PHYLUM PLATYHELMINTHES

PHYLUM PLATYHELMINTHES

Phylum Platyhelminthes contains over 20.000 animal species. They show following characters:

1. They are flat- worms. They range in adult size from 1mm or less to 25 m.
2. Parenchyma that fills spaces between other more specialized tissues, organs and the body wall. Parenchyma is derived from mesoderm.
3. Parenchyma provide support, nutrient storage,  motility and reserves of regenerative eel s. They also have role in transport materials, structural interactions with other tis ies. modifiable tissue for morphogenesis (formation of new structures) and ox gen storage.
4. This is the first phylum that has an organ-system level of organization.
5. Thy are flattened dorsoventrally.
6. They are triploblastic, acoelomate, bilaterally symmetrical.
7. Th y are unsegmented worms.
8. Th y have incomplete gut. Gut is absent in Cestoda
9. Thy are cephalized (head is present). Head has an anterior cerebral ganglion and  longitudinal nerve cords.
10. Excretory/osmoregulatory structures are protonephridia.
11. They are hermaphrodite and they have complex reproductive systems.

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