Download Unsegmented Worms

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
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• 
• 
• 
• 
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?