What is Phylum Aschelminthes?
- Aschelminthes are the organisms that have a cavity inside their They are also called
Roundworms or Nematodes.
- They are a step higher than the Platyhelminthes on the scale of
Roundworm
- They have an organ system grade of The body is usually cylindrical and has a tapering end.
- The mouth consists of prominent structures like suckers and hooks to attach to the host body and derive nutrition from
- The body is bilaterally symmetrical and can be divided into equal halves when cut through the central axis. They are triploblastic with three proper embryonic layers namely endoderm, mesoderm, and
- They also contain a pseudocoelom, a pseudo cavity, present between the gut and the body
- They are very rarely found in marine or freshwater habitats. Most of them are endoparasites, live inside the body of a host
For example, Ascaris, Wuchereria, etc.
Embryonic layers and Pseudocoelom
Which systems are present in roundworms?
- They show a simple digestive system which helps in the breakdown of simple food molecules.
- The excretory system is also quite simple and consists of canals and cells called
protonephridia.
Digestive system and Excretory system
- They lack a proper circulatory and respiratory system. These processes occur with the help of simple
- The nervous system is poorly
- Aschelminthes show sexual reproduction. They are unisexual organisms, males and females are separate individuals. Females are usually larger in size compared to males. Fertilisation is
Reproductive system
Nematodes