Worms- Phylum Platyhelminthes

1. Worms- Phylum Platyhelminthes Link to video

2. Flatworms - General Information • 3phyla in Ch. 14 – We are going to focus mainly on Phylum Platyhelminthes Symmetry: Bilateral • Cephalization- head end concentrated with sense organs and nervous control • Tripoblastic- has a middle germ layer (mesoderm) as well as ectoderm and endoderm • Parasitic in nature • Examples of Flatworms include: planaria, flukes, and tapeworms • 4 Classes : Turbellaria(Planarians), Trematoda (Flukes), Monogenea and Cestoda(Tapeworms)

3. Class: Turbellians - Body Form • Ciliated epidermis • Rod- shaped Rhabdites- swell and form a protective mucous sheath around the body • Dual gland adhesive organs in the epidermis

4. Class Monogenea, Tremotoda, and Cestoda – Body form • Parasitic • Non-ciliated body covering • Ciliated covering is lost once a host is contacted

5. Digestive System: • Includes a mouth, pharynx, and an intestine • GVC- Gastrovascular cavity present • Mainly carnivorous – feed on small crustaceons, nematodes, rotifers, and insects • Flatworms have a system called: protonephridia/ can be used for osmoregulation or excretion • System is mainly osmoregulatory ( regulates the water inside and outside of the body) • Flame Cells- cup shaped cell that has flagella extending out

6. Nervous System- • Simple nervous system (found in turbellarians) – Subepidermal Nerve Plexus similar to the nerve net in cnidarians • May also have one to five pairs on longitudinal nerve cords lying under the muscle layer • Have ganglia and neurons • SENSE ORGANS: • Ocelli: light sensitive eyespots • Tactile Cells -touch • Chemoreceptive cells - • Statocysts for equilibrium • Rheorecptors- sensing direction in water currents

7. Reproduction and regeneration: • Reproduce both sexually and asexually (fission) same as budding like the hydra • Almost all flatworms are monoecious • Some have spiral determinate cleavage typical of protostomes

8. Class Turbellaria – extra information • Often distinguished on the basis of the form of the gut ( present or absent? , simple or branched?, pattern of branching? ) • Creeping forms that combine muscular with ciliary movements to move

9. Class Trematoda • All parasitic flukes • Leaflike in form • Penetration glands / organs for adhesion to hosts like suckers and hooks • Increased reproduction capacity • Sense organs are poorly developed • EX: Liver Fluke in Humans ( common in regions of east Asia, especially China, Southeast Asia, and Japan; also common in cats, dogs, and pigs.) • Blood Fluke (causes schistosomiasis)

10. Life cycle of a fluke

11. Class Monogenea • Are all parasites ( on fish, frogs, turtles, and one on the eye of a hippopotamus) • Cause little damage to hosts • Can be serious if many hosts are crowded together (farm-raised fish)

12. Class Cestoda- • Tapeworms • Long, flat bodies • Has a scolex(for attachment to host)- has suckers/ tentacles for attachment , and proglottids ( linear series of reproductive units) • No digestive system • Well-developed muscles • Excretory system is similar to other flatworms as well as nervous system • No special sense organs • No head

13. Examples of Cestoda : Beef Tapeworm, Pork Tapeworm, Fish tapeworm, Dog Tapeworm • Phylum Nemertea • Often called ribbon worms • Long muscular proboscis • Bilateral • Triploblastic • 1000 species; all marine