Phylum Aschelminthes

Phylum Aschelminthes

In phylum Aschelminthes, the organisms are also called roundworms because the body is circular in cross-section. These organisms are endoparasites. They are cylindrical, unsegmented, and triploblastic animals.

Characteristics Features of Aschelminthes

The characteristics features of Aschelminthes are:

• Habitat– These animals exist as free-living, aquatic, and terrestrial or may be found as a parasite in plants and animals.
• Level of organization– An organ-system level of organization is found.
• Symmetry– They are possessing a bilaterally symmetrical body. the distinct head is absent in Aschelminthes.
• Germinal layer– Triploblastic animals
• The body cavity or Coelom– These animals are pseudo coelomate.
• The alimentary canal is complete.
  • A well-developed muscular pharynx is found within the alimentary canal.
  • A complete digestive system is present.
• Excretion– Waste products are removed from the body cavity by an excretory tube through the excretory pore. In some forms protonephridia or rennet cells or giant cells as excretory organs.
• Circulatory and respiratory system: absent.
• The sense organs are in the form of pits, papillae, bristles, and eyespots.
• The body is covered with a thick cuticle i.e. syncytial, it is flexible, non-living, and made up of protein (scleroprotein)
• Reproduction– sexes are separate- dioecious
  • Dioecious- males and females are distinct. Females are longer than males.
  • Fertilization takes place internally.
  • The development may occur direct – as the young ones resemble the adult or indirectly.

Examples of Aschelminthes:

Some examples of Aschelminthes are Ascaris (roundworm), Wuchereria (Filarial worm), Ancylostoma (Hookworm), Brachiomus, Colotheca, Urodasys, Macrodasys, Echinoderes, Centroderes, etc.

Example of Aschelminthes

Classification of Aschelminthes

1. Nematoda
   • The members are endoparasites
   • The body is Bilaterally symmetrical and vermiform.
   • A complex cuticle covers the body.
   • Example: Ascaris (roundworm), Ancyclostomata (hookworm), Enterobius (pinworm)
2. Rotifera
   • The organisms are microscopic aquatic.
   • sexes are separate
   • Excretion through protonephridia tubes.
   • Example: Brachiomus, Colotheca
3. Gastroticha
   • They are free-living aquatic organisms.
   • Sexes are separate or united
   • Example: Urodasys, Macrodasys
4. Kinorhyncha
   • These are marine and microscopic organisms.
   • Internally segmented body
   • separate sexes
   • Development is indirect (with the larval form)
   • Example: Echinoderes, Centroderes
5. Nematophora
   • The body of these organisms is slender and unsegmented.
   • Also called hairworm
   • Sexes are found separate.
   • example: Nectonema, Gordius

You can also read: 💡

• Phylum – Porifera
• Phylum – Coelenterata (Cnidaria)
• Phylum- Ctenophora
• Phylum- Platyhelminthes

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