Ciliates - protozoans that move with cilia
These protozoans are called Ciliates and have hundreds of tiny cilia which beat in unison to propel
them through the water. Often cilia are fused together in rows or tufts (called cirri) and are used for
special functions such as food gathering. In addition to movement, the Paramecium and other ciliates
like the Stentor use cilia to sweep food down into their central channel or gullet.
Spirostomum
Spirostomum is a one-celled protozoan with a central
digestive tube. Look for a long cylinder-shaped cell. When
you see a spirostomum, look for the structures shown in the
diagram.
Movement A spirostomum’s body has spiral rows of cilia.
The cilia beat back and forth to move the organism with a
snake-like wiggling motion.
Feeding Beating cilia sweep small organisms into the
spirostomum’s mouth.
Reproduction The organism divides in half. The nucleus
splits, too.
Size 1 to 3 mm (the largest and most complex one-celled
protist)
Stentor
Stentor is a very large ciliate measuring from 500-2000 microns long
when extended. There are a variety of species of Stentor.
Stentor coeruleus is a very large trumpet shaped, blue to blue-green
ciliate with a macronucleus that looks like a string of beads (dark
connected dots on the left). With many myonemes, it can contract into
a ball. It may also swim freely both extended or contracted.
The stentor uses the cilia to sweep food down into its gullet.
Stentor polymorphus is 500-1500um long and hosts many
Zoochlorellae which makes this species green. The Zoochlorella live in
symbiosis with the stentor.
Paramecium
Paramecium are the most
commonly observed protozoans and, depending on the
species, they are from 100-350 um long.
Paramecium caudatum (shown at the left) are
characterized by a large macronucleus and a single
compact micronucleus.
The amoebas. They are a blob of protoplasm formed in a single cell. By flowing their protoplasm
forward into a "foot" then bringing the rest of their body into the foot, they can slither along.
The Amoeba proteus is a large protozoan and belongs to the Phyllum Sarcodina.
It has an ever changing shape and is approximately 500-1000 um long. It can almost be seen with
the naked eye.
The Amoeba proteus is the classic specimen used in the classroom to demonstrate the pseudopods
in action. Other species of amoebas are either too small, too fragile or atypical in structure.
Amoeba proteus can sense light and tends to move away from it. Just before it reproduces, it rounds
up into a ball with tiny pseudopodia extensions. Over the next 15 minutes or so, it splits and
becomes two. The image to the left shows one amoeba in the final stages of splitting. Look carefully
and you can see the clear channel between the two new amoebas.
Flagellates
These protists move with a whip like extension.called a flagella. The flagella is
a long fibril that is spirally wound and beats or rotates in the water to move the
protozoan about. Included in this group is the Euglena and the Volvox.
Euglena are 35-55 um long and are a very popular flagellate used in the
classroom. They have one active flagellum, a reddish eye spot and
numerous chloroplasts for photosynthesis. They exhibit both plant and animal
characteristics. Euglena thrive best where there is an abundance of rich
organic waste. There are over 100 different species of Euglena. Euglena are
also able to greatly distort their body to change direction. This
distortion is called Euglenoid motion.
Volvox are colonial flagellates. The colony is large, measuring from
100-6000 microns across.
The colony is comprised of many single, cells with flagella
connected together by strands. It forms a hollow, green sphere.
Individual cells have a red eyespot and, with chloroplasts, can make
food from sunlight. Daughter colonies grow within this main colony
and eventually break free and develop as a parent colony.