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Last Updated : 14 Dec, 2023
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Phylum Platyhelminthes is a phylum of invertebrates that consists of organisms that are bilaterally symmetrical and unsegmented. Usually, species in this phylum are known as flatworms or tapeworms as they have flat bodies. These are dual-parasitic and free-living. They are a part of Kingdom Animalia.

Examples of Platyhelminthes are Schistosoma mansoni, Taenia saginata, Taenia solium, Dugesia tigrina, etc. They are responsible for multiple diseases in humans like Schistosomiasis and Cysticercosis. Meat and Fish should be properly cooked to avoid infection from these organisms.

Phylum Platyhelminthes

In the animal kingdom, there are many different phyla according to their characters and their functions. Here, we will discuss the phylum Platyhelminthes. Approx. there are 13000-20000 species in this phylum. These are acoelomates as they lack a cavity in their body. Different species have different sizes which can vary up to 2-3 feet. The parasites in this phylum are known as blood flukes which can regenerate themselves. They are invertebrates with soft bodies. Few species cause highly damaging diseases in humans. Huge diversity can be seen in this phylum.


Characteristics of Phylum Platyhelminthes

The following are the main characteristics of Platyhelminthes:

  • They are both parasitic and free-living in nature.
  • They have a bilateral symmetry.
  • They have three germ layers and are known as triploblastic organisms.
  • They lack cavities in them so they are recognized as Acoelomates.
  • They lack Cilia and have a soft covering over their body.
  • Platyhelminthes lack segmentation so no segments can be seen in them and they are dorsoventrally flattened.
  • They have a mouth for ingestion but they lack an anus and a digestive system.
  • Respiration is done via the body’s surface through Simple Diffusion.
  • In the same body, both male and female sex organs are present. Hence, they are called Hermaphrodites.
  • Reproduction occurs via both methods. Sexually they reproduce by fusion of gametes and asexually they reproduce by Fission and Regeneration.
  • Internal fertilization is seen in this phylum.
  • One too many larval stages are seen in their life cycles.
  • Transportation of food is done by the fluid and connective tissues present in the space between body walls and organs.

Distinguishing Features of Phylum Platyhelminthes

Every phylum has some special or different characteristics which differentiate them from other phyla. Some of the unique features that Platyhelminthes exhibits are as follows-

  • For excretion, only Platyhelminthes have flame cells.
  • The nervous system is ladder-like which is not seen in any other phylum.
  • Fertilization is done by themselves only. 
  • The body cavity of Platyhelminthes has connective tissues which are a unique feature of this phylum.

Examples of Platyhelminthes

Few examples of Platyhelminthes are:

  • Taenia solium (Pork Tapeworm): Taenia solium is a parasitic tapeworm which causes Taeniasis. Humans can get infected by eating pork that might be infested with Taenia.
  • Schistosoma: These are also known as blood flukes. This falls under the Trematoda class and causes Schistosomiasis. This is mostly found in tropical and sub-tropical regions.
  • Echinococcus granulosus (Hydatid Tapeworm): It is a type of parasitic worm and it also goes by the name dog tapeworm. Dogs get commonly infested with this Hydatid tapeworm. It causes Echinococcosis.
  • Planaria (Dugesia): These are free-living flatworms and are found in both marine and terrestrial habitats. They have a particular trait that have high regenrative power.

Classification of Platyhelminthes

Platyhelminthes are further divided into three classes:


This species is usually found in both freshwater and marine environment. These are not parasitic in nature.In the aquatic ecosystem, these organisms act as detritivores. Some of their features are:

  • The body is flat dorsoventrally.
  • Suckers and hooks are absent in this class.
  • For example, Planaria, Otoplana, etc.


This class includes all the parasitic worms known as flukes. They often inhabit multiple hosts. Some of their features are given below:

  • All the species are obligate parasites.
  • They have an oral and ventral sucker.
  • For example Diplozoon, Fasciola, Hepatica, etc.


This class includes species which are known as tapeworms. These are usually found in the digestive tracts of humans, vertebrates and mammals.Following are some of their features:

  • Hooks and suckers are present in this class.
  • Only parasites are included in this class.
  • Cause diseases in humans such as Taeniasis and Cysticercosis
  • Examples are Beef tapeworm, Fish tapeworm, etc.

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FAQ’s – Platyhelminthes

1. What is Unique to Platyhelminthes?

Every phylum has some distinguishing features which specify its identity among other phyla. Platyhelminthes also have such features that are-

  1. Their body shape is dorsoventrally flattened.
  2. Cover of ciliated epithelium over their body.
  3. The absence of a cavity makes them acoelomate.

2. Do Platyhelminthes Live in Water?

All platyhelminthes are found in aquatic habitats be it freshwater or marine. Flatworms are sometimes found on the underside of wet rocks.

3. What is the Common name for Platyhelminthes?

The organisms belonging to Phylum Platyhelminthes are also called as Flatworms. They are called so as they are dosrsoventrally flattened.

4. What is Platyhelminthes Named after?

The name Platyhelminthes is derived from the Greek word ‘Platy’ which means flat and ‘helminth’ meaning worm.

5. What are the Sexes of Platyhelminthes?

Platyhelminthese are hermaphrodites which means they have both sexes within a single organism. They can reproduce both sexually and asexually.

6. What is Phylum Platyhelminthes?

Phylum Platyhelminthes is one of the phylum of Kindom Animalia. These are invertebrates that lack a backbone and are also known as “Flatworms”

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