 A species as beautiful and innocent looking as a ribbon could also be deadly killer
Classification
Kingdom: Animalia
Phylum: Platyhelminthes
Characteristics
- Unsegmented
- Bilaterally symetrical
- Thin soft bodies
- Acoelomate
- Triploblastic
- Incomplete gut; has a mouth but no anus; food enters and leaves same opening
- Respitory and circulatory system take place by absorption through body wall (Diffusion)
- Free living or parasitic
- Reproduce sexually,asexually, or regenerate
- No skeleton; moves by using tiny bristles known as cilia
Diversity
Due to their soft bodys Platyhelminthes do not preserve very well as fossils. Scientists believe the earliest Platyhelminthes arrived 550 MYA. There are about 20,000 species of flatworms.
Class:
- Turbellaria (Planarians)
- Trematoda (Flukes)
- Cestoda (Tapeworms)
Planarian
Planarians are located in oceans, fresh water, moist terrestrial habitats and only a few are parasitic. They are carnivores even without teeth or scavengers. Excrete a mucus trail that helps them move.
Fluke worms can live in livers, blood streams, lungs, and bile ducts. They cause diseases such as Fasciola hepatica, Fasciolopsis buski, and Schistosome.
Fluke worms
Tapeworm
Tapeworms are parasites that live in the intestines of vertebrates. An added feature to the tapeworm that other flatworms do not have is a scolex. A scolex contains hooks and suckers so it can attach itself to the host. Tapeworms are very harmful because they block a hosts intestines, excrete toxic wastes and absorb the host's nutrients.
Life Cycle
The fluke has a complex life cycle as it passes through a number of juvenile stages attached to intermediate hosts before reaching adulthood and attaching itself to a definitive host.
Adult cestodes reproduce in the digestive tract of vertebrates, but for an egg to become and egg-producing worm, they need to infect a variety of intermediate hosts, and pass though specific developmental stages.
Physiology
A flatworm has a very simple nervous system with two nerve cords running down either side. It has two simple brains called ganglia, which are simple bundles of nerves. It has two eyespots that help it sense light.A flatworm can be microscopic or many feet long and is generally very thin. Playthelminthes will begin to shrink as they digest their own organs when they lack food. These organs will regenerate after the worms eat again.
Works Cited
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