Thesis-PDF - IAP/TU Wien

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