Saltar la navegación

8.8. Flatworms

Phylum Flatworms

Flatworms, also known as flatworms, are a type of invertebrate animal.

Traditionally, flatworms have been included together with nematodes, within a group called "worms". They have simple organs and no apparatus.

Tipos de gusanos: anélidos, platelmintos y nematodos

The main characteristics of flatworms are:

  • They have a flattened body, which is why they are also called "flat worms", although the term worm does not correspond to any taxonomic category.
  • They have no skeleton, neither internal nor external.
  • They do not have locomotor appendages.
  • The alimentary canal does not have an anus, and acts as a digestive cavity. That is, it performs digestion and distributes nutrients, since they do not have a circulatory system either.
  • Some flatworms are free-living, but others are parasites, such as tapeworms or tapeworms that parasitize the intestines of humans and other animals.
  • Most are hermaphrodites.

Planaria en el fondo marino

By Erics [CC BY-SA 3.0 ], from Wikimedia Commons

The two best-known groups of flatworms are:


They are intestinal parasites, also of humans. In the front they have the scolex, a structure that allows them to attach to the wall of the intestine of the animal they are parasitizing. They do not have a mouth, but directly absorb nutrients from the intestine.

Video: Solitary or tapeworm.


Free-living flatworms that live in both the sea and fresh water. They can reproduce sexually and asexually. They show an extraordinary ability to regenerate body parts.