical system of classification:

Level: suffix: example:Domain EukaryoteKingdom/Clade ChromalveolatesPhylum/Division -phyta HeterokontophytaClass -phyceae PhaeophyceaeOrder -ales Laminariales

Family -aceae AlariaceaeGenus Egregia

species menziesii

Algal taxonomy

Phaeophyceae Metabolites:

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Tannins: (a.k.a. polyphenolic compounds and terpenes)

- Anti-endophyte, -epiphyte, and anti-herbivory

- Stored in special vesicles called physodes in the cytoplasm

•laminaran and mannitol are most abundant

•Always sugars, never starch

•Storage products found in cytoplasmic vacuoles (no special name); not associated with chloroplasts or pyrenoids

Phaeophyceae Storage Products:

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Phaeophyceae Storage Products :Mannitol function

•important in osmoregulation- algae make more mannitol to use up ions-> algal salinity decreases

•transporting organic material to different parts of the thallus in large species

•lowers freezing point

Seawater is hypotonic (less saline) than most algal cells

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Heterokont flagella:

Anterior “flimmer flagellum”•used for movement• long flagellum with two rows of stiff hairs (“mastigoneme”) • directed forward

Posterior “whiplash flagellum”•used for steering• short, smooth flagellum• directed backward• contains flavin which functions as a photoreceptor

• an eyespot acts a shading structure or light reflector

Phaeophyceae Flagella:

Flagella attached laterally not apically5

- Advanced forms: complex multicellular thalli

- Not unicellular (except gametes and spores)

- Simplest forms are branching filaments

- More complex forms are parenchymatous and pseudoparenchymatous

- Differentiation of cortex (outer pigmented cells) and medulla (inner non-pigmented cells)

- Medullary cells primarily for storage or transport

- Some browns quite large over 40 meters long

Phaeophyceae Thallus Morphology:

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Phaeophyceae Morphology of Cell Walls

Two main components:

1. Cellulose microfibrils (1-10% of thallus dry weight)Function: structural support

2. Alginic acid surrounds the microfibrills (35% of thallus dry weight)Function: elasticity; flexibility; prevent desiccation; and

osmoregulation (ion exchange)

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Phaeophyceae Alginates:Alginates = salt form of alginic acid; primarily in intercellular matrix

•Alginates = Alginic acid + an Ion

• Details of how alginates are used in helping ion exchange are not well understood.

• One proposed mechanism is that preferentially using some ions and not others helps to balance overall ion levels.

• Common ions that are used to make alginates are Ca, Na and Mg

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Phaeophyceae Alginates:

Human uses for alginates - Ice-cream prevents ice crystal formation

- Frosting water retaining properties; prevent drying

- Paints emulsifying agent; keeps pigments suspended and prevents brush streaking

- Pharmaceuticals

- Food “kombu” in Japan; dried and shredded laminarians

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Plasmodesmata = connections between adjacent cells, formed during cell division

- Used for cell-to-cell transport of photosynthetic products and cell communication

Phaeophyceae Morphology of intercellular connections

Only alga to transport sugar/photosynthate in sieve elements

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Algal life histories : Terminology

Sporophyte: diploid, 2n, multicellular release spores

Sporangia = structure where spores are formed

Spore (mitospore, meiospore): unicellular, must settle & grow, product of mitosis(Mt) or meiosis (Me)

Gametophyte: hapliod, 1n, multicellular release gametes

Gametangia = structure where gametes are formed

Gamete: unicellular, must fuse or die, product of mitosis(Mt) or meiosis (Me)

Unilocular = all spores/gametesare produced in a single compartment

“unangia”

Plurilocular = divided into many small chambers (locules); one spore/gamete per chamber

“plurangia”

Gametangia = structure where gametes are formed

Sporangia = structure where spores are formed

Phaeophyceae Reproduction:

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uniseriate multiseriate

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How do the male gametes find the female ones?


Pheromones = chemicals produced to elicit a specific behavioral or physiological response from another individual.

Many Phaeophyceans produce sexual pheromones, all are chemically similar (unsaturated hydrocarbons). Similarity high cross-reactivity

Male gametes are VERY sensitive to pheromones: very low concentration will elicit a response

Functional Anisogamy

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female gamete male gameteFunctional Anisogamy

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Phaeophyceae habitat:

• Mostly marine (or at least brackish water)

• Intertidal and subtidal

• Dominate colder waters

Northern hemisphere:

# of red species > # of brown species

# of red individuals << # of brown individuals

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Browns are less diverse but more abundant

12 orders within class: Phaeophyceae

Our focus will be on the following 8 orders:


Class: Phaeophyceae

Order:Dictyotales

ChordarialesEctocarpales

Scytosiphonales Desmarestiales

Laminariales Fucales

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Durvillaeales

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Distinguishing among orders based on

1. Life History and Reproduction• Isomorphic/heteromorphic alt. of gen.; diplontic• Isogamous, anisogamous, oogamous

2. Macrothallus Construction:• Filamentous• Parenchymatous• Pseudoparenchymatous

3. Growth• Diffuse• Apical• Intercalary• Trichothallic• Meristodermal-a surface layer of cells (epidermis) that is

capable of dividing (is meristematic)

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Class: Phaeophyceae

Order:Dictyotales




- Saxicolous or epiphytic

- Uniseriate filaments

- Opportunistic spp, excellent colonizers

- Female gametes releases pheromone ectocarpene

Celebrity genus: Ectocarpus

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Durvillaeales

Order: Ectocarpales:

1. Life History and Reproduction:

2. Macrothallus Construction:

3. Growth:

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Life History of Ectocarpales:

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Class: Phaeophyceae

Order:Dictyotales




- Saxicolous- Common in tropical waters; also found locally subtidal- Pheromone= dictyotene

Celebrity genera: Dictyota, Padina

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Durvillaeales

Order: Dictyotales



3. Growth:

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Life history of Dictyota

• Reproductive structures in “sori” = cluster of gametangia or sporangia

• Tetraspores (non-flagellated) released by 2N sporophyte

• Gametophyte dioecious

• Large egg one per “oogonium” = female reproductive structure containing one or more eggs

• Sperm single hairy flagella but has second basal body

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Life History of Dictyota:

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A Dictyota Story:(Stachowicz and Hay 2000)

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Southern Sites + Libinia dubia, the

decorator crab + Dictyota menstrualis,

the chemically defended brown alga (diterpenes)

+ Omnivorous fishes+ Crabs are specialists

in decoration preference

Northern Sites+ Libinia dubia, the

decorator crab+ No chemically noxious

algae

+ Carnivorous fishes

+ Crabs are generalists in decoration preference

Cape HatterasLocal adaptationAssociational defences

The only calcified Phaeophycean: Padina

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Increased Grazing


Class: Phaeophyceae

Order:Dictyotales





- Found locally in higher intertidal shallow pools

- Plurangia always uniseriate(filament in single row)

Celebrity genera: Scytosiphon, Colpomenia

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Durvillaeales

Order Scytosiphonales:



3. Growth:

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Class: Phaeophyceae

Order:Dictyotales





- Common intertidally, tropics to poles

- Plurangia could be uniseriate or multiseriate

Celebrity genera: Leathesia, Ralfsia

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Durvillaeales

Order: Scytosiphonales……….life history not fully understood

Crust stage (‘Ralfsia’-like)Upright stage

Gametophyte?Plurangia

Sporophyte?Unangia

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Order: Chordariales



3. Growth:

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Leathesia = Psuedoparenchymatous;

O. Chordariales

Colpomenia = Parenchymatous;

O. Scytosiphonales

Convergent evolution of form:

Both genera found locally…..do the crunch test!! ☺28

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Class: Phaeophyceae

Order:Dictyotales




- Saxicolous

- Low intertidal to subtidal

- “Acid weed”

Celebrity genus: Desmarestia 29

Durvillaeales

Order: Desmarestiales



3. Growth

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Life History of Desmarestiales

- Morphology variable within the genus

-Subtidal, but grows well in high light (very abundant if disturbance has removed other plants or canopy, e.g. El Nino, orurchin grazing)

- Disappears with kelp growth due to canopy cover; shading

- ”Acid weed”: cells accumulate sulfate ions from seawater which reacts with water to produce sulfuric acid or malic acid, stored in vacuoles

=ANTIHERBIVORY, pH 0.8-1.8, bleaches other algae

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Order Macrothallus Construction Macrothallus Growth

Isomorphic alternation of generations

Ectocarpales filamentous diffuse

Dictyotales parenchymatous apical or marginal

Heteromorphic alternation of generationsChordariales filamentous or parenchyma variable

Desmarestiales pseudoparenchyma tricothallic

Scytosiphonales parenchyma or pseudoparenchyma variable

Laminariales parenchyma intercalary or meristodermal

Diplontic: 2N thallus, the gametes are the only haploid stageFucales parenchyma apical

Durvilleales parenchyma variable

Class Phaeophyceae

heterokontophyta i 4

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