Environmental Engineering Reference
In-Depth Information
116
(115) (a) Cell strawberry-shaped, four lobes
forming an indentation at the ante-
rior end from which the flagella arise
........................
Pyramimonas
118
(117) (a) Cells with anterior end flattened
obliquely (cut off at an angle in lateral
view, as in Plate XVI). Flagella, of slightly
unequal length, arise from the oblique face
near to the front end. . ..............
119
Cell shape is characteristically strawberry
or sub-pyramidal. Cells (12-16 μm wide,
20-30 μm long) are naked (no wall) and
have a cup-shaped chloroplast which is
often four lobed towards the anterior end.
A pyrenoid is present towards the base
of the cell. Widespread in ponds and still
waters, frequently at colder times of the
year although it can occur all the year
round. Prasinophyta. Plate XV.
(b) Cellswithanteriorendroundedorlat-
tened transversely. Flagella inserted at the
end (apex) of the cell and of equal length
..................................
121
119
(118) (a) Cells obovoid but strongly curved
towards the narrowed rear end to form a
hyalinetail...............
Rhodomonas
Rhodomonas
cells are small (8-13 μm
long, 3-8 μm wide) and fairly delicate so
are often overlooked even though the alga
is widespread. The single reddish-golden
chloroplast (contains phycoerythrin) has
a large pyrenoid to one side with a def-
inite starch sheath. A hyaline tail with a
basal granule is present in
R. lacustris
var.
nannoplanctica
, otherwise the end
just tapers. Two slightly unequal flagella
arepresent.Widespreadinplankton.Some
reports suggest that it is able to survive
under low-light conditions but this is not
a prerequisite in its ecology (Wehr and
Sheath, 2003). Cryptophyta. Plate XVI.
Fig. 4.52b
(b) Cells oval or occasionally heart-
shaped but not lobed. ..........
Carteria
Carteria
cells (9-20 μm diameter) are
virtually identical to those of
Chlamy-
domonas
except that they may be pear-
shaped or ellipsoidal and have four, not
two, flagella. The cup-shaped chloro-
plast usually lacks pyrenoids but occa-
sionally one may be present. Frequent
and occasionally abundant in still waters
and habitats similar to
Chlamydomonas
.
Less widespread than
Chlamydomonas
.
Chlorophyta. Plate XVI.
117
(114) (a) Cells fusiform in shape
........................
Chlorogonium
(b) Cells not strongly curved. Tail, if
present,nothyaline................
120
Cells of
Chlorogonium
are elongate
(fusiform or spindle-shaped) tapering at
both ends, with two flagella arising from
the narrow apical end. Cells (2-15 μm
wide, up to 80 μm long) have a rigid cell
wall, a chloroplast which fills most of the
cell and an anterior eyespot. Pyrenoids
are usually present. Can occur in large
numbers in small water bodies, especially
those rich in humic materials. Chloro-
phyta. Plate XVI.
120
(119) (a) Gulletabsent,chloroplastbluetoblue-
green or reddish. . . . . ......
Chroomonas
Chroomonas
and
Cryptomonas
are very
similar except that the colour of the
chloroplast is markedly different in
Chroomonas.
There are two unequal flag-
ella. One chloroplast (rarely two) which is
blue-green in colour as it contains phyco-
cyanin. A single pyrenoid is present. Cells
(7-18 μm long, 4-8 μm wide) are also usu-
ally somewhat smaller than
Cryptomonas
.
(b) Cells not fusiform in shape. . . . . .
118
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