1. PHYLUM PLATYHELMINTHES
FLAT BODIED WORMS
Class Turbellaria (planarians)
mostly predatory
free living
Class Trematoda (internal flukes)
only parasitic
complex life-cycles
Class Cestoda (tapeworms)

2. EXAMPLES PLANARIA – FREE LIVING – AQUATIC AND TERRESTRIAL
Herbivore, carnivore, scavenger
TAPEWORMS – INTESTINAL PARASITE W/ MORE THAN 1 HOST TAENIA
FLUKES – INTERNAL PARASITE W/MORE THAN ONE HOST
BLOOD FLUKE SCHISTOSOMA
LIVER FLUKE FASCIOLA

3. TRAITS ORGAN LEVEL OF ORGANIZATION BILATERAL SYMMETRY
SAC TYPE BODY – 1 OPENING/ no anus
GASTROVASCULAR CAVITY IS BRANCHED
TRIPLOBLASTIC – 3 GERM/tissue LAYERS
CEPHALIZATION – has a head
BRAIN WITH 2 NERVE CORDS & TRANSVERSE NERVES
SENSE ORGANS – light and chemicals
Occeli/eyespots and auricles/ears

4. TRAITS ACOELOMATE – no coelom/body cavity DIFFUSION METHODS FOR:
GAS EXCHANGE - O2 and CO2
WASTE REMOVAL – by FLAME CELLS
CIRCULATION of nutrients and waste
REMEMBER: DIFFUSION IS A SLOW PROCESS; HI TO LO

5. Body Plan Lining of gut =ENDODERM Epidermis/ ECTODERM gut cavity
no body cavity; region between gut and body wall packed with organs within MESODERM tissue
Acoelomate organism
(flatworm)
Body Plan

6. TRAITS MUSCLES FOR LOCOMOTION REPRODUCTION ASEXUAL – REGENERATE
SEXUAL – HERMAPHRODITES BUT CROSS FERTILIZE

7. EVOLUTIONARY MILESTONE
ORGAN LEVEL OF ORGANIZATION
reproductive, excretory, muscular
BILATERAL SYMMETRY
CEPHALIZATION
Anterior and posterior
Dorsal and ventral

8. Platyhelminthes Taxonomy
Classes of Phylum Platyhelminthes

9. Planaria Class Turbellaria --Widely distributed in N. America
-- about 200 species
--Occur in both lakes and streams
-- Stream-dwelling species more differentiated than lake species
--Species diversity increases in temperate areas 20 to 60 species per lake
Planaria
Class Turbellaria

10. Class Turbellaria Free-living flatworms; mostly marine
microscopic to two feet
Locomotion in Turbellaria
move by means of cilia and mucous
2 layers of muscle; longitudinal and circular
Stimulated by nervous system
contractions for turning, twisting and folding of the body

11. Nutrition in Turbellaria
carnivores and predators of other animals or dead remains.
muscular pharynx is inserted into prey
Secretes digestive enzymes
Fragments are pumped into mouth on ventral surface
Further digestion in gastrovascular cavity
branching increases the surface area for digestion and absorption
No anus, only mouth;
Undigested food excreted from mouth and pharynx as in cnidaria
GVC aids both digestion and circulation – distributes nutrients and oxygen to tissues

12. Sensory/nervous Exhibits cephalization
Brain/ganglia
nerve cords
Exhibits cephalization
Group of nerve tissue (GANGLIA) at anterior
Ganglia attached to 2 nerve chords
well developed sensory eyespots for light
auricles for chemical and mechanical (touch) receptors

13. Reproduction in Turbellaria Asexual--- By fission or dividing
Regeneration of missing parts
Sexual-
hermaphrodites w/ cross-fertilization
Internal fertilization
Zygote released to water
genital pore
oviduct
testis
ovary
penis

14. EXCRETION IN TURBELLARIA
Excretory
System
Excretory pore
Flame cells
Excretory tubules
pharynx (protruded)
protonephridia
flame cell
nucleus
cilia
Cilia of flame cells remove excess water and nitrogen wastes of body
Waste moves to tubules
Exits out pores in head
Needs excretory system as tissues become thicker and more cells present
fluid
filters through membrane folds
opening of tubule at body surface
flame cell

15. Class Trematoda – the Flukes
COMMON EXAMPLE
OF COMPLEX
LIFE CYCLE

16. Class Trematoda live as parasites
protected from digestion by protein coat
2 suckers:
1. Oral sucker attaches to organs of the host
2. Ventral sucker or acetabulum attaches to host tissues

17. Types of Hosts Complex life cycles
Alternate between sexual and asexual stages
Most require at least 2 different kinds of hosts to complete their life cycle
1. Definitive host (primary host)
where parasite matures and reproduces (sexually)
host in which eggs are released
2. Intermediate host
Hosts in which larval stages develop and undergo asexual reproduction
Results in an increase in the number of the individuals

18. Fluke Life Cycle Schistosoma a common blood fluke of SE Asia
causes shistosomiasis
Definitive host = humans
Intermediate host = snails
In humans - eggs penetrate and damage intestinal and bladder tissue
constant inflammation and eventual deterioration of liver, spleen and other organs
Fluke Life Cycle

19. General Life Cycle - Chinese liver fluke, Clonorchis sinensis
Adults live in the bile ducts of humans, dogs, and cats
There are 2 intermediate hosts: a snail and a fish
Eggs are passed out of the definitive host and hatch as ciliated larvae called miracidia
The miracidia penetrates a snail molluscan host and becomes a sporocyst
They undergo asexual reproduction producing larvae called rediae
Rediae often asexually produce more rediae, but will eventually give rise to larvae called cercariae
They leave the molluscan host and penetrate fish
They encyst in the fish tissues as the metacercaria
Consumption of infected fish results in the metacercaria excysting in the gut and migrating to the bile duct

21. Class Cestoda Protective protein coat
anterior region is called a scolex;
often armed with suckers and hooks
Extending from neck of scolex is a series of proglottids;
contain sex organs and eggs;
no digestive system
Mature eggs released through an opening in the proglottid
leave the host when the proglottids break off

22. Class Cestoda Tapeworm Lifecycle
b A definitive host eats infected, undercooked beef
a Larvae become encysted in intermediate host tissues
c Scolex of larva attaches to intestine’s wall
d Many proglottids form by budding
f Cattle may ingest embryonated eggs or ripe proglottids to become intermediate hosts
e Ripe proglottids containing fertilized eggs leave host in feces
Class Cestoda
Tapeworm Lifecycle

23. Beef Tapeworm, Taeniarhynchus saginatus
Definitive host = humans;
intermediate host = cattle
Eggs are shed with human feces;
infected persons defecate in a pasture or untreated sewage
eggs are ingested by cattle
Eggs hatch
larvae bore into intestinal wall
get into the circulatory system
transported to muscle
If uncooked beef is consumed the larvae is freed
scolex develops, forming the adult
Symptoms include loss of weight, chronic indigestion, diarrhea