Freshwater Microorganisms

Freshwater Microorganisms
•  Amoebas are composed of just one cell. They are protozoans with no fixed
shape.
•  Amoebas move by making part of its body move in the direction it wants to
travel (a pseudopod). Then slowly the rest of the cell follows. In order to
eat, an Amoeba flows around other microorganisms and then engulfs them.
To reproduce the Amoeba splits itself into two cells.
•  Certain kinds of Amoeba can cause Amoebic Dysentery.
Paramecium
•  This slipper-shaped protozoan is
found in lakes, ponds, and
puddles. Its constantly moving by
beating rows of microscopic hairs,
called cilia, that work like miniture
oars. Paramecium feeds on
bacteria and other
microoriganisms by sweeping
them into its groove shaped
mouth.
•  It has contractile vacuoles to
pump water out to maintain
homeostasis.
Blepharisma
•  The Blepharisma is a common ciliate found in most any pond. If it lives in
bright sunlit ponds it is usually colorless. When exposed to an intense
artificial light, the pink pigment emits a poisonous toxin that
completely disintegrates the creature.
Euglena
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Euglena A genus of unicellular,
green, photosynthetic protists,
sometimes regarded as algae
(division Euglenophyta),
sometimes as protozoa (class
Phytomastigophora). The cell
body is typically spindleshaped but is capable of
broadening and narrowing to
some extent; it is motile with a
single flagellum. Euglena is
common in all fresh-water
habitats, especially when these
are slightly polluted with
organic matter.
Euglena has chloroplasts, so
it gets its energy by eating
and photosynthesizing.
Stentor
•  Stentor, sometimes called
trumpet animalcules are a genus
of filter-feeding, heterotrophic
ciliate protists, representative of
the heterotrichs. They are
usually horn-shaped, and
reaching lengths of 2
millimeters, they are among the
biggest known unicellular
organisms.
•  They are named after Stentor,
the Greek announcer.
Vorticella
•  The Vorticella is a protist (protozoan)
and belongs to the Phyllum Ciliophora.
It is a very interesting, stalked ciliate
with an inverted bell shape. The stalk
contains a contractile fibril called a
myoneme. When stimulated, it
shortens, causing the stalk to coil
like a spring.
•  Vorticella usually anchor themselves to
small particles of material however, it is
not uncommon to see them free
swimming. When they undergo fission,
they split along the longitudinal axis in a
process called budding. When they
finally split apart, one keeps the
myoneme and the other free swims
away and grows its own. The main
purpose for the cilia at the top is to
sweep food down into the gullet.
Didinium
Didinium’s main
prey,
Paramecium
Didinium
•  The Didinium belongs to the Phyllum
Ciliophora. They are from 80-200 um
long.
•  Didinium are fast moving carnivorous
protozoans that feed almost
exclusively on live Paramecium.
•  When its "nose" (shown at top) strikes a
Paramecium it latches on with a
threadlike trichocyst. Once captured and
paralyzed, the didinium devours the
Paramecium whole.
•  The "C"-shaped structure inside the body
is a band shaped nucleus and can
sometimes be seen with a regular light
microscope.
•  Didinium will encyst when the food source
is depleted and excyst when the food
returns.
Volvox
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Volvox is a Chlorophyte, or green
alga. It exists as a grand
spherical colony. Each little alga
within the colony bears two flagella,
whip-like hairs. The individual alga
are connected to each other by thin
strands of cytoplasm that enable
the whole colony to swim in a
coordinated fashion. The individual
alga also have small red eye spots.
The colonies even have what we
could call a front and rear end. Or,
since Volvox resembles a little
planet, a 'north and south pole'. In
the northern region the eyespots
are more developed. This helps the
colony to swim towards the light.
This differentiation of cells make
Volvox quite unique. It is a colony
that comes really close to being a
multi-celled organism.
At the end of its life, Volvox
bursts open and the small
spheres inside it develop into
new Volvox.
Trypanosoma brucei
•  Trypanosoma brucei is a parasitic
protist species that causes African
trypanosomiasis (or sleeping
sickness) in humans and nagana
in animals in Africa. There are 3
sub-species of T. brucei: T. b.
brucei, T. b. gambiense and T. b.
rhodesiense.
•  These obligate parasites have
two hosts – the tsetse fly and
mammalian host (possibly
human). Because of the large
difference between these hosts, the
trypanosome undergoes complex
changes during its life cycle to
facilitate its survival in the insect
gut and the mammalian
bloodstream.
Toxoplasma gondii
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Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive
host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals
(birds or mammals). Toxoplasmosis, the disease caused by T. gondii, is usually minor.
However, it can have serious or even fatal effects on a fetus whose mother first contracts
the disease during pregnancy or on an immunocompromised human or cat.
Plasmodium
• Plasmodium is a genus of parasitic
protists. Infection by these
organisms causes malaria.
• Of the over 200 known species of
Plasmodium, at least 10 species
infect humans. Other species infect
animals, including monkeys,
rodents, birds, and reptiles. The
parasite always has two hosts in
its life cycle: a mosquito vector
and a vertebrate host.
Daphnia
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Daphnia are tiny
crustaceans, never
growing larger than a
couple of millimeters
no matter how well
they eat. They are
sometimes called
water fleas because
they are about that
size and superficially
look like fleas.
• But unlike fleas they are nearly transparent, live in water, have a shell, and are graced
with an interesting array of modified appendages for sensing, feeding, and swimming.
Daphnia are free swimmers, propelling themselves with surprising speed, considering
they use a pair of modified antennae to swim. As they travel they filter even tinier
organisms from the water. They feed on single-celled algae, yeast, and bacteria. Daphnia
in turn are eaten by fish and aquatic insects. It seems that their role in life is to provide a
snack for a larger organism.
• Eggs are carried in the brood pouch on the back. The heart, found just above the
brood patch, can be seen beating in live specimens.