Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
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several species with rigid pellicles to the genus Lepocinclis and including several<br />
species without chloroplasts, formerly classified as Astasia and Khawkinea. Size<br />
varieties range from 25 µm to 500 µm in length and cells can be of various body<br />
shapes.<br />
4.2.2 Diagnostic Features<br />
The euglenoid flagellates are a well-defined group of closely related organisms.<br />
Interestingly, hardly any forms are known which appear to be intermediate between<br />
the Euglenophyta (Euglenida) and other algal phyta or protozoan orders 7 .<br />
The main characteristics of this group include:<br />
• Two flagella, one of which emerges from the canal as the locomotory<br />
flagellum, whereas the other is so short as to be non-emergent from the<br />
reservoir.<br />
• Usually colored green (rarely colorless)<br />
• Phototrophic and heterotrophic<br />
• Chloroplasts discoid, shield-shaped or ribbon-shaped, entire or dissected,<br />
with or without pyrenoids, pyrenoids naked, double-sheathed or inner. Each<br />
chloroplast type is characteristic of a species.<br />
• A stigma (eyespot) and a flagellar swelling (with the photoreceptor inside)<br />
are present.<br />
• The cell is non-rigid or semi-rigid, but never completely rigid. The body<br />
of the cell is enclosed by the pellicle, a very tough but flexible structure built<br />
out of ridged, articulating strips. The alga can actively change its shape to<br />
move forward (metaboly or so-called euglenoid movement). ([91])<br />
• Cell flattening apparent in some species<br />
• The cells are free-swimming and solitary but cysts and palmelloid<br />
stages are known (see 4.2.5). A contractile vacuole (see 4.3.6) is present,<br />
even in marine forms 8 .<br />
7 A phylum (pl. phyta), also called division, is a rank in the classification of organisms, below<br />
kingdom and above class. An order is a rank between class and family. ([90])<br />
8 Why is it noteworthy that a contractile vacuole (see 4.3.6) is present in marine forms? Usually<br />
the concentration of solubilized molecules or certain ions within the cell is higher than in the<br />
outer medium (for example sucherose, sodium ions and chloride ions). This corresponds to the<br />
fact, that the cell actively accumulates and stores carbohydrates for later use. And it indicates<br />
that life took its origin in the sea where those concentrations are much higher. The chemism<br />
of the inner cell represents a "memory" of these past habitats from even millions of years ago<br />
41