FLATWORMS PLATYHELMINTHES

1
FLATWORMS(PLATYHELMINTHES)
2
SPONGES CAN FIGHTPLASTIC DUCKS
3
S C F P D
Ribosomal RNA tree
time
4
FLATWORMS(PLATYHELMINTHES)
gt 20, 000 species Free-living scavengers
carnivores, mainly marine freshwater Parasites,
hosts from all habitats
5
To what extent do modern Flatworms resemble the
first triploblasts?
6
To what extent do modern Flatworms resemble the
first triploblasts? OR Are they specialised?
7
S C F P D
TRADITIONALLY VIEWED AS CLADE
Clade an ancestor ALL its descendents
8
S C F P D
MAY WELL BE GRADE
Grade Excludes some descendents
of last common ancestor
9
Largest 25 metres long
Beef Tapeworm
10
PARASITIC LIFESTYLE

• Need to battle host defences
• Otherwise, living is easy
• Parasites usually have simplified
• body plan of free-living relatives

11
PARASITIC LIFESTYLE

• Often require more than one host
• species in life cycle
• Host you have sex in is called the
• DEFINITIVE HOST
• Getting from host-to-host is hard

12
CLEAVAGE
SPIRAL RADIAL
Protostomes Deuterostomes
13
FLATWORMCLEAVAGE
SPIRAL
14
FLATWORMBAUPLAN

• Flattened worms with bilateral
• symmetry obvious head

15
FLATWORMBAUPLAN

• Flattened worms with bilateral
• symmetry obvious head
• Three tissue layers

16
TRIPLOBLASTS
Three tissue layers
17
No body cavity except gut if present
18
FLATWORMBAUPLAN

• Flattened worms with bilateral
• symmetry obvious head
• Three tissue layers
• Gut nearly always blind if present

19
BLIND GUT ENTERON
head
20
BLIND GUToften complex
Gut
21
OTHER GUTS
NONE Acoel flatworms WITH ANUS
22
S C F P D
GUTS SUGGEST ARE GRADE
Gut
Blind Gut
23
FLATWORMBAUPLAN

• Flattened worms with bilateral
• symmetry obvious head
• Three tissue layers
• Gut nearly always blind if present
• Usually hermaphrodite

24
PHYLUM SPLIT INTO3 MAIN CLASSES
25
FLATWORMCLASS 1
TRUE FLATWORMS
Eating fly larva
Eyes
26
TRUEFLATWORMS
lt5 mm 5-35 mm
Microturbellaria Triclads
27
Microturbellaria Triclads
Simple gut Branched gut
28
ACOEL FLATWORMS
Microturbellarians with no guts
29
ACOEL FLATWORMS
30
TRUEFLATWORMSPHARYNX
31
CANDY-STRIPED FLATWORM
32
TERRESTRIAL FLATWORMS
33
TERRESTRIAL FLATWORMS EATEARTHWORMS
34
FLATWORMCLASS 2
FLUKES Diverse parasites
35
LIVER FLUKE
Sheep or Cow
egg
Pond snail Lymnaea
36
BLOOD FLUKE
Schistosoma
human
egg
freshwater snail
37
SCHISTOSOMIASIS
200 million people - about 1million deaths a year
38
FLATWORMCLASS 3
TAPEWORMS Head with suckers No gut
Proglottid
39
BEEF TAPEWORM
eggs