Difference Between Platyhelminthes and Nematoda

Platyhelminthes vs Nematoda

Platyhelminthes and Nematoda are two major invertebrate phyla in the Kingdom Animalia that show some difference between them in terms of their morphology. Invertebrates are the animals who lack backbone. The other major invertebrate phyla include Porifera, Cnidaria, Annelida, Arthropoda, Mollusca, and Echinodermata. Platyhelminthes and nematodes are non-coelomates and have very simple body structure. Even though they are simple, these animals perform all the vital body functions of life (respiration, food consumption, reproduction, defensive actions, etc.) just like other complex animals. The main focus of this article is the difference between Platyhelminthes and Nematoda; however, the morphology of the individual organisms; that is the morphology of Platyhelminthes as well as that of Nematoda also will be highlighted here.

What are Platyhelminthes?

Platyhelminthes or flatworms are unsegmented, bilaterally symmetrical acoelomates. They have ciliated, soft, dorsoventrally flattened worm-like bodies with an incomplete gut. About 20,000 species of Platyhelminthes are known up to date. Flatworms are hermaphroditic and their reproduction is sexual. However, asexual regeneration is also present in this category. Free-living worms are found in marine, terrestrial and freshwater habitats, and they feed on small animals and organic debris. They have ciliated epithelial cells and muscles, which help in locomotion. Free living worms have a fine network of tubules with flame cells that act as their excretory system. Most of the Platyhelminthes are found inside other animal bodies as parasites.

 Difference Between Platyhelminthes and Nematoda

Phylum Platyhelmineths consists of three classes, namely; Turbellaria, Trematoda, and Cercomeromorpha. Turballarian includes all the free-living species (e.g: Dugesia). Trematoda and Cercomeromorpha include all the parasitic flatworms. Trematoda consists of more than 10,000 known species of flukes (Eg: Liver fluke, blood fluke), and Cercomeromorpha includes tapeworms (eg: Taenia saginata). Parasitic flatworms can cause diseases to humans. Thus they are important medically and veterinary.

What is Nematoda?

Nematodes or roundworms are pseudocoelomates and have unsegmented bilateral symmetrical bodies. Scientists believed that there are more than 25,000 species of nematodes are present in the world. Nematodes are abundantly found in terrestrial, marine, and freshwater habitats and many live in animal and plant bodies as parasites. Most of the species are microscopic. Their worm-like body is flexible and covered by a thick cuticle that is molted as they grow. Their simple bodies do not contain specialized respiratory organs and the exchange of gasses occur only though the cuticle. They lack circular muscles body and contains only longitudinal muscles. A well-developed complete digestive system is present in nematodes. Nematodes reproduce sexually. Most of them are gonochoric and show sexual dimorphism. Hookworm, trichinosis, pinworm, intestinal roundworm, and filariasis are some important, disease-causing , parasitic roundworms.


What is the d ifference between Platyhelminthes and Nematoda?

• Nematodes are called roundworms while Platyhelminthes are called flatworms.

• Nematodes are pseudocoelomates, while Platyhelminthes are acoelomates.

• Species of nematodes are higher than that of Platyhelminthes.

• Platyhelminthes have an incomplete gut whereas nematodes have a complete one.

• Unlike in nematodes, Platyhelminthes have flame cells to do the excretory functions.

• The body length of flatworms may vary from 1 mm or less to many meters. Unlike flatworms, most roundworms are microscopic.

• Platyhelminthes are hermaphroditic and nematodes are gonochoric.