Thesis-PDF - IAP/TU Wien

• Many species are known, mostly fresh-water. A few marine species have also
been recorded.
A good characteristic for differentiation between Euglena genera is the shape
of their chloroplasts. For example E. pisciformis possesses sideways bands of
chloroplasts, E. terricola has a scattered distribution of band chloroplasts and E.
viridis exhibits center orientated band chloroplasts. There are also disc-shaped
chloroplasts like these of E. variabilis, E. intermedia, E. ehrenbergi, E. acus, E.
acutissima, E. oxyuris, E. tripteris, E. deses, E. sanguinea, last of which has red
colored ones. And then Euglena gracilis has cornered chloroplasts. ([92], [93])
4.2.3 Characteristics of Euglena gracilis
4.2.4 Natural Habitat
Euglena gracilis is a relatively rare species amongst other Euglena types found
in nature, characteristically encountered in ponds and ditches containing rotting
leaves or in other nutrient-rich waters.
4.2.5 Lifecycle
A Euglena cell is not born, nor does it hatch. A parent cell divides into two
daughter cells, not to be told apart, which then again enter a new lifecycle. The
cell division primarily takes place in darkness, and thus mostly during nighttime
and along the cells’ long axis. This can happen either in the normal state or in
the palmella state (see below). A division takes usually between two and four
hours. One could argue, (astonishingly enough!) that Euglena cells do not die but
literally live on in their offspring. For cultured cells on the contrary, it has been
observed that, if they live in old cultures, they become packed with phospholipid
vesicles and the culture starts looking brownish.
When turning into the so-called palmella state, Euglena discards its flagellum,
then forms itself into a spherical shape and excretes a muciferous layer covering
all of the body. The colony then flocks together in a jelly like matrix where they
cannot move. When the habitat living conditions improve Euglena can transform
back again into the motile state.
([93]). That means marine forms of Euglena are put under much less stress to preserve the right
concentrations especially of ions. Liquid leaking into the cell through osmotic pressure is already
close in composition to what the cell needs, so ejecting H 2 O periodically through the contractile
vacuole is much less imperative.
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