1. Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa
Flatworms
Gastrotrichs
Gnathiferans
Mesozoa

2. Phylum Acoelomorpha (“without hollow form”)
Clade Platyzoa (lophotrochozoans)
Phylum Platyhelminthes (“flat worm”)
Phylum Gastrotricha (“hairy belly”)
Clade Gnathifera (“jaw bearing”)
Phylum Gnathostomulida (“jaw mouth”)
Phylum Micrognathozoa(“small jawed animal”)
Phylum Rotifera (“wheel bearing”)
Phylum Acanthocephala (“spine head”)
Phylum Mesozoa (“middle animal”)

3. (“without hollow form”)
Ph. Acoelomorpha
(“without hollow form”)
most are free living
incomplete gut
no ganglia
hermaphroditic
no circulatory, respiratory, excretory system

4.  organ-system level of organization
Acoelomate Phyla
 organ-system level of organization
Triploblastic
endoderm
parenchyma
Mesoderm
(muscle layer)
ectoderm
bilateral
cephalized

5. Ph. Platyhelminthes (“flat worm”)
Class Turbellaria (planarians)
Class Trematoda (digenetic flukes)
Class Monogenea (monogenetic flukes)
Class Cestoda (tapeworms)
parasitic or free living
incomplete gut
flame cells
hermaphroditic
no circulatory system

6. Digestive, Nervous, Reproductive, and Excretory Systems
protonephridia

7. Ladder-like Nerve Cord
Nervous System
Ladder-like Nerve Cord

8. Class Turbellaria
ocelli
auricles

9. pharynx
Branched gut

10. Free Swimming
Marine Turbellarians

11. Class Trematoda Parasitic flukes
Structurally similar to the more complex turbularians
Adapations for parasitic lifestyle
glands
attachment structures
high reproductive rate

12. Subclass Digenea complex (indirect) life cycle:
first host (intermediate host) = mollusc
final host (definitive host) = vertebrate
Great diversity in host location
digestive tract
circulatory system
urinary tract
reproductive tract

13. Clonorchis Life Cycle

14. Schistosoma Life Cycle

15. Class Cestoda scolex strobila (chain of proglottids)
mouth & gut absent
reproductive system repeated in each proglottid
parasitic
complex (indirect) life cycle with 1 or more intermediate hosts

16. Cestode Life Cycle evaginated cysticercus invaginated cysts in gravid
proglottid
evaginated
cysticercus
invaginated
cysts in
meat
shelled larvae
(in feces)
Cestode Life Cycle
small intestine

17. developing
cysticercus

18. scolex

21. Phylum Gastrotricha “belly hairs” gastric gland pharynx male gonads
ovary
intestine
pedal gland

22. Phylum Gnathostomulida
“jaw mouth”

23. Phylum Micrognathozoa
“tiny jawed animals”

24. Phylum Rotifera
(“wheel bearers”)

25. Typical Rotifer Life Cycle
environmental
stimulus
meiosis
2N female
1N egg
1N male
1N egg
2N egg
(amictic)
2N egg
1N sperm
fertilization
environmental
stimulus
2N female
(amictic)
2N resting egg
parthenogenesis
sexual reproduction

28. Phylum Acanthocephala
“spine head”
proboscis with hooks & spines
intestinal parasites

29. Acanth Reproduction

31. Phylum Mesozoa
“middle animals”