Phylum Platyhelminthes-

GAMNI MADAAN , Academic Content writer at EDUMARZ

Crucial features : .Because of having a dorso- ventrally smoothened body ( i.e. body is flat from both upper and lower surface side), the organisms of this Phylum are known to be as “flatworms”. They’re substantially endoparasites which live inside the organs of hosts. They’re bilaterally symmetrical ( left and right side of organism is divided equally) , triploblastic ( body wall is formed from 3 layers – ectoderm , mesoderm and endoderm) and acoelomate animals( do not seem to possess a body cavity). They possess specialised cells called “flame cells ” to help them in excretion and osmoregulation. Suckers and hooks are present which help them to sock up nutrients from the host directly through their body surfaces.

Features as per different-different parameters :-

Habitat – Mostly endoparasite.
External morphology : General body is unsegmented (in Planaria and in Fasciola)
Alimentary Canal and Digestion : alimentary canal is present .Mouth is present but there is absence of anus.
Excretion and osmoregulation: flame cells help in osmoregulation and excretion.

Fertilisation : fertilisation is internal .
Development : It goes through many larval stages
Digenetic parasite : life history of Platyhelminthes involves two host( digenetic) – primary and

secondary host.