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GUIDE TO MARINE MACROALGAE

BIO3060 – Field Biology (Coastal and Marine Habitats)

Compiled by: Veronica Farrugia Drakard, Sandro Lanfranco

CYANOBACTERIA

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Prokaryotic: taxonomically distinct from other macroalgal groups, which are eukaryotic.

Benthic colonial forms have a similar ecological role to members of other macroalgal groups.

Pigment is not contained in a chloroplast.

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CYANOBACTERIA

Calothrix spp.

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• Filamentous colonies, epiphytic

• Green to blue-green

• Filaments taper to a point

CYANOBACTERIA

Lyngbya spp.

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• Filamentous colonies

• Filaments do not taper

• Cells wider than long

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CYANOBACTERIA

Symploca hydnoides

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• Colonial ‘thallus’ formed from filaments

• Greyish-white with green tips

• Cells longer than wide

CHLOROPHYTA

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1. Ulvales

Two-layered blades or tubes Parietal chloroplast

Ulva spp. (A) ‘Enteromorpha’-form tubular species. (B) Surface view of cells with parietal plastid (© Elliot Dreujou). (C) Laminar species.

A B C

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CHLOROPHYTA

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2. Bryopsidales

Siphonous: a giant cell with several nuclei

Bryopsis spp. (A) Morphology (© Oksana Belous). (B) Surface view of giant cell.

A B• Fern-like morphology.

• Numerous plastids, each with a pyrenoid(distinguish from Cladophora spp. and Caulerpa spp.).

CHLOROPHYTA

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2. Bryopsidales

• Consist of a creeping stolon with rhizoids and erect axes.

• Numerous plastids without pyrenoids (distinguish from Cladophora spp. and Bryopsis spp.).

• Amyloplasts are present.

Caulerpa prolifera Caulerpa cylindracea Caulerpa taxifolia

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CHLOROPHYTA

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2. Bryopsidales

• Most species branched, only Codium bursa spherical.

• Thallus composed of many utricles, visible microscopically.

• Species may be distinguished from the shape of the utricles: e.g. utricles of C. vermilara narrow slightly towards the tip, utricles of C. decorticatum do not.

Codium decorticatumCodium bursa (© Gianni Felicini)

Codium vermilara –utricles (© Ignacio Bárbara).

CHLOROPHYTA

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2. Bryopsidales

Flabellia petiolata(© marmenormarmayor.es)

Halimeda tuna

• Laminar thallus composed of many siphons.

• Chloroplasts numerous, discoid.

• Slightly calcified.

• Thallus composed of many siphons.

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CHLOROPHYTA

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3. Cladophorales

Siphonocladous: uniseriate filaments of multinucleate cells

Anadyomene stellata

• Laminar thallus composed of multiple filaments which give a distinctive surface pattern.

• More rigid than Ulva spp.

CHLOROPHYTA

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3. Cladophorales

Chaetomorpha sp.

• Unbranched uniseriate filaments.

• Identification to species based on:

• ecology (attached or free-floating)

• size of filaments

• dimensions of cells.

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CHLOROPHYTA

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3. Cladophorales

Cladophora spp. (A) Morphology. (B) Surface view of cells with web-like plastid structure (©

Elliot Dreujou). (C) Pyrenoids stained with aniline blue, showing starch deposits.

A B C

• Uniseriate branched filaments, with branching at the apex of cells.

• Web-like plastid structure with several pyrenoids (distinguish from Bryopsis spp. and Caulerpa spp.).

• Starch is deposited in a broken ring around the pyrenoid.

CHLOROPHYTA

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3. Cladophorales

• Branched uniseriate filaments, with branches originating from the middle of cells.

• Thallus is an aggregation of multinucleate giant cells.

Cladophoropsis sp. (Source:

http://university.uog.edu/botany/474/chloro/cladophoropsis.html)

Valonia utricularis(© marmenormarmayor.es)

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CHLOROPHYTA

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4. Dasycladales

Siphonous: a central axis with lateral verticillate branches

Acetabularia acetabulum Parvocaulis parvulus(© J. M. Huisman)

• > 20 segments in cap. • 10 - 20 segments in cap.

CHLOROPHYTA

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4. Dasycladales

Dasycladus vermicularis(© marmenormarmayor.es)

• Vermiform thallus.

• A principal axis with multiple whorled branchlets.

• Branchlets terminating in pointed apices.

• Colonizes sandy substrata.

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PHAEOPHYCEAE

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1a. Haplostichous construction, stalked pyrenoids ..................................................................................... Ectocarpales

1b. Not as above ............................................................................................................................................................. 2

2a. Reproductive organs organised in receptacles and conceptacles ................................................................. Fucales

2b. Reproductive organs not as above ........................................................................................................................... 3

3a. Radial branching, sphacele present .................................................................................................... Sphacelariales

3b. Planar branching, sphacele not present .................................................................................................. Dictyotales

Key to most common Orders:

Key to Ectocarpales:

1a. Filamentous .............................................................................................................................................................. 2

1b. Non-filamentous ....................................................................................................................................................... 3

2a. Ribbon plastids ............................................................................................................... Ectocarpus (Ectocarpaceae)

2b. Discoid plastids .............................................................................................................................. Acinetosporaceae

3a. Single plastid .................................................................................................................................. Scytosiphonaceae

3b. Several plastids ................................................................................................................................... Chordariaceae

PHAEOPHYCEAE

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1. Ectocarpales - Acinetosporaceae

Acinetospora sp. (© Diane Littler)

• Characteristic short laterals (‘crampons’).

Feldmannia sp.

• Epiphytic.

• Growth occurs at defined meristems.

• Growth is diffuse and intercalary.

Hincksia sp. (physodesstained with cresyl blue)

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PHAEOPHYCEAE

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1. Ectocarpales - Ectocarpaceae

Ectocarpus sp. (stained with cresyl blue) (© Elliot Dreujou).

• Branched filaments.

• Multiple ribbon-shaped plastids.

• Growth is diffuse.

PHAEOPHYCEAE

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1. Ectocarpales - Chordariaceae

• Vermiform thallus.

• Epiphytic.

• Globose thallus.

• To distinguish from Colpomenia, listento the seaweed. Colpomenia is morepapery and crackles when pressed.

Cladosiphon cylindricusLeathesia sp. (© Michael Guiry)

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PHAEOPHYCEAE

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1. Ectocarpales - Scytosiphonaceae

• Thallus grows as hollow tubes, constricted at intervals.

• May appear hairy due to presence of piliferous crypts.

• Globose thallus.

• To distinguish from Leathesia, once again attempt to communicate with the specimen. Colpomenia will crackle when pressed.

Scytosiphon lomentaria Colpomenia sp. (© Oksana Belous)

PHAEOPHYCEAE

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2. Dictyotales

Dictyota spp. (A) Morphology. (B) Lens-shaped apical cells.

A B

Planar ramification

• Growth from a lens-shaped apical cell.

• No midrib present.

• Species may be distinguished by:

• Gross morphology

• No. of medullary layers at the apex and base.

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PHAEOPHYCEAE

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2. Dictyotales

• Growth from a row of several apical cells.

• Midrib present.

• D. lucida has 1 – 2 layers of medullary cells even close to the midrib, while D. polypodioides has many layers of medullary cells throughout the thallus (visible in cross-section).

Dictyopteris polypodioides Dictyopteris lucida (T.S.)

PHAEOPHYCEAE

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2. Dictyotales

• Growth from an apical margin of initials.

• No midrib present.

• Lines of hairs and sporangia give a striated appearance.

Taonia spp. (A) Morphology (© Michael Guiry). (B) Margin of initials.

BA

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PHAEOPHYCEAE

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2. Dictyotales

• Distinctive fan shape.

• Growth from a margin of initials.

• Slightly calcified.

Padina pavonica Zonaria tournefortii(© Ignacio Bárbara)

• Fan-shaped.

• Growth from a margin of initials.

• Midrib present, but does not extend to the apices.

PHAEOPHYCEAE

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3. Fucales

Cystoseira compressa

• Aerocysts, if present, occurring along and within the main axes.

• Identification is extensively complex. Only C. compressa is obviously distinctive, due to the flattened thallus.

• This genus is protected. If you have specimens in your sample, we can only assume they uprooted themselves and migrated there voluntarily.

Cystoseira amentacea Cystoseira sp. receptacles

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PHAEOPHYCEAE

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3. Fucales

Sargassum vulgare

• Flat, leaf-like branches.

• Aerocysts present, occurring terminally on specialised branches.

PHAEOPHYCEAE

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4. Sphacelariales

• Branches originate from both secondary segments of a single primary segment (segments of the main axis resulting from cell division).

• H. filicina branches in one plane, H. scoparia branches in all planes.

Halopteris scoparia Halopteris filicina

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PHAEOPHYCEAE

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4. Sphacelariales

• Branches originate from top secondary segments only.

• Species identification based on reproductive structures.

Sphacelaria sp. Cladostephus spongiosus(© M. D. Guiry)

• Both Halopteris-type and Sphacelaria-type branching observed.

• Branches verticillate.

RHODOPHYTA

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1. Hildenbrandiales

Hildenbrandia rubra (© Meggy Grun)

• Multiaxial growth.

• Tetrasporangia in conceptacles (similar to Corallinales, which have calcified conceptacles).

Encrusting, non-calcified

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RHODOPHYTA

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2. Erythropeltidales

Erythrotrichia carnea

• Stellate plastids.

• Pit connections absent.

• Cells are closer together than in Stylonematales.

Filamentous or parenchymatous

RHODOPHYTA

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3. Acrochaetiales

Acrochaetium sp.

• Stellate or reticulated plastids.

• Usually epiphytic.

• To distinguish from Ceramiales:

• Much smaller

• Only one plastid per cell

Uniseriate branched filaments

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RHODOPHYTA

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4. Nemaliales

Tricleocarpa fragilis(© Eduard and Tamara Titlyanova)

• Filamentous medulla.

• Gelatinous cells in outer part of cell wall.

• Calcified with aragonite(distinguish from Corallinales, which are calcified with calcite: calcite is brittle and breaks, aragonite is softer and more flexible).

Gelatinous, multiaxial, sometimes calcified

RHODOPHYTA

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5. Bonnemaisoniales

Uniaxial, polysiphonous

Spermatangial branches

Gland cells

Heteromorphic life cycles

In cross-section: lots of empty space and large pit connections

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RHODOPHYTA

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5. Bonnemaisoniales

• Alien species, invasive to the Mediterranean Sea.

• Heteromorphic life cycle with filamentous Falkenbergia hillebrandii tetrasporophyte.

• Distinguishable from A. armata by the absence of harpoon-like branches.

Asparagopsis taxiformis (A) Morphology. (B) T. S. through main axis. (C) ‘Falkenbergiahillebrandii’ tetrasporophyte stage.

A B

C

RHODOPHYTA

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5. Bonnemaisoniales

• Heteromorphic life cycle with Hymenoclonium tetrasporophyte.

• Distinguishable from B. clavata by observation of cystocarps: B. asparagoides has spherical cystocarps, while those of B. clavata are asymmetrical.

Bonnemaisonia asparagoides (A) Morphology. (B) Cystocarps. (C) Detail of apex.

A B

C

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RHODOPHYTA

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6. Gelidiales

Uniaxial, but axis is indistinguishable in cross-section

Tetrasporangia develop in stichidia

Cylindrical or compressed thalli

Cartilaginous

Rhizines – filaments running throughout the thallus

RHODOPHYTA

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6. Gelidiales

Gelidium sp.

• Genera may be distinguished by the presence and location of rhizines: Gelidiella has no rhizines, Pterocladiella has rhizines within the medulla and Gelidium has rhizines between the medulla and cortex.

• Parviphycus has tetrasporangia arranged in distinct lines, or ‘chevrons’.

Pterocladia sp. Parviphycus sp. (stichidia)

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RHODOPHYTA

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7. Gigartinales

Extremely problematic order with a huge morphological diversity

Hypnea musciformis Hypnea spinella

• H. musciformis has characteristic curved branches, while H. spinella has antler-like branching (previously H. cervicornis).

RHODOPHYTA

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7. Gigartinales

Chondracanthus acicularis(© Michael Guiry)

Phyllophora crispa Wurdemannia miniata

• Numerous short, spiny branches.

• Filaments visible in cross-section.

• Laminar thallus with wavy margins.

• Forms turfs.

• Impossible to distinguish an axis in cross-section.

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RHODOPHYTA

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7. Gigartinales

Sphaerococcus coronopifolius (A) Morphology. (B) In cross-section.

A B

• Slightly flattened thallus, profusely branched.

• Large cystocarps.

• Axial cell visible in cross-section.

RHODOPHYTA

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8. Gracilariales

Uniaxial, but apical cell and axis are both indistinguishable

Gracilaria spp. (A) Morphology (© Michael Guiry). (B) T.S. through thallus (© Ignacio Bárbara).

A

B

• Extremely difficult to distinguish between species of Gracilaria.

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RHODOPHYTA

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9. Corallinales

Calcified with calcite – hard and brittle

High ecological value

Geniculate vs non-geniculate species

All species are encrusting, but some develop an erect axis

RHODOPHYTA

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9. Corallinales

Amphiroa rigida Corallina elongata

• Geniculate species.

• Branching regularly or irregularly dichotomous.

• Distinction between articles and inter-articles unclear.

• Geniculate species.

• Characteristic coplanar branching.

• Clear distinction between articles and inter-articles.

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RHODOPHYTA

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9. Corallinales

Jania rubens Jania virgata

• Geniculate species.

• Normally epiphytic.

• J. rubens is dichotomously branched, while J. virgata has both dichotomous and tripinnatebranching.

RHODOPHYTA

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9. Corallinales

Lithophyllum incrustans (© Meggy Grun) Phymatolithon lenormandii (© Meggy Grun)

• Non-geniculate species.

• Margins of thallus elevated to form ridges.

• Non-geniculate species.

• Rough, papillose surface.

• Whitish margins.

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RHODOPHYTA

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10. Rhodymeniales

Cylindrical with a cortex of large cells and an empty medulla with medullar filaments

Gland cells may be present

Multiaxial

A few genera are flattened with a cortex of small cells and a medulla of rounded cells (e.g. Rhodymenia)

RHODOPHYTA

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10. Rhodymeniales

• Dense ramification, normally whorled.

• Cortex of an external, discontinuous layer of small cells and an inner layer of larger cells.

• Presence of septa causing constrictions of the thallus at intervals.

Chylocladia verticillata (A) Morphology. (B) Medullary filaments. (C) Septum causing constriction of the thallus.

A B

C

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RHODOPHYTA

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10. Rhodymeniales

• Dense ramification, varying from dichotomous to opposite or alternate, and sometimes whorled.

• Presence of septa causing constrictions of the thallus at intervals.

• Cortex composed of 1-3 cell layers.

Lomentaria articulata (A) Morphology. (B) T.S. showing cortical cells and medullary filaments. (C) L.S. showing medullary filaments.

A B C

RHODOPHYTA

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10. Rhodymeniales

Champia parvula(© Michael Guiry)

Gastroclonium clavatum

• Thallus constricted into segments.

• Very similar to Chylocladia verticillata: segments of Champia parvula are isodiametric.

• Thallus constricted into segments.

• Iridescent.

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RHODOPHYTA

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11. Halymeniales

Acrodiscus vidovichii

• Thallus flattened, cartilaginous.

• Branching is irregularly dichotomous.

• Filamentous medulla.

• Ampullas: filaments around reproductive structures.

Multiaxial, very variable morphology

RHODOPHYTA

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12. Peyssonneliales

Peyssonnelia sp. (© Mat Vestjens and Anne Frijsinger)

• Fan-shaped, prostrate thallus.

• Sciaphilic.

• Slightly cartilaginous.

• Identification to species level requires sectioning the thallusand observing cellular arrangement.

Multiaxial

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RHODOPHYTA

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13. Plocamiales

Plocamium cartilagineum(© Michael Guiry)

• P. cartilagineum has characteristic comb-shaped branching.

• Gland cells present.

• Tetraspores produced in stichidia.

Uniaxial, sympodial growth

RHODOPHYTA

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14. Ceramiales - Ceramiaceae

Acrothamnion preissii

• Invasive species.

• Epiphytic.

• Branching characteristic.

• Gland cells present in forks of terminal branches.

Filamentous, gland cells may be present

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RHODOPHYTA

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14. Ceramiales - Ceramiaceae

Antithamnion sp. (© Ignacio Bárbara) Antithamnionella elegans

• “Whorl-branches” alternate or opposite in prostate axes, and in distichous or decussate opposite pairs in erect axes.

• Gland cells, if present, on modified filaments.

• “Whorl-branches” single, opposite or in whorls of 3 or 4, simple or 1-2 times branched.

• Gland cells formed 1-2 per cell on whorl-branches.

RHODOPHYTA

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14. Ceramiales - Ceramiaceae

• Most species have characteristic incurved apices and striated appearance.

• Nodes are pseudoparenchymatous, with pericentral cells surrounding a central cell, while internodes are filamentous.

• Identification of species based on habit, cortication and number of pericentral cells.

Ceramium spp. (A) Morphology, with characteristic incurved apices. (B) T.S. through nodal (pseudoparenchymatous) and internodal (filamentous) segments. (C) Cystocarp.

A B C

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RHODOPHYTA

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14. Ceramiales - Ceramiaceae

Gayliella flaccida

• Similar to Ceramium.

• Branching is alternate, while in Ceramium spp. it is normally dichotomous.

RHODOPHYTA

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14. Ceramiales - Callithamniaceae

Callithamnion sp.

• Thallus uniseriate, with dense branching.

• Multinucleate vegetative cells present.

• Species identification is based on vegetative features, such as branching pattern.

Filamentous, gland cells absent

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RHODOPHYTA

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14. Ceramiales - Dasyaceae

Dasya sp.

• Thalli radially organised and polysiphonous.

• Branches in a spiral arrangement.

• Tetrasporangia in stichidia.

• Periaxial cells 5-7.

• Primary segment of uniseriatebranchlets is monosiphonous.

• Species identification based on stichidia and branching of pseudolaterals.

Polysiphonous with monosiphonous branches; stichidia present

RHODOPHYTA

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14. Ceramiales - Dasyaceae

Eupogodon planus Heterosiphonia crispella

• “Whorl-branches” alternate or opposite in prostate axes, and in distichous or decussate opposite pairs in erect axes.

• Gland cells, if present, on modified filaments.

• Branches borne alternately in one plane.

• Periaxial cells 9-10.

• Primary segment of uniseriate branchletsis polysiphonous.

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RHODOPHYTA

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14. Ceramiales - Delesseriaceae

Acrosorium ciliolatum(© Heroen Verbruggen)

• Prostrate and erect blades.

• Attached to substratum by peg-like haptera.

• Blades monostromatic except at the base.

• Microscopic veins present.

Foliose; midribs and veins may be present

RHODOPHYTA

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14. Ceramiales - Delesseriaceae

Apoglossum ruscifolium Taenioma spp.

• Midribs and microscopic veins present.

• Distinguish from other genera (Hypoglossum, Erythroglossum) by the character of the apex, apical cell and veins.

• Mostly epiphytic.

• Bearing long filaments at apices.

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RHODOPHYTA

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14. Ceramiales - Rhodomelaceae

Polysiphonia sp.

• Reproductive structures are large and conspicuous.

• Spermatangial branches present.

• Species identification is complex and based on a large number of characters.

Polysiphonous, with trichoblasts

RHODOPHYTA

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14. Ceramiales - Rhodomelaceae

Chondria capillaris Herposiphonia secunda Laurencia sp.

• Attenuated apices with multiple, profusely branched trichoblasts.

• Characteristic incurved apices.

• Prominent apical pits.

• Trichoblasts colourless and borne in apical depressions.

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RHODOPHYTA

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14. Ceramiales - Rhodomelaceae

Palisada tenerrima Palisada perforata

• Pyramidal habit and wart-like branches.

• Similar to Laurencia, but generally more robust and densely branched.

• P. perforata is spirally branched.

RHODOPHYTA

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14. Ceramiales - Spyridiaceae

Spyridia filamentosa Spyridia hypnoides

Polysiphonous, with partially ecorticate filaments

• Highly mucilaginous, with a striated appearance due to partial cortication.

• S. hypnoides has ‘hooks’ borne terminally on the uniseriate filaments.

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RHODOPHYTA

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14. Ceramiales - Wrangeliaceae

• Thallus uniseriate, ecorticate.

• Species identification based on general habit and shape and size of cells.

Griffithsia spp. (A) Morphology. (B) Tetrasporangia. (C) Apical cell.

A B C

Morphologically variable

RHODOPHYTA

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14. Ceramiales - Wrangeliaceae

• Similar to Griffithsia.

• Can be easily identified by the presence of pedicellated monospores, with the pedicels lacking pigment.

Monosporus pedicellatus (A) Morphology. (B) Characteristic monospores. (C) Pit connection stained with aniline blue.

A B C

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RHODOPHYTA

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14. Ceramiales - Wrangeliaceae

Wrangelia penicillata Spermothamnion sp.

• Numerous uniseriate filaments originating at the junctions between cells.

• Highly mucilaginous.

• Filamentous, monosiphonous.

• Composed of a prostrate, creeping stolon attached by rhizoids and giving rise to erect axes.