Introduction to some aquatic protozoa in Essex
Campanella
Campanella is a sessile peritrich with an average size of between 130 -250mm. It is attached to the
substratum by a non-contractile stalk at one end, while at the anterior the cilia are used to set up a
flow of water that directs particles of food, consisting mainly of bacteria and algae and smaller
protozoa, into a food vacuole. A more common member of this class of peritrichs is Vorticella,
which is attached to the substrate with a contractile stalk. The image in Figure 4 (below) was obtained
using an x40 Nomarski objective.
Figure 4. Campanella under x4() objective showing its stalk © Steve Durr
Euglena acus and phase contrast microscopy
Another fascinating organism is Euglena acus, which never seems to move when I have observed it
in the past. The Euglenophytes are a small but remarkable group of flagellates; they are always
solitary and never form colonies. A good source of Euglenophytes is a pool frequented by cattle and
rich in organic substances. When the water is particularly rich in organic matter then the surface of
the pond can be covered with Euglena. It is interesting to note that some species of Euglena can lose
their chloroplasts and find an alternate means of finding nourishment.
Some species of Euglena can also have a very flexible pellicle, which can twist and bend in order to
allow the microbe to wander in and out of the detritus. They have two flagellae; one, which is used
Essex Naturalist (New Series) 18 (2001)
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