Page 57 - Algae

40 Algae: Anatomy, Biochemistry, and Biotechnology

FIGURE 2.6 Heterococcolith of Discosphaera tubifera.

of simple crystals around the rim of the precursor base-plate scale. This is followed by growth of
these crystals in various directions to form complex crystal units. After completion of the coccolith,
the vesicle dilates, its membrane fuses with the cell membrane and exocytosis occur. Outside the
cell, the coccolith joins other coccoliths to form the coccosphere, that is the layer of coccoliths
surrounding the cell (cf. Chapter 1, Figure 1.35).
Holococcoliths consist of large numbers of minute morphologically simple crystals. Studies have
been performed on two holococcolith-forming species, the motile holococcolith phase of Coccolithus
pelagicus and Calyptrosphaera sphaeroidea. Similar to the heteroccoliths, the holococcoliths are

FIGURE 2.7 Holococcolith of Syracosphaera oblonga.