𝙋𝙃𝙔𝙇𝙐𝙈 𝘼𝙎𝘾𝙃𝙀𝙇𝙈𝙄𝙉𝙏𝙃𝙀𝙎:- Phylum—Aschelminthes or Nemathelminthe | Gaurav Gupta sir

𝙋𝙃𝙔𝙇𝙐𝙈 𝘼𝙎𝘾𝙃𝙀𝙇𝙈𝙄𝙉𝙏𝙃𝙀𝙎:-

Phylum—Aschelminthes or Nemathelminthes or Nematoda (Nema — thread; helminth — worms) includes roundworms. They are commonly called as nematodes.

General Feature
Some important general features of phylum- aschelminthes are discussed 𝙗𝙚𝙡𝙤𝙬:-

i. Habitat and Habit They are mostly free living and may occur in water or within the soil. There are several parasitic species which live within the body of animals or plants, e.g., Guinea worms, whipworms, eyeworms, etc.

ii. Symmetry They show bilateral symmetry and have organ system level of organisation.

iii. Germ Layers They are triploblastic animals and have tube within tube body plan.

iv. Body Walt The body wall contains an outer cuticle, syncytial epidermis and a muscle layer. Circular muscles are absent.

v. Body Cavity Aschelminthes are pseudocoelomates as the cavity present between the body wall and gut is not lined by mesodermal epithelium.

Circulatory and respiratory systems are also seem to be absent in Aschelminthes.

vi. Digestive System Alimentary canal is complete with a well-developed muscular pharynx.

vii. Excretory System It consists of a pair of gland cells or intracellular canals or both.

viii. Nervous System It contains a nerve ring around the pharynx with dorsal and ventral longitudinal nerve cords running throughout the length of the body.

ix. Reproduction Nematodes reproduce only by sexual method. Sexes are separate and exhibit sexual dimorphism. The males are generally smaller than the females to aid copulation.

x. Fertilisation It is internal. The fertilised eggs develop directly or indirectly through larvae that undergo moulting and finally grow into adults.