3. Nostoc
Habitat
Primarily occurs in terrestrial habitat.
Association with fungi in lichens and with some
bryophytes and vascular plants.
Moist rocks and cliffs.
Alkaline soil.
In wet meadows.
At the edges of shallow lakes.
Cellular structure
Bent or naked filaments of round cells are held
in a firm mucilaginous matrix to form colonies.
The sheaths colored by yellow, brown or black.
Transiently motile hermogonia are produced
these typically have heterocytes at the ends.
Characteristics
Nostoc is frequently abundant in flooded rice
paddies where it contributes to the fertilization of
some 2 million hectares.
4. Anabena
Habitat
Primarily planktonic in fresh waters and
marine waters such as the Baltic Sea
some forms can be nuisance bloom formers
and toxin producers.
Cellular structure
Consist of filaments of spherical cells
resembling in a mucilaginous matrix .
Molecular phylogenetic analyses indicate
that Anabaena is not monophyletic group
separated into multiple classes.
5. Aphanizomenon
Habitat
Occurs in the Baltic Sea and in eutrophic inland water.
Cellular structure
Consist of distinctive aggregations of filaments (so
large as to be visible).
Molecular phylogenetic within Anabaena as the
Aphanizomenon.
May not be monophyletic.
Characteristics
Aphanizomenon that which makes itself invisible.
Large blooms may form in the Baltic Sea and in
eutrophic inland waters.
6. Cylindrospermum
Habitat
Occurs in freshwaters including soft, acid
lakes.
Forming dark green patches on submerged
vegetation and on moist soil.
Cellular structure
Filaments of vegetative cells ( square or
rectangular cells).
Heterocyte at one end are enclosed in loose
mucilage.
A large ,highly or nemented akinete may
develop from the lowermost vegetative cell.
7. Cylindrospermopsis
Habitat
Plaktonic bloom-former in eutrophic temperate.
Tropical freshwater around the world.
Cellular structure
Rectangular cells occur in linear or coiled
filments having a basal heterocyte.
Akinetes may form basally.
If akinetes are not present , correct species
identification may be difficult.
Characteristics
Important nitrogen – fixing.
C.Raciborskii this species produces the
hepatotoxin cylindrospermopsin
caused
poisoning.
8. Tolypothrix
Habitat
Plaktonic.
Entangled among submergent vegetation in
freshwater lakes (soft or acidic water ).
Cellular structure
Filaments are enclosed in a sheath of variable
consistency .
Highly false branched usually at a heterocyte (
single false and sometimes double false branches
occur).
Characteristics
The frequency of false branching gives these algae a
woolly appearance.
9. Scytonema
Habitat
Forms dark tufted mats in masses of other algae.
Vegetation in lakes.
On terrestrial surfaces ( stones , wood and soil ).
Cellular structure
Often double false branches occur , this result has
been interrupted by death of a cell .
Less commonly by heterocyte differentiation.
Heterocyte wall may be darkly pigmented.
Sheath is tough and sometimes clearly layered (
colored brown or orange ).
Characteristics
It is a phycobiont in several orders of lichen.
10. Gloeotrichia
Habitat
Occurs in freshwater habitat attached to
submerged substrate.
Cellular structure
Akinetes occur adjacent to basal heterocytes
( sometimes appearing in chains).
Characteristics
Gloeotrichia colonies often detach from
substrate , becoming planktonic.
Growths can reach bloom properations.
12. Stigonema
Habitat
Moist rocks.
Soil.
Some species are aquatic , attached to submerged
wood or other algae.
Form tufted mats or cushions on submerged
portions of lake macrophytes.
Cellular structure
The filaments are more than one cell in width as
(multiseriate or pluriseriate).
Are true-branched.
Characteristics
The primary phycobiont in certain lichens and is
associated with boreal mosses.
Contributes to nitrogen availability.