1. The document discusses the classification, characteristics, and life cycle of the red algae Gelidium. It belongs to the division Rhodophycophyta, class Rhodophyceae, sub-class Florideae, and order Gelidiales. 2. Gelidium has a stiff, cartilaginous thallus that is often pinnately branched. It reproduces both sexually, through non-motile gametes, and asexually, through fragmentation and non-motile spores. 3. Red algae like Gelidium are used for medicines, food, and industrial products like agar and carrageenan. Some can also cause harmful algal blo

1. By
Subhananthini jeyamurugan
Roll no 18py17
I M.Sc., Microbiology

3. I. Florideophyceae
I. Nemaliales
II. Corallinales
I. Lithophyllum
II. Corallina
III. Gelidiales
I. Gelidium
IV. Gigartinales
I. Chondrus crispus
II. Used as a source of carageenan
V. Rhodymeniales
VI. Ceramiales
I. Polysiphonia
polysiphonia

4. Division : Rhodophycophyta
class : Rhodophyceae
sub-class : Florideae
order : Gelidiales
Family : Gelidiaceae
Genus : Gelidium
Species : cartilagineum

5. • Accessory pigments!
Phycobilins mask the
Chlorophyll a – thus they look
red.
• Due to these accessory
pigments, red algae can
photosynthesize in deep water
(at different light wave lengths).

6. Floridean starch is a type of a storage glucan found in red algae (also known as rhodophytes), in which it is
usually the primary sink for fixed carbon from photosynthesis. Floridean starch is stored as grains outside the
chloroplast

8. • Thallus – cylindrical or flattened
• It is stiff and cartilaginous and often pinnately branched.
• In many species branch lets bend away from the main axis
• The thallus is based primarily upon the uniaxial type of construction.
• It possess the single apical cell at the apex of each branch.
• The apical cell forms a single axial filament of the adult portion.
• The axial filament, one or two posterior to the apical cell cut off four primary pericentral cells.
• And then each of these cells form a short branched lateral filament.
• The tips of these lateral filaments adhere to each other and form pesudoparenchymatous tissue that
makes the surface of the thallus.

10. Continue…

11. • Red algae have double cell
walls.
• The outer layers contain
the polysaccharides
agarose and agaropectin
that can be extracted from
the cell walls by boiling as
agar.
• The internal walls are
mostly contain cellulose.

12. Vegetative Reproduction is by
fragmentation
Asexually by non-motile spores
Sexually by non-motile gametes
e.g., Polysiphonia,
Porphyra,
Gracilaria,
Gelidium.

13. sexual
Asexual

14. In majority of class it takes place by fragmentation.
In sexual reproduction of the gametophytes takes place by neutral spores,
mono spores and polyspores.
• neutral spores develop in ordinary cells of thallus.
• monospores develop in sporangia.
• polyspores are formed in larger number in the sporangium.

15. Continue…
• The asexual reproduction of the sporophytes takes place by
tetra spores formed in tetrads in the tetra sporangia (Tetra
sporangia produce tetra spores via meiosis)e.g., Polysiponia.
• Paraspore borne inside parasporangia in greater numbers.
• During the development of tetraspores reduction division
takes place.
• In the development of paraspores there is no reduction
division.

16. •The sexual reproduction is always in Oogamous. The
oogamy is a special type.
• Male structure is called the Spematangia developing non-
motile spermatia ( male gametes) in them.
• Female structure is called the procarp. It has a
carpogonium bearing a receptive structure is called
trichogyne.
•The egg develops in the basal swollen part of carpogonium.

17. • life cycle may be haplotonic, haplobiontic or diplobiontic.
• Florideophyceae
• Life cycle typically diplohaplontic, some are haplontic
• Many have a complex modification of a diplohaplontic life cycle
• Triphasic alternation of generations
• Gametophyte (may or may not be dioecous)
• Carposporphyte
• Tetrasporophyte
• The low efficiency of fertilization

18. Life cycle

20. Continue…
Medicines:
• Corallina is capable
of curing worm
infections.
• Polysiphonia has
antibacterial
properties. Agar is
laxative.
• Carrageenan can
coagulate blood

21. A number of red algae are
edible,
e.g., Porphyra (Laver),
Rhodymenia (Dulse),
Chondrus (Irish Moss).
Rhodymenia (also called
sheep’s weed) is also used
as fodder.
 Porphyra is cultivated in
Japan for commercial
exploitation.

23. • Some red tides are associated with
the production of natural toxins,
depletion of dissolves oxygen or
other harmful algal blooms.
• The most conspicuous effects of
these kind of red tides are the
associates wildlife moralities of
marine and coastal species of fish,
birds, marine mammals and other
organisms.