A Key to the More Frequently Occurring Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 161

50 μm

20 μm

Figure 4.15 Zygnema . End of filament showing cells
with two typical stellate chloroplasts.

attached to a substrate by means of rhizoidal
branches and an attachment disc. Entero-
morpha hasaworldwidedistribution,mainly
in marine and brackish water habitats - but
can stray into freshwater sites. The two most
common species are E. intestinalis and E.
compressa. Chlorophyta. (Not illustrated.)

50 μm

Figure 4.16 Mougeotia. Detail of separate cells show-
ing plate-like chloroplast in edge (top) and face (bot-
tom) view. Small refractive pyrenoids can be seen in the
chloroplast (arrows).

(b) Alga not a large tubular thallus, micro-
scopic. ............................... 36

36 (35) (a) Two star-shaped chloroplasts per cell
............................... Zygnema

the cell. When viewed from one direction
the chloroplast fills most of the cell but when
viewed from the other it is a thin line down
themiddle.................... Mougeotia

Cells of Zygnema are cylindrical with the
two star-shaped chloroplasts separated by a
clear area. Each chloroplast has a pyrenoid.
The filaments usually have a soft mucilage
sheath, are unbranched and not very long.
Theymaybeattachedtoasubstratebymeans
of rhizoids. Cells 16-50 μm in diameter and
2 to 3 times long as wide. As members of
the Chlorophyta they store starch. Common
in shallow, acidic to alkaline, waters where it
can form luxuriant growths - often occurring
in a mixed population with other filamentous
chlorophytes. Chlorophyta. Fig. 4.15.

The chloroplast of Mougeotia is suspended
on cytoplasmic strands and can move within
the cell depending upon the light. At differ-
ent times it may be seen face-on, edge-on
or twisted. The cells form long unbranched
free-floating filaments. Cells 3.5-35 μmin
diameter, 5-12 times as long as wide. There
are several pyrenoids per cell and when the
chloroplast is viewed edge-on the pyrenoids
give it a lumpy appearance. Storage product
starch. Common in many habitats including
lakes, ponds, ditches and streams especially
in upland areas. Chlorophyta. Fig. 4.16.

(b) Chloroplast either single or more than
twopercell........................... 37

37 (36) (a) One chloroplast per cell in the form of
a flat plate arranged along the long axis of (b) Chloroplastnotasabove........... 38