Page 89 - Algae Anatomy, Biochemistry, and Biotechnology

72 Algae: Anatomy, Biochemistry, and Biotechnology

FIGURE 2.46 Transmission electron microscopy image of the transition zone of Dunaliella sp. in longitudinal
section showing the “H” structure. (Bar: 0.40 mm.)

Variations in the number of basal bodies mainly reflect variations in the number of flagella. It is
possible to distinguish:

. Cells with only one basal body, carrying one flagellum; this situation is very rare and is
present in the euglenophyte of uncertain affinity, Scytomonas pusilla, and in the gametes
of the diatoms Lithodesmium and Biddulphia
. Cells with two neighboring basal bodies, forming the so-called primordial pair indicated as 2A
. Cells with numerous basal bodies

Inthe case oftwobasalbodies,twopossibilitiesexist:onlyone basalbody,generallysituatedclosetothe
nucleus or linked to it, possesses a flagellum, as in the spores of Hydrurus; or both basal bodies possess a
flagellum. The latter is the most frequently occurring situation in flagellate algae. Most often the basal
bodies are inclined towards each other, sometimes they are perpendicular, or they may also be parallel
facing the same directions or antiparallel facing opposite directions. In the Glaucophyta the two basal
bodies are inclined towards each other; in the Heterokontophyta they are parallel in the Chrysophyceae
MallomonasorSynuraoralmostperpendicularinOchromonas,lieatanobtuse angletoeachotherinthe
Xanthophyceae and Phaeophyceae, and are inclined to each other at an angle of about 908 in the Eustig-
matophyceae and Raphidophyceae; in the Haptophyta the angle between the two basal bodies can be
acute or obtuse; in both Cryptophyta and Euglenophyta the basal bodies are almost parallel, while in
the Dinophyta they lie at almost 1808 to each other and slightly overlap. In the Chlorophyta the
angle between the two basal bodies can vary (about 908 in Chlamydomonas, 1808 in Acrosiphonia
zoid) and the couple can assume three different configurations (Figure 2.47):

. 12 o’clock–6 o’clock configuration, in which the basal bodies are in line with each other
. 11 o’clock–5 o’clock configuration, in which the basal bodies are anticlockwise rotated
relative to the first configuration
. 1 o’clock–7 o’clock, in which the basal bodies are clockwise rotated relative to the first
configuration