LABORATORIO: Parte 1
Filo Platyhelminthes
EJERCICIO 9
Goals for today
• Learn to recognized the Phylum
Platyhelminthes from other animals
• Learn the main ‘diagnostic’ characteristics
• Learn about some free-living and parasitic
species biology
Platyhelminthes: flatworms
These are acoelomate
metazoans
Lophotrochozoa
Protostomia
Radiata
Parazoa
Bilateria
Eumetazoa
Deuterostomia
Ecdysozoa
Annelida
Mollusca
Lophophorata
Rotifera
Platyhelminthes
Cnidaria and Ctenophora
– Bilateral symmetry (distinct head and
sense organs, which allows direct
movement).
– Third germ layer-mesoderm
(triploblastic animals)
– Excretory system made up of
specialized flame cells and tubules for
removal of nitrogenous waste
– Highly organized nervous and sense
organs in the anterior part of the body
(cephalization)
Porifera
More organized than radiate animals in
that:
Lophotrochozoa
Platyhelminthes: Classification
Classes:
Turbellaria:
• Ciliated epidermis
• Paraphyletic group
• Mostly free-living
Trematoda:
• Digenetic flukes
• Syncytial tegument without cilia
• Leaflike to cylindrical shape.
• Organs to attach host in the oral and
ventral part of the body: suckers, NO
hooks
• Parasitic in all classes of vertebrates
Monogenea: don’t have material
Cestoda:
• Syncytial tegument without cilia
• Long ribbon like body shape
• Body divided in proglotids
• Organs to attach host in the oral part of
the body: suckers, hooks
• No digestive system
• Parasitic in digestive tract of all classes
of vertebrates
Platyhelminthes: Your Tasks
Exercise 9A:
– Phylum: Platyhelminthes
– Class Turbellaria
• Genus: Dugesia
Planarias are freshwater usually
under stones or submerged leaves
or sticks. But other members of the
class are marine
Platyhelminthes: Dugesia
1. Take a slide from your box with a planaria: identify
the eyespot, aurículas, intestino, faringe, y boca.
intestino
boca
What is the function of the eyespot and the auricles?
____________
Check your book for answers!
Platyhelminthes: Dugesia
As in cnidarians the digestive tract of turbellarians is
a gastrovascular cavity, the branches of which fill
most of the body.
They don’t have an anus
so undigested food is
ejected through the
mouth! Yikes 
Platyhelminthes: Dugesia
Reproduction: these animals are monoecious
(hermaphrodites) they can reproduce sexually and
asexually by transverse fission
In asexual reproduction, the planarian
detaches its tail end and each half regrows
the lost parts by regeneration, allowing
neoblasts (adult stem cells) to divide and
differentiate. However, several problems
can occur with this, so this does not happen
often.
wikipedia
In sexual reproduction, each planarian
transports its excretion to the other planarian,
giving and receiving sperm. Eggs develop
inside the body and are shed in capsules.
Weeks later, the eggs hatch and grow into
adults. Sexual reproduction is desirable
because it enhances the survival of the species
by increasing the level of genetic diversity.
http://www.youtube.com/watch?NR=1&v=8mXkSdIpFQ8
Platyhelminthes: Dugesia
Excretion and osmorregulation: the excretory system
consist of canals and protonephridia called flamed
cells.
See these cells in action!
http://www.youtube.com/watch?v=Rb_3KIB4CmE
Platyhelminthes: Dugesia
2. Take a slide from your box with a planaria cross
section cuts: identify intestino, diverticulos intestinal,
lumen de la faringe, musculos dorsoventrales.
Planaria – cross section
circular muscle
rhabdites
longitudinal muscle
epidermis
intestine
mesenchyme
pharyngeal pouch
lumen of pharynx
pharynx
Platyhelminthes: Dugesia
3. Observe live planarias. Take a look to their
locomotion. How does it use the head and auricles?
Does it ever move backwards?
http://www.youtube.com/watch?v=VplYBD
SbRmA
Platyhelminthes: Dugesia
4. Observe live planarias. Perform with your instructor
the stimuli experiments described in page 136.
• Response to touch
• Response to food
• Response to directional illumination
Write your answers this is part of the Planaria report
Platyhelminthes: Dugesia
5. Regeneration Experiment: Some planarians exhibit an extraordinary
ability to regenerate lost body parts. For example, a planarian split
lengthwise or crosswise will regenerate into two separate individuals
When a planaria’s head is cut off, the remaining tail section will first
regenerate a head. Even if the cut is made very close to the tail, the small tail
section first regenerates the head and then continues to regenerate the rest of
the tissue between the head and the tail. We will use this property and
compare how long it takes for worms cut in different places to regenerate a
head. If different parts of the planaria body have equal ability to regenerate,
they should all regenerate the head in the same amount of time. If not, they
should regenerate the head in different amounts of time. The regenerative
capacity of different body sections may be an indicator of the location of stem
cells called neoblasts. For instance, if one body segment has a low capacity to
regenerate, perhaps only a few neoblasts exist in the area around the cut.
Additional neoblasts may need to migrate to the area or be created by cell
division, slowing down the rate of regeneration.
http://www.youtube.com/watch?NR=1&v=gZmk80fw0nc
Platyhelminthes: Your Tasks
Exercise 9B:
– Phylum: Platyhelminthes
– Class Trematoda
• Genus: Clonorchis sinensis
Clonorchis lives in the human bile duct
(bilis) where it feeds on bile and
lacerated cells from the inflamed bile
duct very common in Asia
Platyhelminthes: Clonorchis
1. Observe slide of Clonorchis sinensis: identificar ventosa oral,
boca, faringe, intestino, ventosa ventral, glandula de yema, poro
genital, vesicula semina, ovario, receptabulo seminal, testículos,
vejiga, poro excretor
Platyhelminthes: Your Tasks
Exercise 9B:
– Phylum: Platyhelminthes
– Class Trematoda
• Genus: Schistosoma mansoni
Schistosoma are blood flukes of humans that
affect ~ 200 million people in Asia, Africa, the
Caribbean (including Puerto Rico!) and South
America.
Schistosomiasis
Platyhelminthes: Schistosoma
1. Ciclo de vida: Observe slides of Schistosoma
mansoni adults, eggs, and cercariae
eggs
adults
miracidum
cercariae
You need to understand the life cycle
Platyhelminthes: Your Tasks
Exercise 9C:
– Phylum: Platyhelminthes
– Class Cestoda
• Genus: Taenia pisiformis- dog tapeworm
They are extreme parasites in that they don’t
have a digestive system. Their tegument is a
specialized epidermis that absorbs nutrients
and rejects toxins and digestive enzymes.
Live is all about maximize reproduction. In
fact tapeworms are egg factories, some
species can even fertilize their own eggs an
strategy that guarantees offspring.
Platyhelminthes: Taenia
1. Observe slide of Taenia. Noticed the scolex and the body
composed of units called proglottids which are not
segments, but units formed by budding behind the scolex.
proglottids
Platyhelminthes: Taenia
1. Observe slide and model of Taenia scolex which is
equipped with suckers and hooks. Note the neck from
which new proglotids are budded off.
A= suckers
B=hooks
scolex
Platyhelminthes: Taenia
2. Observe slide and model of Taenia mature proglotid. They
have reproductive organs: testículos, vaso deferente, poro
genital, glandula de yema, ovario, vagina, utero, cordon
nervioso, canales excretores.
Uterus
Platyhelminthes: Taenia
2. Observe slide and model of of Taenia gravid proglottid, with
the uterus fulled with eggs or embryos. Where do you find
gravid proglottids? These proglottids break off and shed in
the feces of the host. Outside the host the proglottid breaks
releasing thousands of infected eggs.
Uterus with eggs
Platyhelminthes: Taenia
Taenia life cycle
Important Links
Platyhelminthes
http://www.savalli.us/BIO385/Diversity/05.Platyhelminthes.html
http://es.wikipedia.org/wiki/Platyhelminthes
http://www.pbs.org/kcet/shapeoflife/episodes/hunter.html