Platyhelminthes vs. Aschelminthes

The largest kingdom, kingdom Animalia comprises animals. Members of this classification show a heterotrophic mode of nutrition, and can be classified into different subphyla on the basis of the differentiation and design of their bodies. Platyhelminthes and Aschelminthes are classified under Kingdom Animalia. Both Platyhelminthes and Aschelminthes are invertebrates lacking a backbone.

The key difference between Platyhelminthes and Aschelminthes is that the members of Phylum Platyhelminthes are usually acoelomates, while the members of Phylum Aschelminthes are generally pseudocoelomates.

Platyhelminthes

  • Members of this phylum belong to the kingdom Animalia including close to 13,000 species
  • Also referred to as flatworms, these include parasite as well as free-living life forms
  • Members of this phylum are acoelomate, triploblastic, bilaterally symmetrical and unsegmented metazoans lacking anus. However, they have a mouth
  • Their bodies are dorsoventrally flattened and soft
  • Their members range in size from being single-celled entities to about 2-3 feet in length
  • Ladder-like nervous system, presence of flame cells, self-fertilization, body cavity showing the presence of parenchyma are their unique traits
  • Some members of this phylum are Planaria, Fasciola, Taenia solium, Schistosoma, etc.

Aschelminthes

  • Commonly referred to as roundworms, the members of this group are distinguished by the presence of a pseudocoelom. These are now obsolete phyla of invertebrates
  • They are parasitic or free-living in nature and can be seen inhabiting freshwater, soil or as parasites in animals, plants and in humans too
  • Their body is triploblastic and bilaterally symmetrical
  • The body is long, unsegmented, tapering towards the end and shows no metameric segmentation
  • Some members of this phyla are Enterobius vermicularis, Ascaris lumbricoides, Ancylostoma, Wuchereria, etc

Key Difference between Platyhelminthes and Aschelminthes

The table below depicts the difference between Platyhelminthes and Aschelminthes.

Platyhelminthes

Aschelminthes

Body of members of this Phylum

Flat body – Worms have a bilaterally symmetric body

Cylindrical body – body is distinguished by the absence of a well-developed coelom and the blood vessels

How can the members of this Phyla be described?

Body is soft, thin, resembling the shape of a ribbon or leaf

Obsolete phylum containing invertebrates such as roundworm

Coelom

Acoelomates – do not contain coelom

Show a Pseudocoelom

Development of organs

Restricted

Complex organ systems’ development seen

Excretory structure

Flame cells

Renette cells

Gut – Incomplete or complete

Incomplete – single opening

Complete – with mouth and anus

Body cover

Absent

Present, in the form of a non-living cuticle

Reproductive system

Hermaphroditic

Gonochoric

Other names

Flatworms

Roundworms

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