Algae of unusual habitats
- Halophytic algae - Occur in saline sea water and salt lakes and can withstand high concentration of salts, e.g.,
Chlamydomonas ehrenbergii, Stephanoptera. - Epiphytic algae - Grow on larger algae, bryophytes and angiosperms, e.g., Oedogonium and Microspora are found
attached to larger species of Vaucheria, Cladophora and Rhizoclonium. - Epizoic algae - Grow on animals such as snails, fishes and tortoise, e.g., Cladophora crispata (epizoic on snail).
- Endozoic algae - Occur in tissues of animals, e.g., Zoochlorella in Hydra viridis.
- Cryophytic algae - Grow on ice or snow and impart attractive colours to snow covered mountains, e.g., Haematococcus nivalis
imparts red colour to alpine and arctic mountains while Chlamydomonas yellowstonensis and Mesotaenium species are
responsible for green snow in Europe. - Parasitic algae - Grow as parasites on many plants and animals, e.g., Cephaleuros virescens causes red rust in tea and
coffee plantations. - Thermophytes - Occur in hot water springs (50-70°C temperature) as are able to survive high temperatures due to absence
of well organised nucleus, e.g., Oscillatoria brevis, Heterohormogonium sp.
Classification of Algae
- Based upon phylogeny, affinities and interrelationships, algae is classified into various classes by Dr. F. E. Fritsch. However,
according to Whittaker’s system of classification, algae are mainly divided into three classes: Chlorophyceae, Phaeophyceae
and Rhodophyceae.
Table: Characteristics of different classes of algae
Classes Structure Occurrence Major
pigments
Reserve
food
material
Reproduction
Vegeta-
tive
Asexual Sexual
Chlorophy-
ceae, (Green
algae)
e.g., Spiro-
gyra, Ulothrix
Unicellular, colonial,
coenobial, filamentous,
siphonaceous. Cell wall
cellulosic and pectic,
pyrenoid single or
compound, embedded.
Motile cells with 2-
equal flagella.
Mostly fresh-
water, a
few marine.
A marked
tendency
towards
terrestrial
habitat.
Chl. a and b,
carotenes and
xanthophyll.
True
starch
and
sugar.
Fragmen-
tation or
fission.
Zoospores. Isoga-
mous to
advanced
oogamous.
Phaeophy-
ceae
(Brown algae)
e.g., Fucus,
Sargassum
Filamentous branched,
usually heterotrichous,
outer layer of cell wall
composed of alginic
and fucinic acids and
inner layer is cellulosic,
motile cells with 2 lateral
flagella, pyrenoid single,
stalked or projected.
Mostly marine. Chl. a and c,
fucoxanthin,
flavoxanthin,
b-carotenes.
Lami-
narin,
mannitol.
Fragmenta-
tion or
adventi-
tious
branching.
Zoospores,
aplano-
spores, etc.
Isogamous
to
oogamous.
Rhodophy-
ceae
(Red
algae) e.g.,
Polysiphonia,
Porphyra
Unicellular,
filamentous or
pseudoparenchymatous,
cell wall cellulosic and
pectic, motile cells not
known, pyrenoids simple
or compound, embedded
sometimes stalked.
Mostly marine. Chl. a and d,
phycoerythrins,
phycocyanin,
allophycocyanin,
carotenoids.
Floridean
starch.
Fragmenta-
tion.
Mono-
spores,
carpo-
spores,
etc.
Advanced
oogamous
type.