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Worms- Phylum Platyhelminthes. Link to video. Flatworms - General Information. 3 phyla in Ch. 14 – We are going to focus mainly on Phylum Platyhelminthes Symmetry : Bilateral Cephalization - head end concentrated with sense organs and nervous control - PowerPoint PPT Presentation
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Worms- Phylum PlatyhelminthesLINK TO VIDEO
Flatworms - General Information
3 phyla 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)
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
Class Monogenea, Tremotoda, and Cestoda – Body form Parasitic Non-ciliated body covering Ciliated covering is lost once a host is contacted
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
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
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
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
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)
Life cycle of a fluke
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)
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
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