Page 56 - Algae Anatomy, Biochemistry, and Biotechnology

Anatomy 39

FIGURE 2.4 Box shaped scales of the intermediate layer of Pyramimonas sp. cell body covering.

very different types of coccoliths are formed by these algae: heterococcoliths, (Figure 2.6) and
holococcoliths (Figure 2.7). Some life cycles include both heterococcolith and holococcolith-
producing forms. In addition, there are a few haptophytes that produce calcareous structures that
do not appear to have either heterococcolith or holococcolith ultrastructure. These may be products
of further biomineralization processes, and the general term nannolith is applied to them.
Heterococcoliths are the most common coccolith type, which mainly consist of radial arrays of
complex crystal units. The sequence of heterococcolith development has been described in detail in
Pleurochrysis carterae, Emiliana huxleyi, and the non-motile heterococcolith phase of Coccolithus
pelagicus. Despite the significant diversity in these observations, a clear overall pattern is discern-
ible in all cases. The process commences with formation of a precursor organic scale inside Golgi-
derived vesicles; calcification occurs within these vesicles with nucleation of a protococcolith ring

FIGURE 2.5 Elaborate body scale of Chrysochromulina sp.