Daniel Jaffe
Paige Minteer
Zoey ZoBell
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Phylum: Platyhelminthes
Class
Examples and Characteristics
Turbellaria
Dugisea:
Marine, freshwater, predator and
scavenger, ciliated body surface
Monogenia
Monogians:
Marine and freshwater parasites, ciliated
bodies, infect outer layer of fish skin.
Trematoda
Trematodes and Flukes:
Parasites, two suckers attached to host,
most life cycles attach to intermediate
Cestoda
Tapeworm:
Parasites of vertebrates, no head or
digestive system, one or more
intermediate hosts
Sample Animals
Dugisea
Tapeworm
http://gurungeblog.files.wordpress.com/2008/11/platyhelm_turbellaria_dugesia.jpg
http://www.britishbeef.co.uk/tapeworm.gif
Body Cavity
 No body cavity exists within the Platyhelminthes
 Considered an Acoelomates, which means without a
cavity
http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/Acoelomate.JPG
Body Symmetry
 Platyhelminthes exhibit bilateral symmetry, which
means it has one line of symmetry, similar to humans.
 A bilateral animal has a dorsal side and a ventral side
 A bilateral animal has an anterior end and a posterior
end.
http://www.uic.edu/classes/bios/bios100/labs/bilateral.jpg
Nervous System
 Central Nervous system that processes information
from the eyes and other sensory structures
 The bilateral symmetry of this phylum allows for
sensory equipment concentrated at the anterior end
along with the central nervous system and the brain
 This evolutionary tend is known as cephalization
Circulatory System
 No body or organs for circulation
 Open system
http://www.seaslugforum.net/images/flatworm.jpg
Digestive System
 Pharynx: a muscular tube in which the mouth is
located
 Extends form ventral side
 Digestive juices are sprayed onto pray, and small pieces
are sucked into pharynx, where digestion continues
 Undigested wastes are egested through the mouth
Excretory System
 “Flat” shape in which nitrogenous waste (ammonia) is
removed through diffusion across the body surface.
 No organs specialized for gas exchange or circulation.
They have a basic structure  excretory system is
through osmotic balance with their surroundings.
Locomotion/Musculature
 Motility a.k.a “Going Dumb”
 Move by using cilia on their ventral epidermis, gliding
along a film of mucus that they secrete.
 Some use muscles to swim through water with an upand-down form of motion.
http://www.glogster.com/media/2/3/71/6/3710611.jpg
Skeletal Type
 Platyhelminthes do NOT contain a skeleton type.
 They can literally do the “worm” without risking any
bone fractures.…holy biology!
http://cyberportfolio.st-joseph.qc.ca/classes/carriere/archives/surprised-girl-reading-book.jpg
Sensory Structures/Features
 Ganglia: Located at the anterior end of the worm, they
are dense clusters of nerve cells also known as eye
spots
 Ventral nerve cords: Coming from the ganglia, a pair of
nerve cords that run down the lenth of the body.
Reproduction Methods
 Sexual and asexual reproduction
 Regenerative tissues allow one split
individual to regenerate into two
separate worms
 Mostly homaphrodite
 Self fertilization as well as cross
fertilization is seen
 Direct development (no larva stage)
http://cas.bellarmine.edu/tietjen/images/Chlonorchis01.gif
Gas Exchange
 Lack respiratory systems
 Flat bodies permits flow of oxygen and carbon dioxide
by diffusion
http://cas.bellarmine.edu/tietjen/images/platyh16.jpg
Unique Features
 Restricted to living in wet environments because of the
nature of their open gas exchange making them
susceptible to dehydration
 Their bodies are soft, unsegmented, and resemble
ribbons
 Some of these species are carnivorous, while the rest
are parasitic
 Tapeworm disease, or, Cestodiasis is caused by a
parasitic type of Platyhelminthes
The End
Thanks for
listening!