Unsegmented Worms
3 Types:
I. Phylum Platyhelminthes
• Flatworms
II. Phylum Nematoda
• Roundworms
Flatworms
Flatworms
• Belong to Phylum Platyhelminthes.
(Plat = flat)
• There are three classes:
– Turbellaria
– Trematoda
– Cestoda
Characteristics of Flatworms
• They are acoelomates – solid bodies without
a lined body cavity
• Have 3 body layers: ectoderm, mesoderm,
endoderm
• They have bilateral symmetry
Characteristics of Flatworms
• Show cephalization
• Body cells exchange oxygen & carbon
dioxide directly with environment by
diffusion– BREATHE THROUGH SKIN
• Single opening to digestive tract (pharynx);
two-way digestive tract (bidirectional)
Characteristics of Flatworms
• Some are parasites and some are free living
• Parasitic worms have thick cell layer called
tegument covered with a nonliving cuticle
covering their bodies as protection inside
hosts
Phylum Platyhelminthes
• Includes 3 classes
1. Class Turbellaria (planarians)
2. Class Trematoda (parasitic flukes)
3. Class Cestoda (parasitic tapeworms)
Class Turbellaria
• Spade-shaped head and two eyespots
called ocelli
• Can sense light, touch, taste, and smell
• Have 2 clusters of nerve cells or
ganglia to form a simple brain
• Nervous system composed of a nerve
net
• Capable of simple learning
• Move by tiny hairs or cilia over a mucus
layer that they secrete
Class Turbellaria
• Feed by scavenging for protozoans
(microscopic, unicellular organisms)
• Have a simple opening or mouth-pharynx
• Flame cells remove waste
Class Turbellaria
• Are hermaphrodites (have male and
female reproductive parts)
• Can reproduce asexually by
fragmentation
• Are free-living
Class Trematoda
• Includes parasitic flukes
• Require a host to live
• Have suckers on both
ends of the body
• Can be endoparasites
(live inside a host) or
ectoparasites (live
outside of a host)
Class Trematoda
• Nervous and excretory
systems like
turbellarians
• Hermaphrodites
• Schistosomiasis
(disease caused by
parasitic blood flukes)
Schistosomiasis
• Contracted by coming
into contact with water
contaminated with
human urine or feces or
touching certain snails
that carry the blood
fluke.
• Worms can penetrate
the skin.
Blood Fluke Life Cycle
Fluke Life-Cycles
The long and complex life-cycle of the fluke can
be made easier to
understand through the use of a nonsense
mnemonic :
Every - Egg
Mirror - Miracidium (free-living in water)
Spotted - Sporocyst (in snail)
Red - Redia (in snail)
Certainly - Cercaria (free-living in water/snail)
Met - Metacercaria (in 2nd intermediate host)
Approval - Adult
Class Cestoda
• Includes tapeworms
(parasite)
• Tough outer tegument
prevents being digested
by host
• Anterior end called
scolex contains hooks
and suckers for
attachment to intestine
of host
Class Cestoda
• Long, ribbon-like bodies
• Nervous system extends
length of body but lacks
sense organs
• Lacks mouth and
digestive tract but
absorbs digested
nutrients from host
• Grows by making body
segments called
proglottids
Class Cestoda
• Each proglottid
produces egg and sperm
that cross-fertilize with
other segments and also
self-fertilize
(hermaphrodites)
• Oldest, mature
proglottids containing
eggs at posterior end
break off and pass out
with feces
Tapeworm
Anatomy
Roundworms
Roundworms
Roundworms
•
•
•
•
•
Belong to phylum Nematoda
Pseudocoelomates (fluid filled body cavity)
Slender bodies that taper on both ends
Have mouth and anus
Can be free-living or parasitic
• Pinworms live in the
human intestine.
• Often get passed
from child to child.
• Only live in humans—
cannot get pinworms
from pets.
Trichinosis—a
disease from
eating infected
pork (cysts in
pork
contaminated
with Trichinella
species of
worm)
Cysts in Contaminated Pork
Hookworms
• Live in small intestine of mammal host
(such as human, dog, cat, etc)
• Suck blood and can cause anemia
Heart worms
• Parasitic roundworm that is spread from host to
host through mosquito bites
• Mosquitos spread the
larva to the host, then
the larva grow into adults
in the heart and/or lungs
of the host.
• Only spread through infected mosquitos.
There must be an incubation period in the
mosquito before another animal can be infected
by it.
• Usually affects dogs, cats, wolves, coyotes, etc.
Rarely affects humans.
Parasitic Worms Poster
• EVERYONE MUST PARTICIPATE!
• Get creative and make it colorful!
• NEATNESS COUNTS!
• You will present your information next
class period.
Bellringer
Write the questions and the answers.
1. What are the 3 classes of flatworms?
2. What does cephalization mean?
3. What type of body cavity do flatworms
have?
4. What is the mouth/anus of flatworms
called?
5. How does Class Turbellaria reproduce?
6. What is the head end of the tapeworm
with hooks and suckers called?
Bellringer
Write the questions and the answers.
1. What phylum are roundworms in?
2. What type of body cavity do roundworms
have?
3. List 3 types of parasitic roundworms.
4. How do heart worms spread?
5. What is the most common host for the
Trichinella worm (the host that humans
can get the worm from)?
Bellringer
Write the sentence and fill in the blank with the
proper vocabulary word.
1.
2.
3.
4.
5.
An ________ is a parasite that lives inside a host, while an ______
lives on the outside of the host.
_________ are segments that can ________ because the sperm
from one can fertilize the eggs of another.
The _______ of a parasitic worm is a living protective layer, while
the _____ is a nonliving protective layer.
The _____ serves as the mouth and anus of flatworms and is part
of a bidirectional digestive system because food enters and exits
the same opening.
The two _______ form a simple brain in flatworms, and the
________ can sense light and shadows but not detailed images.