Rhodophyta
Rhodophyta
I.
II.
III.
“Red Algae”
General Characteristics
Thallus Construction and Growth
Reproduction
Generalized life history
Polysiphonia type
Porphyra type
Rhodophyta
One class, two subclasses:
Class Rhodophyceae:
Florideophycidae (99%)
Bangiophycidae (1%)
• filamentous
• pseudoparenchymatous
• apical growth
• complex oogamy
(triphasic)
• pit connections
• unicell, filament, blade
• diffuse growth
• simple life histories
e.g. Porphyra
General Characteristics cont.
General Characteristics
no Flagella - different from
other groups (except diatoms)
Chloroplast
• separate thylakoids
• double membrane cynanophyte ancestor
• thylakoids have
phycobiliproteins
• chromatic adaptation
(color adjustment)
Photosynthetic pigments
Chl a
phycobilisomes (like Cyanophyta)
composed of phycobiliprotiens
• phycoerythrin (red color)
• phycocyanin (blue color)
• allophycocyanin
General Characteristics cont.
General Characteristics cont.
storage product:
α-1,4 linked glucan (starch)
• “Floridean starch”
• similar to glycogen
• stored in cytoplasm
branches at
6th carbon
cell walls
• cellulose fibrils
• some species have aldose sugars
(mannose, xylose) Bangean
• mucopolysaccharides (outer
walls)
• agar, carageenan
• both are important
commercially as emulsifiers and
gels
1
General Characteristics cont.
pit connections cont.
Cellular features
• one (usual) or more nuclei
• pit connections
• formed from incomplete cell
division (furrowing)
• polysaccharide/protein plug
forms in pit
• secondary pits sometime form
between adjacent cells
• mostly floridean
taxonomic importance
Thallus Structure
Pit connections
mostly
bangean
uniaxial
Thallus Structure
• most are filamentous or
Pseudoparenchymatous
• thallus is branched
• encrusting (calcium
carbonate)
• crust forming
• some unicells
• some parenchymatous
Polysiphonous
Pseudoparenchymatous thallus
construction
Thallus
two types
mostly
axis
Corallina
uniaxial
multiaxial
Thallus
mostly
branches
Batrachospermum
2
Multiaxial forms
Thallus Structure cont.
Encrusting and calcified thalli
• many species heterotrichous
m
m
ulu
ulu
nic
nic
ge
ge
er
t
in
• often calcify (Corallines)
• CaCO3 (and MgCO3 7-30%)
• precipitated in in cell walls
(extracellular)
• predominantly in side branches
upright Corallines
calcified side branches
uncalcified joints axial branches
Porphyra sp. (sheet)
Thallus Structure (Bangean)
Filaments and sheets (parenchymatous)
Bangia sp.
Reproduction
Highly Specialized reproduction
• two or three(!) distinct life
history stages
• advanced form of oogamy
spermatangium
monospores
trichogyne
Carposporophyte
branched filaments (2n)
carpospores (2n)
Carpogonium
(oogonium)
Gametophyte (n)
tetraspores (n)
me
often a
crust
tetrasporophyte (2n)
3
Reproduction cont..
Reproduction in Bangean Reds
Porphyra
macrothallus and conchocelis stages
conchocelis stage (2n or n)
• filamentous growing on shells
• produces conchospores (2n)
• meiosis occurs in conchospores
• germinates into macrothallus
Tetraspore arrangement
• characteristic of species
• produced via meiosis
zonate
cruciate
Porphyra
spermatia (n)
tetrahedral
carpogonial cell (n)
monospores
fuse
carpospores (2n)
(n)
carpospores (n)
me
(n)
carposporangia
gametophyte (n)
conchospore
(2n)
spermatia
conchocelis filament (2n)
4