1. Phylum: Platyhelminthes
Porifera
Cnidaria
Chordata
Mollusca
Ctenophora
Phoronida
Annelida
Ectoprocta
Arthropoda
Rotifera
Nematoda
Brachiopoda
Nemertea
Echinodermata
Platyhelminthes
“Radiata”
Deuterostomia
Protostomia
Bilateria
Phylum: Platyhelminthes
Eumetazoa
Metazoa
Ancestral colonial
flagellate

2. Phylum: Platyhelminthes
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
parasitic flukes
Class: Cestoda
parasitic tapeworms
Class: Turbellaria
free-living planaria

3. Phylum: Platyhelminthes
flatworms
most primitive animal that has/is...
bilateral symmetry
dorsal/ventral; anterior/posterior; left/right
triploblastic
endoderm- digestive system
ectoderm- outer covering, nervous system
mesoderm- muscle, excretory, reproductive systems
tissue level of organization
true organs
believed to be first animal that could hunt for food; aided by bilateral symmetry and paired sense organs at the head
acoelemate
no body cavity (i.e. “solid body”)
only internal cavity is the gut

4. Phylum: Platyhelminthes
acoelemate
no body cavity (i.e. “solid body”)
only internal cavity is the gut

5. Phylum: Platyhelminthes
no organized circulatory or respiratory systems
thin,flat bodies allow diffusion of nutrients and gases
centralized nervous system (cephalization)
brain and sensory organs at head
2 nerve cords run length of body
digestive system
free-living planaria has branched one; single opening
parasitic tapeworm has none
reproductive system
sexual- hermaphrodites
both testes and ovaries, uterus in mesoderm layer
cross- or self-fertilization
asexual
binary fission
fragmentation and regeneration

6. Phylum: Platyhelminthes
Class: Turbellaria
free-living flatworms
may have ciliate as ancestor
size range from <1-60 cm
locomotion
layers of muscles
cilia
some have glands that secrete mucus to glide along
most are carnivorous, scavengers
habitat
most marine or freshwater
some on humid land

7. Phylum: Platyhelminthes
Class: Turbellaria
well-defined nervous system w/ sense organs
ganglia concentrated as simple brain at head
sensory cells (statocysts sense gravity, light sensory cells at eyespots, chemosensory cells)
2 nerve cords run length of body
simple excretory system- protonephridia
consists of flame cells (specialized ciliated cells)
move fluid through branched ducts to outside via excretory pores
maintains osmotic balance

8. Phylum: Platyhelminthes
Class: Turbellaria
digestive system (2-way system)
branched w/ single opening serving as mouth/anus
mouth, muscular pharynx, intestine
digestion is extracellular and intracellular
digestive enzymes secreted into digestive cavity
small food particles enter ameboid cells by phagocytosis and digested in food vacuoles

9. Phylum: Platyhelminthes
Class: Turbellaria
Reproduction
asexual by binary fission
sexual- hermaphrodites
cross-fertilization
some mate by “penis-fencing”
sperm injected in body wall
fertilization and early development inside “mother”
juveniles that resemble adult released

10. Phylum: Platyhelminthes
Class: Turbellaria
organ systems
digestive
nervous
reproductive
excretory

11. Phylum: Platyhelminthes
Class: Turbellaria
Convoluta roscoffensis
mutualistic relationship
ingests photosynthetic flagellates
flagellates lose flagella and cell wall and take up residence in worm gut
as adult, worm no longer feeds and survives off of flagellates
later in life, worm digests flagellates and all die

12. Phylum: Platyhelminthes
Class: Turbellaria
Genus: Bdelloura
commensalism with horseshoe crab
attaches to gills or appendages of horseshoe crabs
worm gets transportation, shelter, food scraps

13. Phylum: Platyhelminthes
Classes: Cestoda, Trematoda ”The parasitic flatworms”
most have 2 or more hosts during life cycle
intermediate host- juvenile stage
definitive host- adult stage
much of structure devoted to reproduction
produce lots of offspring to make it to the next host
do not survive long outside of host
contain unusual epidermis called tegument
protects against detection/digestion by host
some have microvilli to aid absorption of host nutrients
some syncytial (cells have continuous cytoplasm) to aid in distribution of nutrients
some secrete their own digestive/protective enzymes

14. Phylum: Platyhelminthes
Class: Trematoda
parasitic flukes
live in intestine, liver, lungs, bladder and blood vessels
involve at least 2 hosts
reproduction
asexual in early life stages
sexual in adult stages producing large numbers of eggs stored in uterus

15. Phylum: Platyhelminthes
Class: Trematoda
Genus: Schistosoma
causes human disease schistosomiasis
major world health problem
common in Africa, Asia and South America
chronic disease
acute symptoms: fever, rash, body pains, cough, dysentery
long term: can cause organ damage; rare lesions in central nervous system
hosts-
intermediate is aquatic snail
definitive is human (or other vertebrates)

16. cercaria
adult

17. Phylum: Platyhelminthes Class: Trematoda
Genus: Schistosoma
Life cycle stages:
eggs hatch into miracidium (larval stage, swimming ciliate, can only live 24 hrs outside of host)
miracidium enters snail and becomes sporocyst (loses cilia)
sporocyst reproduces asexually to produce more sporocyst or redia
redia becomes cercaria (swimming stage that resembles adult form)
cercaria leaves first host and enters vertebrate host (release digestive enzymes to help bore through skin)
once in host, cercaria migrates through blood to large intestine and becomes adult to produce more eggs

18. Phylum: Platyhelminthes Class: Trematoda Chinese liver fluke
Hosts:
snail>fish>mammal (human)
In definitive host...
cysts digested in intestine releasing fluke
fluke travels up bile duct to liver
attaches with suckers and feeds on blood
causes anemia and liver disease
may block bile duct

19. Phylum: Platyhelminthes
Class: Trematoda
Liver flukes

20. Phylum: Platyhelminthes Class: Cestoda
tapeworms
parasitic
as long as 100 feet
most have at least 2 hosts
no digestive system; nutrients absorbed from host
scolex = specialized head that has sucker discs and hooks for anchoring to host

21. Phylum: Platyhelminthes Class: Cestoda
long flat body made of many units called proglottids
proglottid = complete reproductive unit with male and female gonads
youngest proglottid behind head
older proglottids w/ eggs shed in feces of definitive host
reproductive output high
many proglottids per tapeworm
many eggs per proglottid

22. Beef tapeworm life cycle
Phylum: Platyhelminthes
Class: Cestoda
Beef tapeworm life cycle

23. Phylum: Platyhelminthes
Class: Cestoda
Beef tapeworm life cycle (Taenia saginata)
cattle ingest human feces with eggs and egg covering digested off to reveal larva with scolex that bores through intestinal wall to blood vessel to muscle
larva grows in muscle to form a cyst called “bladder”
human eats undercooked meat with “bladder”
cyst digested open releasing tapeworm
scolex attaches to intestinal wall and tapeworm grows, makes new eggs

24. Phylum: Platyhelminthes Class: Cestoda
Pork tapeworm
similar to beef tapeworm but pig is intermediate host
can also develop bladders in human host
can grow in eye or brain (interfere with vision or cause seizures
Broad fish tapeworm (Diphyllobothrium latum)
eggs reach freshwater to produce free swimming larva
eaten by copepods (small crustaceans)
copepods then eaten by fish
humans can get by eating raw or undercooked fish
absorb vitamin B-12 and can cause megaloblastic anemia

25. Platyhelminthes- The Table
Symmetry- bilateral
Segmentation- N/A
Mesoderm present- yes, triploblastic
Determinant cleavage
Type of body cavity- acoelomate, “solid body”, lack body cavity other than digestive cavity
Ciliated larva- trocophore-like in some (free-swimming, ciliated)
Protostome- N/A; mouth=anus
Nervous system- cerebral ganglia form simple brain, 2 nerve cords, specialized sensory cells
Respiratory system- none, flat and thin for respiration by diffusion across cell membranes

26. Platyhelminthes- The Table
Digestive system- Turbellaria has highly branched one but still 2-way (mouth=anus); Trematoda has some digestive tract; Cestoda has no digestive tract, absorbs food through external surface
Excretory system- Excrete using ciliated flame cells that push wastes through excretory ducts and out excretory pores
Reproductive system- contain testes and uterus; planaria are hermaphrodites; can reproduce by binary fission and fragmentation/regeneration

27. Platyhelminthes- The Table
Circulatory system- none; relies on flat thin body for diffusion across cell membranes
Members- Most are parasitic including Cestoda (tapeworms) and Trematoda (flukes). Turbellaria are free-moving and not parasitic.