FLATWORMS
Belong to the KINDGOM ANIMALIA
PHYLUM PLATYHELMINTHES
“Platyhelminthes”
comes from the
Greek meaning
“flat worm”
Examples: blood
flukes, tapeworms,
planarians
http://shapeoflife.org/video/animation/flatworm-animation-body-plan
http://shapeoflife.org/video/behavior/flatworms-invasive-flatworm-hunts-earthworms
VOCABULARY
Brain (ganglia) - planarian can process
information about their environment
Pharynx - a tube that the flatworm pushes out of
its body in order to feed. Used for suckling food in
(the mouth is at the end of the pharynx)
Eyespot - simple eye, can detect light
Flame cells - located along the lateral edges,
used for excretion
Intestine - digestion (does not have an anus)
Parasite: organism living in or on another species getting its food
from the tissues or fluids of its host.
Cilia: a hair-like growth from a cell that, when present in large
numbers, can produce currents to move water.
Stereo senses: paired senses (like ears and eyes) that are on
both sides of the head allowing an object to be accurately located
in space.
Hermaphrodite: an organism that produces both female and male
sex cells.
Bilateral symmetry: a body form with a central longitudinal plane
that divides the body into two halves that mirror each other.
Fission: asexual reproduction in flatworms.
Characteristics
1.Three germ layers (endoderm,
ectoderm, mesoderm)
2.Bilateral symmetry
3.Cephalization (has a head)
COELOM = fluid filled body cavity
Acoelomates = without coelom
FORM AND FUNCTION
FEEDING
Free-living - carnivores
or scavengers; they
have a digestive
cavity, mouth and
pharynx
Parasites – feed on
blood, tissues or
pieces of cells from
within a HOST Most do not have a complete digestive system
because they absorb material directly from host
Question Time!
•Flatworms are
a. Acoelomates
b. Pseudocoelomates
c. Coelomates
Question Time!
•Flatworms have
•A. Radial Symmetry
•B. Bilateral Symmetry
•C. No Symmetry
Question Time!
•True or False
Flatworms can be parasites,
carnivores, and/or herbivores.
Respiration, Circulation, and
Excretion
1.Thin bodies allow for materials to diffuse
(respiration, excretion, etc)
2.Flame Cell – specialized cells that remove
excess water
Response
Ganglia – group of nerve cells that
control the body (like a brain)
Eyespot – group
of cells that can
detect light (like
an eye)
Movement
Flatworms move in 2 ways
1.Cilia helps them glide through the
water
2.Muscle cells help them twist and turn
Question Time!
•What is the name of the
specialized cells that function in
excretion to remove excess
water?
Question Time!
•What is the name of the
specialized nerve cells that
control the body, like the brain?
Question Time!
•What are the 2 ways by which
flatworms move?
ANATOMY OF A PLANARIAN
Reproduction
Sexual Reproduction – most flatworms are
hermaphrodites (have both male and female sex
organs)
Asexual Reproduction by fission – flatworms can
split in two and regenerate
Planarians are hermaphrodites
They can also regenerate body parts and
will sometimes split in half to reproduce
(FISSION)
Question Time!
•How do flatworms reproduce
asexually? (What is the
vocabulary word?)
Question Time!
•How do flatworms reproduce
sexually? (What is the vocabulary
word?)
Groups of Flatworms
CLASS TURBELLARIA
- free living flatworms
- live in fresh or marine
water
- ex. Planarian
Dugesia lives in
freshwater, mostly a
scavenger but can also
feed on protists
●Class Trematoda = parasitic
flatworms
●a.k.a “flukes” live in mouth, skin, or
gills of host
Primary host = the host in
which a parasite
reproduces sexually
Intermediate host = the
host in which asexual
reproduction occurs
Larvae use intermediate host to develop, then enter final
host mature and are released again.
Schistosoma mansoni - multiple host:
Primary host = human
Intermediate host = snail
Causes Schistosomiasis -in humans; decays
lungs liver, spleen, or intestines, occurs in tropical
areas with poor sanitation/sewage.
Class Cestoda =tapeworms
Long, flat, parasitic
Live in intestines
Scolex = a structure that contains suckers
and/or hooks
Proglottids = body segments of the
tapeworm
Each mature proglottid is a
hermaphrodite
Testes produce sperm, fertilize the
eggs to produce a zygote
Zygotes are
passed out
through the
feces.
Sometimes, a dormant, protective cyst is
formed in the intermediate host muscles
****This is why you should never eat
incompletely cooked meat.