Phylum Platyhelminthes includes 13ooo species. These are found as free-living as well as parasitic life forms. These are also called Flatworms because of having a dorso-ventrally flattened body.
Characteristics features of Phylum- Platyhelminthes
- They may be found as free-living or parasite
- These are mostly endoparasite, found in various animals including human beings.
- Symmetry: These are Bilaterally symmetrical.
- Germinal layer: triploblastic animals.
- Triploblastic– In a developing embryo, the third germinal layer called mesoderm is found in between ectoderm and endoderm. These animals are called triploblastic animals
- The body cavity: Acoelomate animals
- Level of organization: organ level of organization is found.
- In parasitic forms of the hooks and suckers are present.
- Some parasitic organisms absorb nutrients directly from the host body’s surface.
- Flame cells: these are specialized in this phylum which helps in osmoregulation and excretion. Chief excretory waste is ammonia.
- Hermaphrodites ( bisexual or monoecious) Sexes are not separate, internal fertilization.
- The development occurs through many larval stages.
- Some members of this phylum possess a high regeneration capacity. e.g., in Planaria.
- Some examples of Platyhelminthes: Taenia solium (tapeworm), Fasciola hepatica (Liver fluke)
Classification of Platyhelminthes:
- These are mostly found in fresh-water
- These animals are free- living
- Hooks and suckers are absent
- Example; Planaria, Otoplana
- The animals are mostly parasitic
- Presence of Hooks and suckers
- Example: Fasciola hepatica, Diplozoon
- The members are exclusively parasitic
- presence of hooks and suckers
- Example: Taenia sps. Convoluta
Planaria: Found in freshwater. The Body comprising cilia, and having the power of regeneration of the lost part. They possess a pair of eyes and two lateral lobes.
Schistosoma: These are called blood fluke because found in mesenteric blood vessels and the hepatic portal system of humans. It shows well-marked sexual dimorphism.
They spread many diseases by contaminating the water.
Taenia solium: also called pork tapeworm and found in all countries where the consumption of pork occurs. The larva of this organism found in the pig’s muscles. Taenia solium lives as a parasite in the intestine of the human. It is a hermaphrodite organism and it undergoes self – fertilization.
Fasciola: Also called the liver fluke, as it lives in the bile duct of sheep and goats. It is also hermaphrodite but in these organiasms cross-fertilization takes place.
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