19
General Overview
present in Spyrogyra spp. (Chlorophyta) and Dinophyceae (Myzozoa) (Figure 1.26). Hypnospores
and hypnozygotes enable these green algae to survive temporary drying out of small water bodies
and also allow aerial transport from one water body to another, for instance, via birds. It is likely
that dinoflagellate cysts have a similar function.
Statospores are endogenous cysts formed within the vegetative cell by member of Chrysophyceae
such as Ochromonas spp. The cyst walls consist predominantly of silica and so are often preserved
as fossils. These statospores are spherical or ellipsoidal, often ornamented with spines or other projections. The wall is pierced by a pore, sealed by an unsilicified bung, and a nucleus, chloroplasts
and abundant reserve material lie within the cyst. After a period of dormancy, the cyst germinates
and liberates its content in the form of one to several flagellated cells.
Akinetes is of widespread occurrence in the blue-green and green algae. They are essentially
enlarged vegetative cells that develop a thickened wall in response to limiting environmental
nutrients or limiting light. Figure 1.27 shows the akinetes of Anabaena cylindrica (Cyanophyta).
They are extremely resistant to drying and freezing, as well as function as a long-term anaerobic
FIGURE 1.25 Nonmotile coenobium of Pediastrum sp. Scale bar: 100 μm.
FIGURE 1.26 Dinoflagellate hypnozygote. Scale bar: 10 μm.
General Overview
present in Spyrogyra spp. (Chlorophyta) and Dinophyceae (Myzozoa) (Figure 1.26). Hypnospores
and hypnozygotes enable these green algae to survive temporary drying out of small water bodies
and also allow aerial transport from one water body to another, for instance, via birds. It is likely
that dinoflagellate cysts have a similar function.
Statospores are endogenous cysts formed within the vegetative cell by member of Chrysophyceae
such as Ochromonas spp. The cyst walls consist predominantly of silica and so are often preserved
as fossils. These statospores are spherical or ellipsoidal, often ornamented with spines or other projections. The wall is pierced by a pore, sealed by an unsilicified bung, and a nucleus, chloroplasts
and abundant reserve material lie within the cyst. After a period of dormancy, the cyst germinates
and liberates its content in the form of one to several flagellated cells.
Akinetes is of widespread occurrence in the blue-green and green algae. They are essentially
enlarged vegetative cells that develop a thickened wall in response to limiting environmental
nutrients or limiting light. Figure 1.27 shows the akinetes of Anabaena cylindrica (Cyanophyta).
They are extremely resistant to drying and freezing, as well as function as a long-term anaerobic
FIGURE 1.25 Nonmotile coenobium of Pediastrum sp. Scale bar: 100 μm.
FIGURE 1.26 Dinoflagellate hypnozygote. Scale bar: 10 μm.