Phylum Platyhelminthes: In 1859 the scientist Gegenbaur proposed the name phylum platyhelminthes. Originally the animals of this group were placed in the taxon vermis by Linnaeus in 1735 along with other worms. In 1876 Minot recognized Platyhelminthes as a separate phylum. The animals of this group are commonly known as flatworms or tapeworms. Phylum Platyhelminthes belongs to kingdom Animalia. This phylum includes 13,000 species. The organisms are also known as flatworms. These are acoelomates and they include many free-living and parasitic life forms.

Characteristics of Phylum Platyhelminthes

Phylum Platyhelminthes have the following important characteristics:

1. They are triploblastic, acoelomate, and bilaterally symmetrical.
2. They may be free-living or parasites.
3. The body has a soft covering with or without cilia. Their body is dorsoventrally flattened without any segments and appears like a leaf.
4. They are devoid of the anus and circulatory system but has a mouth.
5. The space between the body wall and organs is filled with connective tissue parenchyma which helps in transporting the food material.
6. They are hermaphrodites, i.e., both male and female organs are present in the same body.
7. They reproduce sexually by fusion of gametes and asexually by regeneration by fission and regeneration. Fertilization is internal.
8. The life cycle is complicated with one or more larval stages.
9. They possess the quality of regeneration.
10. They have flame cells that help in excretion and osmoregulation.

Classification of Phylum Platyhelminthes

The classification of Platyhelminthes are given below:

• Turbellaria

• Trematoda

• Cestoda

Turbellaria

• These are free-living organisms found mostly in fresh water.

• The body is dorsoventrally flattened.

• Hooks and suckers are not present.

• For eg., Planaria, Otoplana

Trematoda

• These are mostly parasitic.

• Hooks and suckers are usually present.

• Eg., Fasciola hepatica, Diplozoon

Cestoda

• These are exclusively parasitic.

• They have hooks and suckers.

• Eg., Taenia spp., Convoluta

Follow on Facebook

By Team Learning Mantras