1. Acoelomates and other groups
Flatworms!
Chapter 10

2. Basics Multicellular Primary bilateral symmetry
Digestive system incomplete
Most are monoecious
Triploblastic- have three germ layers
Lack a coelom or a pseudocoelom

3. Taxonomic Groupings P. Platyhelminthes P. Nemertea C. Turbellaria
C. Trematoda
C. Monogenea
C. Cestodoa
P. Nemertea

4. Acoelomate Characteristics
No body cavity
ectoderm
mesoderm
Gut
endoderm

5. Acoelomate Characteristics
Triploblastic
Mesoderm (mesenchyme, parenchyma)
Gut
Ectoderm
Endoderm

6. Parenchyma Form of tissue Loose Vacuolated
Contains more cells and fiber than mesoglea of the cnidaria.

7. Acoelomate Characteristics
Bilateral Symmetry
Anterior: toward the front of the body
Posterior: toward the rear of the body

8. Acoelomate Characteristics
Cephalization
the concentration of sensory organs in the head of the animal
Eye spots
Auricles

9. Flatworms are triploblasts with well-developed organ systems
digestive
excretory
nervous
reproductive

10. Excretory System
Flame Cells or
Protonephridia

11. Nervous System Ladder-type. Brain, and 1 or more
ventral nerve cords and
Transverse nerves.

12. Four Classes Class Turbellaria: (the planarians) mostly free-living.
Class Trematoda: (the flukes) all parasitic.
Class Monogenea: (monogeneans) all parasitic.
Class Cestoda: (the tapeworms) all parasitic.

13. I. Class Turbellaria (planarians) photosynthetic endosymbionts
Acoels
Rhabdocoels
Polyclads
Triclads

14. Triclad flatworm with “3-branch” gut
diatoms
Triclad flatworm with “3-branch” gut
Acoel flatworms do not have a well-formed gut cavity
Polyclad flatworms have a many branched gut

15. Rhabdocoel turbellarian
phalloidin stain (ventral body wall musculature)
longitudinal and circumferential (circular) muscles
bulbous, muscular pharynx
© Matthew Hooge

16. Polyclads swimming with undulatory body waves
statocyst of acoel

17. Turbellarians are often predatory specialists
ascidian
polyclads feeding
bryozoans
planarian feeding on a midge

18. Asexual reproduction and regeneration

19. Sexual Reproduction

20. Turbellarian Diversity

22. Variation in color patterns and shapes among polyclad turbellarians

23. Flatworm mimicry of nudibranchs
Aposematic coloration in nudibranch families Chromodorididae and Phyllidiidae
Mimicry by flatworm family Psuedocerotidae

25. Phylum Platyhelminthes, Class Turbellaria Bipalium

27. Terrestrial Planarians!

28. Lake Baikal Planarians
Up to 2.0 feet long!

29. Temnocephalan Turbellarians
Live as either ectocommensals or ectoparasites on the surface of crustaceans, insects, molluscs and turtles

30. Temnocephalan Turbellarians
Live as either ectocommensals or ectoparasites on the surface of crustaceans, insects, molluscs and turtles