Features of Platyhelminthes

Introduction to Features of platyhelminthes

Platyhelminthes are commonly called as Flatworms. The word Platyhelminthes is derived from the Greek word platy for flat and helminthes for worms. Platyhelminthes belongs to an ancient phylum, nothing much is known about their evolutionary history because of their very soft bodies which do not preserve well as fossils. Scientists believe that they might have evolved around 550 million years ago. Since the Platyhelminthes look like worms like creatures they are called with different names such as Flatworm, Tapeworm, Fluke and Planarian.

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The Platyhelminthes are divided into groups


Turbellaria
Monogenea
Trematoda
Cestoda


Turbellaria are mostly free-living and a few of them are parasitic. They are found in fresh water, oceans and in moist terrestrial habitats.

Monogenea are commonly known as flukes. The Monogenea are mostly external parasites of fish and have a simple life-cycle involving only one host.

Trematoda are commonly known as flukes. Trematoda are mainly endoparasitic in nature and have a life-cycle involving more than one host which is more complicated.

The Cestoda are commonly known as tapeworms, they are intestinal parasites in vertebrates.

Let us see the important Features of platyhelminthes.

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Important Features of platyhelminthes:


Bilaterally symmetrical and triploblastic body (composed of three fundamental cell layers) Are the important features of Platyhelminthes.
The body is usually flattened dorsoventrally and No true segmentation is present.
The Epidermis is soft and ciliated, or covered with cuticule and it has external suckers or hooks, or both for connection to host.
Absence of the body cavity except the gut is one of the important features of  platyhelminthes.
It has a Digestive system which is incomplete i.e. it has a mouth but no anus and usually much branched.
Another important features Platyhelminthes is it has a Protonephridial excretory organ instead of an anus.
Absence of  skeletal, circulatory or respiratory system is one of the features of platyhelminthes
It has normally a nervous system of longitudinal fibers with transverse commissures.
As they are hermaphrodites the reproduction is mostly sexual and the Fertilization occurs internally.