Page 76 - Algae Anatomy, Biochemistry, and Biotechnology

Anatomy 59

structure of calcium carbonate and organic matter in the Haptophyta, and a completely organic
nature in the Chlorophyta.
Members of the Chrysophyceae with flagellar scales (Heterokontophyta) fall into two
groups: one possessing exactly the same type of scale on both flagellar and body surface, the
other showing flagellar scale different in structure and arrangement from body scales.
Example of the first group is Sphaleromantis sp., whose flagella and cell body are closely
packed with scales of very peculiar appearance, resembling the branched structure of a tree.
Examples of the second group are Mallomonas sp. and Synura sp.; in both genera, flagellar
scales are not arranged in a regular pattern, are very small (under 300 nm) and possess different
morphological types, the most characteristic being the annular type. As the body scales, flagellar
scales are produced in deposition vesicles, extruded from the cell and brought into correct pos-
ition in relation to the other scales and the cell surface.
As described earlier, flagella of the Haptophyta are usually equal in length and appearance
(isokont), however, members of the genus Pavlova possess two markedly unequal flagella, the
anterior much longer than the posterior, and carrying small, dense scales in the form of spherical
or clavate knobs. These scales are often arranged in regular rows longitudinally, or can be randomly
disposed on the flagellum. Scales are formed inside the Golgi apparatus, and then released to the
cell surface by fusion of the plasmalemma and the cisternal membrane.
Flagellar scales are known from almost all the genera of the class Prasinophyceae (Chloro-
phyta). These algae possess non-mineralized organic scales on their cell body and flagella, the
same type of scale being rarely present on both surfaces. On the flagella, the scales are precisely
arranged in parallel longitudinal rows, sometimes in one layer, two layers, or even three layers
on top of each other. Each layer usually contains only one type of scales. The four flagella of
Tetraselmis sp. are covered by different types of scales: pentagonal scales attached to the flagellar
membrane (Figure 2.30), rod-shaped scales covering the pentagonal scales, and hair scales orga-
nized in two rows on opposite sides of the flagellum. A fourth type termed “knotted scales” is
present only in some strains, but their precise arrangement is not known. In Nephroselmis
spinosa the flagellar surface is coated by two different types of scales arranged in two distinct
layers. Scales of the inner layer, deposited directly on the membrane, are small and square,
40 nm across (Figure 2.31); scales of the outer layer are rod-shaped, 30–40 nm long, and are depos-
ited atop the inner scales. As in Tetraselmis, hair scales of at least two different types are also
present covering the flagella. In Pyramimonas sp., the scales are extremely complex in structure
and ornamentation, and belong to three different types. Minute pentagonal scales, 40 nm wide,
form the layer covering the membrane, which in turn is covered by limuloid scales, 313 nm long
and 190 nm wide, arranged in nine rows (Figure 2.32); each flagellum also bears two rows of
almost opposite tubular hair scales, 1.3 mm long. Spider web scales with an ellipsoid outline are

FIGURE 2.30 Pentagonal scale of the flagellar FIGURE 2.31 Square scale of the flagellar
membrane of Tetraselmis sp. membrane of Nephroselmis spinosa.